Aftmast rigs???

[Corley]

I agree that its not a performance idea, but a cruising one. That, done well could well be faster for cruising reasons. The main reason being that cruisers often sail under headsails only because they could not be bothered raising their large mainsails. They might not raise them because they are single handing and have a large boat, or they are only sailing a shorter distance where its just not worth the time and effort to raise the main.

The "moot point" about not needing the main anyway when cruising is not moot at all. Passage speed is important. When the main is smaller and the headsails are larger, you will be going faster under headsails alone. BUT, the important part is the mainsail (I am saying still use a decent size and high performance main) is that bit smaller so is easier to raise anyway. So for cruising reasons I think it could be faster, even if for racing reasons its not.

I'm just using my own boat as an example, 70m2 main. 40m2 genoa. And a 70m2 screecher which is a fragile setup on a 2.5m pole and endless line furler (pic in this thread). Its not to be left up in strong winds (even furled) and certainly not for use single handed. Setting up is a PITA with the pole etc, and you would want a decent helmsman to get it down if the **** hit the fan rather than an auto pilot.

The main is a PITA to raise and pack up alone. I think the boat would still have very good performance with say a 55m2 high aspect square top main (same height as now), and 35m2 heavy jib for windward work. I think this setup would be as fast or faster to windward than what I have now once the wind got to the point where I would have to reef my current setup (which happens fairly quickly) thanks to the higher aspect ratio. Sure in lighter winds, it will have less power.

However, I now also have room for a larger headsail (say 70m2) on a real furler (single handed safe) so the power will be the same or even greater than before, but with this up it might not point quite as high (not as good for racing). Downwind, speed will be comparable, as sail area will be similar (the cutter rig means I can use both headsails), but it will be much faster with headsails only as the headsail area will be much larger.

So its not fastest for racing, but for cruising its probably faster unless you cruise your boat like a race boat.

I would just like to add, I am usually the one flying thier mainsail when everyone else is just using thier jibs (when I'm not alone anyway). Seems a normal affair in Moreton bay for the weekend cruisers to not even bother with unpacking their mainsail bag, even in light winds. For them, the main is a waste.

Fair enough but you have already answered your own question just use a smaller main on the existing mast. The alternative is to have a smaller rig but then your passage average speed will take a hit due to poor performance in light conditions.

I'm not trying to push any particular stance on the issue and as I noted there are a lot of good reasons to break up sails into smaller areas and your main being a PITA to raise and deal with could be as good a reason as any.

Sailing performance from a certain point of view could be defined as having the maximum amount of sail that can be easily dealt with for whoever owns the boat. Sails that are zipped away in their bag are not helping performance.

 

[DennisRB]

Hey Corley. I just got new sails and went max size on everything for better performance and do not regret it. I very much do care about performance. There was no way I would get a smaller main on my existing rig, I went bigger. Its lighter than the last one so easier to raise. Just putting a smaller main on does nothing to increase foretriangle size. So no sail area would be traded. Just making the whole rig or main smaller does nothing to equalize sail area, and does nothing to bring extra sail area to easy to unroll headsails.

I am also not pushing a stance at all either. My hypothetical idea was for a hypothetical version of my boat/rig. Where sail area stays the same as now by way of moving the mast back a bit for ease of use and pretty similar the same outright performance, but easier cruising performance.

Some people in this thread have been trying to say more headsail and less main actually has BETTER outright performance. I also do not believe it. But I explained why the cruising speeds would be higher in many cases, and why this setup does not have to be inherently low performance. Even if it might be a bit slower to windward in light wind, it would be equal or better in higher wind thanks to a higher aspect main and smaller jib designed for high wind upwind work compared to a partially furled genoa. Yes there would be air drag from the additional large masthead genoa.

What I am saying is the base rig would be similar to a shrunk down version of what you might see on something like this. Made smaller so that it all fits on the boat with no pole, and the code zero just being a very large foresail on a real furler. Of course then you could also have a pole for hipo sails as well, which I would want. I don't think this idea is new or special in anyway. I just think it might be a good way to go for cruising boats even if they do care about performance.

 

[DennisRB]

One of the slowest cat brands around. The lagoon. But I don't think the rig would be slow if it was on a light boat. Charter cats are the worst offenders when it comes to never raising the main and with tripple story deck houses I would be scared to pack the sail up too

http://lagoon-inside.com/2013/01/matrix-evolution/

 

[Corley]

I agree the Lagoon sailplan would do well on a lighter boat. The worst thing on those boats are the very heavy rigs and gear required to deal with the high righting moments. The high booms are frankly scary and look to have the potential to cause serious injury if you were to fall from the top deck.

 

[CT249]

I'm not sure if others have the same experience, but I've seen some terrible squaretop or big-roach mains on cruising cats. The problem is that the boats are not light or really quick, so they need a fair bit of depth in the head - but the sails and booms are heavy and no one is trimming them intensively. So in light winds the deep, wide roach often seems to get terribly choked up and one can practically see the handbrake being pulled on.

We've got a fairly small roach and big jib on our 1993 20' beach cat, and in the really light stuff we often pull away from the squaretop F18s, which are theoretically faster but seem to have more problems with the upper leach choking - on a cruiser the problem would be much greater.

Originally Posted by Spiv View Post
....
My next boat will not have a main with battens on a track, but on a furler.

My family's first cruising cat had a furling main because it was just a cruising boat - for the first cruising season. After that it was replaced with a roachy mainsail with full battens, because otherwise the boat just had to motor everywhere.

Obviously it's a matter of different personal situations and tastes. I was just recalling our experience.

 

[Corley]

The heaviest cruising cat I've been on with a squaretop main was our club commodore's Chris White cat Peccadillo it's about 6 tonne so pretty svelte compared to many cruising cats getting around and has a decent set of sails. I didn't see any trim issues but then we were checking its trim every 5 - 10 minutes or when the speed dropped even on the night watches. You seem to spend a lot of time looking at the instruments on big cats it's hard to feel the breeze on deck. Performance wise we were seeing 13-14 knots of boatspeed in 18-22 knots of TWS which seemed pretty good for a large cat in delivery mode. We were not running any extras only full main and jib.

 

[CT249]

Sorry, I should have made it more clear that there are also squaretops that work on cruising cats! I was thinking of the heavier boat (or even lighter cruisers sailed without much trimming) and heavy, stretchy low-tech sails and booms, where no one is really thinking about sail trim and which often wander around with a terribly choked head, or conversely with the head falling away;

There's heaps of stuff on the net showing such boats with the squaretop twisting off so much it's doing nothing on a reach. There's also room to wonder whether the higher mainsheet and vang loads of a squaretop, and the extra weight, are worth it in many situations, like laid-back cruising.

Peccadillo's rig obviously works, as do squaretops in other situations. They're great sails, but it's just that they seem to be over-sold in some situations.

 

[DennisRB]

Gday CT249. I thought you meant the leach would be too tight thanks to there being effective vanging just from the weight of a heavy boom even with the sheet fairly loose? IE the angle of attack of the head would be too high for optimal performance. The opposite of your picture.

Then you go on to say the opposite, that in a reach the head will be doing nothing because it would twist off so far? You sound like you know what you are talking about so can you please tell me what I am not understanding? Is this a high wind/low wind prob. Where in light wind you have problem one, and in heavy wind the sail stretches and there is no appropriate traveler system/vang and you get problem 2?

My boat, a crowther 226A has an overbuilt rig that would make some charter cats look small. Bit of a disappointment really, but at least I know its strong.

My sails are cruise lam and I certainly have no prob preventing the head from falling away, but as you say perhaps in very light wind the is not enough wind pressure to lift the boom to apply enough twist.

I'm still learning to use this sail, and well really sail this boat in general. Its my first large multi and I have only done maybe 2000 miles. I don't have a vang even though there are attachment points for it. They seem redundant on cats these days. I would much prefer the boom to sweep the cabin top (one complaint I have is access to the stack pack).

Seems the almost full width traveler, and then 4:1 preventer do the job of vanging without the enormous loads of a vang. Perhaps the boom could have been much lighter if the vang was ruled out? When sailing I am always playing with main trim. I have no highly experienced trimmers to give me tips, so its all just what I think I know from sailing pinheads. Mainly trial and error. I am always moving the main up and down by adjusting the traveler and sheet to suit. Often I see gains in boat speed at odds to what I might be seeing from the telltails by what appears to be oversheeting the head. But its clear the twist of the sail has big effects on performance. It also seems to give a weather helm more easily.

These pics are on the first hoist of the sail (the ones without the screecher up). You can see it hits the shrouds easily so IMO the head has to be tighter than optimal for performance sometimes just to prevent damage. With the screecher we can create enough apparent wind which solves the issue mostly, unless its really light.

 

[CT249]

Gday CT249. I thought you meant the leach would be too tight thanks to there being effective vanging just from the weight of a heavy boom even with the sheet fairly loose? IE the angle of attack of the head would be too high for optimal performance. The opposite of your picture.

Then you go on to say the opposite, that in a reach the head will be doing nothing because it would twist off so far? You sound like you know what you are talking about so can you please tell me what I am not understanding? Is this a high wind/low wind prob. Where in light wind you have problem one, and in heavy wind the sail stretches and there is no appropriate traveler system/vang and you get problem 2?

My boat, a crowther 226A has an overbuilt rig that would make some charter cats look small. Bit of a disappointment really, but at least I know its strong.

My sails are cruise lam and I certainly have no prob preventing the head from falling away, but as you say perhaps in very light wind the is not enough wind pressure to lift the boom to apply enough twist.

I'm still learning to use this sail, and well really sail this boat in general. Its my first large multi and I have only done maybe 2000 miles. I don't have a vang even though there are attachment points for it. They seem redundant on cats these days. I would much prefer the boom to sweep the cabin top (one complaint I have is access to the stack pack).

Seems the almost full width traveler, and then 4:1 preventer do the job of vanging without the enormous loads of a vang. Perhaps the boom could have been much lighter if the vang was ruled out? When sailing I am always playing with main trim. I have no highly experienced trimmers to give me tips, so its all just what I think I know from sailing pinheads. Mainly trial and error. I am always moving the main up and down by adjusting the traveler and sheet to suit. Often I see gains in boat speed at odds to what I might be seeing from the telltails by what appears to be oversheeting the head. But its clear the twist of the sail has big effects on performance. It also seems to give a weather helm more easily.

These pics are on the first hoist of the sail (the ones without the screecher up). You can see it hits the shrouds easily so IMO the head has to be tighter than optimal for performance sometimes just to prevent damage. With the screecher we can create enough apparent wind which solves the issue mostly, unless its really light.

Hi Dennis. These are just some observations from someone with no real claim at expertise in this particular area, looking at typical boats.

I think that both problems often apply; it's a light wind/high wind problem and an upwind/downwind problem. In light airs upwind it's easy to over-sheet and close the leach off, particularly in slower boats which tend to have deeper sails, heavier cloth and heavier booms. The downward force of the heavier boom tends to pull the battens to windward and choke the leach. The deeper the sail in the head, the worse the choking will be. Even boats as disparate as Tasars, Etchells and TP52s carry the traveller to windward at times in light winds to generate enough twist (which would be almost unknown on some of the roomarans with squaretops, it's not what they are into), and their upper-leach profiles are arguably much less prone to choking than that of a typical "roomaran".

On the other hand, when there is a bit more wind a squaretop is so large and has so much leverage that if the traveller is not being used properly (as you obviously do) the sail can just twist way too much.

Basically, in my humble opinion squaretops are great IF they are being used properly, as yours seems to be, but I (and a significant number of others) feel that for low-key cruising where people don't care about sail trim they can be inferior to a more conservative roach. It's not that squaretops themselves are not great a lot of the time, it's just that some of the stuff written about them, especially for slow boats, over-sells them and they can be a negative when not handled more carefully than a smaller roach.

The whole cat-and-vang thing is an odd one. I'm certainly not a great cat sailor (I never train in them for logistical and other reasons and they just don't suit my strengths, so I can't win above club level) but when I've sailed with and against good guys it's interesting to see how often they sail with the lee side telltales stalled. I can't work it out, and all the theory indicates (as far as I can tell) that high aspect rigs should perform very poorly when oversheeted, but guys like Steve Brewin used to stall out their leeward telltales and go like stink. The same thing happened in windsurfers, but not much in skiffs. It's all very confusing.

That's a fine boat you have there; a real Crowther. Vague memory tells me that Lock was moving to a squarer profile with Duguello (sp) but that didn't work out well. I sailed with him on Wahoo but that was in pre-squaretop days.

PS- Re vangs - I wonder if Paper Tigers (which have vangs) are more like cruising cats in terms of angles, Bruce Number, rig design etc?

PPS - nice flat squaretop on your boat!

 

[brian eiland]

the Genoa Staysail, a secret weapon

Sorry, to disrupt this interesting conversation, but I ran across this short summation this morning while googling IMAGES of genoas. Had to post it before I forgot it (don't know why I never bothered to look thru 'google images' and their links :?


THE GENOA STAYSAIL: A Secret Weapon?

In the last few years, I have learned more then I can remember when it comes to sailboat racing. One thing that keeps coming back is this lesson: Genoa Staysails can add a lot of speed to a lot of boats.

During a sail development program for a local Santa Cruz 50 in California, we started to incorporate a Genoa Staysail into the inventory. With these ‘lighter’ boats that carry the apparent wind forward, the Genoa staysail proved more efficient than a spinnaker staysail in all conditions except true running conditions. We discovered that we could carry the Genoa staysail efficiently under the Code Zero, the #1 Genoa (when the outboard lead is used), the 1A Spinnaker and the 135% Jib Top! We witnessed speed gains of over a half of a knot

....Ullman Sails.

Hmmm....my 'mainstaysail'

 

[DennisRB]

A modern cutter rig is great for cruising, and does not have to be slow as shown above...

Take a look at the pic of my screecher and where the genoa is. Obviously if you unfurled the whole genoa out at the same time, all that it would do is slow the boat down due to too much interference. But the pole is long enough that I thought with a half rolled out genoa it might add to speed, but I have been unable to get more speed yet. But I have only tried once or twice. I think the shape of the 2 headsails must be similar for best results.

 

[DennisRB]

Basically, in my humble opinion squaretops are great IF they are being used properly, as yours seems to be, but I (and a significant number of others) feel that for low-key cruising where people don't care about sail trim they can be inferior to a more conservative roach.

I wonder if the extra sail area makes up for it most of the time in these very heavy condomarans that never sail to windward anyway?

The whole cat-and-vang thing is an odd one... I've sailed with and against good guys it's interesting to see how often they sail with the lee side telltales stalled. I can't work it out, and all the theory indicates (as far as I can tell) that high aspect rigs should perform very poorly when oversheeted, but guys like Steve Brewin used to stall out their leeward telltales and go like stink. The same thing happened in windsurfers, but not much in skiffs. It's all very confusing.

Yes I was also very confused when I saw consistent speed increases with the lee telltails stalled on the upper part of the sail in certain conditions. This is exactly what I was taking about. I think that the issue is mast drag on my large non rotating mast. Simply, the main needs to be let out too far for the flow to become streamlined very close to the sail up high. That's because the mast is a large percentage of the chord width of the sail higher up. Quite possibly the air is flowing correctly in the lee even though telltails are stalled in some sort thick turbulent boundary layer caused by the mast?

That's a fine boat you have there; a real Crowther. Vague memory tells me that Lock was moving to a squarer profile with Duguello (sp) but that didn't work out well. I sailed with him on Wahoo but that was in pre-squaretop days.

My rig is measured to be standard size, the large roach main was supposed to be 60m2 on that rig, but we managed almost 70 with the new sail. I'm reckon Lock would be onboard with the current squaretop trend now that a lot has been learned. Sail materials which can handle it are cheap now. My cruise lam sails were cheaper than dacron (well not crap dacron that would not work on a cruising multi for long). Too bad I will never meet Lock, and his son seems to have just gone where the money is.

PPS - nice flat squaretop on your boat!

Thanks, we are happy with it.

 

[brian eiland]

A modern cutter rig is great for cruising, and does not have to be slow as shown above...

Take a look at the pic of my screecher and where the genoa is. Obviously if you unfurled the whole genoa out at the same time, all that it would do is slow the boat down due to too much interference. But the pole is long enough that I thought with a half rolled out genoa it might add to speed, but I have been unable to get more speed yet. But I have only tried once or twice. I think the shape of the 2 headsails must be similar for best results.

Too much interference, I agree.
Simply inserting a staysail between the headsail and the mainsail is not the cure-all, just as certain cutter designs where not that great. There are 2 articles by Avrel Gentry I would suggest you have a look at.
The Double Headed Rig
The Aerodynamics of Sail Interation
....the PDF's can be found here: http://arvelgentry.jimdo.com/articles/

Because of these findings by Gentry, and my own personal experiences with a staysail equipped older wood ketch design, I have paid particular attention to providing a fairly wide slot between the genoa and the 'staysail' on my aftmast design. Plus my mainstaysail is not crammed in between a genoa and a big mainsail,...in fact no mainsail at all

Furthermore my 'mainstaysail' is 'broader in size', such as to provide a leach trailing edge that is behind, and parallel, to that leach of the genoa sail. This all goes into providing greater 'driving production' from the genoa sail.

Excerpted from aerodynamicist and North Sails consultant Paul Bogataj’s paper, “How Sails Work” (attached PDF)

‘Sails in Combination’, “Each sail by itself is much simpler than the combination of a foresail and mainsail as in the sloop rig. The sails are operating so close to each other that they both have significant interaction with the other. The most interesting feature of this is that the two sails together produce more force to pull the boat than the sum of their forces if they were each alone.
The foresail of a sloop rig operates in the upwash of the mainsail. The wind as far upstream as the luff of a genoa is influenced by the upwash created by the mainsail. Hence, a jib or genoa in front of a mainsail has a higher flow angle than it otherwise would have by itself, causing an increase in the amount of force that the forward sail produces. So, while the mainsail is experiencing detrimental interference from the foresail, the foresail benefits from the interference of the mainsail. Notice that more air is directed around the curved leeward side of the foresail. This causes higher velocity (lower pressure) and more force. The net result is that the total force of the two-sail system is increased, with the foresail gaining more than the mainsail loses”

Both of these very experienced gentlemen are saying basically the same thing.

I have tried to combine these things into one lower aspect ratio sailing rig, with NO mainsail, yet a mizzen for balance (and additional reaching sail area), and all 3 sails that roller furl,...an easy to use cruising rig.

 

[brian eiland]

I might be able to 'straighten-up' my forward canted mast, and place my mizzen sail (or a full battened mainsail) on it in a more traditional manner. But I would want to come up with some new methods of staying that aft stepped mast arrangement to try and avoid the 'Prout situation' where the aft staying was less effective at preventing sag in the forestays. Its probably doable for those that can't accept my forward rake. I'll think about it.

(But then I think back to what those 2 gentlemen above say about the effectiveness of the trailing sail vs the headsail, and I say why all this emphases on the a full battened trailing sail,...just be sure it helps the leading sail(s) properly, and that the rig has a good amount of total sail area to accomplish the job, and that it can be 'reefed down' for varying conditions)

There was a time in the past where I had a potential client with a big 65 trimaran design that he was hoping to sail by himself and his wife. It had a TALL rotating fractional rig. I decreased the rake of my rig to 6 degrees (rather than 10), and gave him a bigger mizzen. At the same time I tried to make it such that if he was totally discouraged with the idea, he would be able to straighten up the mast to vertical, and make the big mizzen into a low aspect mainsail.

Aft Mast Alternative on Big Trimaran

 

[brian eiland]

Overlapping Genoa and all-furling rig

I was looking around for this posting I had made on another forum, and had a little trouble finding it.

Why Do Catamarans Motor Nearly 100%
http://www.cruisersforum.com/forums/f48/why-do-catamarans-motor-nearly-100-a-148849-35.html#post1957198

The points I was trying to make for my aft-mast rig with its big genoa is that I was trying to meet a big variety of conditions with a limited sail inventory (my 3 sails are the only ones I have onboard, and are set up to be reduced in size by roller furling, not hoisted or replaced by alternatives).

As such I wanted a good size genoa sail for those often encounter 5-15 knot winds that we would really like to sail in rather than turning on the engine(s). This size sail, in those conditions, should be relatively easy to handle, ...(and when out cruising I would NOT be looking at getting into tacking duals). I was seeking to get the best from this genoa sail by giving it the best help from the 'cutter jib' (mainstaysail as I refer to it), and providing for its best dumping traits as described by Tom Speer.

I'm also quite convinced that modern sail materials such as the tape-drives or these Titanium sails would allow for a very light weight sail that would maintain their shape even in higher wind conditions. These materials should also allow for sailing under a partially furled sail. As I have said before I believe a hefty size ROUND furling 'tube' (headstay) should utilized to negate some difficulties of stalling the sail due to a 'too-sharp' leading edge to the headsails. Combine this type of headstay foil with a modern 'shaped foam insert' in the leading edge, and this sail should set pretty well in the roller-reefed condition. It would be nice to be able to utilize this reef-able genoa up to the 30 knot range.
Code Zero Sails, aerodynamic questions - Page 2 - Boat Design Forums

For storm conditions that we see coming we slip another sail over that furling staysail:
Storm Sail Configurations