Ive often heard ppl say that fully battened sails are an imposibility for models but I cant see that it would be that hard to set up, anyone tried it?
If its not blowing it sucks!
A fully battened main is currently under construction for sail testing in early spring if all goes well. It will be tried in the MultiONE Class, and if succesful will also be used in the F-48 Class.
Two problems exist - 1) is the difficulty to “pop” battens over during very light air tack. (No crew to assist) and 2) most full battens are in a nylon “pocket” which presses against the luff groove at the rear of a rotating mast when battens are under tension to form camber. Since most models use a round mast, there is an issue of how to get the leading edge of battens to stay against the back of the mast. Full length batten work best when foil shaped mast rotates, as battens “fair” the leeward side of the sail to the leeward side of the mast. Using a round mast kind of negates this “fairing” effect.
Not sure how to address #1 - perhaps a “main” twitcher? For #2, battens with a leading “Y” shape to press against mast, coupled with a sleeve sail might be a possible answer. Another idea is to use “C” shaped sail-to-mast connections, with full length battens terminating at the back of the “C” connection.
Finally, full length battens really should have variable flexibility along their entire length. Soft for the forward 1/3 and stiffer as they transition toward the leech end of the batten.
Because of flexibility and needing stiff battens in heavy and lite air, and softer battens in medium air or chop, it is yet one more tuning issue to be considered. In some cases it might make sense, but in other cases, the KISS principle seems better. Some of us have enough to do with “standard” standing rigging and it’s tuning!
If the trials prove successful, will let you know. If unsuccessful, will also advise.
There are plenty of full size sails where the full batten does not contact the mast or even come close to it–ending just in a batten pocket. Then there are sails using camber inducers that can range from simple to complicated with the main purpose of inducing camber in the battens.
The biggest drawback in the past to full battens was just as Dick mentioned: not being able to tack very well because of the compression on the
batten. Rectangular(more or less)sail shapes with the head supported can adapt to compressionless full battens which I am experimenting with using layers of batten material or even stiff mylar. I’ve tried a couple different sails so far and the results are just about neutral: neither here nor there. The sail does make less noise when it luffs.
I think this is fertile ground for experimentation.
This is kind of off in la la land for the moment but a friend who does animatronic engineering for Disney showed me some “memory wire” and the application to full length battens occured to me. Applying a small voltage could bend a batten and releasing the voltage allows the batten to straighten out-food for thought.(one wire each side of the batten material to bend two directions)
Doug Lord
–High Technology Sailing/Racing
The AC15 class uses full length battens without any problems. The trick is to keep the tension just right and not have the batten push on the mast.
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nerds of the wold untie
I tried full lenght battens once and I used styrene plastic for the battens. The plastic was bendy enough for the size of the sail.
You could experiment with making the battens thicker and stiffer in certain places to achieve sail shape
On full size boats the battens force the sail to stay in shape, it should be imposible to lay a properly set up fully battened main flat. The mast does take a bit of a push from the battens, but if a tracked/groovy mast section is used I cant see too much of a problem. The only reason it will be taking a push is because the luff curve of the sail is forcing the mast to bend, and the bend causes point loads on the batten ends. I’m thinking that thin strips of unidirectional glass or carbon would make the best battens, just because the flex is easy to adjust when you make them, if you used plasticard you would want several different thicknesses to play with. If the sail is cut to be fully battened, there should be no need to have varying stiffness in an individual batten, all the battens do is hold the shape, they dont make it. As to the light wind problem, if you could adjust the batten tension, it could be slacked right off in light winds, which makes them easyer to pop, you don’t nomally do that on dingys 'cos popping the battens is a good excuse for a big pump after a tack!
If its not blowing it sucks!
If you take a look at the full size battens on a beach cat, you will see most are made in a foam sandwich, and they “are” tapered, in order to have the most bend in the forward 30% +/- of the main sail, while the remainder of the sail stays flat to keep flow attached.
In addition, the pressure needed to deflect the battens changed depending on which batten it was. Of eleven battens on a mainsail, the top several required nearly 10 lbs. to deflect (in essence keeping the top of the sail very flat and depowered) while the battens near the bottom of the main needed about 3 to 6 lbs. in order to deflect the sail to it’s proper camber for the wind conditions. All were string adjustable (on shore) to allow different amounts (and location) of camber.
Finally, unless you rotate the mast, or sleeve a sail there still remains a very turbulent area directly behind the mast if you are using a round mast. Remember the whole idea it to fair the leeward side of mast and sail into the appropriate camber. The proper angle of attack with the leading edge of the mast is critical as well. It is hard to describe, but sailing a rotating mast with full battens, you can actually “feel” it when the mast/sail are at proper angle of attack and the flow is strongly attached. Hard to describe, easy to feel.
Therein lies the problem of r/c sailing - it is hard to pick up the slight nuances of the interaction between wind, hull and sail if not on board - and only visual stimulus is the feedback. Also, in the case of a multihull, it is hard to read a stalled sail easily, because often the apparent speed/wind makes the telltales “look” like they are flowing properly.
Just another example of why a multihull doesn’t sail like a monohull.
Ive got full length battens on my rg65, to do so you need something pretty thin I have found X ray film ideal, with double sided tape aplying one strip each side at the top and just on one side for the lower half. My first efforts were with very thin glass laminate and they were too stiff to allow shape into the sail or flick over.
Cheers,
Babs
Possible but tricky to get right.
We use full batten mains on our 2 Meter ACC one design.
