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-   -   mainsail roach, battens, weather helm, and mast placement (http://www.sailnet.com/forums/sailboat-design-construction/42409-mainsail-roach-battens-weather-helm-mast-placement.html)

stipakb 04-20-2008 01:35 PM

mainsail roach, battens, weather helm, and mast placement
 
I am prompted to make this post because of a boat I saw and sailed recently, and am evaluating for possible purchase.

The boat is a Charles Whitholtz Chance 33 design, a semi-custom steel cutter built by Topper Hermanson. Her underbody is full-keel with a cutaway forefoot with a keel-hung rudder, very much like a Cape Dory, except that she has tiller steering with an outboard rudder hung off the transom as well as the keel. The staysail stay is removable, and the owners usually sail her as a sloop, with a 130 headsail, which was how I sailed her.

When sailing close-hauled I expected to be able to get her to track perfectly, like I was able to do when sailing a Cape Dory 33. However, I always had a slight amount of weather helm, regardless of how I trimmed the main and the headsail.

To my surprise, the mainsail was battenless with no roach, which seems a bad idea to me for a full-keel cruising boat. It bothers me that if I replaced the mainsail with a full-batten main with substantial roach, which would be my preference, then it seems to me logically that would increase the weather helm. However, when I searched the Sailnet archives I found that some people disputed that adding roach would increase weather helm, while some agreed.

The questions I am left with about which I would invite enlightenment are:

1. Will replacing the battenless, roachless mainsail with a full-batten main with roach likely increase weather helm?

2. Are there any good reasons for having no battens and no roach on the mainsail of a cruising boat? None of the reasons I have heard seem very persuasive to me.

3. Is a cutter-designed boat, with the mast positioned further aft, inevitably going to have some weather helm when sailed as a sloop.

Thanks for any enlightenment!

Brian Stipak
Portland, Oregon
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Faster 04-20-2008 02:27 PM

Quote:

Originally Posted by stipakb (Post 302643)
The questions I am left with about which I would invite enlightenment are:

1. Will replacing the battenless, roachless mainsail with a full-batten main with roach likely increase weather helm?

Logically it should; you are adding area aft of the current center of effort. However this may be offset with a newer sail that should have a flatter more efficient shape that may in fact contribute a bit more drive and less helm. (though to be honest if this will in fact apply to a full keel boat I'm not sure)

Quote:

Originally Posted by stipakb (Post 302643)
2. Are there any good reasons for having no battens and no roach on the mainsail of a cruising boat? None of the reasons I have heard seem very persuasive to me.

No reason I can think of unless it's a furling main (ugh)

Quote:

Originally Posted by stipakb (Post 302643)
3. Is a cutter-designed boat, with the mast positioned further aft, inevitably going to have some weather helm when sailed as a sloop.

Others can say better, but I wouldn't expect the staysail to significantly change the C of E of the overall sailplan.

You should look into mast rake as a way to try to alleviate the helm if indeed it's a problem.. a little is a good thing on most boats, but not, I suppose, if you expect it to steer itself on its own.

JohnRPollard 04-20-2008 03:28 PM

Faster makes a good point about mast rake. Too much rake could induce excessive weather helm. That's something worth checking. But there are a lot of other factors that come into play in the overall design -- it might be worth researching to see if this particular design has a reputation for exessive weather helm. Just tossing out possibilities -- it may have nothing to do with the sails or rig, it could be e.g. that the rudder is not adequately sized.

I have seen mainsails on cruising boats where the (short-handed) owners went to a negative roach and eliminated battens. The idea as explained to me was to deliberately depower the main a bit, to thereby postpone the point when a reef bacame necessary, and to eliminate a source of chafe on the sails for long-distance voyaging. But with the advent of full-batten mainsails systems even for cruising boats, I haven't seen that done much anymore.

Hopefully JeffH or some of the other knowledgeable designers here can offer additional insight.

sailingdog 04-20-2008 03:47 PM

One problem with full-batten mainsails is that batten pockets are often major sources of wear and tear on the sails.

They are also heavier than non-battened sails...since the battens add weight to the sail...and so does the additional roach area.

They are often harder to raise or lower due to the pressure that the battens put against the sailtrack on the mast, and many people resort to expensive battcar systems to deal with that issue.

They're more expensive to buy, since they require additional work and materials.

That said... they can often give better performance than un-battened sails. They tend to flog less and are often easier to reef and flake, since the battens tend to keep the sail aligned. They allow you to carry more sail area than you could with out them.

Classic30 04-20-2008 08:00 PM

Quote:

Originally Posted by sailingdog (Post 302689)
That said... they can often give better performance than un-battened sails. They tend to flog less and are often easier to reef and flake, since the battens tend to keep the sail aligned. They allow you to carry more sail area than you could with out them.

SD, it's true that battens require extra cost/work, but unless the mainsail in question has an extremely high aspect ratio (not likely to be found on a cruising cutter), an un-battened conventional-variety mainsail will never be able to hold an aerofoil shape properly.

Adding roach will only make it worse because there is nothing to support the leech. Heck, I've even see people battened jibs! :D

By not having the stiffness aft that the battens provide, maximum draft will be a lot further aft than normal and this could induce weather helm.

Sailormann 04-21-2008 12:19 AM

Quote:

1. Will replacing the battenless, roachless mainsail with a full-batten main with roach likely increase weather helm?
I think it will, but the difference will be quite slight. I think that you'll find the increased lift from the better sail shape will help the boat track more steadily.

Quote:

2. Are there any good reasons for having no battens and no roach on the mainsail of a cruising boat? None of the reasons I have heard seem very persuasive to me.
You mention that this is a "one off" cruising boat. It is possible that the sails were not made by a commercial loft, in the interests of economy. The only logical reason I can think of for no roach and no battens is to save money.

Quote:

3. Is a cutter-designed boat, with the mast positioned further aft, inevitably going to have some weather helm when sailed as a sloop.
If the foresail is too small (i.e. - if you are using one of the cutter headsails) - yes. You could probably balance it with a 130 (or larger) genoa.

SimonV 04-21-2008 01:51 AM

I can only answer the question in relation to the batten less main. (Fresh from the boat show) For a cruising vessel not having battens has a number of advantages. e.g. There is less wear on the sail and it should last three times longer than a battened sail, it can be reefed without having to head up wind, in fact it can be reefed while still powered up, it can be let out further when running. A good sail maker can make a proper main without battens work perfectly well, if they say they can’t, find a proper sail maker. There were other reasons but a kid at the back of the seminar would not shut up.

Jeff_H 04-21-2008 08:05 AM

I believe that this may be a boat that I worked on while I was working with Charlie in the early 1980's. If so she was designed to have a mainsail with roach and battens. These boats were intentionally slightly under canvased because they were also slightly under-ballasted for their drag and need every inch of sail area that these boats can have.

Now to correct the misinformation above. Talk to almost any knowledgeable sailmaker, if you care even slightly about sail shape, going battenless with a hollow leech greatly shortens the life of a mainsail since it requires much higher leech loadings to avoid leech flutter, in fact the shortest of all sail batten options. Without battens in high winds you need to carry a very tight leech line to minimize leech flutter, and that tight leech induces more weather helm than the sail area in a properly shaped roach with long battens. Going to heavier sail cloth simply aggrevates the light air problems with battenless mainsails but does little for the bias loading with battenless mainsails.

A mainsail with full length battens has the longest lifespan of all of the three choices, followed by mainsails with full length head battens and extended but not full length lowers. As SD notes it is important to have sacrificial chafe patches where the battens hit the shrouds. (Mine lasts approximately 2,000 sailing hours and are quick and easy to replace using dacron stickiback.)

Jeff

wakked1 04-28-2008 03:02 AM

Quote:

Originally Posted by SimonV (Post 302912)
I can only answer the question in relation to the batten less main. (Fresh from the boat show) For a cruising vessel not having battens has a number of advantages. e.g. There is less wear on the sail and it should last three times longer than a battened sail, it can be reefed without having to head up wind, in fact it can be reefed while still powered up, it can be let out further when running. A good sail maker can make a proper main without battens work perfectly well, if they say they canít, find a proper sail maker. There were other reasons but a kid at the back of the seminar would not shut up.

Don't believe everything the Pardees have to say.

SimonV 04-28-2008 09:19 PM

Ah... where you there, was it yor kid making all the noise.:D Not everything but quite a bit made you think.


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