Best rig for small catamaran circumnavigator?

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

 

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

 

I second Rob's motion. So moved?

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.

 

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/

 

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

Richard Woods

www.sailingcatamarans.com

 

Slot Effect....again

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.

 

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

 

"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

 

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/

 

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" 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

 

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.

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

 

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