Best rig for small catamaran circumnavigator? [Archive]

sharpii2

01-25-2006, 09:32 PM

I would go with a cat ketch or even a cat schooner with stayed masts. A catamaran has a very large righting moment and making unstayed masts out of conventional materials, such as wood, that can stand that kind of strain may require either too large a section (diameter) or too complicated a design or both. This could make the rig expensive and/or heavy. Niether of which is desireable in your case.

I would go with the jibless working rig so I wouldn't have to extend the deck all the way to the bows of the boat. If you plan on doing that anyway, then I would go with a jib as well. The idea is to have as many sail combinations as possible so you can prtetty much 'ballance' the boat by the sails and not rely so much on electromechanical self steering rigs.

Keeping the Center of Area (CA) as low as possible is another good idea.

A 3/4 fractional sloop rig would be my next choice, because it is simple and sturdy and does not put a lot of rigging strain on the hulls and connectors. It also requires just one mast. And we are talking pretty small here, boat wise.

My third choice would be a mast head cutter, where the mainsail area above the jib is cut off and replace with another jib foreward of the first with the forward jib stay attached to the same tang. That might be a good bet to get the (CA) lower and thereby make the boat safer. The mast could be much shorter too. You would, however pay for this in windward ability. The two jibs will not only interfere with each other, but interfere with the main as well. Not only that, but there would be considerable (visable) luff sag as well. Hence this rig would be my third choice. But, in its defence, I would say that it would be a handy one. You would reef the main and drop the outer jib as soon as it started to breeze up. The inner jib would now be within easy reach should it need to come down as well. More likely, you would leave it standing and strike the main, so you could keep your boat moving in a controlable downward drift once it got really nasty.

The Prout rig, in my opinion, would be a poor choice. It worked on the Prout boat because the Prout boat was essencially one piece. It was really, structially, like a skinny scow with weight supporting sponsons tacked on. The bridge deck whent all the way from the extreme bow to the extreme stern. This dridge deck section had a very deep bottom that swept up to the deck at the ends. For a catamaran, it was an extremely rigid design. My advice would be: don't copy the rig design unless you plan on copying the hull design as well. Otherwise, you may see the jib stay sagging off to the point of windward usellesness.

Good luck on your adventure.

Bob

randy quimpo

01-28-2006, 04:35 AM

Hi everyone,
Thank you for your valuable suggestions. I am just wondering why no-one has brought up the Wharram soft-wingsail rig. Does it work as advertised, particularly since much of the sailing I am designing for will be in the trades?

Thanks/ Randy Quimpo

sharpii2

01-28-2006, 07:12 AM

I haven't commented on the wharram sail for two reasons.

1.) I know next to nothing about its performance improvement over a standard gaff rig of the same size and proportions. (it would be an interesting experiment to have two nearly identical wharram cats race each other, one with the fairing on the sail and the other without.)

2.) The fairing appears to be a sock that goes around the mast and is, otherwise, integrel to the sail. The problem with this is that it may bunch up as you try to lower the sail. Kind of the way a shirt sleve does when you try to push its cuff up your arm. This could slow the procces of reefing and/or lowering the sail. In my opinion, not a good idea on a boat that has only initial stability and one in which getting the sail down quickly may mean the difference between capsize and minor scare.

For what you want to do, I would think that:

1.) Safety,
2.) Simplicity, and
3.) Reliability

should be the main criteria in chosing a rig.

Bob

Crag Cay

05-20-2006, 08:25 AM

For what you want to do, I would think that:
1.) Safety,
2.) Simplicity, and
3.) Reliability
should be the main criteria in chosing a rig

In that case, I think you would want to consider the Wharram Soft Wing very carefully, as it meets all these criteria perfectly.

In fact, if you want to circumnavigate in a small epoxy/ply catamaran, I would buy some plans off Wharram and follow them to the letter. Unless of course, you believe your first efforts at design will be better than a man with 50 years experience.

http://www.wharram.com/tiki_wingsail_article.shtml

If you are determined to forge your own path, then Erik's suggestion of a bi-plane rig is a good one. Imagine a windsurfer rig in each hull.

Eric Sponberg

05-20-2006, 09:35 AM

A contact recently sent me this link which shows exactly what you suggest in a bi-plane configuration.

http://www.schionningdesigns.com.au/www/page.cfm?pageID=266

Eric

sharpii2

05-20-2006, 04:23 PM

Hi fellows,
I'm an amateur designer working on a design for a small (27 foot) epoxy-plywood catamaran circumnavigator (please be patient - I dont know too much at this point). I need a recommendation as to what the best rig to use is. The cat will be sailed singlehanded, and mostly in trades (the leisurely route around the world - none of this cape stuff ). No carbon fiber masts please - plain wood prefered.

Priorities will be ease of use (to be sailed singlehanded but lazily), reasonable performance and cost.

I was thinking of a Prout-style large genoa / small main type. Or even ripping off some ideas from the Wharram tiki sail.

I like unstayed masts due to the simplicity, but doesn't this mean that I need a thicker mast, therefore less efficient airfoil?

One more thing - do any of the traditional rigs qualify? Cat ketch / Yawl anyone? I've heard so many good things about the Cat ketch rig but for the life of me I can't imagine how this will work on a catamaran.

rgds / Randy Quimpo

A cat schooner may be more to your liking than a cat ketch. I understand that multihulls don't like Center of sail Area too far forward. Also, the weight of the biggest mast being near the bow will effect a narrow multi water plane more than it would a wider mono one.

The old fractional sloop may be your best bet. That way the mast is more likely to end up on a cross beam. The jib can go 3/4ths the way up the mast and the main can be a gaff or a marconi. This give you very good stay geometry and it puts the biggest sail within easy reach for reefing and furling.
I know that that type of rig is so commonplace that it is boring. But maybe it is so for a good reason. Unless I had full length sail battens, I would have no battens at all. Short battens are a BIG pain in the arse. And they do cause chaffe. Full length battens that run parallel to the boom, however, may save your sail from beating itself to death every time round up into the wind.

Since this is to be a blue water/trade wind boat, I would want to keep the rig height as low as possible. Competitive upwind performance should be a distant secondary conern in view of what you want to do with this boat.

The hull design should take into account a much more generous payload capacity than is typical with the present day performance oriented catamaran. I would want at least 1,000 lbs of payload capacity minimum for a single handed boat. The size and shape of the underwater sections should reflect that reality.

Just my 2 cents.

Bob

grob

05-22-2006, 07:50 AM

Imagine a windsurfer rig in each hull.

http://www.fourhulls.com/assets/images/xcat1.jpg

You mean like this .....

Gareth
www.fourhulls.com

Crag Cay

05-24-2006, 06:41 PM

Looks good. A completely free standing and free to rotate sytem would have lots of advantages for a long distance voyager. Simple carbon or even ally poles would do it on the size of boat suggested by the original poster.

sharpii2

05-25-2006, 06:30 AM

Thomas Firth jones tried such a rig on his coastal cruising catamaran named Dandy, but after two seasons gave up on it. Apparently it works best on very fast cats because, along with the faster speed comes an aparent wind that is further forward. This may explane why it is given so much praise in the faster sailing multi community.

The boat in question will not be nearly that fast. Most likely it will be a D/L 100 boat or damn near. Especially when all the long voyaging stores are loaded aboard. Although it will most certainly be faster than a mono pocket cruiser of the same length, it will probably be too slow to benifit from the biplane rig.

Mr. Jones reports in his book MULTIHULL VOYAGING: "...On a reach, the leeward sail flopped idly about, and we were driving the boat with only half her sail area..."

And there was much more after that. And most of it wasn't flattering. The only good thing he said about the rig was how few times he had to reef it.

Its best point of sailing was dead down wind, because the two side by side mains could be flown wing and wing.

Bob

bilbobaggins

06-07-2006, 08:21 AM

The Soft Sail rig has certainly been shown to work well. 'Jeckells Sails' did the sails. Neville and Annie Clement built the prototype 'Tiki 46' on a farm near here, launched it at Bristol, England, and have sailed it trans-Atlantic to the Caribbean and US East Coast, where they commute with the seasons between the Bahamas and Providence, RI.

I've known and sailed on Wharram cats for decades - I was crew on the maiden voyage of his/their 65' 'Spirit of Gaia' - and I know that the merits and otherwise of his/their designs generate almost as much 'steam' as does Ould Jimmy himself.

If I were to advise a member of my family, or a close friend who asked, about JWD designs, I'd say that many sailing families and enthusiasts worldwide have built and sailed these boats, for many tens of thousands of miles. However, they are far from maintenance-free, and a thoughful read through any of the 'Wharram forums' will show that EVERY one of those designs have been modified/enhanced/improved/beefed-up by owner-builders somewhere. Sometimes, these 'mods' become incorporated by Hanneke into the new plans.....

IMHO it is important to avoid 'blind faith', and to 'think critically about everything critical'. You will note, if you read the newsletters from Annie Clement ( Letters from Peace IV ) on Wharram's website, that they've had major problems with their foremast, its support, the beam lashings, the crossbeam troughs, the 'boomless' rig, and several other matters. The point is, they managed ( with a lot of help from friends ) to keep their boat together, and improve it. A 'work in progress'.....

Look here:

http://www.wharram.com/

:)

rayaldridge

06-19-2006, 01:50 PM

This rig seems appealing in theory, but as Tom Jones discovered, it has certain drawbacks in practice. I don't think faster boats can entirely sail away from the lee blanketing problems on a reach. I've read correspondence from a person in Thailand who built a Radical Bay (Schionning design) and still acknowledged that the problem occurred. They were overall very happy with the design, however, and felt that this inefficiency was a tradeoff that could be endured to get the other advantages of the rig.

One big disadvantage for a cruiser is that when the lee sail is outboard, there is very little deck underneath it to work at the boom, for reefing and sail shape controls. A great advantage of cats in general is that you can stand by the boom in the middle of a wide deck and do this work in security and comfort, and that is a big advantage to give up.

Ray

bilbo

06-19-2006, 07:38 PM

Masts should always be designed to the righting moment of the hulls

I'd find it very helpful if you could elaborate on this just a little, say, using a Righting Arm GZ of 11.5 feet, a max loaded displacement of 5 tonnes, and consequently a Righting Moment of 57.5 ft-tons....?

I can provide a 'bury' of 2 metres.

What do I need to consider and calculate in respect of a pair of carbon unstayed spars, in biplane configuration, and the 'well' in each hull that must take the loads?

Please, and thanks.

:confused:

sharpii2

06-21-2006, 06:05 AM

I'd find it very helpful if you could elaborate on this just a little, say, using a Righting Arm GZ of 11.5 feet, a max loaded displacement of 5 tonnes, and consequently a Righting Moment of 57.5 ft-tons....?

I can provide a 'bury' of 2 metres.

What do I need to consider and calculate in respect of a pair of carbon unstayed spars, in biplane configuration, and the 'well' in each hull that must take the loads?

Please, and thanks.

:confused:

Bilbo:

You need to either learn some engineering yourself, or find someone who is not only familiar with structual engineering, but familiar with the matterial you want to make the masts out of as well.

Here, I will offer what little help I can.

First off, you have not provided enough imformation. You need to know your mast height. You now have to take this load (57.5 ft/tons) and multiply it, expressed in pounds, by the height of the mast in inches then divide that by 2.0. As you see, this will come out to a huge number. This is your 'Bending Moment'.

Once you've done that, you now need to find your minimal 'Sectional Modulus'. This is done by dividing your 'Bending Moment' by the by the 'Allowable Stress' of your matterial, which is usually expressed in pounds per square inch. If it is expressed in kg per square centimeter, make sure the weight and the mast lengh are also expressed in kg and cm. This will give you your Sectional Modulus (SM) expressed in either inches cubed or cm cubed.

Now you need to draw a mast section that has at least that value.

As I hope you can see by now, there is a lot involved here.

And that is not the half of it. This is just the preliminary stage.

I hope you follow my original suggestion. This stuff is learnable by just about anybody, but it takes a considerable amount of time to learn (at least it did for me).

Best of luck.

Bob

georgelewisray

07-16-2006, 06:44 AM

Take inspiration from others and then go beyond.

as Isaac Newton said .... " if I have seen further than others, it is because I have stood on the shoulders of giants." J. Wharram may well be one of those giants.

Eric Sponberg

07-16-2006, 10:50 AM

Bilbo:

You need to either learn some engineering yourself, or find someone who is not only familiar with structual engineering, but familiar with the matterial you want to make the masts out of as well.

Here, I will offer what little help I can.

First off, you have not provided enough imformation. You need to know your mast height. You now have to take this load (57.5 ft/tons) and multiply it, expressed in pounds, by the height of the mast in inches then divide that by 2.0. As you see, this will come out to a huge number. This is your 'Bending Moment'.

Once you've done that, you now need to find your minimal 'Sectional Modulus'. This is done by dividing your 'Bending Moment' by the by the 'Allowable Stress' of your matterial, which is usually expressed in pounds per square inch. If it is expressed in kg per square centimeter, make sure the weight and the mast lengh are also expressed in kg and cm. This will give you your Sectional Modulus (SM) expressed in either inches cubed or cm cubed.

Now you need to draw a mast section that has at least that value.

Sharpii,

You have an error there. Bilbo's maximum righting moment is 57.5 Ft-tons. You do not multiply that by the mast height, and you do not divide it by 2 or the depth of bury. 57.5 Ft-tons is the live load bending moment on the mast at deck level. You have to express this in inch-lbs, and then divide by the allowable stress (in psi) of the material you are using to get the required section modulus, which comes out in units of inches^3. Allowable stress should be one third the yield stress (as for aluminum) or one third the ultimate stress if there is no yield stress (as in wood or composites).

For example, assuming long tons = 2,240 lbs: 57.5 Ft-tons = 128,800 Ft-lbs = 1,545,600 inch-lbs.

If high quality carbon fiber laminate is used (standard grade, vacuum cured epoxy), ultimate stress is going to be about 70,000 psi (could be 100,000 to 120,000 psi if made in an autoclave), so one third of 70,000 psi is 23,333 psi.

Required SM = 1,545,600 inch-lbs/23,333 = 66.24 inches^3

Then you have to calculate what the section size should be to have the section modulus that achieves the required value. Section modulus is a function of the geometry of the section. You need to calculate moment of inertia first. For a round tube, for example, the moment of inertia is I = PI/64 x (OD^4-ID^4). Then Section Modulus SM = (2 x I)/OD. This actual section modulus, as I said, has to be equal to or greater than the required section modulus. This I and SM for a round section are the same in every direction. For a non-round section, I and SM are different longitudinally and transversely, and that has to be taken into account depending on which direction the mast is loaded (usually some in each directtion, but certainly to the maximum transversely). Calculate SM by trial and error until you get to a reasonable solution.

You have to be careful, too, that you do not make the wall thickness too thin. If it is too thin, then the mast section can buckle prematurely before the laminate reaches full strength. So in every design, there is an optimum section size for the design at hand.

Finally, one has to consider deflection, which is dependent on the modulus of elasticity of the material times the moment of inertia of the section, ExI. the larger the ExI, the smaller the deflection. This is a whole separate engineering problem that is done at the same time as the strength calculations. It is easy to have too much deflection, and you hardly ever have too little deflection. One strives to design for just the right amount.

The equations are more complicated for non-round sections, but they can be figured out. This is why I like to use elliptical sections for my wingmasts because the equations for I and SM are nearly as simple as for a round section. For an aerofoil section, the method for determining the I and SM requires a complicated procedure using Simpson's rule, and the engineering process gets really complicated and drawn out. Elliptical sections have very favorable aerodynamic characteristics, so the whole package of design and engineering is doable in a reasonable amount of time and results in easy construction and very good boat performance.

Eric

Seafarer24

07-24-2006, 09:38 AM

For a multihull, especially a small multihull, there is nothing more economic than a stayed, rotating aluminum mast. It will still be efficient and light-weight. At these sizes you could save equal weight by using modern fiber rigging instead of wire rigging, instead of going with a free-standing, rotating, carbon-fiber rig.

For cruising conditions a gaff rig could work very well, though I would go with a fractional (fully-battened, square-top) marconi sloop rig with a roller-furling reacher set on a pole ahead of the jib.

terhohalme

07-27-2006, 02:09 AM

Something like this:

OldYachtie

09-15-2006, 06:21 PM

Unstayed alloy can fatigue over time. Unlike steel, aluminum accumulates sub-critical stresses over time, and suddenly breaks. If you want aluminum, you need staying to reduce the whipping. This is what Tom Colvin does with aluminum junk masts. Actually, Douglas Fir is good for unstayed masts, with its bending strength of 8000 psi.

As far as bi-plane rigs go, bi-plane sailors let the weather sail out a bit more than usual when beam reaching, and haul the lee sail in a bit more than usual. In overview, it would look a bit like one sail, with the different angles combining to make camber.

Looks good. A completely free standing and free to rotate sytem would have lots of advantages for a long distance voyager. Simple carbon or even ally poles would do it on the size of boat suggested by the original poster.

ron17571

09-15-2006, 08:46 PM

Randy i read your question with much interest,ive wondered the same thing,for a mast in your neck of the woods i would research using nipa or mabe bamboo for a mast,mabe wrapped in fiberglass n epoxy.i like lateen style sails and kinda like a junk rig.mabe a rig thats not so tall so less load.low tech and low cost,consider using rope to hold the mast up,some of the new high tech stuff,stronger than steel stuff.All the magazines ive read over the years always talk of people fixing wire rigging thats failing in the middle of nowhere.

brian eiland

05-23-2007, 03:38 PM

An email I recently sent in reply to subject of biPlane rig choice

SUBJECT: DynaRig, 40-ish Catamaran motorsailer
Client wrote:
Hi Brian,

I am of the definite opinion that all these rigs you talk about are
inefficient and heavy, not what one wants on a catamaran. It has been
proved time and again, what makes an efficient rig for windward work, a
wingmast and a sail of high aspect ratio, and some means of minimizing tip
vortices.

Why make it more difficult?

I have decided to go for a bi-plane rig on my 45 ft. cat, using unstayed
masts, and the masts will have a wingshape. The masts and booms can turn
360 degrees. Can easily be released and reefed at any angle to the wind.

XXXX

_______________________________________________________________
Brian replied:

Actually XXXX I am not trying to “make it more difficult”. I am just following aerodynamic principles that end up leading me to the rigs I chosen to promote and expand upon. I try to consider these rigs in light of cruising sailboat designs rather than racing designs, or specialty applications.

I’m having trouble understanding your choice of a ‘bi-plane rig’? I understand the desire to get a lower COE of the total sail area, and I do know these rigs have distinguished themselves in a few specialty applications (smaller vessels, and a few speed record seekers), but at what cost to all-around performance on a cruising vessel?? (I believe this is the type of vessel you are seeking?)

The bi-plane rig can certainly be made to perform to windward. And the use of higher aspect ratios and wingmasts will assist in this effort. But now you have tall narrow triangular sails that are the worst form, that produce considerable induced drag from vortices off of their tips, and you have two of them. Your induced drag on this bi-plane rig is going to be considerable higher than a single free-standing uni-rig.

My real concern with the bi-plane rig is with its performance in reaching and running, two of the primary and preferable sailing angles for cruising vessels. I just do not see any way to make the leeward twin rig effective at all in a beam-reaching situation. And remember EFFECTIVE downwind sailing is not just about projected sail area to the push of the wind, but rather FLOW over the sails, that will not easily be attainable with the bi-plane rig. Here are a few excerpts from a forum discussion on Sail Aerodynamics I made; Aspect Ratio (AR) of rigs on cruising vessels (http://boatdesign.net/forums/showpost.php?p=93500&postcount=168)

In general we have three basic sailing directions we need to consider, upwind, reach, downwind. And for the cruising sailor the upwind 1/3 of the total is not even an equal partner (as many cruisers often chose not to fight upwind work). As Marchaj and many others have reported, high aspect ratio is principle beneficial for upwind work.

When we talk of speed, are we talking of ‘around the race course’ speed, or straight-line, head-to-head speed? From a purely aerodynamic point of view, I would prefer to compare the vessels with different sailing rigs on a head-to-head basis in each of the 3 primary sailing directions. So hopefully you can see where I have some problems with your statements such as “the most efficient boats of all use cat rigs”, and “fractional rigs generally go faster than masthead rigs”. If you are talking ‘around the race course’ your statements could well be considered correct in many cases, but on a head-to-head basis they might not hold up so well.

Are you proposing fully battened sails on these freestanding wingmast? Are they to be reefably? …on each mast?, or just one up, one down? I would not want to be the autopilot unit trying to cope with the turning moments generated by COE shifting from one side to another.

I’m just not impressed with the idea of a bi-plane rig on a cruising vessel.

I don’t know how you conclude that my mast-aft design is “ heavy and inefficient”? It shouldn’t weight much more than the ketch rig it is intended to replace. As concerns efficiency I will just say I’ve written quite a lot about this in the past and won’t bother to rehash it here. Suffice it to say it will perform very well on all 3 major points of sail.

The email I sent out on the Dynarig was meant to show how the Falcon's dynarig could be brought down in complexity, price, and weight. Certainly it is still a 'square rigger', a very modern version at that, and will never compete with a free-standing unirig in expense nor weight aloft. But it has shown its capabilities in performace, and on all 3 points of sail

OldYachtie

05-23-2007, 08:49 PM

People who have used the bi-plane rig report that you just let the windward sail out more than usual when reaching, and haul the leeward sail in a bit more. From a seagull's eye view,(overview), I visualize the two sails in concert looking rather like one sail, as this trim would make the greatest draft in the combined middle, and least draft in the combined luff and leach. For this reason, I find claims that it works well to trim a bi-plane rig like this quite credible. Also, when running, you have zero back-winding, as neither sail is down-wind of the other. My next boat (a catamaran) will have a bi-plane rig.

brian eiland

05-24-2007, 11:36 AM

... Also, when running, you have zero back-winding, as neither sail is down-wind of the other. My next boat (a catamaran) will have a bi-plane rig.

I'll excerpt a comment I included above and re-emphasize it:
"And remember EFFECTIVE downwind sailing is not just about projected sail area to the push of the wind, but rather FLOW over the sails, that will not easily be attainable with the bi-plane rig."

People who have used the bi-plane rig report that you just let the windward sail out more than usual when reaching, and haul the leeward sail in a bit more.
I would refer you to the two contributions above:
Thomas Firth jones tried such a rig on his coastal cruising catamaran named Dandy, but after two seasons gave up on it. Apparently it works best on very fast cats because, along with the faster speed comes an aparent wind that is further forward. This may explane why it is given so much praise in the faster sailing multi community.

The boat in question will not be nearly that fast. Most likely it will be a D/L 100 boat or damn near. Especially when all the long voyaging stores are loaded aboard. Although it will most certainly be faster than a mono pocket cruiser of the same length, it will probably be too slow to benifit from the biplane rig.

Mr. Jones reports in his book MULTIHULL VOYAGING: "...On a reach, the leeward sail flopped idly about, and we were driving the boat with only half her sail area..."

And there was much more after that. And most of it wasn't flattering. The only good thing he said about the rig was how few times he had to reef it.

Its best point of sailing was dead down wind, because the two side by side mains could be flown wing and wing.
Bob

This rig seems appealing in theory, but as Tom Jones discovered, it has certain drawbacks in practice. I don't think faster boats can entirely sail away from the lee blanketing problems on a reach. I've read correspondence from a person in Thailand who built a Radical Bay (Schionning design) and still acknowledged that the problem occurred. They were overall very happy with the design, however, and felt that this inefficiency was a tradeoff that could be endured to get the other advantages of the rig.

One big disadvantage for a cruiser is that when the lee sail is outboard, there is very little deck underneath it to work at the boom, for reefing and sail shape controls. A great advantage of cats in general is that you can stand by the boom in the middle of a wide deck and do this work in security and comfort, and that is a big advantage to give up.
Ray

jamez

05-26-2007, 06:14 AM

BiPlane rigs have been shown to work well on heavier disp cats
http://www.flyingcarpet.co.nz/about.html
as well as light ones like the previously mentioned Schionning.
However the successful ones all seem to use freestanding masts (as opposed to the stayed rig used by TFJ) and in some cases have taken a bunch of tweaking to get right.

Most cats in the 27 foot region use a single masted bermudan sloop rig, either mast head or fractional. These rigs are well proven and easy to find appropriate specs for. Sure you could try something unique, but other than the challenge of designing it I can't see the point.

brian eiland

05-26-2007, 10:14 AM

Here's another reference to a very nice looking biplane rigged cat

http://www.sailcoolchange.co.nz/

...but I don't see anything definitive on their true performance on all points of sail :?: :?:

PS: Click on the 'accomodation button' and take note how close the mast are, and with respect to the boom lengths, then tell me how you effectively broad-reach this rig?

jamez

05-27-2007, 01:17 AM

Cool Change looks very swoopy. I found the design on the Kelsall site

http://www.kelsall.com/s7.html

She is approx 26 foot beam on 56 foot LOA. Assuming the hulls are say 6 feet wide and the masts are stepped on the centre line there would be approx 20 feet between them. Not sure of the implications of that, but it does seem to be a different approach to the Schionning which uses a much more low aspect sail plan on a relatively wider hull spacing. To me one of the reasons for the bi-plane should be to get more SA lower down. Not sure I'd want to swap one hi-aspect rig for two.

There are several articles on Schionnings website about sailing the Radical Bay that may answer some of the handling questions. There is also a 12 metre Schionning bridgedeck cat in build in Australia which will have a bi-plane rig of similar proportion to the Radical Bay.

I have an aquaintance who, 25 years ago, built a heavily modified Pahi 31 and fitted a biplane rig - in cahoots with Bernard Rhodes of Flying Carpet (see link above). I never sailed on this boat but according to the builder it went well - once he got used to the idiosyncracies of the rig. That boat (the Pahi) is still around and still sports the same rig.

Trevlyns

05-27-2007, 02:59 AM

Hi guys!

I’ve followed this thread with great interest but am wondering why no one has yet mentioned the vane controlled wingsail.

I’ll be using this on an 8 meter ply/epoxy cat which I designed and my rationale for going this route is as follows.

1. Ease of handling is important – both my wife and I are in our late fifties.
2. Expensive hardware like masts, rigging and winches are eliminated.
3. The wingsail adds a third dimension – thickness. I think this makes for greater efficiency and because it is streamlined, offers little resistance when head to wind.
4. Angle of attack is set by the vane and therefore follows any wind shifts; keeping the rig efficient.
5. The wing will simply weathervane in gusts and angle of attack can easily be reduced as the wind strengthens and indeed neutralized when the going gets tough or when in port.
6. It can be used in conjunction with a conventional spinnaker for downwind work.

I value and respect all opinions and would encourage any other thoughts on this matter.

brian eiland

05-28-2007, 02:48 PM

...an observation offered on another forum just recently...

Ross wrote:

Hi Everyone, I have been following the talk on the bi-plane rigs and thought I might relate my observations from sailing against one.

I sailed with Mark Pescott in the King's Cup regatta (Phuket, Thailand) on one of his Firefly 850 cats. (www.markpescottmultihulls.com) if you want to see what they look like.

One of the competitors was a Schionning designed Radical Bay 8000 with the bi-plane rig.
http://www.schionningdesigns.com.au/www/page.cfm?pageID=271

Conditions over the 5 sailing days varied between 5 to 10 knot days to 20 to 25knots on the Ko Racha race which is about 28 nautical miles and a reach both ways. On one of the lighter days the race ended up being about 4 hours long and we had to beat the Radical Bay by around 1 and a half hours on handicap. We worked hard and won the race on handicap by 0.38 of a second on corrected time but to have to win a race by an hour and a half is a bit ridiculous. They were no where to be seen when we crossed the finish line. The OMR handicap favours twin rigs as the second mainsail is only measured at 50%, a legacy of the days when ketches and yawls were still around.

The twin rigs worked quite well in breeze above 15 knots and they were hard to beat on handicap on those days but they suffered badly in light airs. We observed that the leeward rig gets blanketed a bit on a beam reach but not as much as you would think. This would be worse on a heavier displacement cruising boat, (that particular Radical Bay weighed 1100kg). I was fairly impressed with its tacking ability. It tacked fairly quickly although on the few occasions we cover tacked we noticed the Firefly was faster through and out of the tack. Mind you there are few cats that could tack as well as us.

The other observation was that it was a very boring boat to sail, as there wasn't a hell of a lot to do around the bouys. We had kites to launch and jibs to drop at the marks and all they did was ease or trim the mainsheets. Not what you would call an adrenalin rush. I guess my point is, that it certainly would have it's advantages on a cruising boat (ease of handling, etc) but it is not the ideal all round rig, especially for those of us that want to cruise in comfortable conditions ie; under 15knots of breeze, unless you have light, easily driven hulls. One might find the auxiliary gets used a bit more.

rob denney

05-30-2007, 10:55 AM

G'day,

I design and build unstayed carbon masts for multihulls, both harryproas and cats. Some facts after reading this thread:

A carbon mast will be considerably lighter than a wooden or alloy one. It will also last much longer, with less maintenance.

A correctly designed and bench tested unstayed carbon mast has nothing to break or wear out apart from the halyard sheave. A stayed rig has maybe 100 individual bits (wires, tangs, rigging screws, spreaders, chainplates, etc etc) all of which should be checked regularly and replaced every 5 years or so. Any one of these fails, the mast falls down.

An unstayed rig may or may not be heavier and more expensive than a stayed version, depending on who builds it. However, if the boat is designed for the unstayed rig, the overall package will be both cheaper and lighter.

An unstayed rig is safer. The tip bends off in a squall, delaying the need to reef. Gybes are painless, in any wind strength. The sail can be eased to weathercock on any point of sail. This also makes raising and lowering easier.

An unstayed rig can be faster, as it has much less windage than a stayed one. The Radical Bay/Firefly comparison is flawed, in a number of areas.

The best option for a cruising cat is an unstayed wing mast in one hull. Next best is the biplane rig. Everything else is a very distant third.

Anyone who wants more elaboration on any of the above points, please let me know.

regards,

Rob Denney
www.harryproa.com

jamez

05-31-2007, 03:37 AM

Brian,
Thanks for posting that excerpt from the other board. I had wondered how the RB 8000 would stack up against a boat able to fly extras. I think these are both cool designs. It would be interesting to see an RB 8000 with a conventional rig (the way the boat was originally designed for the International Multihull Design Competition 2002 run by Norske Flerskog) and see how it performed against the Firefly. I don't think there would be much difference. The bi-plane is described as boring but some people want easy handling as opposed to absolue performance. If I wanted a race boat I would lean towards the Firefly. If I wanted an easily handled fast boat to cruise the RB8000 has some attraction. That said they both seem bloody expensive to me for what they offer.

Trevlyns,
Don't know how much info you already have but suggest you check the Jim Antrim website for examples. Te Marama was a cat built to his design with a full wing rig that has cruised the Pacific - not allways without problems, but I'll leave it to you to research that on Google.

2c worth
I think what some people tend to miss is that most people just want boats they can (sometimes build and) just go out and sail. Without the problems of optimising someone elses 'next great idea'. Therefore they use proven configurations, rigs etc. And thats just fine. There will always be those who feel they have to push the envelope and thats just fine too. I don't see the point in some of the soapboxing that goes on. At the end of the day most people don't need to be 'converted' and will own what appeals/they can afford.

catsketcher

05-31-2007, 06:16 AM

I have to agree with the last writer. The reason the sloop rig is ubiquitous is because it works well on many different points. I don't agree with Rob, although I respect his view, that normal rigs are a distant third.

Sailing our East coast we often square run. In these conditions being able to hang a reacher or kite off the bow of the boat pulls it docilely downwind. It is fabulous and the autopilot can do it with ease. The main stays often stays bagged.

Reaching or going to windward I like the ability to balance helm by trimming the headsail and mainsheet. This is how the boat talks to me. I also like the way it is easy to reduce sail using my cutter rig. Most of the time multihull cruiser are slowing their boats down. To worry too much about optimum performance is not in keeping with the cruising philosophy. Above 8 knots average on our 38 footer and the ride usually starts getting too rough.

In fact the bending masts and rotating masts of racers probably would slow a cruiser down. This is because of an effect called mechanical sympathy. Basically many people get worried when big things with big things under lots of stress - masts and rigs - start wobbling around. Even though the engineer may say it is safe a cruiser will probably ease off to stop the movement. I did when cruising with a rotating stick on my Twiggy. I didn't like it and it made me worried. My non rotating stick on my cat has lots of wires and has never shown me it has any concerns.

I also don't agree with Rob's point about things to fail. There may be more objects in a normal rig but this does not mean they are therefore more prone to error. The aluminum extrusion is easily checked for damage and is produced to close tolerances but after the carbon mast has had a coat of paint can you be sure the builder has vacuumed it properly - was the carbon marine spec or a leftover laminate someone got cheap. There are many ways to fail here too. Most normal rigs have been up an awfully long time and are still going strong. In thirty years of sailing I have broken more unstayed windsurfer masts than normal masts. Engineer the rig properly no matter what type.

It is very important to properly understand the use of the rig you put on your boat. Modern cruising multihulls do not go fast enough to tack downwind in many conditions - I have tried it against friends who went faster straight downwind. Some of our cherished beliefs evaporate out cruising. The amazing rig that should work may not. I will be looking closely at the twin mast rigs being built and will be most interested to see how they stack up in typical cruising situations.

cheers

Phil

Ross Blair

05-31-2007, 08:53 AM

Hi Rob, I was wondering if you could elaborate on what was "flawed" in the Firefly/Radical Bay comparison. At my typing speed it is hard to cover all details. I would like to hear your questions and see if I have an answer.
Your comment made about the standard fractional bermuda rig was a little harsh. Yes, there are a few bits to check but to say that a hundred components need to be checked is not really true as most of it should be engineered well enough to almost never be checked. Mark Pescott has just been over here (Australia) and bought with him a set of stays from his cat "Summersalt" that, only now, need replacing and she was launched in 1987!
Yes he was a bit slack and should have replaced them years ago but he does check them from time to time. For the record Summersalt has done over 40,000 nautical miles.
I am not trying to put down the Bi-plane rig I was just saying that the fractional rig sloop is going to be a faster all round rig. It has to be, with the potential for increasing sail area when required.
I know what my choice would be for a cruising cat and I don't really care what someone else wants on theirs. As with almost everything to do with sailing it is a compromise and you live with the decision or make steps to change it. Happy sailing all! Meanwhile I'll get back to my dusty shed and keep building boats for others - mutter, mutter. Cheers, Ross Blair.

rob denney

05-31-2007, 10:32 AM

Phil I have to agree with the last writer. The reason the sloop rig is ubiquitous is because it works well on many different points. I don't agree with Rob, although I respect his view, that normal rigs are a distant third.

Rob
Your reasoning implies that monos are better cruisers than multis as they are more "ubiquitous". I believe that stayed sloop rigs are ubiquitous because a) they are what racing boats use and b) because sailors are very conservative.

Phil
Sailing our East coast we often square run. In these conditions being able to hang a reacher or kite off the bow of the boat pulls it docilely downwind. It is fabulous and the autopilot can do it with ease. The main stays often stays bagged.

R Do you leave that rig up overnight? Can you get it down singlehanded in the rain in a 40 knot squall at 2 am? The unstayed rig does not need a spinnaker to be hoisted, or a main to be lowered to fly the spinnaker. Just ease the sail out to square with the boat and you have the same result. In the squall, dump the sheet, the rig weathercocks and everything is immediately under control.

P Reaching or going to windward I like the ability to balance helm by trimming the headsail and mainsheet. This is how the boat talks to me. I also like the way it is easy to reduce sail using my cutter rig. Most of the time multihull cruiser are slowing their boats down. To worry too much about optimum performance is not in keeping with the cruising philosophy. Above 8 knots average on our 38 footer and the ride usually starts getting too rough.

R Sure, the more strings, the more you can talk to your boat. This, and Ross' desire for lines to adjust and adrenaline rushes are definitely pluses for sloops, minuses for unstayed rigs. Whether they are what cruisers want is a moot point. Reducing power on your cutter cannot be as easy as reducing it on an unstayed rig. You have to drop or furl a (possibly flogging) sail, the unstayed rig flexes, and pressure is relieved. No work required. Being able to stop the boat and unload the sails on any point of sail to tie in a reef on an unstayed mast is far easier than any sail reduction I have ever been involved with on a stayed rig.

P In fact the bending masts and rotating masts of racers probably would slow a cruiser down. This is because of an effect called mechanical sympathy. Basically many people get worried when big things with big things under lots of stress - masts and rigs - start wobbling around. Even though the engineer may say it is safe a cruiser will probably ease off to stop the movement. I did when cruising with a rotating stick on my Twiggy. I didn't like it and it made me worried. My non rotating stick on my cat has lots of wires and has never shown me it has any concerns.

R This is about stayed rotating rigs, not unstayed ones.

P I also don't agree with Rob's point about things to fail. There may be more objects in a normal rig but this does not mean they are therefore more prone to error. The aluminum extrusion is easily checked for damage and is produced to close tolerances but after the carbon mast has had a coat of paint can you be sure the builder has vacuumed it properly - was the carbon marine spec or a leftover laminate someone got cheap. There are many ways to fail here too. Most normal rigs have been up an awfully long time and are still going strong. In thirty years of sailing I have broken more unstayed windsurfer masts than normal masts. Engineer the rig properly no matter what type.

R No "may be" about it. There are more things to fail in the stayed rig. And they are more prone to fail. The alloy extrusion is the least of your worries, the rigging and all it's connections is what needs to be checked and replaced regularly, and if one fails, down it all comes. I assume a reputable mast manufacturer of the carbon tube. There are numerous checks which can be made of a carbon mast (which is why carbon has finally made it into commercial aeroplanes) including static bend tests and ultrasound tesing. Both are one offs. Windsurfer masts are a bit different. They are highly stressed and frequently subject to impact damage for which they were not designed such as dropping them off the roof rack.

P It is very important to properly understand the use of the rig you put on your boat. Modern cruising multihulls do not go fast enough to tack downwind in many conditions - I have tried it against friends who went faster straight downwind. Some of our cherished beliefs evaporate out cruising. The amazing rig that should work may not. I will be looking closely at the twin mast rigs being built and will be most interested to see how they stack up in typical cruising situations.

R The unstayed rig works brilliantly down wind. No crash jibes, no need to luff to reduce sail, no stays to chafe against. But mostly, no flogging spinnaker to raise and lower and scare the wife and kids.

regards,

Rob

cheers

Phil[/QUOTE]

rob denney

05-31-2007, 11:47 AM

Ross
Hi Rob, I was wondering if you could elaborate on what was "flawed" in the Firefly/Radical Bay comparison. At my typing speed it is hard to cover all details.

Rob
Firefly is near enough 20% lighter, 5% longer, with a 50% higher mast (critical in light air sailing) with 10% more working sail and near enough 100% or more downwind/light air sail area. Therefore it should be faster. The Firefly is a superb boat, we did well in the Brisbane Gladstone in it many years ago, despite being too scared to fly a spinnaker in the dark after being hit by a squall in the middle of the night. But as a cruiser, the rig is far too much like hard work. You see this as a plus, I see it as a minus, for cruisers. see below for a more meaningful comparison of an unstayed rig vs Firefly.

Ross
I would like to hear your questions and see if I have an answer.
Your comment made about the standard fractional bermuda rig was a little harsh. Yes, there are a few bits to check but to say that a hundred components need to be checked is not really true as most of it should be engineered well enough to almost never be checked.

Mark Pescott has just been over here (Australia) and bought with him a set of stays from his cat "Summersalt" that, only now, need replacing and she was launched in 1987!
Yes he was a bit slack and should have replaced them years ago but he does check them from time to time. For the record Summersalt has done over 40,000 nautical miles.

Rob
So, are you saying that stayed rigs do not need to be checked or have anything replaced until they have done 40,000 miles? Didn't think so. 20,000? No. 10,000? No. At the end of every season, and before, after (and during) a long passge or a gale? Yes. I would not expect to have to check or replace anything in a well built, unstayed carbon mast for at least 40,000 miles. Not because I am more gung ho than you, but because there simply is nothing to check.

You say a few. On Firefly, there are 3 stays, 2 or 3 diamonds, 5 or 6 rigging screws, 10 or 12 clevis pins, 10 or 12 swages, 7 attachments for the wires on the mast, 3 on the deck, a seagull striker (with another piece of wire, rigging screw, 2 swages, and 2 cotter pins), maybe a dolphin striker with another piece of wire, rigging screw, 2 swages, and 2 cotter pins, a traveller with a ball bearing car, blocks and cleats and at least two sheet winches and cleats. Not quite a hundred unless you include all the rivets, nuts and bolts holding it together, but it is only a 28 footer. None of these are on the unstayed rig, so do not have to be over engineered, bought, checked or replaced.

Ross
I am not trying to put down the Bi-plane rig I was just saying that the fractional rig sloop is going to be a faster all round rig. It has to be, with the potential for increasing sail area when required.

Rob
Sorry, but I disagree with this as well. The unstayed rig can use extras (with the same handling problems) as on stayed rigs. But, more importantly, if speed is the criteria, then an unstayed rig can be a lot bigger to start with (as it flexes and does not need all the wires and resultant compression loads), will have far less windage, and can be mounted in a much lighter and longer (no forestay trying to wrench the bows off) boat, all of which are speed producing factors. An example is my solo Transpac boat. Lighter, wider, longer and cheaper than Firefly, more sail area, more accommodation and far drier, easier and more comfortable to sail. Any chance of you doing the next Sydney Hobart or Brisbane Gladstone in a Firefly so we can compare them?

Ross
I know what my choice would be for a cruising cat and I don't really care what someone else wants on theirs. As with almost everything to do with sailing it is a compromise and you live with the decision or make steps to change it. Happy sailing all! Meanwhile I'll get back to my dusty shed and keep building boats for others - mutter, mutter.

Rob
Give yourself a break from the sanding and sticky resin and come down to Urunga next weekend to see the dustless future of boat building! We are holding a KSS workshop from 7th-10th. At the end of the 4 days there should be a 50' hull, decks and bulkheads, faired, gel coated and ready to assemble. Materials cost for the finished hull, $Aus5,500/$US5,000. A couple of these and a sensible unstayed rig rig and you could afford to stop building boats for others and get back to cruising. ;-)

regards,

Rob

catsketcher

06-01-2007, 07:15 PM

jamez

06-01-2007, 08:24 PM

Rob,

"Your reasoning implies that monos are better cruisers than multis as they are more "ubiquitous".

Actually it doesn't (although many mono's of course have sloop rigs). Mono's are ubiquitous because for most people they also work well. That is not to say that in some respects a multi can't do some things better but that is something people often have to experience before they will countenance a change (like me;-).

"I believe that stayed sloop rigs are ubiquitous because a) they are what racing boats use"

And racing boats use them use them because in spite of the inherent drawbacks described above, in general, if they are properly engineered, they work well (and in the vast majority of cases stay up).

"and b) because sailors are very conservative".

Absolutely agree. Further, I would suggest that sailing conservatism is kind of self perpetuating as it is fuelled by the knowlege and acceptance of what is familiar and what people feel comfortable (in some cases to trust their lives) with.

While I would describe myself as a conservative (now cat) sailor in a lot of ways, I've got an alloy mast on my Wharram so I'm not a complete Luddite ;-). It has been interesting following the development of the various Harryproa and I look forward to seeing Solitarry launched and campaigned.

rob denney

06-04-2007, 10:25 AM

Thanks Rob for your comments. I think we will remain unmoved by each other and it will be our boats that will win the argument. I can't put into words the security my boat with its rig gives me with all its wires. You like your rig but I think that until I experience it for myself I won't get where you are coming from. Then I will either change my view or agree to disagree.

I like diversity - I love watching metre boats sail, going for a fang on a skiff or a good ride on a sailboard. Nigel Irens, who I think is the greatest multi designer we have, sails old style monos with a modern twist because he likes them. Most people sail monos because monos are the best boats for what most people do. My wife wants a Dragon because they are great boats that talk to her. There is no one super boat - no one super rig. There are many reasons to choose a boat/rig. Logic and argument can only unveil a few. You gotta love this thing that takes all your time and effort.

cheers

Phil

G'day,

I have experienced both types of rig, whereas you have yet to sail, maintain or buy an unstayed one. I look forward to taking you for a sail later this year. I also like to watch and sail on all types of boats, but when it comes to buying or maintaining them, the unstayed rig wins hands down. For a round the world cruiser (original subject) or a fast boat (morphed subject) the unstayed rig has far more going for it than the stayed rig.

I would also like to apologise for the unnecessarily caustic tone I adopted for my reply to you and Ross. Been a bit full on getting the design for the 50- footer finalised and the workshop sorted, so I was a little less careful with my editing than normal.

Regards,
Rob

sigurd

06-04-2007, 06:19 PM

masts suck

(edited to remove offensive slant :P )

leemolou

06-30-2007, 11:23 PM

What about 2 hulls you can sail in both directions (like a proa) but with the masts not exactly at the same distance of the bow... that way, you could always have the windward sail behind...

M = Mast

----M-------
--|-------|
-------M----

just a thought!

MAINSTAY

01-31-2008, 07:49 AM

Speng

01-31-2008, 04:49 PM

While I might not agree that an unstayed biplne rig is the "best" rig (mainly because it is difficult to say what "best" means for everyone) I will say that an unstayed carbon (or other composite tube) should be very reliable. The design is fairly trivial, the material is highly resistant to fatigue, the lack of fittings eliminates, almost completely, stress concentrations. Also the repairability of aluminum is not as simple as you think for a circumnavigator as you may find yourself hard pressed to find a rigger or Aluminum welder in many parts of the world not to mention the specialised fittings you might need because yacht chandleries aren't everywhere.

The Radical bay rig concept isn't the only one out there for a simple unstayed rig. I'm personally a big fan of windsurfer style rigs (they usually look weird because somebody's stuck a fiberglass winsurfer rig on a ordinary looking hull - e.g. a Wyliecat) but they work pretty well for many cruisers and racers and the design of the mast is further simplyfied because the boom is connected to the mast differently (or not at all). Also to be taken into account is the simplicity of the running rigging: two (lightly loaded) mainsheets, cunningham, outhaul and that's it.

I think a problem many have is the lack of foresails esp for light air and downwind work but there's no reason why they can't be added.

sharpii2

01-31-2008, 05:48 PM

I suggest the best rig for a small catamaran for curcumnavigation is one that is simple to build, easy to operate, and reparable at any landfall. One without exotic materials, without moving parts, yet still get the most from your sails.

Specifically I suggest a modified three-stay rig. With it you can use a fuller roach for more sail area or a shorter mast with the same area. The fuller roach also improves the efficiency of the sail area you have. There are 3 modifications as shown in the attached xls drawings:
1) Relocate the maststep forward 1/3 the distance toward the forestay and then 1/6 the beam either port or starboard, choose one, (the masthead is to remain in it original position and the mast raked and canted),
2) Relocate the shroud on that same side to be abeam the mast,
3) Relocate the other shroud to the original maststep.

The mainsail is flown from #3 (now a mainsailstay) and no sail is on the mast. The mast is mainly in compression without major bending or torsional stress. The step is closer to the end of the cross beam rather than at its midpoint.

There is more drive from the mainsail because there is no wind shadow at the luff. Other boats with aft masts and bipod rigs have reported that there is a 15% increase in speed when the mast is not shadowing the luff. That added speed can mean quicker passages and less exposure to stormy weather at sea.

I also suggest exterior blocks and halyards for ease of inspection, maintenance, and repair of the running rigging in any port.

Fair weather and happy sailing,
LarryModes@aol.com

I see three problems with this proposed sail plan.

1.) The mast will be too far forward. Multihulls have been known to dislike this mast placement. It tends to make them steer wildly and even pitch pole.

2.) The rig would put enormous compression forces on the cross beam not to mention enormous tension loads on the outer hulls and/or crossbeams, forcing the designer to design them much stronger and probably much heavier.

3.) the sail would be difficult to reef and, once reefed, the Center of Area (CA) of the sail plan will be too far forward, which would, not only make the boat hard to sail any direction but down wind, but would also help encourage it to pitch pole.

With a fractional sloop rig, the jib can come down by the first or second reef, removing the considerable compression forces needed to make it stand well in strong winds. This relieves an impressive amount of strain on the rig when it faces its greatest structural challenge. Not only that, but as the mostly triangular mainsail is reefed, its CA moves forward close to where the CA of the combined jib and main used to be, allowing the boat to keep its former balance.

Such a rig can be remarkably cheap and easy to set up if one is not too enamored on high windward performance. The one I had on my weekender had a considerable amount of slop, but had no trouble getting me to windward (though not fast enough to win any races).

And for that reason, it can be more easily maintained and repaired. Maybe that's why it is so ubiquitous.

Bob

OldYachtie

01-31-2008, 06:23 PM

To see a catamaran with a wingsail biplane rig designed for home building, see www.dunnanddunnrealtors.com/Catamaran.html . Why build a wing mast when you can build a fairing using foil-shaped battens? You don't get the "clingyness" of a cloth fairing if the batten fairings hold the cloth away from the mast. There are many wing sail and biplane rig links there, as well.

Also featured on the site is my idea for making radius chine designs easily built in fiberglass.

Richard Atkin

02-01-2008, 04:07 AM

rob denney

02-01-2008, 06:25 AM

I am considering putting a crab claw rig on my future catamaran. The bottom line is this...the sail is more powerful than any other type of sail, except when pointing high to windward. It has a low centre of effort, and puts very little loading on the rigging and hulls compared to a fractional rig.

However, it seems to be a very misterious thing, because nobody seems to know much about it. Maybe the sail area becomes too far forward for a cat, when sailing downwind??? Does this cause handling problems?

Anyone have any reasons why a cat claw should not be considered?

G'day,
The arabs (dhows with lateen rigs) and the Pacific Islanders (proas with crab claws) seem to know a fair bit about them.
The thought of those two booms/yards thrashing about in a gale is enough to put me off them for offshore work. Still, they are pretty cheap to try so give it a go and let us know how they work. Check into the proafile group at Yahoo and ask your question there. A lot of them have small and medium sized crab claw experience.

regards,

Rob

Richard Atkin

02-01-2008, 06:35 AM

excellent...I'll do that

cheers Rob

JCD

02-01-2008, 07:05 AM

G'day,
The thought of those two booms/yards thrashing about in a gale is enough to put me off them for offshore work.
regards,

Rob

Rob,

I have huge respect for your hands on and practical thinking, but why would any skipper allow anything at all to be thrashing about in a gale? Inshore, offshore or even on the hard?

I may have been there in a former life, sadly I don't remember, but I think the Poly's crossed oceans with crabs and even they may have had enough sense to reduce forces on the sails or at the very least rig up some preventers. Would you agree?

My memory fails me at the moment and I am really racking my brain to think of it, but does anyone remember the crossing of one of the Cape's with a claw? I might be wrong or could have read it wrong.

J:cool:

OldYachtie

02-01-2008, 04:09 PM

I have read claims that the crab claw sail actually develops lift and so depresses the lee hull less than any other rig. It was, of course, invented to use on catamarans, so it must surely be suitable. It doesn't look very versatile for reefing. One brails the yard and boom closer together instead of reefing, but I would think that you would have to quit sailing sooner as the wind picks up than you would with any other sail type.

Sizable crab claw rigged boats would traditionally have had large crews, so I am not sure that it will be easily handled on a boat of any size beyond a daysailor. I think you have to dip it to come about, which sounds rather scary. I wouldn't put it inside a bipod mast, because that would limit the sails ability to lift its boom. If you google "proa" you might find more info.

This rig is still in use in Tuvalu, Kiribati, the Marshall Islands, and in the Caroline Islands. I saw it in use in Tuvalu (the island of Nukufetau) and in Kiribati in the late 1970s.

I am considering putting a crab claw rig on my future catamaran. The bottom line is this...the sail is more powerful than any other type of sail, except when pointing high to windward. It has a low centre of effort, and puts very little loading on the rigging and hulls compared to a fractional rig.

However, it seems to be a very misterious thing, because nobody seems to know much about it. Maybe the sail area becomes too far forward for a cat, when sailing downwind??? Does this cause handling problems?

Anyone have any reasons why a cat claw should not be considered?

MAINSTAY

03-11-2008, 02:42 PM

Bob,
Sharpii2 wrote I see three problems with this proposed sail plan.

1.) The mast will be too far forward. Multihulls have been known to dislike this mast placement. It tends to make them steer wildly and even pitch pole.

2.) The rig would put enormous compression forces on the cross beam not to mention enormous tension loads on the outer hulls and/or crossbeams, forcing the designer to design them much stronger and probably much heavier.

3.) the sail would be difficult to reef and, once reefed, the Center of Area (CA) of the sail plan will be too far forward, which would, not only make the boat hard to sail any direction but down wind, but would also help encourage it to pitch pole.

Response 1) Only the maststep is moved forward. The sails remain unmoved. The main is NOT set on the mast but on a vertical stay at the mainluff. The CE does not move forward and cause the problems you list. And since ther is no backstay, the mast could (with corresponding movement of CLR) be moved aft until the vertical mainluff stay rises from the transom, and there is a mezzin-like mainsail.

Response 2) The rig does puts lower compressive forces on the cross arms, and may put minimal compressive forces on it since the step may be at or neat the side of the hull. See the attached file. The lateral base of the rig is simmilar to that of a monohull, so the design would have to be of similar strength and weight.

Response 3) Reefing the main is the same as for the jib. No more difficult, and perhaps safer because the crew is not on the foredeck. The main can be roller furlled like a jib because the main is on a stay, like the jib. The movement of CA during reefing is no different than on the sloop rig.

What else?

Larry Modes

sharpii2

03-11-2008, 03:48 PM

Bob,
Sharpii2 wrote

Response 1) Only the maststep is moved forward. The sails remain unmoved. The main is NOT set on the mast but on a vertical stay at the mainluff. The CE does not move forward and cause the problems you list. And since ther is no backstay, the mast could (with corresponding movement of CLR) be moved aft until the vertical mainluff stay rises from the transom, and there is a mezzin-like mainsail.

Response 2) The rig does puts lower compressive forces on the cross arms, and may put minimal compressive forces on it since the step may be at or neat the side of the hull. See the attached file. The lateral base of the rig is simmilar to that of a monohull, so the design would have to be of similar strength and weight.

Response 3) Reefing the main is the same as for the jib. No more difficult, and perhaps safer because the crew is not on the foredeck. The main can be roller furlled like a jib because the main is on a stay, like the jib. The movement of CA during reefing is no different than on the sloop rig.

What else?

Larry Modes
Hi, Larry.

I still maintain my main points. And here's why.

If the mast is on one end of the crossbeam, the 'luff stayed' main is going to act much like a conventional jib. It is going to need enormous tension to hold the luff reasonably straight. This, in addition to the enormous mechanical disadvantage the mast is going to have, being that it is tilted toward the luff stay, is going to put much more tension on the stay on the other side of the mast than even the luff stay is experiencing.

This, in turn is going to increase the compression on the mast step by a larger degree than even a mast aft rig.

I do see, however, how the bending moment on the cross beam will be less than I thought. I was and still am unable to see your actual drawing. But the tensions on the rigging in general, and the opposite stay in particular, may make the idea unworkable. Bending moment on the mast in compression has to be watched as well, as the mast is tilted and under a great deal of compression. Moving the mast closer to the luff stay and further away from the opposite stay may help a great deal, yet still maintain spirit of the design.

Since the Main sail is presumably triangular, the center of area moves forward no matter how you reef it. This can be corrected by either having tandem boards, where the aft most one can be retracted as the sail is shortened, or by having a modest mizzen sail which stays set as the main is reefed. Either way, proper balance could be maintained. And on an ocean sailing boat, balance equals good course keeping qualities.

Pericles

03-11-2008, 04:54 PM

http://www.omerwingsail.com/

Ask for details from Ilan Gonen.

Pericles

masalai

03-11-2008, 07:29 PM

Hey Pericles, This thread was started over 2 years ago - I hope he is cruising by this??? still can't beat John Hitch for simplicity and ease of everything for multihulls - see "X-IT"

MAINSTAY

03-14-2008, 04:52 PM

still maintain my main points. And here's why.

If the mast is on one end of the crossbeam, the 'luff stayed' main is going to act much like a conventional jib. It is going to need enormous tension to hold the luff reasonably straight. This, in addition to the enormous mechanical disadvantage the mast is going to have, being that it is tilted toward the luff stay, is going to put much more tension on the stay on the other side of the mast than even the luff stay is experiencing.

Since the mainluff stay is shorter than the forestay, the "enormous" tension can be less than the normal tension on the forestay to result in the same sag. And the mainluff stay tension may be less than the tension of a normal backstay, which is absent in this rig.

In addition, yes, the rake of the mast will put more tension on the forestay, and this is desirable. The forestay is longer and requires more tension to limit sag to the same number of inchers (or centimeters) as the mainluff. But these tensile values are within normal ranges used by riggers. They are not "enormous" nor do they make this rig "unworkable" (quoted from below).

This, in turn is going to increase the compression on the mast step by a larger degree than even a mast aft rig.

You're going to have to show me the numbers. My numbers show less compression of the mast with the mainluff stay rig than with an aftmast rig or a sloop rig.

Homework assignment:
Get a sailplan of any Aftmast rig. Get two pens with different colored ink. Pencils, crayons or markers also work.
A1) Draw a vector from the masthead along the foremost stay about an eighth of the stay length. If much longer than that, you may need to attach another sheet to complete the vector diagrams.
A2) Draw a vector parallel to the masthead backstay from the lower end of the first vector to the mast centerline. This is the backstay tension.
A3) From the lower end of the backstay tension vector draw a vector the same length as the first, but parallel to the inner stay. This is valid for
masthead and fractional stays, as in the DynaRig (TM).
A4) Draw a vector parallel to the backstay (or inner backstay as in DynaRig(TM)) from the current vectors' end to the mast centerline. This is the tension in the inner backstay or the additional tension in the backstay. All other complexities in the rigging increase mast compression, but are to be ignored in this assignment.
A5) Draw 2 vectors down along the mast. The number is the same as the number of halyards, and represent the tension in the halyards. For this assignment, the length is exactly half the length of the first vector. There is no vector for the tension of the sail luff, because the stay tension is relaxed by the tenstion in the halyard. When the halyard tension exceeds the stay tension there is no tension in the stay. While this conditions seldom exists in a rig, but it illustrates the principle.

Use the second color to:
M1) Draw a vertical line (for the mainluff stay) from masthead to deck.
M2) Draw a mast centerline from the existing masthead to a point 2/3 of the distance from forestay to mainluff stay.
M3) Draw a vector parallel to the mainluff stay (vertical) from the lower end of the first vector (drawn in A1 above) to the mast centerline. This is the mainluff stay tension.
M4) Draw 2 vectors down along the mast. These are the tension in a) the jib halyard, and b) the main halyard. For this assignment the length is exactly half the length of the A1 vector.

A vector from the masthead to the end of the vector set represents the magnitude of the compression in the mast. This is a two dimensional analysis which is valid for monohulls where the maststep remains on the hull centerline. It is indicative, as far as it goes, of the relative magnitudes of the compression resulting from a 3D analysis. The vector diagrams should show that compression in the half-A-frame mast is NOT increased "by a large degree", but is less than the aftmast.

But the tensions on the rigging in general, and the opposite stay in particular, may make the idea unworkable. Bending moment on the mast in compression has to be watched as well, as the mast is tilted and under a great deal of compression. Moving the mast closer to the luff stay and further away from the opposite stay may help a great deal, yet still maintain spirit of the design.

Again, show me the numbers that the tensions make this unworkable. What in this rig causes bending moment in the mast? There is no sailtrack on the mast. There is no sail to induce bending or torsion in the mast. If you mean one of the modes of compressive failure, then yes, it would be calculated as part of the design. But there is not a great deal of compression as you wrote, and as I've shown if you did the homework. The compression is not abnormally high.

If the mast is closer to the luff the advantage of clear air is lost. If the mast is separated from the luff by 10% of the chord of the sail, 20% of the lift is lost; at 0%, 30% is lost. That is exactly why we are considering aftmast rigs.

Since the Main sail is presumably triangular, the center of area moves forward no matter how you reef it. This can be corrected by either having tandem boards, where the aft most one can be retracted as the sail is shortened, or by having a modest mizzen sail which stays set as the main is reefed. Either way, proper balance could be maintained. And on an ocean sailing boat, balance equals good course keeping qualities.

Your presumption is wrong. Since there is no backstay, there is no reason to keep the induced drag losses at a maximum with a triangular mainsail, and every reason to use a more efficient planform.

You are correct that the CE moves forward with roller reefing, and what you suggest is a proven way to adjust for it. But every rig with roller reefing has this problem. There are other ways also.

Larry Modes

sharpii2

03-17-2008, 09:46 PM

Hi, Larry.

I guess the word 'unworkable' may have been a bit extreme.

But what I do know is that mast aft rigs have had considerable problems with fore stay sag.

Phil Bolger and Gary Hoyt both had one built recently.

The Hoyt one had so much sag that it performed much lower than expected and was, IFIRC, inferior to a conventional fractional sloop.

The Bolger one did much better.

He knew exactly what he was up against and designed accordingly. His boat was a vertical sided sharpie with massive chines and sheer clamps, making the hull a very rigid box beam.
the fore stay sag was correspondingly smaller and the boat was definitely superior to a fractional sloop up wind and, to a lesser extent, reaching.

This extra performance came at a price. The price was constant vigilance on the set of the sail. A degree or two off, one side or the other, knocked the performance level back down to the more normal category.

The rig you are proposing, as far as I can surmise, is going to be more complex.

The buckling loads I mentioned in my previous post are more from luff tension than from halyard tension. There is actually going to be a downward component somewhere between the halyard and the luff, but since I can only guess what this rig is going to look like, I am not clever enough to say where.

This, in itself, causes the mast to act more as a bow than a straight compression strut.

With the mast aft rig, this is dealt with with large, aft extending spreader, which extends at least to the transom or even beyond. Your rig could have a similar spreader opposite the luff, off to the side. This could keep the mast from bowing away from the luff. Having the mast curve slightly away from the luff can keep it from bowing the other way, just in case.

This extra structure, complete with trussing wires, will be beside the sail rather than behind it, as in the aft mast rig. This could make a difference in performance, as the drag might be higher.

As far as your sail shape goes, I don't have a clue. If you are going to roller reef the sail around the fore stay, I don't see how you can escape a triangular plan form. Perhaps you intend to use vertical battens which run parallel to the luff. That's about the only way I can see getting any kind of a roach or shoulder into a sail that has to wrap around a luff wire.

Or do you plan to slab reef?

All in all, I don't see how this proposed rig would be any better, after all the engineering necessities are added, than a conventional fractional sloop. And I see it being much more complicated and expensive and harder to repair.

A conventional fractional sloop can work with quite a bit of slop in the rigging because the jib is usually the last sail up and the first to come down. And, besides, it is usually the much smaller sail.

I know this because I owned a fractional sloop that had such slop, due partly to inadequate turnbuckle tightness (due to the laziness of the skipper) and partly to the give of the light fiberglass hull. And it never failed to go to windward, even when pressed, with the saggy jib up. It just went to windward better with out it.

Simple fractional sloop rigs can arguably work better on multihulls than on monos, because the wideness of the multi's beam. This allows the the shroud/stays to be further apart, greatly reducing the compression loads on the mast, especially when the jib is furled, than on a usually much narrower mono. This often allows spreaders to be dispensed with entirely. The mast can then be made lighter or taller as well.

With a boat that is supposed to circa navigate the globe and sail in very remote waters, I would vote first for simplicity and reliability, even at the cost of some considerable efficiency.

I have a feeling that, even if your proposed rig was able to produce the hoped for efficiency, it would not be able to do so untended, as it would be most of the time on a long voyage.

I would encourage you to build your proposed rig and try it yourself in real life conditions.

I could be wrong.

Other innovative designs have been poo pooed in the past and have ended up working. Perhaps yours is one of them.

Best wishes.

Bob

sharpii2

03-17-2008, 09:50 PM

oops.

Paul B

03-17-2008, 10:08 PM

Phil Bolger and Gary Hoyt both had one built recently.

The Hoyt one had so much sag that it performed much lower than expected and was, IFIRC, inferior to a conventional fractional sloop.

The Bolger one did much better.

He knew exactly what he was up against and designed accordingly. His boat was a vertical sided sharpie with massive chines and sheer clamps, making the hull a very rigid box beam.
the fore stay sag was correspondingly smaller and the boat was definitely superior to a fractional sloop up wind and, to a lesser extent, reaching.

Can you explain how this was tested against a well-designed modern fractional sloop rig?

sharpii2

03-18-2008, 11:00 PM

Can you explain how this was tested against a well-designed modern fractional sloop rig?

Hi, Paul.

Actually, I don't remember.

I think the Hoyt boat was actually raced against a fractional sloop of roughly the same proportions.

I think Bolger just went by feel, using himself and other sailors as judges. But even then, there are some absolutes. Like how close it can sail to the wind and how fast it can reach with a given wind strength, compared to a fractional sloop of roughly the same size and D/L ratio.

The important thing was that neither boat was much copied.

Another important thing to note is that Bolger was not so much looking improvements in speed performance as he was better sea keeping qualities.

With the mast aft, the boat rides much better at anchor and rises to the sea better.

These two qualities alone, even if the performance slacked a little, were in his eyes, worth it.

The balance while reefed problem was quite real, though. But it could be solved by using twin jibs and reefing them differentially.

All in all, It was looked at, at least by Bolger, as a very expensive way to build a sail boat for a given amount of sail. And Bolger thinks that a sailboat should be built as inexpensively as possible.

Bob

RHough

03-19-2008, 03:10 PM

Since the mainluff stay is shorter than the forestay, the "enormous" tension can be less than the normal tension on the forestay to result in the same sag. And the mainluff stay tension may be less than the tension of a normal backstay, which is absent in this rig.
Poppycock, to get X amount of forestay tension the tension in the aft-most wire(s) can be lower than the forestay or higher depending on the ratio of fore and aft distance between the two. When you replace a conventional backstay with wire(s) that have lower angles to the masthead the total tension (stays + mainsheet) will be the same for any forestay tension. The effect of increasing mainheet tension to create forestay tension will cause sag in the mainluff. If you want to maintain both mainluff tension and forestay tension you cannot sheet the main hard enough to control the roach of the main (much less use mainsheet tension to increase forestay tension).

In addition, yes, the rake of the mast will put more tension on the forestay, and this is desirable. The forestay is longer and requires more tension to limit sag to the same number of inchers (or centimeters) as the mainluff. But these tensile values are within normal ranges used by riggers. They are not "enormous" nor do they make this rig "unworkable" (quoted from below).
The rake of the mast creates forestay tension? How? Forestay tension is balanced by other stays and mainsheet tension (assuming the forestay, backstay, and shrouds are at the masthead). Where the mast butt is (rake) has no effect on forestay tension unless there is an off column load in the mast.

You're going to have to show me the numbers. My numbers show less compression of the mast with the mainluff stay rig than with an aftmast rig or a sloop rig.
You aren't a rigger are you? :) I really mean no offense, but I am a rigger. Anyone that has actually built a rig can see how wrong the angles are and knows how much heavier the section and rigging will have to be to get this rig to work.

Again, show me the numbers that the tensions make this unworkable. What in this rig causes bending moment in the mast? There is no sailtrack on the mast. There is no sail to induce bending or torsion in the mast. If you mean one of the modes of compressive failure, then yes, it would be calculated as part of the design. But there is not a great deal of compression as you wrote, and as I've shown if you did the homework. The compression is not abnormally high.
You were the one that said the rake increases forestay tension, thus there MUST be a bending moment in the mast. You want numbers? Scale your rig to fit something like a Hobie 18. Calculate what wire size and tensions you will need to support a 200 ft^2 sailplan. How long can the mainluff wire be? What will the static tune tensions be? What will the sailing tensions (at maximun RM) be? If you use the Hobie as an example, you have an 8 ft beam, so the total shroud base for your rig can be 4 ft (if the mainluff is on centre). To get 200 ft^2 (150 ft^2 main + 50 ft^2 jib) you will need a 20-25 ft mainluff ... what is the mast to shroud angle 25 ft off the deck on a 4ft shroud base? How will sailing loads change it? What moment of inertia will the mast section need to stay in column? Now do the math on the standard rig ... compare the compression in the mast.

Your presumption is wrong. Since there is no backstay, there is no reason to keep the induced drag losses at a maximum with a triangular mainsail, and every reason to use a more efficient planform.
Again, what effect will the sheet loading of a large roach sail or square top sail have on mainluff sag?

I think you need to plug some real world numbers into your rig. If it comes out lighter and more efficient than a conventional rig or unstayed rig I'd be very surprised.

MAINSTAY

03-19-2008, 03:29 PM

Sharpii2 wrote:

But what I do know is that mast aft rigs have had considerable problems with fore stay sag.

I agree. The half-A-frame rig I propose avoids sag problems by keeping the mast between the main and foresails, rather than aft of both.

The buckling loads I mentioned in my previous post are more from luff tension than from halyard tension. There is actually going to be a downward component somewhere between the halyard and the luff, but since I can only guess what this rig is going to look like, I am not clever enough to say where.

This, in itself, causes the mast to act more as a bow than a straight compression strut.

I agree. The bowing of a mast is due to the component of the halyard tension perpendicular to the mast centerline, the force opposing it, and the leverarm between them. I believe a solution to be within the current materials and mathematics.

I recognize your point. A mast must be designed to resist the bowing caused by halyards and other forces. In the fractional rig example you give, the bowing force would have a leverarm of some feet, and in a masthead rig of inches. So, even though the halyard tension may be larger in the masthead rig, it will not be 12x as large, and the bowing would be less than in the fractional rig where it seems to be no problem.

With the mast aft rig, this is dealt with with large, aft extending spreader, which extends at least to the transom or even beyond. Your rig could have a similar spreader opposite the luff, off to the side. This could keep the mast from bowing away from the luff. Having the mast curve slightly away from the luff can keep it from bowing the other way, just in case.

This extra structure, complete with trussing wires, will be beside the sail rather than behind it, as in the aft mast rig. This could make a difference in performance, as the drag might be higher.

I agree that aft extending spreaders are needed on some aftmasts, and also that shroud spreaders are needed on many boats. I recognize that there are needed to reduce the shroud or stay tension, and therefor the mast compression when there is a narrow base. These spreaders induce bending forces in the mast, which the mast or additional shrouds (etc.) must be designed to resist. I recognize that jumper struts are needed on some fractional rigs where they are used to reduce bowing of the mast when the mast itself can not handle it.

While the aftmast may have a base of 10% to 15% of the LOA, the half-A-frame mast may have 35% to 45%. So spreaders, with their drag and weight aloft, are not needed

As far as your sail shape goes, I don't have a clue. If you are going to roller reef the sail around the fore stay, I don't see how you can escape a triangular plan form. Perhaps you intend to use vertical battens which run parallel to the luff. That's about the only way I can see getting any kind of a roach or shoulder into a sail that has to wrap around a luff wire.

Or do you plan to slab reef?

Reefing with the half-A-frame rig can depend on the use.

A coastal crusing single or couple can use roller reefing, with electrical help if senior or they wish. Roller reefing the main is without large mast or boom extrusions (or the need to quiet them), and as simple as jib reefing.

A racer, regardless of crew size, or blue water or not, could use slab reefing, to minimize the forward shift of COE, to reduce the overturning leverarm, and to keep more SA with efficient shape driving toward the finish.

A circumnavigator (and the others) have the option of setting smaller sails on stays placed in the plane-of-sails between the mainluff stay and the forestay. These stays would allow balancing the boat like a yawl or ketch. 123 up in light weather, 1-3 as it builds, and -2- when it rages, and a stormtrysail in survival mode.

The half-A-frame rig gives a designer and a sailor reefing options, not limitations.

All in all, I don't see how this proposed rig would be any better, after all the engineering necessities are added, than a conventional fractional sloop. And I see it being much more complicated and expensive and harder to repair.

I hope I have shown that the problems you raised, which are real problems, have solution are easily within the current materials and mathematics, and that there are rigs where these problems are of greater magniture and have been successfully solved.

I hope I've shown how the half-A-frame rig is not more complicated, and hopefully less expensive and easier to repair.

Larry Modes

RHough

03-19-2008, 08:38 PM

Some simple numbers for the Half A rig:

Assume transverse load at the masthead is X.

Assume that a shroud to mast angle of 15deg on a 4ft lever balances that load. The compression load on the mast will be about 15X.

Now move the mast so the shroud has a 2ft lever. To balance the same load X, the mast compression is now 30X.

Just to keep the same mast up when you cut the shroud base in half, you double the compression load.

Now look at the reduction in fore/aft stay base for the forestay and backstay. It looks like another doubling of the compression load.

Now you have at least 4x the compression load on the mast that you had before you started. And you haven't provided for more than normal sailing loads. Now try to keep the mainluff wire under tension when it is on the leeward side ...

No matter how hard you try, the mainluff will sag on one tack and be straighter on the other tack. That will require a complete re-trim of the main after each tack ... is that what you want on a low effort cruiser?

MAINSTAY

04-06-2008, 07:17 PM

RHough, thank you for your comments.
I agree that the relationship of the forestay tension and mainluff stay depend on the angles. But, my statement was not that there would be equal tension in the stays, but that it would not take an enormous amount of tension to prevent sag; and that since the mainluffstay is shorter, it would take less tension to in the mainluffstay to get the same sag as in the forestay.
I agree that using the main sheet is an unacceptable way to get forestay tension. Why are you making that comment about this rig? I’ve never said anything about the mainsheet.

A raked mast creates forestay tension because centroid of the mast is aft the step which causes a moment force. That force is counteracted either by tension in the forestay in a mast stepped on desk, or by added forces in the partners if stepped on the keel. With near vertical masts the additional tension is negligible or zero. But with a rake of about 20 degrees the additional is about 5% of the weight of the mast. It’s not much, but now you know it’s there. There is no bending of the mast to get the 5%, just gravity.

Did you do the vector diagrams I suggested on 3/14? You’re a rigger. It’ll take you minutes. Until you do, you will be guessing that the tensions will be “enormous”, the compression “abnormally high”, and “much heavier” sections will be needed. Your 2x and 2x are good rules of thumb, but don’t apply here. Look, it took me a year plus half a dozen methodologies to get past that rule of thumb and finally believe my own math. If nothing else, do the diagrams just to show me where I went wrong. Or to see where the benefits come from. It’s all there in the arrows.

I’ve started modifying my Hobie 16 (not quite 18) with a raked mast. It will NOT be a half-A-frame, since the mast will be on centerline. There are some practical limitations on where steps, chainplates, etc can be placed without major changes to the hull. But it will be a good test platform, and may show that some hull changes may be justified. The current design is to keep the same step, but rake the masthead 23”aft and use a bridle between the existing shroud chainplates to support the lower end of the mainluff stay, similar to the forestay bridle, with a tie to the fore crossarm. It’s looking like I may have to move the shrouds to the ends of the crossarm to keep the bridle forces within the hull’s strength at that point.

I’m looking at two options for the jib: 1) to keep the stay attachment to the mast where it is, with or without a masthead stay to counteract the mainluff stay forces (oops, that’s 2 options already) and 3) to fly it on a masthead stay but keep the clew the same, which coincidentally keeps the sail in almost the same position as before the changes. In addition, the 23” gap is really minimal. The theoretical benefits will lost in the top fifth of the sail, and may be negative in the next lower fifth. But, 100% drive over a fifth, plus 85% over a fifth and 115% over three-fifths which averages 107% drive, which is better than 100%.

On the Hobie modifications, I will not have the one problem you mention about the half-A-frame rig. One for which I have no solution, yet. Yes, the sag is different on different tacks. So, should I put a backstay tensioner on the shroud? That addresses it directly, but a what cost? Would replacing the plastic parts of the rig (the hull) make it negligible? Maybe not. I don’t have an answer. Yet!
Larry Modes

RHough

04-06-2008, 08:12 PM

RHough, thank you for your comments.
I agree that the relationship of the forestay tension and mainluff stay depend on the angles. But, my statement was not that there would be equal tension in the stays, but that it would not take an enormous amount of tension to prevent sag; and that since the mainluffstay is shorter, it would take less tension to in the mainluffstay to get the same sag as in the forestay.
I agree that using the main sheet is an unacceptable way to get forestay tension. Why are you making that comment about this rig? I’ve never said anything about the mainsheet.
Okay, I was feeling bad about hammering your mainstay rig so hard, so I'll try to be a clear as possible.

Let's assume that you know how much tension you need in the forestay to create the desired sag. You are correct in that a shorter wire needs less tension to produce the same sag. Your conclusion that the shorter mainstay tension will be lower in the rig as you have drawn it is in error.

A raked mast creates forestay tension because centroid of the mast is aft the step which causes a moment force. That force is counteracted either by tension in the forestay in a mast stepped on desk, or by added forces in the partners if stepped on the keel. With near vertical masts the additional tension is negligible or zero. But with a rake of about 20 degrees the additional is about 5% of the weight of the mast. It’s not much, but now you know it’s there. There is no bending of the mast to get the 5%, just gravity.
When the mast is not vertical, you are right. I won't bother with the math, I'll take your 5% of mast weight as an addition to forestay tension. A Hobie 16 mast weighs what? 30 lbs? (I know I can pick one up and carry it around on my shoulder) ... 5% of 30lbs = 1.5lbs of extra forestay tension. For a forestay, 1.5lbs might as well be zero. If the mast weighs 100lbs, you still only get 5lbs, still zero as far as real world rig loads.

Did you do the vector diagrams I suggested on 3/14? You’re a rigger. It’ll take you minutes. Until you do, you will be guessing that the tensions will be “enormous”, the compression “abnormally high”, and “much heavier” sections will be needed. Your 2x and 2x are good rules of thumb, but don’t apply here. Look, it took me a year plus half a dozen methodologies to get past that rule of thumb and finally believe my own math. If nothing else, do the diagrams just to show me where I went wrong. Or to see where the benefits come from. It’s all there in the arrows.
I'll re-read what you posted. From memory, you had vector directions, but not magnitudes. I'll check again.

I’m looking at two options for the jib: 1) to keep the stay attachment to the mast where it is, with or without a masthead stay to counteract the mainluff stay forces (oops, that’s 2 options already) and 3) to fly it on a masthead stay but keep the clew the same, which coincidentally keeps the sail in almost the same position as before the changes. In addition, the 23” gap is really minimal. The theoretical benefits will lost in the top fifth of the sail, and may be negative in the next lower fifth. But, 100% drive over a fifth, plus 85% over a fifth and 115% over three-fifths which averages 107% drive, which is better than 100%.

On the Hobie modifications, I will not have the one problem you mention about the half-A-frame rig. One for which I have no solution, yet. Yes, the sag is different on different tacks. So, should I put a backstay tensioner on the shroud? That addresses it directly, but a what cost? Would replacing the plastic parts of the rig (the hull) make it negligible? Maybe not. I don’t have an answer. Yet!
Larry Modes
I have respect for anyone that thinks outside the box. It seems to me that you are chasing a holy grail of reduced drag and higher efficiency of a wire supported sail compared to one behind a mast.

There has been some discussion of late in the sail aerodynamics thread. If have not slugged through that thread, it is a good read. In a nutshell, the free standing mast may very well have higher drag w/o a sail attached. The drag from the mast exists on either rig, the total drag of the mainstay rig may be higher than a conventional rig and still have the practical issues I've laid out.

Before you go too far, consider the dynamic response of the rig. Also factor in the mainsheet tension and it's effect on forestay tension. To have equal sag in the forestay with the mainstay rig, you have to consider both the load on the windward shroud and the mainsheet tension to estimate tension required.

If it is alright with you. I'll draw out and post the vectors you described, the vectors in a standard rig, and the estimated vectors in the mainstay rig.

I think they will show that the mainstay rig will create more challenges, rather than solve problems. I'm always happy to be proven wrong. :)

MAINSTAY

04-09-2008, 09:09 PM

RHough,
Yes the drag on a bare mast is greater than on a mast with a sail (ignoring the drag on the sail, so DO NOT hoist your mainsail in survival conditions to reduce the drag on the mast.):) Tom Speer has said that the drag of the bare mast is 25% higher. That's a big number. But how much does that increase the boat's total D? Perhaps <1%?

I can think of no worse location for a mast than at the luff of a sail, where it nullifies the most powerful area of the sail. Doesn't one of Marchant's graphs show the difference in lifts between a sail with a mast, without a mast, and with a gap between the mast & luff? There was a 20% higher drive on the sail without a mast (at the point most favorable to my point, of course). If the 15% improvement in speed that has been reported by Procyon, by the aft-mast rigs, and others are true, then 1.15L/1.01D is a mighty attractive goal. Even with an A-frame this would be 1.15L/1.02D, and just as attractive.

That goal may turn out to be an unattainable grail. Perhaps your vectors will show that. If so, are those giants or windmills I see out on the plains??
Post away, sir.

Larry Modes

sharpii2

04-25-2008, 03:37 PM

Hi, Larry.

I have attached two drawings of your rig.

Please look at them and tell me if I got it right.

They are drawn in scale so the proportions are more obvious.

I went with a 20 ft luff length because I thought that was the least I could get away with. The boom would be about 16 ft and the sail would have quite a shoulder on it. It would have full length battens all the way up that run parallel to the foot, for easy reefing. It's area would be either side of 200 sf.

A fore shroud is shown because, with two stays lined up with the mast (the luff line and its opposite) and only one left as an aft shroud, the mast would topple backward. Other than that, I drew the rig I think you described.

Bob

PS- What if you moved the mast to the center Beam and moved the luff stay 1/6 of the Beam over from that? Then you would get better staying angles and probably better luff tension.

brian eiland

05-12-2008, 06:51 PM

In this subject thread I've expressed some concerns about the reaching and running capabilities of a bi-masted rig. But I don't think the subject of tacking problems has come up as anything negative.

I just happened across this discussion about tacking a bi-masted vessel on another forum. I've not had time to digest it, but there are some follow on discussions.

"Have now returned from my weekend of racing the Radical Bay 8000
- 70 miles feeder race on Friday (no wind to Bft2 beam reach)
- 25 miles double S-shaped bay race with lots of tacking, wind 15 - 40 kts on Saturday.

What I can now tell you about tacking this boat is:

1) In wind under 20kts-ish just before commencing the tack release the windward sheet totally and tack on the leeward sail. Wait for the (new) windward sail to fill and push the bows around, then slowly sheet in the leeward sail and off you go. Only in really flat conditions would we play around with the daggerboards to assist the tacking effort.
Results 10/10

2) In wind in the 20-25-ish kts we have a problem! Depending on wave action we cannot tack and have to gybe.
Results 4/10

3) In winds of approx. 30kts and more we cannot tack nor gybe!!
When tacking the boat would stall 10 degrees from the turn, even sailing backwards did not work to push the bows through the wind.
Attempting a gybe, the pressure on the rudders was incredible, could run down-wind but not turn further to the leeward side. Ended up anchoring in 40kts of wind on a lee shore! (Can really recommend the Fortress anchor!). And managed to break the mast / gooseneck boom connection due to a gybe which went wrong.

This weekend's experience has put a big damper on my otherwise positive aspects of this rig design!
Regards Roger"

CruisersForum.com
http://www.cruisersforum.com/forums/showpost.php?p=135630&postcount=41
http://www.cruisersforum.com/forums/f48/new-bi-rig-performance-cruiser-12688-3.html

masalai

05-12-2008, 06:59 PM

Don't go via the southern tips of SA, SA, Au or NZ etc., use the canals (Suez & Panama)...

Richard Woods

05-13-2008, 02:52 PM

rob denney

05-13-2008, 09:55 PM

I am not surprised by the handling problems of the Radical Bay. I believe Team Phillips, for example, suffered in the same way.

Another problem I have observed is that when close reaching the lee sail can become ineffective and actually drift up to windward. I've even seen it touch the windward sail. After all you don't ever deliberately sail close to lee of another boat, so it seems strange to me that one would design a rig like that.

Another major problem is one of handling. One of the great things about catamarans is that the boom is basically always inboard so is easy and safe to reach. On a monohull, and especially on a boat like the Radical Bay, which has narrow hulls, the lee rig will always be hanging out over the water.

Before developing any new rig you have to ask "why has no one else done it?"

Why are there so few mast aft rigs around, even though they have been promoted for at least 50 years?

Would the Chinese have stuck with the junk rig if they had access to a sail cloth that wasn't made from woven bamboo??

I have a couple of articles on multihull rigs on my website

www.sailingcatamarans.com

Enjoy your sailing,

best wishes

Richard Woods of Woods Designs

G'day,

Team Phillips did have trouble tacking. So did first and second generation cats. Took 30+ years to sort it out, but now they seem to have it sussed. The Radical Bay has gone from not tacking at all to managing it in 15 knots. With a bit more practise, and maybe with a hull and rig design more optimised for it, I am sure they will be tacking on a sixpence.

The lee sail does get blanketed. Apparently a 20 degree change of course corrects this. Compare that to a sloop, where the headsail is blanketed and the mainsail chafes on the rigging through an angle of about 120 degrees then decide which is worse. I have to call BS on the lee sail touching the windward one. Not because it is aerodynamically impossible, but because no one would make the booms so long that they would not pass between the masts and this would be necessary for the sails to touch on a reach.

There should be no reason to reach the end of the boom, but if there is, drop the sail (dead easy to do and you cankeep sailing with the other one) pull it in and fix it. This is a lot easier than trying to reach the end of a boom 8' above the cockpit floor which is typical of most bridge deck cat rigs.

Why has no one done it, before? Some of the reasons are: lack of suitable materials, high priced materials, designers scared to experiment, cruising boat designs based on race boats whose rules are made to favour the status quo, and of course, because it looks different and boat owners are incredibly conservative. Carbon and low cost build techniques are now available to make unstayed masts cheaper than stayed alloy masts, and boats designed for unstayed rigs cheaper than those designed for stayed ones. They can also be home built, whoch makes them even cheaper.

The advantages are many:
1) The ability to easily hoist, lower and reef the sails on all points of sail, in any wind strength. Much easier than reefing a sloop dead down wind in 30 knots.
2) Almost nothing to break, compared to over 50 individual items on a stayed rig, any one of which breaks and the whole lot falls down
3) Almost nothing to maintain or replace.
4) Automatic reefing because the masts flex.
5) Cheap as the entire boat does not need beefing up to accept the huge stay and compression loads.

Biplane rigs don't make as much sense (to me) as a single rig in one hull (or even in the centre) of a cat, but they make a huge amount more sense than a stayed rig.

regards,

Rob

BigCat

06-29-2008, 04:57 PM

Hi, Rob

I second your remarks about biplane rigs. They make sense if you have a big boat and a little crew, however, as does any rig that splits up the sails into more easily handled units. My BigCat 64 should be easy for an arthritic couple advancing in years to sail.

Despite all of the nonsense through the years about the slot effect, fewer sails is for the best from an efficiency standpoint. The slot effect merely reduces the inefficiency of having two sails working together, it doesn't make them more efficient than one sail with the same CE as the two working together.

Suggesting that the biplane rig has steering problems from one or perhaps two examples is anecdotal evidence, and neglects anecdotal evidence to the contrary, from many more examples of twin rigged cats that don't have steering problems - Cool Change, Magic Carpet, Pho, Dragon Wings, Cat2fold, and a number of 'go fast' racing machines. See various links to biplane rigged cats at the bottom of my web page at: http://www.dunnanddunnrealtors.com/Catamaran.html for more supporting evidence.

Pointing out that something hasn't caught on in sailboats doesn't prove that it doesn't work, it proves that people are afraid to experiment with something expensive, and that they don't understand that a racing boat can come in last and win a race due to the prevalence of handicap rules.

rayaldridge

06-29-2008, 05:17 PM

Hi, Rob

Pointing out that something hasn't caught on in sailboats doesn't prove that it doesn't work, it proves that people are afraid to experiment with something expensive, and that they don't understand that a racing boat can come in last and win a race due to the prevalence of handicap rules.

Yes, but when a boat comes in last and wins on handicap, the designer has not designed a fast boat. He's designed a rule-beater, which is something else entirely.

Ray

http://slidercat.com/

Richard Woods

06-29-2008, 07:01 PM

Not necessarily. the guy with the slowest boat may be the best sailor in the fleet!

Richard Woods

www.sailingcatamarans.com

rayaldridge

06-30-2008, 12:05 PM

[QUOTE=Richard Woods;212215]Not necessarily. the guy with the slowest boat may be the best sailor in the fleet!
/QUOTE]

True, but I don't think designers can count on this when drawing up a racing boat.

All kidding aside, how often does the best sailor in the fleet have the slowest boat?

Ray

http://slidercat.com/

brian eiland

06-30-2008, 12:47 PM

...Despite all of the nonsense through the years about the slot effect, fewer sails is for the best from an efficiency standpoint. The slot effect merely reduces the inefficiency of having two sails working together, it doesn't make them more efficient than one sail with the same CE as the two working together.
Bad mouth my mast aft idea all you want...no problem. BUT please don't persist to cling to this idea that the slot effect doesn't exist.

Grab yourself a copy of "Aero-Hydrodynamics of Sailing" by Marchaj, and go to pages 627-653. This guy did EXTENSIVE study on the subject.

Granted some of the extra lift derived from a multi-foil system will be offset by the extra drag that is experienced, but there can also be other side benefits, for instance:
"As a rule, the genoa, as well as other types of headsail, is a splendid driving sail with its center of effort (CE) relatively low. As shown in (wind tunnel photo), at heading angles near 30 degrees, i.e. in the close-hauled condition, for each square foot of sail area the genoa alone produces 30 percent more drive than the mainsail alone. Moreover, the genoa contributes 45 percent less to the heeling moment than the mainsail."

And here I will show where the genoa contributes far less bow burying force to the vessel.

rob denney

07-01-2008, 12:21 AM

G'day,

Brian, I don't have Marchaj's book, but would have the following real life vs wind tunnel questions:

1) What size and shape mast did he use?
2) Did he use cloth sails with all their stretch and tension variables, or rigid foils?
3) Did he realistically represent the forestay, shrouds, stays, spreaders, sundry halyards and other items which are in the wind flow on real boats.
4) Did he allow for the constant trimming required to get a sloop to sail to it's potential in normal, fluctuating breezes?
5) Did he include the extra weight in the boat required to apply the large loads required (straight forestay, stiff hulls, stiff bridgedeck, high sheet loads) to make a headsail set well, and to trim it?
6) Did he allow for the huge amount of time (and effort) required to change headsails when the wind strength changes, or for the less than ideal shapes available from partially furled headsails?
7) Did he heel the boat and add lifelines and all the other deck level stuff that upsets the wind flow onto the lower 10% or so of the headsail?
8) Did he comment on the utter uselesness of a jib at more than 120 apparent, the difficulty of sheeting it wide enough to be efficient at 45-120 and the offwind inefficiency of a mainsail which cannot be eased past the swept back shrouds on most modern cats?

The stayed sloop rig is a very expensive, very complex way to go cruising compared to an unstayed wing mast.

I cannot open your reference to a genoa reducing bow down trim. Is there an URL for it?

regards,

Rob
www.harryproa.com

Richard Woods

07-01-2008, 11:36 AM

"All kidding aside, how often does the best sailor in the fleet have the slowest boat?"

Quite often if you believe

1) that bigger boats are generally not only faster but also more expensive
2) Just because you have money doesn't make you a better sailor.

as an example, the Round the Island race in the UK attracted 1800 boats including about 50 multihulls.

First to finish was Rob Greenhalgh , in the Extreme 40 TeamOrigin. First monohull was Mike Slade’s ICAP Leopard

Then from the Yachts and Yachting report

"The results overall in IRC showed a real mixture at the top of the leader board. First came a big boat from IRC0, Ran – TP52, followed by Darren Masters’ diminutive quarter tonner Catch. Last year’s Gold Roman Bowl winner Edward Donald came third in his 25 foot Folkboat Madelaine with another TP52, Henri Lloyd Cutting Edge, eight seconds later on corrected time."

Richard Woods of Woods Designs

www.sailingcatamarans.com

rayaldridge

07-01-2008, 12:05 PM

Actually, the answer is: "At least once in every race."

I don't know much about racing, but my study of human nature suggests that the worst sailor in the slowest boat is often invincibly certain that he's been screwed by the rule.

I'd probably be that guy.

Ray

http://slidercat.com/

brian eiland

07-01-2008, 07:47 PM

Brian, I don't have Marchaj's book, but would have the following real life vs wind tunnel questions:

I cannot open your reference to a genoa reducing bow down trim. Is there an URL for it?
At this time I don't have the time nor inclination to defend this subject of the 'slot effect' again. I might suggest you go to the search button on this forum and type in "slot effect" (http://www.boatdesign.net/forums/search.php?searchid=1279316) if you are interested in debating this particular subject. I think this will bring up quite a few discussions on the subject.

Granted the slot effect subject is primarily concerned with 'std stayed rigs' and maybe not so much with free standing rigs. I was not trying to sell the std rig over the freestanding rig, just trying to clarify the slot effect itself.

I have not finished the genoa trim subject yet

rob denney

07-01-2008, 10:25 PM

At this time I don't have the time nor inclination to defend this subject of the 'slot effect' again. I might suggest you go to the search button on this forum and type in "slot effect" (http://www.boatdesign.net/forums/search.php?searchid=1279316) if you are interested in debating this particular subject. I think this will bring up quite a few discussions on the subject.

Granted the slot effect subject is primarily concerned with 'std stayed rigs' and maybe not so much with free standing rigs. I was not trying to sell the std rig over the freestanding rig, just trying to clarify the slot effect itself.

I have not finished the genoa trim subject yet

G'day,

My concern is that people recite "facts" often enough and they become accepted wisdom. Occasionally, someone needs to look a little critically at the data.

I do not want to discuss the slot effect either. Whether it works for sails is irrelevant to me as a designer, given the ridiculous effort, cost and weight of achieving it. I do want to discuss the basis of your claim so people do not accept it as fact, if it is not based on real life.

You found the time and inclination to state slots are superior, based on "EXTENSIVE study" and to type the relevant passage from the book. Surely someone who spends as much time posting to forums as you do can find the time and inclination to open the book and answer some questions about that claim?

I leave it to the readers to decide whether your "clarification" of the slot effect was an effort to sell your multi headsail, multi slot, aft mast rig or not.

Look forward to the genoa trim stuff.

regards,

rob

brian eiland

07-01-2008, 11:53 PM

..My concern is that people recite "facts" often enough and they become accepted wisdom. Occasionally, someone needs to look a little critically at the data.
It sounds like you are disputing the fact, so I suggest you spend some time looking at the facts as expressed in a number of excellent books on the subject...so go read one

I do not want to discuss the slot effect either. Whether it works for sails is irrelevant to me as a designer, given the ridiculous effort, cost and weight of achieving it. I do want to discuss the basis of your claim so people do not accept it as fact, if it is not based on real life.
You are the one disputing my claim. In fact it is not just my claim but the many books that have found the older explainations for the slot effect were wrong and then sought to explain it correctly. A few of them were well respected aerodynamic academics.

As I said you may not have an interest in the subject since its not applicable to the rig concepts you are selling. BUT it does applicability to a GREAT MAJORITY of sailing rigs that present exist in the world. So if you have no use for it then ignore it.

You found the time and inclination to state slots are superior, based on "EXTENSIVE study" and to type the relevant passage from the book. Surely someone who spends as much time posting to forums as you do can find the time and inclination to open the book and answer some questions about that claim?
Surely if you are so disturbed by my interest in getting the correct explaination out there, then maybe you should open a book every once in a while.

Here is one of my other postings:
Subject: How Sails Work, the slot effect
http://www.boatdesign.net/forums/showpost.php?p=5685&postcount=3

...excerpt...
Now lets see how many people are going to tell me I’m wrong-- that like a restricted water hose, the air is speeded up in the slot. This is another of those axioms that the textbooks have got wrong and have taught us wrong for so many years. But as Tom Speer* noted, “there’s no way to finally put a stake through the heart of that old explanation—it just keeps coming back to life”.

*Tom Speer is another well respected contributor to these forums

rob denney

07-02-2008, 11:12 AM

It sounds like you are disputing the fact, so I suggest you spend some time looking at the facts as expressed in a number of excellent books on the subject...so go read one

You are the one disputing my claim. In fact it is not just my claim but the many books that have found the older explainations for the slot effect were wrong and then sought to explain it correctly. A few of them were well respected aerodynamic academics.

As I said you may not have an interest in the subject since its not applicable to the rig concepts you are selling. BUT it does applicability to a GREAT MAJORITY of sailing rigs that present exist in the world. So if you have no use for it then ignore it.

Surely if you are so disturbed by my interest in getting the correct explaination out there, then maybe you should open a book every once in a while.

G'day,
As I said, I am not "disputing" the existence of the slot effect, just the basis on which you supported it in this thread.

It leads directly to the question: Are the benefits of the slot effect worth all the drawbacks associated with achieving it on a cruising boat? Your reticence to discuss this here indicates that maybe you agree that they are not?

Please, don't waste your time answering this until you have found the time to answer the main questions.

For the record, I sell slotted and unslotted rigs. see http://www.youtube.com/watch?v=8chR6DAFjGA

I do not see the relevance of the number of boats using slots to what is possibly an unrealistic wind tunnel test.

regards,

Rob

RHough

07-02-2008, 02:50 PM

Despite all of the nonsense through the years about the slot effect, fewer sails is for the best from an efficiency standpoint. The slot effect merely reduces the inefficiency of having two sails working together, it doesn't make them more efficient than one sail with the same CE as the two working together.

This is either gospel truth or pure horseshit, depending on your definition of efficient. :)

Is lift per unit area the goal or high L/D ratio?

Alan M.

07-02-2008, 07:13 PM

Despite all of the nonsense through the years about the slot effect, fewer sails is for the best from an efficiency standpoint. The slot effect merely reduces the inefficiency of having two sails working together, it doesn't make them more efficient than one sail with the same CE as the two working together.

So why do they use leading edge slots, and slotted flaps on aircraft during takeoff and landing? Wouldn't they simply extend the wing area without opening slots, if this were more efficient?

brian eiland

07-02-2008, 11:08 PM

As I said, I am not "disputing" the existence of the slot effect, just the basis on which you supported it in this thread
I supported it with a reference to Marchaj's book. Are you disputing this book?

Then how about these references that won't involved you having to go read a book:
Technical Papers by Arvel Gentry
http://www.arvelgentry.com/techs.htm

The Aerodynamics of Sail Interaction
http://www.arvelgentry.com/techs/The%20
Aerodynamics%20of%20Sail%20Interaction.pdf (http://www.arvelgentry.com/techs/The%20Aerodynamics%20of%20Sail%20Interaction.pdf)

How do Sails Work
http://onedesign.com/articles/article6-1.html
________________________________________________

On a similar subject, I had submitted this quote, This is another of those axioms that the textbooks have got wrong and have taught us wrong for so many years. But as Tom Speer* noted, “there’s no way to finally put a stake through the heart of that old explanation—it just keeps coming back to life”.

The subject I speak of here is that old description of how an airfoil develops lift. It's another of those descriptions that many just continue to get wrong....but those old explanations just won't go away.

How Airplanes Fly
http://www.allstar.fiu.edu/AERO/airflylvl3.htm
Almost everyone today has flown in an airplane. Many ask the simple question "what makes an airplane fly"? The answer one frequently gets is misleading and often just plain wrong. We hope that the answers provided here will clarify many misconceptions about lift and that you will adopt our explanation when explaining lift to others. We are going to show you that lift is easier to understand if one starts with Newton rather than Bernoulli. We will also show you that the popular explanation that most of us were taught is misleading at best and that lift is due to the wing diverting air down.

RHough

07-03-2008, 12:46 AM

I supported it with a reference to Marchaj's book. Are you disputing this book?

Fact: The air "sees" the sailplan as a single unit.
Fact: Total lift force is a function of angle of attack.

The idea that that the Genoa or Jib provides a greater percentage of the lift than the main is a misunderstanding. If you look at the pressure distribution of the Genoa and the Main and the two combined you will find that the pressure differential is higher on the forward portion of each. The front 1/2 of each sail 'does more work' than the aft 1/2. Since the air 'sees' the two sails as a unit (single flow pattern around the combination), the forward part does more work ... leading to the assumption that the Genoa is a better left producer than the main.

The air 'in the slot' is not accelerated, it is slowed. Placing the mast in this area of reduced velocity can mitigate the drag caused by the mast and reduce it to a value less than one would think it would have in free stream.

The reason that soft sail rigs of Genoa and Main can produce higher lift, is because they can operate at a higher angle of attack without stalling. A hard sail of equal area as the Genoa/Main combination that could operate at the same angle of attack would produce the same lift. This would require a highly cambered wing. Slots and separate flaps on aircraft serve to create such an airfoil.

On sailing craft the lift requirement changes. The sails do not operate at their maximum lift above the design point windspeed. Below the design point the boat can use more power than the rig can provide, above the design point the sails can produce more lift/power than the boat can use. Once this point is reached, drag reduction through reduced camber is the trim goal, there is more than enough power available.

It is possible to size a rig that fully powers the boat in 10 knots apparent wind, it is also possible to design a boat that sails at a multiple of wind speed. A 2X windspeed boat would be fully powered in very light air. Above that very low wind speed, drag reduction becomes the primary goal and single element rigs and hard sails have higher L/D than the Genoa/Main combination.

The problem that most designs face is that a practical rig is not big enough to fully power the boat at less than maximum lift in lighter air. This makes the multi-element rig a winner since it can operate at angles of attack higher than any single element rig that I know of. If you can cram on enough area to power the boat in 6-8 knots of breeze, it would be a better solution than increasing the number of sails.

IMO a good choice for a rig is a full batten main set on a rotating mast with a fractional jib. Off wind sails can be masthead. The jib can be self-tacking, the main/mast combination can be tuned to have correct gust response. If the jib is roller furling, the only issue is how to fly storm canvas. A storm tri-sail track on the mast allows the main to come down, but a provision for a storm jib must be made. For a small boat, a wire luff storm jib with a hoist point at the head of the storm tri-sail might be a viable solution. Larger boats should probably have an inner forestay with the hounds at the tri-sail head so the sheet load and inner stay to not act to take the mast out of column.

rob denney

07-03-2008, 04:53 AM

[QUOTE=brian eiland;212961]I supported it with a reference to Marchaj's book. Are you disputing this book?

Then how about these references that won't involved you having to go read a book:
Technical Papers by Arvel Gentry
http://www.arvelgentry.com/techs.htm

The Aerodynamics of Sail Interaction
http://www.arvelgentry.com/techs/The%20
Aerodynamics%20of%20Sail%20Interaction.pdf (http://www.arvelgentry.com/techs/The%20Aerodynamics%20of%20Sail%20Interaction.pdf)

How do Sails Work
http://onedesign.com/articles/article6-1.html

G'day,
Am I disputing Marchaj's, Gentry's and North's explanations? No.
Am I disputing whether those references are the complete picture? Absolutely.

None of them makes any mention of, nor allowance for, all the additional weight and windage required to make a sloop rig work the way they say it should. Nor for the reality that sails stretch, wind strength varies, cruising crews are not constantly trimming and few, if any, sails are perfect straight from the loft.

The complexity and loads required to set up a of a sloop rig make these factors much more critical than for an unstayed, wing masted mainsail only rig.

To quote all your sources as proof that the slot effect exists is valid. To blithely jump from there to a slotted rig is superior is totally unjustified without taking into account the cost of achieving it.

Funny how the availability of time and inclination to discuss things varies, isn't it?

Regards,

Rob

Richard Woods

07-03-2008, 11:23 AM

Years ago I spent several evenings at Tony Marchaj's house talking about boats and design. (read the frontpiece to his first book and you'll see how I knew him)

He told me that the most "efficient" rig was a single solid wing. Closely followed by an big mainsail/small jib combination.

However this thread is all about rigs for small ocean cruisers. So in practise that means a single mast. It also means a roller reefing headsail (to keep sail locker space to a minimum). Plus the fact that probably the interior layout will influence the choice of rig more than it should.

Lets get back on topic, or start a new one called "Unusual Rigs"

Richard Woods of Woods Designs

www.sailingcatamarans.com

rob denney

07-04-2008, 12:17 AM

Bruce Woods

07-04-2008, 01:29 AM

G'day,

Sorry about the diversion. Back on topic.

Why so adamant about a single mast and roller furling jib for a small ocean cruising cat?

regards,

Rob

From personal experience its so easy to cruise with. Stow the main when the wind goes aft of the beam (cruising), and you now have a rig that is instantly reef-able to any size with the C of E right up near the bow where you want it. One seems to spend most of ones time trying to slow a cruising cat down to a comfortable speed and the roller furling head-sail makes that task so easy. You are more likely to have the correct amount of sail up for the conditions if you can adjust it so easily with a roller furler system hence better passage times. Tacking a cat with head-sail assistance is also easier in the sloppy stuff. Pretty much an impossible maneuver to accomplish with main only on a vessel with such high wind-age and inability to carry much way through a tack. In the rough stuff I can ballance my cruising cat with the two sails and lash the helm slightly to lee and the whole shooting match will self steer to windward all day long. Try doing that with main only.

Regards

sandy daugherty

07-04-2008, 11:57 AM

Rob: I love your work, an hope to see one of your masterpieces here on the Chesapeake one day. However:
Skene, Marchaj, North, Wallace Ross, and others did consider, and test with masts, shrouds, sheets and other itty bits, as well as with pure forms. As well, they calculated scale error for air density, motion in a seaway, and other conditions in several of their studies.
Further, sail combinations continue to be studied at the Naval Academy as part of several undergraduate engineering courses.
Moral: Slot effect is real. Slot effect is good. Slot effect is real good. Good enough to make up for all the twitchy complications. Thus sang the fat lady.

I move the original question: What would you suggest someone in Manila could build out of plywood for long distance, non-heroic cruising. Assume pylwood is cheap, glass is expensive, aluminum extrusions have to be imported, hardwood is rare, labor is cheap, but temperatures and humidity are high. Scrounging a mast is probably not likely, and stainless rigging is so expensive it must be limited to the absolute minimum.

Could he really build a wing mast?

Is a Wharram his only choice?

Richard Woods

07-04-2008, 03:51 PM

Why not try my 34ft Romany?? designed for comfortable ocean cruising. Safe, fast, lots of room for the amount of work involved, and easy building in plywood.

I even bought one myself!

Anyone who is building away from the normal yachting hotspots can always find someone to make a wood mast and someone else to make the associated metal fittings for gooseneck and hounds. It doesn't have to be a wing mast to be a wood one. After all, all masts were wood until the 1960's. Galvenised rigging wire is available anywhere (cranes, bridges, farmers etc use it) An ocean sailor can sail to say, Australia, using "temporary" gear and upgrade there.

Some of the largest sailmakers in the world operate out of the Phillippines so no problems on that front.

I agree with Bruce's commments above (still no relation!)

I have cruised several thousand miles on an unstayed masted catamaran, and briefly sailed several others.The (professionally built) rigs were much more expensive than a (professionally built) new metal mast, conventionally stayed and massively more than a secondhand mast.

An ocean cruiser has no time to experiment and no inclination to take risks. Rob agreed with me earlier that the bi plane rig still had handling problems, but that one day maybe it would work.

As the current Americas Cup is to be raced in multihulls with no rule restriction one can assume that the designers will be using the most efficient rig.

Will it be a mast aft rig? a Dynarig variant? A biplane rig? A balestrom rig? or a "conventional" rig?

We'll know soon enough

Sorry but I won't be writing on this forum for a bit - we are going sailing, I hope you can all get on the water this summer as well.

Richard Woods of Woods Designs

www.sailingcatamarans.com

masalai

07-04-2008, 08:49 PM

Richard, may you have fair winds and calm seas - - God speed...

rob denney

07-05-2008, 04:02 AM

G'day,

Bruce,
Dropping the main to go down wind (and having to hoist it again if the direction or course changes) is not as easy as trimming one lightly loaded sheet on a ballestron rig, or one slightly higher loaded sheet on a una/cat rig.

Roller furling (pulling a string and the sail disappears) is a great concept, until it breaks or jams. Roller reefing (pulling a string and part of the sail disappears) is a great way to destroy a sail shape and will not go to windward any where near as well as an unrolled sail.

Furlers are a nightmare in a seriously big breeze when you have to remove all unnecessary windage, but have to unfurl it to do so. They are also expensive, as are headsails and the winches and stays required to support them.

Tacking a cat rig is no problem with a correctly designed hull. There are many examples of these, and a few examples of ones that are not.

Balance is not a problem with a single sail as long as it is in the correct location.

Sandy,
Glad you like the boats.

I would appreciate some references for the work done on the cost of achieving the slot effect. Specifically how it applies to cruising boats with stretched sails, crew who don't constantly trim the sails and overbuilt rigs which are not set up with the care racing sailors use. Then add in the cost of the stays, winches and hull beefing up to get it all to hang together and any performance gains are quickly negated. In actual use, the sheer hard work and vigilance required for a sloop vs an unstayed una/cat rig makes it a far less pleasant option for cruising.

Can a wooden mast with gal rigging and cheap fastenings be built? No problem. This was the standard before alloy and ss. On passage you need to check it every day, and before and after any bad weather. Ideally climb or remove the mast every month or so to make sure all is well. Expect to replace the rigging and paint the mast every few years and replace any rotten bits if you are not careful with your checking.

Can an unstayed wooden mast be built? Certainly can. It will need almost no maintenance (no holes in it, no fittings to break or cause rot) and should last forever. You only have to buy one sail, which never flogs so it lasts much longer, the first reef is automatic as the mast bends in strong wind and is easier to handle as it is held on two sides. The sail can be hoisted and lowered, easily, on any point of sail in any breeze. It will be heavy, but the cog will be quite low, possibly lower than a stayed masthead alloy rig.

Carbon is not the expensive material it once was, and there are easier and cheaper ways to build from it than the aircraft crowd use. If you are able to use a vacuum pump, you could easily build your own carbon mast, and it would be cheaper than a good quality timber one, and way cheaper than an off the shelf alloy one. I could send all the materials from Australia, and at the moment they would be a very similar price to buying them over the counter in the USA, depending on import duty to the Philippines. Let me know the boat weight and the centre to centre beam of the hulls and I will give you a ball park price.

Richard,
Rigging a boat, sailing a couple of thousand miles and rerigging it is probably not the cheapest, nor the safest option.

The mindset which uses the AC boats as a reason for a sloop rig on a small cruiser is the reason why so few advances have been made in multihull cruising rigs for the last several decades.

Enjoy your sailing.

regards,

Rob

sandy daugherty

07-10-2008, 04:09 PM

rob denney

07-11-2008, 03:07 AM

Fair winds and reliable weather reports, Richard!
Rob: You've peaked my interest; can you recommend some reading on carbon masts? Its off the wall, but I would like a masthead platform that did NOT rotate when the rest of the mast does.

G'day,

All the carbon mast stuff I know about is for expensive manufacture using heat and high pressure for money no object results. Google carbon masts and you will see what I mean. Any questions on low cost options, feel free to ask.

How big a masthead platform? A tricolur light can be kept fore and aft with a rigid tube up the inside of the mast. A crows nest would probably require a bearing and at least one line to the boat. However, unstayed masts are pretty flexible, it is not much fun being at the top of them, especially in a seaway

masalai

07-14-2008, 05:02 AM

rob denney

07-14-2008, 10:17 AM

I seem to feel that randy quimpo who started this thread may well be disappointed at the direction this thread has taken....

My 2cents, - would be rig for absolute simplicity, easy repair-ability whilst at sea and a robust design and build.... **** happens, and to reduce that risk is (should be) the prime and only concern...

Efficiency and all the fancy go-fast add on stuff will only complicate matters.... Don't piss into the wind - stand side on and with a bit of luck you won't even get blow-back... The same sensible thought should be applied to setting up your boat for ocean crossings.....

G'day,

I should think Randy would be very happy. He has received the conventional wisdom from possibly the most popular small multi designer in the world (Richard) and a couple of other options. Why would he be disappointed?

Your 2c worth is on the right track, but I don't think it goes go far enough. A rig so simple that there is nothing to break is much better than one that is easy to repair. A single unstayed mast, with a fixed boom and single main sail is as uncomplicated and unbreakable as it is possible to get. The fact that on a cruising boat it is also the most efficient and easiest to use is a bonus.

regards,

Rob

RHough

07-14-2008, 02:05 PM

To quote all your sources as proof that the slot effect exists is valid. To blithely jump from there to a slotted rig is superior is totally unjustified without taking into account the cost of achieving it.

One could use a spoon to dig the Panama Canal. Just because the sppon is simpler and less expensive than a shovel does not make it a superior choice.

The "best" solution is the one that works with the least complexity for a given performance. A single unstayed mast has not been the choice for many boats bigger than a dinghy when performance is one of the design goals. Unless the boat is fast enough to sail with the wind forward of the beam at all times (not the case with a small catamaran circumnavigator), extra sail area will be needed when off the wind. Good light air performance requires either high lift or large area, the split rig (jib and main) has proved itself to be a very easy to handle sail plan than provides decent light air performance without the added area that a single sail would need to give equal force. A single sail that can drive a relatively heavy boat well in light air and less than ideal sea state would be much too large much of the time and would be reefed much of the time. In contrast, the high lift mode of a split rig can be trimmed to a low lift / high L/D mode. Splitting the needed area into 2 (or more) smaller sails makes those sails easier to handle. Add to all this the structure needed to support an unstayed rig in the middle of a catamaran cross-beam and the cost/complexity of hull/beam design replaces and offsets the cost/complexity of the stayed rig.

Richard Woods

07-14-2008, 02:41 PM

Sorry for not replying sooner, but as you know I was away sailing. Yesterday we were in a crowded anchorage in quite a strong wind. We decided to sail off the anchor rather than motor. We pulled the anchor up short, unrolled part of the genoa, backed it, lifted the anchor and were away. Simple, quick and in full control.

You cannot sensibly "back" a una rig except on a dinghy when it is easy to push the boom into the wind. Furthermore, I wouldn't have liked to have had the mainsail (or any other sail) hoisted (even with reefs in to keep the speed down as we sailed out) while hauling the anchor up short.

In my experience most rot in masts occurs under the sail track, which I assume you'd use even on an unstayed mast? Ocean cruisers must assume they will be hit by lightning at some stage. Most carbon masts don't survive a lightning strike so for that reason alone I'd steer clear of one. Also, although you want to show off your black mast, if it is unpainted (and the paint maintained) you will eventually have a failure from UV degrading the epoxy. Electrolysis also causes major problems.

To be honest I'd have thought that even in the Philippines it would be easier/cheaper to ship in a mast along with the deck gear, interior fittings, engines etc.

I think Rob misunderstood my comments on the Americas Cup rigs. Obviously racing boats have different requirements to cruising boats. They just need efficient rigs. Cost, complexity, handling problems when shorthanded and durability are irrelevant. That is why I said it will be interesting to see what the America Cup designers think is the most efficient racing rig (as opposed to the "best" rig for a cruiser)

I write a bit about the Aerorig style balestrom rigs on my FAQ's page. In short, getting the balance right when reefed seemed to be a problem, and don't try motorsailing unless the jib is furled!

I made the temporay wood mast comment to make people think of different options. I did look into having a boat built in the Phillipines myself, but didn't. Partly because I thought I should be there to supervise, partly because it seemed a difficult place to sail away from.

Richard Woods of Woods Designs

www.sailingcatamarans.com

rob denney

07-15-2008, 01:28 AM

R Hough

All the expensive earth moving equipment in the world would not have dug the canal any quicker than a spoon if there was no maintenance facility available, or the operators could not afford it. This is the case with the low cost world cruiser, exacerbated by the fact that a rigging failure on a stayed mast is usually terminal, causing the mast to fall down. This simply does not happen with unstayed masts.

Unstayed masts have been expensive, sailors are very conservative people. Which is why they have not been used. At least with the expense, this is no longer the case.

Tall masts and long booms are one way of getting a lot of sail area on a single mast, and as the top mast is light and small section, the weight and windage when reefed is not as big a problem as a stayed rig. The cog of the unstayed rig will be lower as well. In light air, it will have more area up high where there is more breeze. See Bethwaite for the comparative advantage of high area vs low area. Also, the rest of the boat can be built much lighter, so a smaller, cheaper rig is possible. Take this to it's logical conclusion and you have a 15m/50' harryproa weighing 2,000 kgs/4,500 lbs; less than half the weight of a comparable cat.

If rig height/sail area is a problem, another option is temporary runners for light air sails, or a ballestron rig, see below. Both are better than a conventional stayed rig.

The rig does not have to go in the middle of the beam, but even if it does, the beefing up is far less than that required to support a stayed rig. We put a 14m high rig on an overweight 11m cat with 600mm/24" high beam Added maybe 15 kgs/33 lbs of structure to hold it up. It works well. http://www.harryproa.com/MASTS/Taywun/Taywun.htm

Richard,

Unstayed rigs sail on and off anchors by hoisting the main and letting it weathercock. Take the anchor warp to the stern, pull it up and trim just enough main to give you steerage. A lot easier than having to raise the main once you have left the anchorage, especially if it has lazy jacks fitted in which case you probably have to start the motor anyway. It also does not involve jib sheets flailing round the anchor lifter, nor does it need the single hander to be running from one end of the boat to the other while the boat is drifting backwards. On boats big enough to need anchor winches, it is easier to sail backwards with the main up than it is to back the jib.

Of course, the ultimate backing rig is a proa, but that is another subject.

Most wood rot happens round highly stressed fitttings, such as the hounds. Regardless, we bond sail tracks to carbon masts, would do the same to a wooden mast.

We have motor sailed the boat in the video at http://www.youtube.com/watch?v=8chR6DAFjGA. No obvious jib related problems, but even if there were, dropping the jib in motor sailing conditions is hardly a deal breaker. Reefing is also not a big deal. The first reef is automatic as the mast bends, spilling power. The second reef is to drop or furl the jib and use a winch for the mainsheet. Third reef is a deep reef in the main.

I appreciate the difficulty of keeping FAQ's up to date, but with all due respect, yours are well out if date.

The ballestron advantages are correct, especially the 95% efficiency possible for Joe average vs the 70% he will achieve on a sloop rig, which is very relevant to this thread and masalai's and RHoughs points.

The disadvantages you list as cost and weight. Both are correct for Carbospars (out of business 5+ years ago) masts, but are wrong compared to what is currently available.

The mast on the boat in the video weighs 120 kgs, comparable to a stayed alloy rig for a similar rm cat. It cost less than a stayed mast bought from Allspars, Australia's biggest rig supplier. By the time the extra bits required to support the stayed mast were added (forebeam, seagull striker, substantial bulkheads, chainplates, winches and traveller tracks, multiple headsails or a furler), the ballestron is way cheaper. If the ballestron rig was home built (no harder than the rest of the boat and not an option for the stayed alloy mast) it would have been one quarter the price.

Lightning is a worry for any boat, although strikes are very rare. I would be interested in the details of any carbon mast strikes you know of, maybe on a new thread. I guess you need to ask whether dissipating the energy by melting the mast (I have never seen a melted carbon mast) is a better bet than it blowing a hole in the bottom of the boat, possibly after passing through the crew holding onto the backstay.

Painting carbon masts is a no brainer. We supply big stickers for people who want the world to know what the painted mast is made of. ;-) Electrolysis is a big deal with different materials, notably stainless steel and aluminium. Modern unstayed carbon masts have no metal in contact with them, so it is not a problem. Nuts, bolts, screws, rivets and structural metal really have very limited use in modern boats generally and modern masts specifically.

regards,

Rob

RHough

07-15-2008, 02:48 AM

Rob,
The ballestron rig has much to recommend it. The jib area is useful over a wide range of sailing angles. The gust response is correct and assuming the sails and spar are matched well it should be a near ideal cruising rig. I like the idea very much. It seems to retain all the advantages of a sloop rig while eliminating some of the weaknesses.

IIRC this rig was tried on a moderate displacement mono and the expected increase in performance was not realized. Perhaps it is time to take another look?

For cruising, weight carrying ability governs the range of the boat. Interior volume to LOA is a common measure, how does interior space on a 50' PROA compare to a 50' cat? Is comparing total displacement to interior volume a better comparison? Most 50' cruising cats are sleep 8, feed 16, cocktail 32boats. How does a 50' PROA compare? For a 4500# boat does the PROA have the same tankage and storage as a 50' cat?

Gary Baigent

07-15-2008, 03:33 AM

Richard
You wrote: "You cannot sensibly "back" a una rig except on a dinghy when it is easy to push the boom into the wind."
Not true, mon ami. I learnt to sail backwards like an expert (from getting caught in irons and wanting to escape) on my 32 foot cat Supplejack but also did it on 58 foot catamaran Sundreamer with just the main up (headsail sheet off) at a photoshoot at Great Mercury Island years ago when Sundreamer had just been launched - (and had just taken line honours in the Auckland/Tauranga). We sailed on the wind for the camera, came head to wind, Chis Barker (designer's brother) winched the boom back and off we merrily reversed half a mile back into the bay to start up for another pass. No one thought it would be possible with such a large boat. You steer facing aft reversing everything. We did four times until the photographer (Ena Hutchinson) was satisfied.
And on my una rigged 11 metre foiler, absolutely no problem to sail in reverse - but I hold the wing mast spanner back so the mast acts like a jib. IMO it is an essential skill for light multihulls. And I'm sure you'll get similar stories from monohull sailors.

rob denney

07-15-2008, 07:07 AM

G'day,

Rhough,
"Near ideal for cruising" sums up modern ballestrons pretty well. Doing away with the jib and foreboom is the next step towards simple, but does require some layout changes at the design stage.

Ballestrons have been tried on a few boats. Handling has been easier and maintenance less in every case i have heard of. Performance has been difficult to compare. The only actual tests I know of were done by Yachting World on a couple of Sigma 36's (I think), one with the standard rig, the other with a ballestron, with the following results: ballestron is a little less good upwind as long as the standard rig is being tweaked continually (until a tacking match was started when the ballestron was much quicker), faster on a reach and much faster downwind, even when the sloop got their headsail poled out. Safer and easier on all points.

These was an expensive carbospars rig, with small headsails and no roach mains. Ours have big jibs and a lot of roach and from now on, most of them will be wing masted, which is less drag, stiffer and almost as light and cheap as a tube mast.

I was not comparing the harryproa to a 50' cat. I was comparing it to a "comparable cat". ie one with two queen size doubles, two singles, huge galley, toilet and shower, enclosed cockpit seating 8 and able to sail at wind speed up to 15 knots. And cost $400,000 pro built, ready to cruise. The harry weighs 2 tonnes ready to sail. Any cats with anything close to these specs that weigh less than 4 tonnes?

The best comparison I can offer to the 50' cat is the charter harryproa half way down http://www.harryproa.com/newsletter0608.htm Four queen size double cabins, each with en suite shower and toilet, 2 of them with island beds. Unstayed schooner rig, electric motors, 7 tonnes chartering weight. And costing less than the 50 footer above. Probably won't do wind speed in charter mode, but in cruising mode it should. It is not built yet, so no proof of the numbers, but the spreadsheet was as detailed as the 50 footer, which came in bang on the design weight. Any cats with this capacity, speed and price weighing less than 14 tonnes charter ready?

Gary,
Sailing skills we kiwi sailors take for granted are considered unusual elsewhere. ;-). It's a small world, I raced to Hobart with Chris, back when I was young and foolish.

regards,

Rob

sharpii2

07-15-2008, 11:26 AM

R Hough

All the expensive earth moving equipment in the world would not have dug the canal any quicker than a spoon if there was no maintenance facility available, or the operators could not afford it. This is the case with the low cost world cruiser, exacerbated by the fact that a rigging failure on a stayed mast is usually terminal, causing the mast to fall down. This simply does not happen with unstayed masts.

Unstayed masts have been expensive, sailors are very conservative people. Which is why they have not been used. At least with the expense, this is no longer the case.

Tall masts and long booms are one way of getting a lot of sail area on a single mast, and as the top mast is light and small section, the weight and windage when reefed is not as big a problem as a stayed rig. The cog of the unstayed rig will be lower as well. In light air, it will have more area up high where there is more breeze. See Bethwaite for the comparative advantage of high area vs low area. Also, the rest of the boat can be built much lighter, so a smaller, cheaper rig is possible. Take this to it's logical conclusion and you have a 15m/50' harryproa weighing 2,000 kgs/4,500 lbs; less than half the weight of a comparable cat.

If rig height/sail area is a problem, another option is temporary runners for light air sails, or a ballestron rig, see below. Both are better than a conventional stayed rig.

The rig does not have to go in the middle of the beam, but even if it does, the beefing up is far less than that required to support a stayed rig. We put a 14m high rig on an overweight 11m cat with 600mm/24" high beam Added maybe 15 kgs/33 lbs of structure to hold it up. It works well. http://www.harryproa.com/MASTS/Taywun/Taywun.htm

Rob

Hi, Rob.

With all due respect, a stayed rig on a small catamaran will be certainly cheaper.

The reason it would be cheaper is that the boat builder of this voyager can build the mast himself. It can be either solid, box sectioned, or birds mouth. The stays don't have to be expensive and they can be engineered to a very high safety factor. I have known such rigs that have stood for decades. It's only on certain racing boats, where they are engineered to very low safety factors, to cut the most weight possible, that you see a lot of failures.

There is really no restriction on the height of the mast if a fractional sloop rig is used. The top part of the mast does not have to be supported.

Unlike a HarryProa(r), a catamaran usually has its mast stepped near the centerline of the deck. That along with the wide beam of the boat provides an excellent staying base. To put an unstayed mast there would require a massively reenforced deck house or bracing rack.

Un doubtably, the unstayed mast system, if it could be afforded, would have certain advantages. But I just don't see my voyager building his/her own carbon mast system. Nor do I see her/him repairing it should it get damaged. The stayed mast can be easily jury rigged, if it should fail. Depending on how it is made, the unstayed mast could be jury rigged as well, by pulling out the shorter broken section and putting the longer section in its place. The stayed mast would definitely be cheaper to replace, especially if it is built by the owner. And it can be done anywhere in the world where there is wood or suitable metal. The replacement carbon mast would have to be shipped.

So, I think you win out on most of the arguments, but with the 'it's cheaper' one, I think you are all wet.

As for efficiency. If it were my boat to be used for this stated purpose, I would have the following design priorities for my rig, in descending order:

1.) strength,
2.) repairability,
3.) ease of construction,
4.) ability to balance the sail plan easily with a wide variety of sail areas set,and
5.) efficiency

I think much of this is ironic, because, so far, the only masts I have designed are unstayed ones :)

Go figure.

Bob

Richard Woods

07-15-2008, 02:04 PM

I haven't yet done nearly enough multihull sailing, nor am I as skilful as any New Zealander or as brave as any Frenchman. Furthermore, both Jetti and I are getting old and frail. However that does mean I am much more "normal" than those who are more expert than me and so I feel can relate to most peoples sailing abilities better than others.

So having said that, I still think it is much easier to unroll part of a headsail than hoist a mainsail and winch it to windward to bear off. I know for sure which Jetti would prefer to do. It's crazy to suggest you have to take the anchor warp to the stern to raise it if you want to sail off the anchor. OK, even I could do it on a small boat, but on a big boat, with no stern roller or anchor winch aft???? And what's this about having to start the engine to hoist a mainsail????

From reading the rest of Rob's posting it seems that at least one America's Cup boat must be a Harry proa.

More seriously, I think Rob would advance his cause greatly if he were to fit one of his rigs on say a F27.

A F27 is cheap enough and anyway his rig would presumably increase its value so he cannot lose money (especially as they are so cheap to make). Then if he lends the boat to an average sailor (if there are any in New Zealand) and races it against standard F27's we would know for sure which was the better rig.

No doubt he has already worked out how to easily step an unstayed mast.

I was hit by lightning when sailing my Eclipse. When sailing in the tropics in the rainy season I reckon you have a 1 in 3 chance of being hit. I write more about it on my website (see my Articles page). I know at least one carbon mast that shattered when hit by lightning, apparently shards of carbon mast pierced the deck (a good thing everyone was below). A monohull superyacht sank last winter after being hit by lightning. I once saw a J24 that had been hit 4 times. Ewen Thompson, the world expert on lightning strikes on boats, told me that he'd replace a carbon mast if it were hit by lightning.

Richard Woods of Woods Designs

www.sailingcatamarans.com

Bruce Woods

07-16-2008, 08:00 AM

Richard, The f 27 test bed for the rigs is a great idea. It would certainly shorten this debate considerably.

We often sail on and off our mooring. Quite often we get under- way by unrolling the head-sail and hoist the main later . Mainsail hoisting is easily accomplished when sailing to windward as the head-sail tends to back-wind the main as it is hoisted, keeping it off the shrouds and nicely lined up. No motor is required.

rob denney

07-16-2008, 12:48 PM

G'day,
Bob,

Let's talk specifics.

Randy Quimpo says he is looking at a 27' cat. Let's use Richard's Gypsy design for some numbers. This is 28'/8.8m long, weighs 2.4 tonnes fully loaded and is 5.4m wide, say 4.6m between hull centrelines. Therefore the righting moment is 4.8*.5*2.4 = 5.5 tonne metres. Sail area is 38 sqm.

Richard, do you know how heavy the mast and standing rigging are on this boat? Maybe the current cost? If you can also tell us the weight and cost of the forebeam, striker, (or extra material required for the split forestay), traveller, chainplates, bulkheads, jib tracks and the additional material to beef up the boat to take these it would be a bonus.
Using the single main sail rig, based on a 12m harry rig http://www.harryproa.com/Builders/Ba...son/Bain_4.htm, which we have built and know that it works. The harry has 31 sqm mainsail and 6 tonne m righting moment, which is less sail area on a stiffer boat but near enough for a first stab. This mast weighs 60 kgs complete. I would provide the materials for this for $Aus1,387.00. Need to add on some wastage, which will depend on the user, say 10%. $US12/lb, 16 Euros/kg. Plus another $100 for a vac bag, sealant tape, bleeder and mdf for the mould frames. Say $1,650 all up. A complete novice could build this mast in a couple of weeks, including doing some samples to learn how to vacuum. Someone who had just built a boat would do it in a week. An unstayed wing mast would cost maybe 20% more, and is almost as easy to build.
Maybe Randy could scrounge some demolition timber, gal wire, bunch of bulldog grips, hounds fitting, curtain track, baling twine, old clothes line, worn out second hand headsails and some lumps of steel to make the chainplates for an 11m rig cheaper than this.

But let us assume he buys the materials and uses best practise to put them together, the same as for the unstayed mast. Over to you for the gal rigging, wood mast option and Richard (ss and alloy) for the comparable weight and cost of the alloy and timber rigs.

Re stepping it on a beam. See prior post on the 11m open deck cat. Building the beam up for an unstayed rig is no more of a big deal than making it strong enough to support a stayed rig. Putting it in the hull is a smarter move, but you need to learn to live with assymetry, or build two masts.

Re repairing damage. A well built carbon unstayed mast can be subjected to simple static bench tests to prove it's suitability for a given boat. Barring capsize or hitting a bridge, it will never exceed these specs. There is no rigging to set up wrongly, wild gybes, flogging sails or other causes of stayed mast failure. Carbon/epoxy has excellent fatigue properties so the mast will not wear out. The main halyard sheave may eventually get worn, but that is all there is to go wrong. There are no other fittings to check, maintain, replace or break. Therefore, there will never be any damage to fix. This feature alone makes unstayed masts the best option for cheap cruising.

Of your 5 criteria for a cruising rig, the first is a given, the second does not apply to unstayed masts which win on the 3rd, lose on the 4th (with reservations) and win on the fifth.

I thought i knew most of the unstayed mast designers. Do you have a web page i could look at?

Richard,
Apologies for my tasteless joke.

It would be interesting to compare sailing on and off moorings with the two rigs. While we were at it, we could compare the ease of hoisting the mainsail on the mooring vs on the open sea, upwind and down, crewed and solo.

Mooring is one of many scenarios where both rig types work, but there are vastly more, mostly safety related, where the unstayed rig is superior.
Gybing in a breeze, sailing in gusty winds, reefing, performance while reefed, windage with no sails up, maintenance and cost to name a few. Whether you sail backwards or back the jib to leave a mooring really is really pretty small beer.

The America's Cup and harryproas is way off topic, but seeing as you mention it, it may be relevant that the fastest sail boats (not boards) on the planet for the last 30 odd years (Crossbow, Crossbow 2, Yellow Pages, Macquarie Innovations, maybe SailRocket and Wotrocket) have all been proas. All the AC guys need to do is figure out how to make them go in both directions (they could look at www.harryproa.com for some ideas), and maybe they would be the fastest round the buoys as well. Unstayed masts were shown to be viable on Team Phillips, one of (maybe the) fastest offshore boats ever built, so they would be smart to check these out as well.

All the evidence to date is that me putting a rig on an F27 would have no more effect on the views of conventional rig pundits than any of the other unstayed rigs out there. Quite the opposite, in fact. What might change your minds is if you were to build and sail one. To that end, I will offer you, Bruce and any other doubters the materials at the above per kg rate for a mast to suit whatever boat you want to put it in. If the rig is not as easy to build and sail as I have said, I will take the mast and refund the money. If nothing else, at least we will both then be discussing it from experience.

Along with how to build them cheaply, I have indeed figured out how to step and unstep an unstayed mast. One person can do it and lay the mast on the deck under complete control, in about the same time as it takes to undo the forestay turnbuckle on a stayed rig. see post 12 at http://www.boatdesign.net/forums/showthread.php?t=23282 I have done this (afloat in a fresh breeze) with a 12m mast and a piece of 4 x 2, no reason why it could not be done with a 20m mast, as long as the gin pole is strong enough and has a winch.

One in three chance of sail boats in the tropics getting hit by lightning each year? I am sceptical. Are there any references for this?

I am also sceptical about the "carbon shards piercing the deck" after "the mast you know shattered". Why? Presumably it is the heating of the epoxy that causes the shattering. To do this with any force would require the epoxy to turn to vapour. Not sure what this temperature is, but i am pretty sure that it would cause the surrounding epoxy in a relatively thin laminate to heat up above 100C. At 100C mast epoxy goes soft, so carbon shards at this temperature would be about as sharp as lettuce leaves. Could be wrong, would welcome some more information, the name of the boat, any crew who are prepared to discuss it, magazine articles (would make very impressive photos) etc.

Your lightning article is interesting. I wonder if we would be discussing stayed vs unstayed rigs if you had been walking forward and touched the cap shroud when it struck? I would not advocate throwing away a carbon mast that had been struck. I would bench test it, maybe ultrasound test it and if nothing showed, then put it back in.

The terminal, earth and conductor are the solutions we are using for an unstayed rig we are building for a boat in the eastern USA. The owner found almost as many insurance companies and experts who said it would not help (and may even cause a strike) as he did that said it was necessary. Hence my interest.

regards,

Rob

sharpii2

07-16-2008, 10:38 PM

Bruce Woods

07-17-2008, 01:46 AM

rob denney

07-17-2008, 03:54 AM

Well..... no, The gypsy mast I suspect is designed for a spinnaker. Lets take a guess at 60 sqm. So lets hang a kite off your harry rig at the same point and see what happens.

G'day,

As the mast is sized for a large headsail, then flying a spinnaker from the easyrig hounds would be no big deal. The mast would bend, the mainsail leech would tighten up (not a bad thing) and the spinnaker would fly pretty much as normal, but with some give in strong puffs or sailing into the backs of waves. I would prefer to have a larger rig with better light air performance and not mess with spinnakers and all their paraphernalia, but it could be done.

The great thing about unstayed carbon masts on multis is that they are stiffness limited. That is, if they are stiff enough they are way over strength. Therefore, all the spinnaker will do is bend the stick, it will capsize the boat before it breaks the mast.

regards,

Rob

Bruce Woods

07-17-2008, 05:01 AM

G'day,

As the mast is sized for a large headsail, then flying a spinnaker from the easyrig hounds would be no big deal. The mast would bend, the mainsail leech would tighten up (not a bad thing) and the spinnaker would fly pretty much as normal, but with some give in strong puffs or sailing into the backs of waves. I would prefer to have a larger rig with better light air performance and not mess with spinnakers and all their paraphernalia, but it could be done.

The great thing about unstayed carbon masts on multis is that they are stiffness limited. That is, if they are stiff enough they are way over strength. Therefore, all the spinnaker will do is bend the stick, it will capsize the boat before it breaks the mast.

regards,
Rob

Rob, its probably best you follow Richards advice regarding actual testing on actual sailing platforms ( F27 ). I suspect no one wants to see another one of your design disasters . ie , your proa rudder systems which have required multiple expensive rebuilds by the owners, as it appears some of your design solutions, which may appear to work in your head ,don't cut the mustard in the real world..

rob denney

07-17-2008, 11:53 AM

G'day,

If you want to see an unstayed mast working, watch the video at http://www.youtube.com/watch?v=8chR6DAFjGA If a first generation $400,000, overweight (for it's mast design) 50' cruiser sailing effortlessly at wind speed does not convince you of unstayed mast potential, then I doubt you will be convinced by seeing one on a production boat half the size. If small production boats with unstayed masts are what it takes, check out Wylie cats, although if the ease of handling, lack of maintenance and reduced windage associated with an unstayed rig are not obvious to you then I suspect that nothing will ever convince you.

Sorry for the thread diversion, stop reading if you are only here to discuss unstayed masts.

This is the 11th of Bruce's 26 posts on this forum which have been antagonistic towards me, adding little or nothing except that antagonism to the discussion. He seems to have joined a group of people in various forums who get their jollies from knocking harryproas which they have neither seen nor sailed on. He follows the general trend, which is to start with general sniping, jump on any bandwagons that happen to be passing (eventually to the embarrassment of the people they are supporting), and when they feel they are losing the discussion (usually shown by former sceptics changing their minds, as in this thread), introduce increasingly wild off topic subjects they think might diminish me personally. In some cases this gets to the point of a serious complex http://www.wingo.com/proa/articles/moderating_the_proa_list.html

The harryproa rudder story in brief.

Apart from my many and varied prototypes, there are 5 harryproas sailing and one about to be launched. All 6 have similar rudder set ups which were designed and implemented 2-3 years ago.

Harryproa design never stops. After much experimenting on my boat, I came up with a better rudder solution. This is the fifth or sixth major improvement since I first started playing with proas. The last 4 have been safer than the standard rudder and daggerboard systems on conventional catamarans. I advised all the current owners and builders of the improvement. One of the owners thought the new solution was a worthwhile improvement over what he already had. I therefore paid (a lot) for the engineering, drew the plans and gave them to the owner free of charge. Four of the other five owners are happy with what they have got, the 5th is dead. Only someone with a serious grudge could turn this scenario into "multiple expensive rebuilds by the owners"

What any of this has to do with unstayed masts is a mystery to me. If you and Richard want to discuss harryproas, start a new thread.

Your tacky insinuation says more about you than it does about my "design solutions", and nothing about unstayed masts.

regards,

Rob

Richard Woods

07-17-2008, 01:40 PM

Rob, you wrote several long messages which will take time for us all to fully digest. (I wrote this offline before seeing the post above, and for those who might get confused, Wylie cats are cat rigged monohulls)

But as a starter, and assuming I have this right. (I may not, as I write in haste, having got up this morning at 4am to move our boat onto the beach at high tide to scrub off. In half an hour I go back to antifoul it)

My 11.3m Gypsy mast as a bare tube weighs 45kgs, 100lbs. However my rig uses a 13sqm genoa and 25sqm mainsail to get the total area of 38sqm. If it were a una rig the mainsail will clearly have to be bigger, but the boom cannot be much longer. So all the extra area must come from increased mast length. Roughly 4m extra. Then, as it is unstayed, there must be some bury. Say 1.5m

Thus the total mast length for an unstayed una rig Gypsy is about 16.8m or 55ft. And that is adding no extra sail area to compensate for the lack of a screecher or spinnaker.

It seems to me that a unstayed 55ft mast, even in carbon, will weigh over 100lbs?? Especially as unstayed masts, by their very nature, have to be heavier than stayed ones.

I also am surprised that a professional boatbuilder could build such a mast, starting from the raw materials, to a professional finish, with carbon gooseneck, sail track and feeder, halyard entry and exit, fully painted as agreed it must be, and ready to fit in the boat in 35 hours (the average working week in Europe) or as you put it " Someone who had just built a boat would do it in a week"

It takes me less than a minute to undo the turnbuckle on my forestay. I am very impressed to learn that you can step a 55ft mast by yourself in such a short time. Although I only have dial up internet access on the island where I live I can probably cope with downloading a 1 minute video, so, as I assume you have a youtube video to show how you do it, please give us the link.

As a small aside, I prefer to use a masthead tricolour light when sailing in congested waters or when cruising short handed. How do you do fit one on a rotating mast? To my mind this one fact alone is one of the major disadvantages of using a rotating mast on a cruising boat.

That's it for now. As I say I probably misunderstood your message. Maybe others can help clarify it for me. More to come when the boat is afloat again.

Richard Woods of Woods Designs

www.sailingcatamarans.com

RHough

07-17-2008, 02:08 PM

Wow. Rob may be evangelical about proas and unstayed masts, but why the animosity? There is no doubt that a big roach main/small jib combo on a flexible mast is an almost ideal rig. If only 80% of Rob's claims are true, it is still a good rig. On fast boats, the BAW is always forward of the beam so mainsheet tension would share the longitudinal load of a screacher or A-Sail. The only concern I would have is a slow boat trying to sail deep with extra downwind area. A centreline rig on a cat might be better than a proa if you intend to use flying sails, adding a traveler would allow the mainsheet to help control the rig on both gybes.
As far as cruisers and stayed rigs go, it is my experience that many cruisers do not perform what I consider minimum maintenance. They ignore tune, and hardly ever replace wire until something fails. An unstayed rig that needs none of the maintenance that cruisers don't do anyway is another point in favour.
The proa vs other multi debate is for another thread. As far as rigs go, no one here is making a very good case for tradition ... except as a mounting for a masthead tri-colour. :)

rob denney

07-17-2008, 10:46 PM

G'day,
Richard,
Sorry about the long posts, They seem necessary as you seem so determined to read what you what you want to hear, rather than what I write. You did misunderstand my message, but I think this is a philosophical problem, not a time one.

So you do not have to read so much I have condensed all my previous posts into a simple Q and A for you to answer:

1) Unstayed masts are near enough zero maintenance. Yes/No/can't see why they would be
2) Unstayed masts automatically depower in a gust. Yes/No/Can't see why they would
3) Unstayed masts are low cost. Yes/No/Never built one, can't comment
4) Unstayed masts are easily built. Yes/No/Never built one can't comment
5) Any boat designed for an unstayed mast will be lighter than a boat designed for a stayed mast. Yes/No/Have not added up all the components can't comment
6) Unstayed rigs are easier to sail to optimum performance than stayed ones. Yes/No/See the Woods Design Faq

Answer these and I will go into more detail on anything that is not a Yes. Or just wade through the rest of my posts, most of it is explained there.

To help you with 3) and 4) I suggested that you experience the building and sailing with an unstayed mast and then comment from a position of experience. I offered to supply anyone who wanted to try it the materials to build one and added a money back guarantee if I was wrong. If you just want to test the building, it will be even cheaper and quicker. I can supply enough materials for about 50 bucks.

I will correct your specific misunderstandings in my next post.

RHough,
Wow, indeed, but nothing compared to what we can expect from him in the future, if he continues like the other trolls. Answers to your specific points later as well.

regards,

Rob

Gary Baigent

07-18-2008, 01:07 AM

Hi Richard Wood
It was meant as a facetious joke about my becoming an "expert" at sailing in reverse - to spell it out to those who take things literally, getting caught in irons was/is poor sailing - and the joke was on me. However in getting out of the in irons situation, practice makes perfect and that is why I could reverse Sundreamer and stay in reverse. If you want to see the really skilled, check out the last AC starts where the boats come head to wind and then stay there for ages, even reversing as a duet - that is real skill.

Alan M.

07-18-2008, 03:01 AM

Just a quick question about the unstayed masts. What kind of bearings do you mount them in? I would have thought something pretty substantial would be needed. Do you have to try to keep water out of the bearings? How would you do this?

I'm kind of committed to a stayed rig now, but If I could build a carbon mast for a similar price to what I will be paying for an alloy one, ($2500 for 16m of 235 x 154 section) I'd be interested.

Bruce Woods

07-18-2008, 04:26 AM

They ignore tune, and hardly ever replace wire until something fails. An unstayed rig that needs none of the maintenance that cruisers don't do anyway is another point in favour.
:)

You are dead right. No I'm not arguing that eliminating the stays is a bad thing. That would be a great thing if all the other good aspects of a stayed rig were maintained. What we are saying is that Rob continually overstates his case, Ignores the negatives and attempts to sell , yes sell, his products on this forum. I can't speak for Robs "problems" ? on other forums, but it appears if one points out the downsides to his "products" one is labeled as a general sniper.

Getting back to the thread. The best rig for a small catamaran circumnavigateor is probably a stayed masthead sloop in my opinion..

Because...
1 low centre of effort
2 Ability to utilize readily available cheap second hand materials and sails
3 Proven technology.
4 easily handled (low aspect)
5 able to tune the rig to the conditions and boat load.
6 easily repairable
7 can fly extras

rob denney

07-18-2008, 10:51 AM

Rob, snip

But as a starter, and assuming I have this right. (I may not, as I write in haste, having got up this morning at 4am to move our boat onto the beach at high tide to scrub off. In half an hour I go back to antifoul it)

My 11.3m Gypsy mast as a bare tube weighs 45kgs, 100lbs. However my rig uses a 13sqm genoa and 25sqm mainsail to get the total area of 38sqm. If it were a una rig the mainsail will clearly have to be bigger, but the boom cannot be much longer. So all the extra area must come from increased mast length. Roughly 4m extra. Then, as it is unstayed, there must be some bury. Say 1.5m

Thus the total mast length for an unstayed una rig Gypsy is about 16.8m or 55ft. And that is adding no extra sail area to compensate for the lack of a screecher or spinnaker.

It seems to me that a unstayed 55ft mast, even in carbon, will weigh over 100lbs?? Especially as unstayed masts, by their very nature, have to be heavier than stayed ones.

Richard Woods of Woods Designs

www.sailingcatamarans.com

You assume wrong.
The bare tube is only part of the rig. Add in the spreaders, wires, turnbuckles, fittings, jib halyard and the furler to get a comparable weight. This will be about 50% of the bare tube. Then add in the chain plates, jib sheet winches and tracks, traveller, etc and the additional fastenings, bulkheads and beefing up they require and you have the added weight of the boat. I will understand if you don't have these numbers, a lot of traditional rig designers don't. But until you do have them, you cannot compare the two rig types.

I was using Gypsy for the numbers, not suggesting it for a una rig. The single sail mast would need to be further forward, the boom could be longer.

Comparing rigs is a little more complex than just equalising the sail area.
Your FAQ states that a stayed rig will be sailed at 70% vs 95% for a ballestron by Joe average. Given the nature of cruising sailors, I agree with these numbers. A single mainsail is even easier to set and forget than a ballestron, so it is closer to 100%, but let us stick with a 25% difference. Using this on your sail area results in a useful 28.5 sq m of sail area for at least some of the time.
The unstayed rig boat will be lighter. Therefore will not need so much sail.
The unstayed rig boat will spend less time reefed, especially in puffy conditions.
Adding additional length to an unstayed rig adds very little weight. Adding 10% more length adds maybe 2% to the weight. Another complex subject.
Spinnakers and extras need to be included in the equation.
A rotating mast is more efficient than a fixed one, and a rotating wing section is more efficient again. Unstayed rigs rotate.

As I said, it is far more complex than just comparing sail area, but 55' is way more than required for the same performance. The boat in the video sailing effortlessly at wind speed has a Bruce number of 1.27, comparable to your Miranda performance cruiser design less than fully loaded. Are there any videos of her in flat water under plain sail performing this well?

Building:
If you could read what I write, rather than rewriting it to try and trip me up, I would not have to write such long posts.

The mast would have a sail track, could add a mast head unit if you liked, internal halyards are another hand me down from racers, they have no place on cruisers, but could include them if you wanted. Goosenecks, vangs and mainsheet travellers are not required on sensible rigs. Paint and standard of finish would depend on how professional your builder actually was. Even with all your add ons, I reckon it could still be done in a week. It would not be ready to step as the bearings need to be added and this can take a while (depending on the section) as you spend a lot of time waiting for epoxy to cure. Until you have actually built one, you can't really compare it to anything.

Mast stepping:
Again you are focusing on the wrong part of the discussion. You wanted to know if it could be done quickly and simply. It can.

Tricolours:
At least this is a (marginally) better reason than the ability to back the jib on a mooring! It is possible to mount a rigid tube up the mast and mount the tricolour on that. Adds some complexity to the bottom bearing, but can be (and has been) done. I personally detest masthead tricolours, ever since one failed in a shipping lane on a foul night and no one noticed until we got a vhf call from a ship. I like anything that can break to be within reach. I guess this is not a big deal to someone with a rig held up with up to 100 individual items (list them before you start typing, please), all of which need maintaining, checking and replacing periodically, because the failure of any one of them causes the mast to fall down.

Hope this clears up your misunderstandings. Look forward to the actual rig weights and answers to my 6 questions.

Sharpii2
Carbon is easier to use than wood. The trick is to use a vacuum bag, which gives you pro quality with very little ability required. Start using tow and you will wonder how anyone builds boats without it.

Your tippy mono would benefit vastly from a carbon stick. It will weigh 60% of a carefully built wooden one. Let me know the dimensions and I will see what I can do, especially if you can wait until later in the year when I will be able to offer you a much better deal.

Fore and aft loads have to be got out to the hulls. But the problem is the reverse of getting the loads from the middle of a hull to the beams on a proa. Surprisingly little extra +/- 45 on either the beam or the hull to take the twisting loads is sufficient.

Unstayed masts on proas may be obvious to you (and me), but they were no more obvious to most people when I first used them than they are to the traditionalists on this thread.

RHough
80%? Look forward to taking you sailing if/when the 50 hits the water and demonstrating the other 20.

Spinnakers can be flown, but are a dangerous and expensive solution to the problem of having a rig where half the sails cannot be used on half the courses sailed. How much faster do cruising boats actually sail down wind with the spinnaker up than they do with a poled out jenny? Very little. If you can use the entire sail area (either all of a single main, or a main and poled out jenny) you save a huge amount of hassle, unless the main is restricted by swept back spreaders. These and spinnakers on cruisers are yet another manifestation of the "Race boats have one, so I need one", syndrome, which is basically what this thread is about. Broad reaching is where spinnakers and A sails can be handy, but that is at least partly because the headsail is blanketed by the main so is doing nothing.

Our booms are self vanging so no traveller, vang or huge main sheet loads are required. The masts are stiff enough to support a hounds height spinnaker. The mast will bend, but won't break. The chute will look ordinary on a strong air reach (not recommended), but be fine down wind and reaching in light air. If i was cruising, I would not bother. My serious race proas do not have spinnakers, or any special light air or off wind sails. Their weight makes them not worth the effort.

Alan M
We use UHMWPE, a modified nylon. Works on the 50 footers, not sure yet whether it will be man enough for the 60 and 66'ters. Need to know your mast wall thickness (or weight/m) to give you a ball park weight, and hence cost for the mast.

Bruce
see previous posts.

regards,

Rob

Richard Woods

07-18-2008, 02:16 PM

For the record. I have sailed over 2000 miles singlehanded in an unstayed balestrom (Aerorig) catamaran and sailed briefly on two others. I have also sailed a lot of single sail dinghies, some unstayed, some stayed, some with metal masts, some with wood, some with carbon. Including Optimist, Topper, Europe, Solo, numerous International Moths, OK, Comet, Byte, Blaze, Stealth, Laser, EPS, RS600. Agreed some only briefly, but some for several years and some successfully.

I have also sailed two proas, one briefly, one for a 3 month cruise, thus living on board. I have also "sailed" RC model yachts (mono and multi) fitted with balestrom rigs.

OK, dinghies aren't multihulls but some principles are the same. For example I know that the unstayed rigs are always heavier, even when the rigging is included. Clearly a balestrom is always heavier than a standard boom.

You are right, I don't have the Gypsy data with me, it is the UK and I am in Canada right now. So I could only give the accurate bare mast weight. However I do know that I struggled to lift the mast by myself (thus proving it weighed about 100lbs) but could easily carry all the rigging in one hand and the roller reefing gear in the other. So I agree with you. A standard Gypsy mast 11.3m long with stainless rigging and roller reefing gear will weigh in total about 150 lbs.

I would never build a carbon mast myself. I know I am not a good enough boatbuilder to even try. But I have drawn two boats for Aerorigs (to Carbospars specifications) and helped build one. I know there is a lot of weight added to the structure to take the loads from the rig. I also know first hand that fitting the bearings is not easy. They need very careful lining up, made trickier when there is no mast available. Certainly much more labour intensive than bolting on a mast step and chainplates.

I take my designing very seriously. I only want customers to spend their money, time on this earth and risk their lives on proven concepts. If I am not 100% certain about a design then I will usually build a prototype to test it myself before releasing the plans. So I will not draw a unarig boat with/without rigging unless I have real proof that it is a better solution.

I feel one can only sensibly do this by making real comparisons. There is no point in, for example, putting a unstayed mast on a Harry proa and saying it is better than a Gypsy. You don't know whether it is the rig that is better or the proa. That is why I suggested trialing a standard F27 against one fitted with one of your rigs.

Even though your posts are long they are still not always clear to me.

You say "The mast would have a sail track, could add a mast head unit if you liked .... Goosenecks.... are not required on sensible rigs.....Paint and standard of finish would depend on how professional your builder actually was...."

The only way I can see that you don't need a masthead sheave or gooseneck is if you have a sleeved sail (like a Laser) and a boomless rig. I am assuming that you aren't talking about a balestrom rig here as obviously if you are then you must include making and fitting the balestrom itself for it to be a fair comparison.

I was assuming that when you said a builder could make one of your masts in a week that it would be to the same finished standard as a metal mast. Again if not then you aren't making a fair comparison.

You say "Adding additional length to an unstayed rig adds very little weight. Adding 10% more length adds maybe 2% to the weight."

Now I would have expected a mast that was 10% longer to be at least 10% heavier, not 2% heavier. Can you see how I get confused by what you write???

To Bruce.

I agree. In my experience there is a drawback to everything. If someone is promoting a product without mentioning that disadvantage then they are "selling" it not "promoting" it.

To Gary

I agree one can sail backwards in multihulls (we ran a fun regatta once years ago when one leg had to be sailed backwards). But given the choice when sailing off the anchor in a crowded anchorage, 60ft water depth and two crew would you sail off under a partly rolled genoa or backwards under mainsail alone?

My boat is now cleaned and antifouled so I am off for a 2 week cruise/race.

Richard Woods of Woods Designs

www.sailingcatamarans.com

Alan M.

07-18-2008, 02:42 PM

Alan M
We use UHMWPE, a modified nylon. Works on the 50 footers, not sure yet whether it will be man enough for the 60 and 66'ters. Need to know your mast wall thickness (or weight/m) to give you a ball park weight, and hence cost for the mast.

regards,

Rob

The section is 8.2kg/m.

RHough

07-18-2008, 03:19 PM

Here is an interesting bit about a uni-rig:

Is the ballestron rig a solution? Yes, but it, too, has weaknesses. For one, it is way heavier than a stayed solution. Weight aloft is critical in a multi. At the least, it aggravates pitching, a major challenge to all multis, especially proas, and a factor that easily can contribute significantly to dangers such as pitchpoling. The ballestron's geometric limitations and large-diameter mast also limit sail efficiency. Brown's rig offers great versatility. One can easily drop the rig for inspection or maintenance without outside assistance. The rotating mast is efficient yet remains light. Sailors can set different headsails to best suit light airs and offwind efficiency. During days of extreme light air in the doldrums, under a beautiful asymmetrical chute, Jzerro averaged wind speed on course, though we actually tacked through large angles downwind. The ballestron rig just doesn't compare, and I know of zero race results on any type of craft that indicate otherwise, including on such boats as Elf Aquitaine during the 1984 singlehanded transatlantic in which such hopes for even a wing-masted carbon version were trounced by reality.

The idea that a Balestron or Uni-Rig can be lighter than a conventional rig is novel. In a conventional rig, the hull has to take the longitudinal rig loads (forestay tension vs backstay (or main sheet)), on a Balestron rig, the boom must take these loads. Weight in the hull is traded for weight in the boom, this has to raise the CG.

Another design challenge is the trade-off between mast cross-section, weight, and windage. To be light, the section must be large (unless the laws of physics have been changed), large sections are performance problems WRT mast/sail interaction. Shaping the section as a wing mast raises other challenges. On a Balestron Rig, unless the wing section can rotate above the boom the performance will suffer. That leaves us with an easy to build, rather large mast with rotten aero's or a more complex challenge of getting a wing section mast to rotate above the Balestron 'boom'.

When compared to a conventional sloop rig, how does one get the 5-10 deg difference in AoA between the Jib and Main on a Balestron? The Jib must 'tack' and sheet to leeward of the mast for the rig to be effecient. This would seem to require jib sheeting points somewhere on the boom? Not a point, but an adjustable track of some sort. There is still a requirement to be able to control headsail shape if performance is to equal a conventional sloop.

I'll return to my orginal thought; a conventional fractional rigged sloop with a rotating mast for my boat. ;)

Richard Woods

07-18-2008, 06:44 PM

Don't know where you got the quote, but I saw Jzerro and Russell last week. He was heading south from Lasqueti, we were going north and passed close by each other, both motoring. Stopped for a chat, a lovely, beautifully built boat. You'd never know it had crossed the Pacific twice. But I wouldn't sail it offshore.

The Jim Brown sons are both highly talented builders/designers. Clearly being brought up on a trimaran works wonders!

Just curious, where/what do you sail? I am on Saturna right now. Glorious sunshine and a good sailing breeze. That is why this will be my last message for a week.

Richard Woods of Woods Designs

www.sailingcatamarans.com

Gary Baigent

07-18-2008, 07:43 PM

I wouldn't be in such a hurry to denounce Elf Aquitaine's 1984 baelstron wing mast rig - the boat came in second across the line in '84 OSTAR - and that is no mean achievement in my opinion, mate. Umupro Jardin won that year but Fleury Michon took line honours and Fauconnier on Umupro was recompensed time after he had stopped to help Jeantot when he capsized the drastically shortened to 60 foot Credit Agricole - anyway that is bye the bye, doesn't alter the fact that Elf Aquitaine performed exceptionally well. Pajot did say however that after sleeping he sometimes awoke to find the boat caught aback and reversing - and at the finish he only lost out taking line honours by 23 MINUTES!!
Later when Gilles Ollier redesigned the boat with new, longer 75 foot hulls and even taller balestron wing mast rig, the cat (renamed, Saab-Turbo) set a new Mediterranean crossing record broad reaching for long periods at 30 knots speed in very savage winds. An advantage of the baelstron is that the headsails and reaching spinnakers could be set off the baelstron bow (naturally) which rides higher off the waves than a conventional forward cross beam arrangement (this cat was one, if not the first, to have an X central beam design, no fore beam) and therefore did not bury in the large waves set up by the gusting 60 knot winds. This is an important safety feature and a large plus for the baelstron setup. Food for thought, mateys.

RHough

07-18-2008, 08:36 PM

At the risk of being labeled a old fuddy-duddy ...

Even among the wacky-racer crowd of high performance multi-hulls, the Balestron Rig is not a popular choice. Why?

For a rig that showed as much promise in 1984 as is suggested here, why don't we see further development? What happened to AeroRig(tm)?

The loads for a given area and wind speed are the same. Given good design, the same weight in material should be required to handle those loads. Much of the load must be contained in the Balestron Rig's structure, so the CG *must* be higher as well as pitching moment.

Even in an unlimited budget arena like the AC, we don't see either unstayed rigs or Balestron Rigs. Why is that? If the claim that an unstayed rig is lighter is true, that means more weight in the keel on an AC boat. Only if the sailing performance of the rig was poor would a designer give up the extra RM a lighter rig would give.

Now, in the context of this tread, for cruising, the rig may have some benefits for no maintenance, poorly trimed boats. Once the Balestron Rig is poorly trimed, it doesn't get any worse. This equates to better cruising performance than a once set then ignored conventional rig. ;)

Gary Baigent

07-19-2008, 01:58 AM

RHough

07-19-2008, 06:55 PM

Quite right RHough, we don't see many balestron rigs about - but that doesn't mean it is a poor rig concept. You know, as everyone else does, that mainstream yachting is ultra conservative, even timorous - and only grudgingly changes to new developments after, say, an average of two decades have passed before being slowly accepted. Look at foilers: superb examples appeared in that (golden?) decade of the 1980's, set records, won races and then they disappeared - to now become (grudgingly) with the popularity (in a few circles) of the foiling Moths; so foilers are reappearing. There is also that extreme beast l'Hydroptere that definitely gets even the most bigoted monohuller's attention. So foilers are on the way back - and no one will be surprised if some innovative, peer leading individual appears with an outstanding yacht and a balestron rig. Then balestron rigs will be fashionable, flavour of the month - and all the minions will be scurrying to catch up.

:)

Not quite sure if I want to yank the chain a bit more or not ...

The reason that I said "Even among the wacky-racer crowd of high performance multi-hulls, the Balestron Rig is not a popular choice." is to preempt the "You know, as everyone else does, that mainstream yachting is ultra conservative, even timorous - and only grudgingly changes to new developments ... " response that I was sure someone would use. Everyone that thinks they have built a better mousetrap uses some version of that to explain why they have vision and the rest of the world wears bifocals. ;)

The entire mutlihull segment of sailing can use that argument with facts to back it up. Of all sailors, multihullers seem to be the least moribund, new, non-mainstream ideas tend to flourish in multihulls compared to the greater monohull sailing community. Your argument would have more weight if l'Hydroptere didn't have a relatively conventional (by large multihull standards) rig.

I did not say or mean to imply that the Balestron Rig a poor concept. Like any rig it has good and bad qualities. The fit between the rig's character and the boat's usage (and budget) are what determine the goodness or badness of the rig. I do intend to point out that some of the claims do not seem to follow the laws of physics that I am familiar with. Lower total weight and lower cost are two.

I am somewhat familiar with the treatment that cruising rigs get in the real world. Things like UHMW bearings inside a hole in the deck of a cruiser's sailboat sound like a horror story waiting to be written. I could be wrong, but from what I've seen in the field those bearings will see zero maintenance and be expected to perform as new during the 3 days each year that the boat actually gets used ... after about year 5 the second owner won't even be aware of any maintenance requirement ... at year 10 the third owner will be trying to use scrap plastic from a dusty corner of the local sailor's exchange to make replacement inserts, get the fit wrong, and point load the spar to failure along the stress riser caused by years of grit never being flushed out of the original system.

If that sequence of events does not ring true for you, you deal with a different bunch of cruisers than I do. ;)

Foilers are not and will never be a popular solution for Joe Average sailor. JA does not keep his boat clean enough to allow the foils he has (keel and rudder) to work properly.

I expect the marinas to be full of Balestron Rigged, CBTF, foiling cruisers on my way back from the third coming of Christ. I do expect them to be full of lower maintenance, more bang for the buck boats. I expect more cruising multi's, maybe not for the reasons I would choose, but more of them. The small catamaran circumnavigator is a type that has more potential than most. Once the mass producers of sailboats figure out a way to build and sell small 30-40 cruising cats to the folk that now buy 30-40 cruising mono's (Benetaeu, Catalina, Hunter, Etc.) they will take off like nothing we have seen before. The hint is to watch mother at the boat show. Compare her expression when looking at the accommodation of a 40 ft mono compared to a 40 ft Multi. ;) She sees a kitchen (not a galley) and bedrooms (not oddly shaped closets with "Guest Cabin" on the door), she steps on the edge of the boat (what the hell is a gunwale?) and it does not tip alarmingly, she has seen father watching the AC boats tilted at 30deg in a light breeze and hears evey word when the factory rep talks about sailing all day and not spilling your wine. This is where a Balestron Rig might seal the deal ... simple, no deck clutter, none of those wires with funny names ...

For those of us that *like* trimming sails an inch or two every 30 seconds, the Balestron Rig is not so attractive. ;)

bill broome

07-20-2008, 01:00 AM

.... with a few full length battens, and a sprit boom.

wood's discusses this stuff on his site, and very well. i still back a gaff for a small passagemaker, because you can use a round tube and save a lot of money. a small jib on a club may not be very efficient, but it takes care of itself, and every once in awhile you're going to be busy enough elsewhere.

Gary Baigent

07-20-2008, 02:35 AM

hey, nice commentary RHough - agreed, I strayed off topic bringing in racing developments.

RHough

07-20-2008, 11:16 AM

hey, nice commentary RHough - agreed, I strayed off topic bringing in racing developments.

I'd like to replace my aging leadmine with a cruising multi ... but mama has to like it. We are chartering a 4 stateroom cat in OZ this October. If my child bride likes sailing on a cruising multi, the chances of having one on my dock go up exponentially! I think sailing without worrying about spilling her wine might be a deal maker ... :)

If she *really* likes it, I'll show her a Gunboat ... :D

rob denney

07-27-2008, 09:35 AM

G'day,

Richard,

All the sailing experience in the world is not much use if you do not apply it to making better rigs and boats. Basing your dislike of carbon masts on your Carbospars experience was fine 5 years ago, but as far as I can tell, it is out of date now as there has been a lot of development since then. Carbospars overbuilt (and overcharged for) unstayed masts and boats, as an independant engineer would have confirmed. Overbuilding is not necessary, as indicated by the numbers I quoted for the mast in the video and the mast on the open deck 11m cat.

From your post:
You overlook that carbon is stiffer and stronger for a given weight than aluminium and stainless steel and can be tapered in section and laminate, unlike alloy cruising masts. A carbon mast (stayed or unstayed) is 40-60% the weight of an alloy one, if the loads are the same.

You are wrong about goosenecks, they are not required on a sensible rig with a boom. Nor does such a rig require a sleeve luff.
A mast head unit for an unstayed mast is a couple of hours work. Whether you include it in the week or not is no big deal.

I was not comparing the proa performace to Gypsy, but to your highest "performance" cruiser. Yet again in this thread, you ignore the question and/or try to introduce a red herring.

A tri is less like a cat than a harryproa is, so why would you give any credence to tests I did on an F27?

The top of the comparison mast is 40mm diameter and 2mm wall. The bottom is 150mm x 20mm wall (how does this compare with the bare tube dimensions on Gypsy?). The diameter and wall at the bottom are based on the righting moment, so they do not change for a longer or shorter mast. Making it longer is more complex than just extending the top, but it adds far less weight than the linear increase you suggest. This is pretty basic engineering.

The bearings are very simple to make, and to align. It can be made into a long and difficult job if you have a mug client paying you by the hour, but it does not need to be.

The essence of my posts on this thread is how easy it is to sail and build an unstayed carbon mast. Yet, knowing nothing about what is involved in the building, you say you can't do it. A surprising attitude for an experience based designer. For the record, it is far easier than building a sheet ply boat.

Your attitude to your clients is noble (and normal for boat designers), but if I am even partly correct, you are exposing them to more likely harm and expense with a traditional rig than with an ustayed one. Surely it is worth more than a blanket denial, especially one based on such flimsy reasons?

So far you have said unstayed masts are prone to lightning strikes (supported by 2 unreferenced, so presumably incorrect, claims),
dislike for sailing backwards off moorings,
a desire to use a tricolour,
lack of confidence to build even a sample piece to try it
and quibbles about the finish after a week's work and whether it would have a halyard fitting.

In the overall scheme of rig selection for cruising boats for round the world voyages (or any other use), these seem to be pretty pathetic excuses for ignoring all the benefits.

It is also noticable that you have not addressed most of the benefits that I have mentioned, such as the lack of deck gear, automatic depowering, lack of maintenance, cost (how much does a Gypsy rig, ready to fit, cost?), low load sheet, ease of reefing, hoisting and lowering the main.

Alan M,
Sorry for the delay, I have been in Singapore talking to a venture capitalist about carbon mast manufacturing in China. Richard may not see the potential of lightweight masts, but he is one of a very few.

You can work on a carbon mast tube being about 60% the weight of your alloy one. So alloy =16x 8.2 = 130 kgs. 60% is 80 kgs x $12 = $1,000. This is just the materials, you still need the consumables and the space.
If you have it engineered ($1,000), the weight will probably drop to 40-50%.
Plans for amateur builders are $1,000, which includes making virtually all the fittings from composites. The weight and cost savings from this are also appreciable.

Or, you can wait until the end of the year, at which time, all going well, we will be producing carbon masts (stayed and unstayed) in China at lower prices than your aluminium extrusion.

R Hough,
Your quote is by Steve Callahan (journalist, survivor, designer, editor of Cruising World), one of the people I was referring to in my earlier post. He knows about as much about what what is happening with low cost carbon and rigs as Richard does; ie not much.

You need to be clearer about what you are comparing. A carbon ballestron "mast" is cheaper and lighter than an alloy/ss stayed "mast" with it's rigging. 60 kgs/132lbs for the12m/40' Aroha harryproa vs 67 kgs/150 lbs for the 8m/27' Gypsy cat.

A ballestron "rig" is probably heavier than an alloy "rig", including the stays, boom, furler, and other bits attached to the mast.

The ballestron rigged "boat " is lighter than a stayed alloy/ss rigged "boat" (including all the extra gear and beefing up required to support and sail the rig) as far as I can tell. Most designers are like Richard, they do not want to talk about how much weight and cost actually goes into their boats to support the rigs.

The weight/windage tradeoff is indeed a compromise that has to be made, but as you can see from the video, not as big a problem as it is made out to be. The windage of shrouds, forebeams and strikers on traditional rigs is not to be sneezed at either. An unstayed wing section is the best solution and they also require some compromises. These are mostly eliminated if the mast can telescope, but that is another story.

Making the boom and mast rotate independantly of each other is no big deal, if you get away from racing boat nonsense such as vangs, goosenecks, travellers and highly loaded mainsheets.

The jib track is the same as a self tacker, mounted on the beam just ahead of the mast. See the pictures on http://www.harryproa.com/Builders/BainRobertson/Bain_4.htm

I agree with your description of (some) cruising sailors, but not your comments on UHMPWE for bearings. Unstayed mast bearings are high load, large diameter, low speed and protected from the elements so they do not see excess wear or contamination. If they do, it will be pretty obvious and easy enough to fix. UMPWE is an amazingly tough and tolerant material, both to point loads and foreign matter. A point load from a worn bearing will not break the mast, just make it a loose fit. This will show as a problem motoring in a seaway when the mast will shake back and forth a little. There will still be a lot of wear before the bearing disappears. Compare this to "a little bit of wear" on any of the bits holding up a stayed mast.

Which part of my cost and weight comparison do you disagree with? And why?

When you show your wife the million dollar plus Gunboat, make sure you do lots of reefing, tacking and gybing, especially in a breeze. Then show her a $400,000 harryproa (same build quality, more room, similar power to weight, much easier to sail) and let her decide which is less likely to spill the drinks. My wife has always called the harry windward hull the chardonnay hull. She cannot understand why all sail boats don't have one.

regards,

Rob.

Boston

07-27-2008, 11:17 AM

Ive got this old book
high speed sailing
its got a pyramid rig design in there that you might look into
its pretty slick looking and its on a rotating mast

oh
and take all with a grain of salt as Ive been out of the field
or water as the case may be for quite some time
although
I have started a redesign project of my own
so hopefully
Ill be seein my share of
a fair wind
and a followin sea

Richard Woods

07-27-2008, 04:29 PM

Rob, please don't be too personal. I'm not the only one designing boats with a single aluminium mast. But I am one of the few who have sailed on a balestron rigged catamaran.

So I have some experience with them, unlike most. For example I agree with Mark Pajot's findings as reported by Gary Baigent '' Pajot did say however that after sleeping he sometimes awoke to find the boat caught aback and reversing".

That happened to me as well, something that never has with a conventional rig. Although I may not be as experienced a catamaran sailor as I would like to be, Mark Pajot did win an Olympic gold medal before sailing offshore so I guess he at least knows how to sail.

After 40 years of boatbuilding I think I know my capabilities better than you do, even though you have seen one of my own home built boats, and may even have been on board (I can't remember as it was over 25 years ago that we met)

Richard Woods of Woods Designs

www.sailingcatamarans.com

Bruce Woods

07-28-2008, 07:44 AM

G'day,

It is also noticable that you have not addressed most of the benefits that I have mentioned, such as the lack of deck gear, automatic depowering, lack of maintenance, cost (how much does a Gypsy rig, ready to fit, cost?), low load sheet, ease of reefing, hoisting and lowering the main.

Rob.

Good one Rob.

So we are still just addressing the benefits and ignoring the down sides. You don't seem to be listening .
So what about reefing? what standing on top of the balestrom boom stuck in a leeward wave piercing hull of a lopsided catamaran , 3 meters in the air , sorting out a reef is safer. WTF are you thinking rob.

So the Coffs harbour elementary mast broke on the beach, Rare Birds mast is too soft (re your own comments) Blind date is overweight so one must assume their rig stiffness is not matched correctly to the boats righting moment, and your now advocating telescoping unstayed masts are a good thing when you haven't actually tested one yet in the real world.

Mmmmmmm.....

rob denney

07-28-2008, 12:19 PM

G'day,
Richard,
Most of your posts on this thread have been "personal". Your day to day existence and your experience, with little or nothing about the merits and drawbacks of unstayed rigs. All I want to do is discuss the rig options.

We all know you have sailed unstayed rigs and you think they are 25% better than stayed ones for Joe Average, as per your FAQs. Getting you to discuss them, rather than just dismissing them out of hand is like getting blood from a stone. When you do deign to toss off a criticism, it is to point out the most inane problems conceivable, which leaves me wondering why you don't like them?

Waking up in reverse is right up there with shards of carbon piercing the deck after a lightning strike. How can it happen unless the main was reefed and the jib wasn't or there was a massive windshift, which would have been much more disastrous with a conventional overlapping headsail? Or in Pajot's case, maybe the rig hit the shrouds? Could you explain the circumstances, please.

If you did somehow manage it, or any other problem arose , you simply release the lightly loaded main sheet and the rig weathercocks and the boat stops, whatever the wind direction or strength. Pull in a couple of feet of lightly loaded sheet and the boat will start sailing again. None of the flogging sails, huge loads or extensive winching associated with a genoa (or spinnaker) which has been caught aback.

You know your capabilities better than I do, but I know how simple it is to build a carbon mast (or beam, boom or rudder stock). I can assure you that if you can use a jigsaw, a string line, epoxy resin and a vacuum pump, you will have no difficulties. You are refusing to try something you know nothing about.

You are indeed one of many designers using stayed alloy rigs, but as far as I know you are the only one who is advocating alloy masts over lower cost, lower weight carbon ones.

Fun times 25 years ago. I had just designed and built (with help from Ian Howlett, designer of the Aerorig and Ian Armstrong, one of the founders of Carbospars) a balls to the wall, ultra cheap, stayed alloy masted, sloop rigged racing cat which I capsized while leading our class in the 2 handed Round Britain race. From memory you were cruising in the same very well built type of boat and rig you are cruising in now.

Bruce,
Did not take you long to revert to type.

I think even Richard agrees that reefing is one of the major advantages of an unstayed rig. It could hardly be simpler. The first reef is automatic as the mast bends and depowers. This is particularly handy in squally weather. To put in the second reef, you ease the single sheet, the rig weathercocks and the boat stops. You then drop the headsail on the ballestron, or tuck in a reef on the una rig. The third reef, you dump the sheet, the rig weathercocks, the boat stops and you lower half or more of the main. Turn and drift downwind with the waves if the motion is uncomfortable.

All are far easier and safer than reefing a stayed rig. Unless it is raining, you don't get wet. You don't have to go on the foredeck, generally don' t even need to clip on, although I would recommend you do. Compare this with the plunging foredeck on a semi depowered boat being thrown all over the ocean, jammed furlers, poorly setting headsails, main plastered against the shrouds typical of high wind reefing on stayed rigs.

This is not about harryproas, but since you mention them, Rare Bird (the boat in the video) is heavier than the rig was designed for. Still does windspeed under plain sail in flat seas, and I have not seen any videos, or even anecdotal evidence of any cruising boat with the same accommodation and cost which does the same, with as little fuss. If it was a stayed rig designed to the same spec, it would have broken by now.

I broke both masts in the workshop on my Elementarry 4 years ago, and rebroke one of them on the beach a year later testing a new sail shape with huge downhaul pressure. The boat is the test bed on which I try new ideas before including them in my plans. I expect things to break on this boat. If they don't they are not being tested thoroughly enough. I repaired the masts and they have performed well since.

Blind Date weighs two and a bit tons in cruising trim. Spot on it's designed weight. Not bad for a first of it's type cedar strip 15m/50'ter. This boat is regularly used for it's intended purpose of taking sight impaired people sailing so they can feel the thrill of sailing fast and safely.

I look at things (multihull design, rig cost, rig efficiency and boat building techniques to name a few) and see they can be improved (harryproas, low cost carbon masts, telescoping masts and frameless flat panel building). I then spend my time and money trying to do so. Some work, so I sell them to people who agree that the current state of affairs can be improved upon. Others join the pile of failures in my garage and back yard. What is your problem with this?

If you want to start a discussion on harryproas, telescoping rig potential, why you dislike me or a history of my testing failures (see www.harryproa.com for pictures and details of other breakages), start some new threads.

I am happy to discuss the disadvantages of unstayed rigs, but it is getting boring waiting for you to start pointing them out. Also still waiting for you to discuss their advantages, or even acknowledge that they exist.

regards,

rob

Gary Baigent

07-28-2008, 08:11 PM

Hey, Marc Pajot was singlehanding a lightweight, avant garde 60 foot cat and he awoke to find there had been a wind change or the boat had luffed in waves and stopped and Elf Aquitaine then reversed while he was sleeping. You mean that has never happened to you while sailing a lightweight multihull? Singlehanded?? And this one with a 1.5 metre wing mast chord. Large wing masts sail backwards at high speed. My point was that although Pajot found himself in this position once, maybe twice, he lost the race by only 23 minutes - it was not a criticism of balestron rigs and certainly not of Pajot's skill. Any lightweight with any type of rig could have done the same. Critics write off Elf Aquitaine 11 and its rig as a failure because it did not win the '84 OSTAR - get real you jokers.

Freenacin

07-28-2008, 11:44 PM

G'day,
This is not about harryproas, but since you mention them, Rare Bird (the boat in the video) is heavier than the rig was designed for. Still does windspeed under plain sail in flat seas, and I have not seen any videos, or even anecdotal evidence of any cruising boat with the same accommodation and cost which does the same, with as little fuss.

Here's one, a 44 year old, 33 foot boat, built of ply I think, doing 100% windspeed in 10 knots.

http://www.youtube.com/watch?v=k3D1PTqLdPw

rob denney

07-29-2008, 12:00 AM

Here's one, a 44 year old, 33 foot boat, built of ply I think, doing 100% windspeed in 10 knots.

http://www.youtube.com/watch?v=k3D1PTqLdPw

G'day,

So it is. Thanks. makes you wonder what has been happening to "performance" multihull design for the last 44 years, doesn't it.

Alan M,
I mixed up my kgs and pounds in your materials quote. As per the original, it is $12/lb, which is $26.4 per kg. Sorry.

regards,

Rob

Alan M.

07-29-2008, 06:00 PM

Thanks for the info Rob. Looks like the materials alone would cost about as much as the alloy section delivered to my door. Then I'd still have to build the mast.

rob denney

07-29-2008, 09:58 PM

Thanks for the info Rob. Looks like the materials alone would cost about as much as the alloy section delivered to my door. Then I'd still have to build the mast.

G'day,

Sure would. Need to decide whether it is worth it for the 40% (probably 60% if it was engineered) weight saving and the cost saving of not having to buy any of the fittings on the mast, nor worry about them falling off.

regards,

Rob

RHough

07-30-2008, 12:15 AM

G'day,

R Hough,
Your quote is by Steve Callahan (journalist, survivor, designer, editor of Cruising World), one of the people I was referring to in my earlier post. He knows about as much about what what is happening with low cost carbon and rigs as Richard does; ie not much.

You need to be clearer about what you are comparing. A carbon ballestron "mast" is cheaper and lighter than an alloy/ss stayed "mast" with it's rigging. 60 kgs/132lbs for the12m/40' Aroha harryproa vs 67 kgs/150 lbs for the 8m/27' Gypsy cat.

A ballestron "rig" is probably heavier than an alloy "rig", including the stays, boom, furler, and other bits attached to the mast.

The ballestron rigged "boat " is lighter than a stayed alloy/ss rigged "boat" (including all the extra gear and beefing up required to support and sail the rig) as far as I can tell. Most designers are like Richard, they do not want to talk about how much weight and cost actually goes into their boats to support the rigs.

The weight/windage tradeoff is indeed a compromise that has to be made, but as you can see from the video, not as big a problem as it is made out to be. The windage of shrouds, forebeams and strikers on traditional rigs is not to be sneezed at either. An unstayed wing section is the best solution and they also require some compromises. These are mostly eliminated if the mast can telescope, but that is another story.

Making the boom and mast rotate independantly of each other is no big deal, if you get away from racing boat nonsense such as vangs, goosenecks, travellers and highly loaded mainsheets.

The jib track is the same as a self tacker, mounted on the beam just ahead of the mast. See the pictures on http://www.harryproa.com/Builders/BainRobertson/Bain_4.htm

I agree with your description of (some) cruising sailors, but not your comments on UHMPWE for bearings. Unstayed mast bearings are high load, large diameter, low speed and protected from the elements so they do not see excess wear or contamination. If they do, it will be pretty obvious and easy enough to fix. UMPWE is an amazingly tough and tolerant material, both to point loads and foreign matter. A point load from a worn bearing will not break the mast, just make it a loose fit. This will show as a problem motoring in a seaway when the mast will shake back and forth a little. There will still be a lot of wear before the bearing disappears. Compare this to "a little bit of wear" on any of the bits holding up a stayed mast.

Which part of my cost and weight comparison do you disagree with? And why?

When you show your wife the million dollar plus Gunboat, make sure you do lots of reefing, tacking and gybing, especially in a breeze. Then show her a $400,000 harryproa (same build quality, more room, similar power to weight, much easier to sail) and let her decide which is less likely to spill the drinks. My wife has always called the harry windward hull the chardonnay hull. She cannot understand why all sail boats don't have one.

regards,

Rob.

Now that you have stated that a Ballestron Rig (complete and ready to step) is probably heavier than a conventional rig (also complete and ready to step) I don't disagree with the weight comparison so much. To compare the carbon Ballestron Rig to an untapered alloy spar and rig is hardly fair. The fair comparison is between a tapered carbon mast and carbon boom as part of a stayed rig and the Ballestron. The Ballestron rig will be *much* heavier than its stayed carbon counterpart.

I also question your conclusion that the rig loads add that much weight to a conventional design. There is a finite amount of material needed to handle the loads. How does moving it from the boat's structure to the Ballestron boom result in an overall weight savings? I may not understand how you are getting to your conclusion.

Sailing loads are another concern. How does a Ballestron rig maintain forestay tension? If a permanent backstay is used, you lose the performance of a large roached fully battened main. If you have no permanent backstay, the leach load on the main and the longitudinal stiffness of the mast must counter forestay tension. If leach loading is used in to keep the forstay tension, you have to keep the leach tight in heavy air. On a stayed rig with swept spreaders of aft leading cap shrouds the shrouds keep the forestay tight and the jib flat while the mainsheet is eased to allow the roach to twist of and depower the rig. I don't see how the Ballestron handles this very well unless the mast below the hounds is *very* stiff (and heavy).

Not having seen the detail of how you are using UHMW for the bearing, they may not be the problem I foresee. I has been by experience that keeping bearing clean and running free on boats is an engineering challenge. If you have come up with a no maintenance solution, that is a feather in your cap. If it can be duplicated by an amateur builder, even better.

As far as reefing and tacking etc. I'm blessed, my last mate is sailor. She can hand, reef and steer. Being able to do it while not standing on a 20-30 deg deck would be heaven. If my sailing partner had fewer boat handling skills, I would see more value in rigs designed with easy sail handling over performance.

The "self reefing" feature of a bendy, tapered, carbon spar would not be lost if the rig was stayed. It is the mast tip above the hounds that needs to have good gust response. If you have figured out how to have the entire mast bend and depower without losing forestay tension and powering up the jib you have my attention.

IMO a good cruising rig can lose any one stay and still stand. The mainsheet serves to back up the backstay, the jib halyard backs up the forestay. If the mast section is a proper choice for cruising, any one stay can fail and the mast should stand, granted the remaining wire(s) may get stressed mast their elastic limit and require replacement after the event, but the mast should be fine.

Although there are many potential points of failure in a conventional rig, the little bits are easy to inspect and easy to replace (if I build the mast). I can see the signs of impending failure. I cannot see the beginning of a delam problem in a composite spar.

I can see that the Ballestron Rig and a PROA are a good match. In the Harryproa (as I understand it) the longer, leeward hull is the 'light' hull and the windward hull is the heavy hull. There is little need for the leeward hull to be strong enough to support the crew walking around on it. There is also no convenient place for a conventional rig's stays. When you add the requirement that the rig sail both ways, the Ballestron becomes a near perfect answer.

On a cruising catamaran, none of the PROA's rig limitations exist, some of the problems a Ballestron Rig solves for a PROA just don't apply to a cruising cat. I'll take the tapered carbon spar, a stayed rig with mast rotation, a big roach main and a long traveler. ;)

rob denney

07-30-2008, 08:54 AM

Now that you have stated that a Ballestron Rig (complete and ready to step) is probably heavier than a conventional rig (also complete and ready to step) I don't disagree with the weight comparison so much. To compare the carbon Ballestron Rig to an untapered alloy spar and rig is hardly fair. The fair comparison is between a tapered carbon mast and carbon boom as part of a stayed rig and the Ballestron. The Ballestron rig will be *much* heavier than its stayed carbon counterpart.

Rob
The rig will be, the boat won't be.

RH I also question your conclusion that the rig loads add that much weight to a conventional design. There is a finite amount of material needed to handle the loads. How does moving it from the boat's structure to the Ballestron boom result in an overall weight savings? I may not understand how you are getting to your conclusion.

Rob Concentrates the loads, the same as the unstayed mast does. To support a forestay, the entire boat needs to be beefed up. It also needs high bows to keep the (heavy) forebeam out of the water. It is a difficult discussion as no one will supply the numbers and there are few, if any cats designed specifically for unstayed rigs, so we only have anecdotal evidence. For instance. The 15m proa weighs 2 tonnes and has similar righting moment and accommodation to Richard's 12m performance cruiser. The proa could sail on both tacks with no structural changes. So the boats are "roughly" equivalent. The 14m cat weighs 3.5 tons. We would need to get the surface area from Richard to compare them exactly, but I bet the cat does not have the 75% of extra area that the weights imply. If you can get accurate weight and surface area numbers for any performance cat round this size we can make a better comparison.

RH Sailing loads are another concern. How does a Ballestron rig maintain forestay tension? If a permanent backstay is used, you lose the performance of a large roached fully battened main. If you have no permanent backstay, the leach load on the main and the longitudinal stiffness of the mast must counter forestay tension. If leach loading is used in to keep the forstay tension, you have to keep the leach tight in heavy air. On a stayed rig with swept spreaders of aft leading cap shrouds the shrouds keep the forestay tight and the jib flat while the mainsheet is eased to allow the roach to twist of and depower the rig. I don't see how the Ballestron handles this very well unless the mast below the hounds is *very* stiff (and heavy).

Rob All correct, (unless the mast is rotating, when mainsheet tension provides the forestay tension), which is why it is not a good full crew racing rig. It is also not the rig that I suggested for the subject of this thread. Nor is it the rig I put on my boats if performance is the requirement. If the last couple of per cent of performance is your goal think how the boat in the video would go with a 3m higher wing mast and no jib.

RH Not having seen the detail of how you are using UHMW for the bearing, they may not be the problem I foresee. I has been by experience that keeping bearing clean and running free on boats is an engineering challenge. If you have come up with a no maintenance solution, that is a feather in your cap. If it can be duplicated by an amateur builder, even better.

Rob The protection is a simple boot around the mast and a raised lip around the bearing. It's primary purpose is to stop water getting into the hull, which it does well, so presumably no contamination is getting in there either..

RH As far as reefing and tacking etc. I'm blessed, my last mate is sailor. She can hand, reef and steer. Being able to do it while not standing on a 20-30 deg deck would be heaven. If my sailing partner had fewer boat handling skills, I would see more value in rigs designed with easy sail handling over performance.

Rob Remind her of that when the rain and squall comes through at 2 am, the furler line has jumped the drum and there is land to leeward, just after she has got into her pj's after a long watch.

RH The "self reefing" feature of a bendy, tapered, carbon spar would not be lost if the rig was stayed. It is the mast tip above the hounds that needs to have good gust response. If you have figured out how to have the entire mast bend and depower without losing forestay tension and powering up the jib you have my attention.

Rob Would not be lost, but is not very good either. Without a jib, the entire rig depowers, not just the top 10%.

RH IMO a good cruising rig can lose any one stay and still stand. The mainsheet serves to back up the backstay, the jib halyard backs up the forestay. If the mast section is a proper choice for cruising, any one stay can fail and the mast should stand, granted the remaining wire(s) may get stressed mast their elastic limit and require replacement after the event, but the mast should be fine.

Rob My opinion about the rigging as well. Not shared by 95% of multihull designers, unfortunately. If the mainsheet has any load on it, the backstay will not break. However, if you have just eased the mainsheet, or done a crash jibe, the mast will go over the front. If the forestay breaks, the jib halyard is unlikely to survive, unless it is stronger than the forestay. You then have the joyous task of going up the mast to install another stay.

RH Although there are many potential points of failure in a conventional rig, the little bits are easy to inspect and easy to replace (if I build the mast). I can see the signs of impending failure. I cannot see the beginning of a delam problem in a composite spar.

Rob That is because, unless you bang it into a bridge, there will not be any, same as there will not be any hull, rudder shaft or daggerboard delam issues unless you bump into something. Think about this next time you are up the mast checking all the little bits.

RH I can see that the Ballestron Rig and a PROA are a good match. In the Harryproa (as I understand it) the longer, leeward hull is the 'light' hull and the windward hull is the heavy hull. There is little need for the leeward hull to be strong enough to support the crew walking around on it. There is also no convenient place for a conventional rig's stays. When you add the requirement that the rig sail both ways, the Ballestron becomes a near perfect answer.

Rob Near perfect, but tossing the jib and the foreboom makes it even more so.

RH On a cruising catamaran, none of the PROA's rig limitations exist, some of the problems a Ballestron Rig solves for a PROA just don't apply to a cruising cat. I'll take the tapered carbon spar, a stayed rig with mast rotation, a big roach main and a long traveler. ;)

The only difference is the proas shunt, so you don't get caught in irons or require slow, easily tacked hull shapes. Still leaves you with the crash jibe, the difficulty of reefing (and sailing) downwind, and the maintenance issues, which are much more relevant to cruisers than performance, particularly when, as Richard points out, that performance requires 100% attention to achieve it.

Your ideal cruising rig is not the one you have described avove. Big roach mains, rotating masts and backstays are a no no, so you will end up with a 3 stay rig with diamonds with the stays wearing away on the hounds, and fatiguing in the breeze as they are not tight, the same as everybody else. I suppose i should be glad, The rigs you describe fall down often enough that there will never be any shortage of business.

regards,

Rob

RHough

07-30-2008, 03:26 PM

The only difference is the proas shunt, so you don't get caught in irons or require slow, easily tacked hull shapes. Still leaves you with the crash jibe, the difficulty of reefing (and sailing) downwind, and the maintenance issues, which are much more relevant to cruisers than performance, particularly when, as Richard points out, that performance requires 100% attention to achieve it.

Your ideal cruising rig is not the one you have described avove. Big roach mains, rotating masts and backstays are a no no, so you will end up with a 3 stay rig with diamonds with the stays wearing away on the hounds, and fatiguing in the breeze as they are not tight, the same as everybody else. I suppose i should be glad, The rigs you describe fall down often enough that there will never be any shortage of business.

regards,

Rob

LOL ... I've never seen a rig come down that could not have been prevented.

You have mentioned one of my pet peeves ... the crash gybe. IMO crash gybes fall into the "operator error" folder. I refuse to discuss the ability of any rig to stand while being abused. Faulting a rig for falling down after a crash gybe is like faulting a hull for leaking after being driven at speed onto a rock.

Fast cruising boats should never be sailing deep angles. If the BAW is forward of the beam a crash gybe requires a *huge* deviation from course or an 'act of god' change in wind speed and or direction. If the boat cannot track well enough and yaws enough to be in danger of a crash gybe, the design is poor, the sailor inept, or the speed is too high for conditions. I'm no fan of "idiot proof design", God builds better idiots faster that the best designers can account for. ;)

Not to argue, but a 10mm Spectra Jib halyard will keep a mast up just fine after a 6mm SS wire fails.

As far as 2am reefing drills go ... there should also be enough crew on deck or on call to handle any reasonably foreseeable weather event. ;) In the case of being off a lee shore with squalls possible, she won't be in her PJ's ... she has the choice of napping in her deck gear or reefing naked ... which come to think of it *is* her deck gear ... :)

I think you have pointed out that a case can be made for more than one rig, and that the requirements and desires of the crew/owner should be considered when making that rig selection. I don't think that there will ever be agreement on what rig is "best" any more than there will ever be agreement on blonds over brunettes or redheads. Different splices for different skippers.

Alan M.

08-06-2008, 07:47 PM

masalai

08-06-2008, 09:00 PM

Just being cheeky, but if one is cruising (not racing) then why the need to "point high"? - - - - If one is racing then the "rules" will determine what rig....

rob denney

08-06-2008, 10:42 PM

Just wondering, how well do these Ballestron rigs go to windward? How high can you point? Can you maintain forestay tension?

What about stayless bi-plane rigs? Would they be able to point as high as a conventional rig on an equivalent boat? Would they go to windward with no headsail?

On both types of (stayless) rig, how does the variable mast bend affect sail shape? Can you predict mast bend for various wind strengths and cut sails accordingly?

Just curious, since nobody seems to mention this stuff much.

G'day,

According to Richard Woods, they are 25% more efficient than a conventional crusing rig sailed by a set and forget type of sailor (your average cruiser). I think this overstates the case, but they are certainly superior. Windward performance is as good as most cruisers, but as the breeze gets up the rig works the wrong way. That is, the forestay gets slacker, the jib fuller and pointing deteriorates. Some people put a running backstay on (can be attached to the end of the boom) to combat this but it needs tacking, and is not ideal as the mast still bends sideways. A ballestron with a wing mast and no jib (this is the 3rd reef, the first is automatic, the second is removing the jib) points extremely well, better than any cruiser under similar conditions as there is way less windage.

Reaching, running and general usability they are vastly superior to any other main/jib rig.

Biplane rigs get to windward pretty well and are invariably set up to sail without jibs (mast further forward). They would do better if they were wing masts rather than tubes, although Eric Sponberg has had success with oval sections.

Mast bend is highly predictable and the predictability does not vary once the mast is up. The one in the video was within a couple of mms in the static bench tests we performed. The more we build, the better this prediction becomes.

Cutting the sails is a bit trickier as few sailmakers have experience with large rigs, as can be seen in the video. Our sails have big roaches and bigger jibs than the aerorig guys use, which makes it much harder for the sailmaker. However, most sails I have seen are pretty good after the sailmaker has had a look and made any adjustments required. Lesson is to ensure the final payment is not made until the sailmaker has been for a sail in 10 knots and 20 knots and the sail looks like the picture on his computer. This is quite easy to check using a camera and standard sail photo techniques.

masalai,
The famous lee shore in 40 knots scenario requires good pointing, but otherwise I agree.

Rhough,
I wish my sailing was as predictable as yours obviously is.

regards,

Rob

sharpii2

08-07-2008, 12:03 AM

Exactly what is a 'Ballestron rig'?

I've tried looking it up without success.

rob denney

08-07-2008, 12:36 AM

Exactly what is a 'Ballestron rig'?

I've tried looking it up without success.

Otherwise known as an aerorig or an easy rig. The boom extends past the mast and has the jib attached to the front end and sheeted to a track in front of the mast. Sheet loads are reduced and no vang is required. A very easy rig to use.

regards,

Rob

Gary Baigent

08-07-2008, 01:20 AM

I may be mistaken but I thought the first spelling of this rig I saw, it was actually spelled baelstron - is it Scandinavian? - and then more commonly - balestron - and I see Rob uses ballestron. The French used the term with Paul Lucas 5.5 metre planing monohull designs back in the 1980's and later of course with Elf Aquitaine 11. Anyone spread more light?

Alan M.

08-07-2008, 04:17 AM

Just being cheeky, but if one is cruising (not racing) then why the need to "point high"? - - - - If one is racing then the "rules" will determine what rig....

Even cruising you still have to go to windward sometimes. And the higher you can point the less distance you have to sail. When it's choppy it's better to sail high and slow rather than low and fast.

Rob, can you give some examples of pointing angles and speeds in various windspeeds? "As good as most cruisers" doesn't really say much to me.

rob denney

08-07-2008, 09:35 AM

Rob, can you give some examples of pointing angles and speeds in various windspeeds? "As good as most cruisers" doesn't really say much to me.

G'day,

Not really as I have never had wind gear on my boats, nor the necessary cables to download the tracks from gps to the computer for analysis. But even less helpful is they all been on proas, so it is difficult to know how much is boat and how much rig. All my boats have easily tacked through 90 degrees, if that is any help.

The 15m proa in the video has just been sold (previous owner died) to someone who looks like he will use it a lot, so we should get some numbers from him this summer.

regards,

Rob

sharpii2

08-07-2008, 01:04 PM

Otherwise known as an aerorig or an easy rig. The boom extends past the mast and has the jib attached to the front end and sheeted to a track in front of the mast. Sheet loads are reduced and no vang is required. A very easy rig to use.

regards,

Rob

Thanks, Rob.

I thought the 'Ballestron' rig was different to the aerorig.

BTW- why do you call your boats 'Harry Proas'. Why aren't they called 'Rob Proas'

brian eiland

08-07-2008, 02:18 PM

..I do expect them (marinas) to be full of lower maintenance, more bang for the buck boats. I expect more cruising multi's, maybe not for the reasons I would choose, but more of them. The small catamaran circumnavigate is a type that has more potential than most. Once the mass producers of sailboats figure out a way to build and sell small 30-40 cruising cats to the folk that now buy 30-40 cruising mono's (Benetaeu, Catalina, Hunter, Etc.) they will take off like nothing we have seen before. The hint is to watch mother at the boat show. Compare her expression when looking at the accommodation of a 40 ft mono compared to a 40 ft Multi. ;) She sees a kitchen (not a galley) and bedrooms (not oddly shaped closets with "Guest Cabin" on the door), she steps on the edge of the boat (what the hell is a gunwale?) and it does not tip alarmingly, she has seen father watching the AC boats tilted at 30deg in a light breeze and hears every word when the factory rep talks about sailing all day and not spilling your wine.
We (Chesapeake Catamarans) used to sell a lot of Stiletto 27 foot catamarans. And the factory guys would come visit us at the Annapolis Boat Show every year. For several years they were contemplating new models...what to do in a new model and/or how to modify their existing one to have more appeal to the market. I forget now how many times I told them to watch the woman's reactions, expressions, etc as you talked to her husband about the catamaran product you were trying to sell them. And then later on see if you can find this same couple looking over other boats. Watch the difference in the woman's reaction between those long slim hulls of the cat with the trampoline in between, and that cozy little monohull they would likely end up buying.

I finally discovered the 25 foot Dragonfly trimaran over in Denmark, and immediately recognized I could sell this product to the woman. It was like a small monohull with 'training wheels'. I began to import them, but ran into a serious problem with supply. The acceptance of the vessel was indeed excellent, so I had to set about designing our own variation, the Firefly 26'. I am firmly convinced that in the under-30 category the trimaran configuration is superior to the the cat for all-around usability. In the 30-40 size range its open territory, and over 40 its a catamaran world unless you are single-handed racing.

My point is I agree with this need to address the woman part of the buying decision...very important

..Things like UHMW bearings inside a hole in the deck of a cruiser's sailboat sound like a horror story waiting to be written I considered this material as a possibility everytime I get a chance. On the Firefly tri we actually utilized it as a rudder stock material rather than conventional alum casting or stainless bracket. We just sawed a block of thick UHMW into the trapezoidal shape we needed for the slot in the hull's transom, cut out some lightening holes, and drilled a big whole thru for the SS rudder shaft....simple to construct, self-lubricating, non-fouling, inexpensive....

I even suggested it as a potential bearing material for a rotating mast, but the potential problem is its 'static friction coeff' as opposed to the dynamic coeff.

rob denney

08-07-2008, 11:34 PM

Thanks, Rob.

I thought the 'Ballestron' rig was different to the aerorig.

BTW- why do you call your boats 'Harry Proas'. Why aren't they called 'Rob Proas'

G'day,

Wife's suggestion, she has no idea why she said it. ( I blame alcohol, perhaps an old boyfriend, or harrsion Ford). It is a lousy marketing choice, but we have had a lot of fun coming up with names. harrigami for the folding one, solitarry for the solo one, harriette and elementarry for the little ones, visionarry for the one for taking blind people sailing, etc. A little bit more imaginative than the usual run of model names.

The visionarry in the video has just sold. New owner is a keen and knowledgable cruiser, wants to sail it round Australia in the near future, maybe do the Brisbane Gladstone race next year, as well as lots of local cruising.

Brian,

Static friction of UHMWPE for unstayed rigs is usually not a problem as the lever arm is so big.

BigCat

09-02-2008, 02:42 PM

waterbird

09-03-2008, 04:09 AM

Hi, does anyone out there now anything about corinthian Trimarans?
Like windward ability, Resin used and so on.
Would be grateful for any comments.:D

Gary Baigent

09-03-2008, 07:13 AM

Be more specific - do you mean classic wooden multihulls? - like the designs from Newick, Irens, Crowther, Tennant, Given, Myers, Brown and others.

waterbird

09-04-2008, 07:00 PM

Well, the Corinthians have that charm of the sixties. They've been build by Corinthian in Florida, Ketch and Cutter rigged to my knowledge with asymmetrical shaped Amas and a shallow draft of less then 3 ft.
They should be solid fiberglass but I am not shure. A few must have been build and the design can't be to bad, I read about one build in the sixties and another one in 1985.
Thanx

ropf

09-08-2008, 04:03 AM

Hmm - the disscussion is now far away from the main topic - a small catamaran cirumnavigator rig.

The engineers like to push the envelope - on the cost of the bulder/owner. They provide some basic strength calculations for *expected* loads and behind this there will always be some try and errror - what usually means something is breaking.

A circumnavigation is definitly not the place to do that. Circumnavigation means the *unexpected* will be happen. The handling of these situations in the middle of nowhere makes the difference between a great adventure and a great disaster. Following the all the books and articles one can easily identify some common facts:

- Starting fast - all the longtime sailors and live-abords slow down very soon. There is almost more performance then needed. Following the tradewind routes the most used configuration is jibe only.

- The high performance rigs are worth nothing when their upwind efficience is mostly needed - the sugested 40+ kts lee shore situation. In this case the upwind ability of the boat is limited by windage/sail area ratio rather then sail (peek-)efficience. On a bridgedeck cabin cat a strong engine is the only thing would help while on a open bridgde deck a very simple rig will do the job.

- There will always come the moment the electronics fail. Then you need to balance the boat by the sails only...

So my personal favourite is the Wharrams Tiki Wingsail rig. And yes - i like carbon masts. I use them for windsurfing - and replace them every year.

ropf