Sailboard rig

[Paul B]

Originally Posted by Doug Lord

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Here is a bit on the Wylicat( Jim Wylie) design

The Designer of the Wyliecat boats is not JIM Wylie. If you're going to continue to drop names you should at least try to get them right.


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Originally Posted by Doug Lord

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I'm using a variation of a wishbone /sailboard
rig on a new model(F100), on the aeroSKIFF 14

There is no such thing as as aeroskiff 14.

My apologies to Tom!

Originally Posted by Doug Lord

Alex, sailboard rigs have certainly led the way in performance and especially high speed sailing . Barry Spanier designed the rigs on Russell Long's sailing hydrofoil "Longshot" based on his extensive sailboard sail design experience.(He has also agreed to consult on the aeroSKIFF 14 rig, see below) The square top main was seen first or close to first on sailboard rigs. But the most significant advances in sailboard rig design started out with "RAF"(Rotating Asmymetric Foil) design that addressed the serious problems of mast disturbance on the lee side of a sail. Later, "camber inducers" were used that allowed the sock luff to be designed so that the windward and leeward sides of the sail were smooth. The camber inducers started out as little plastic and cloth devices and have progressed to molded plastic units into which a full length batten fits. Camber inducers help to lock in the draft in a sailboard sail. Sailboard sails are also designed for a very narrow range of wind speeds and for different types of sailing such as course racing, wave sailing ,speed sailing etc. These different types of sail mainly vary the aspect ratio.
In the last few years the Moth class has used camber induced sails similar to the windsurfer sail but w/o the wishbone. Moth Foilers are arguably the fastest or close to the fastest sailboats under 20' beating much larger cats,skiffs etc. At Moth speeds- like at sailboard speeds- the camber induced sail has tremendous advantages over a "normal" rig.
On almost every sailboard rig I've seen the wishbone is tied to the clew of the sail with an adjustable outhaul like any other sail; the lines are run up each side of the wishbone to allow some adjustment while sailing. Because of the rig design and placement of the wishbone sailboard rigs do not require boom vangs with the out haul doing some double duty.
Here is a bit on the Wyliecat( Tom Wylie) design that uses what is called a "choker" on the wishbone to vary camber in the sail instead of
an outhaul:
Wyliecat Performance Yachts: Rig FAQ
Address:http://www.wyliecat.com/info/wishbone_rig.html Changed:6:46 AM on Sunday, August 3, 2003
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I'm using a variation of a wishbone /sailboard
rig on a new model(F100), on the aeroSKIFF 14 and on my new personal boat. The idea is that the wishbone is parallel to the deck like a normal boom but allows the sail to come all the way down to the deck like it does on sailboard with the rig raked aft. But on my version the mast doesn't rake very much(compared to a sailboard rig) so I wanted some way to get at least the forward third of the sail down as close to the deck as possible to reduce drag. Since the wishbone on my system is not being used like a "normal" wishbone it still needs a vang which is actually a double vang with lines diagonally from the mast base to each side of the wishbone. Another variation incorporated in this system is a midboom mainsheet connected to a carbon tube fixed between the two sides of the boom. When a sailboard TYPE rig using camber inducers and a square top planform is adapted to boats such as the Moth (and the new Hoot) it has to be different in that it must function over a much wider range of windspeed than a typical sailboard sail-but the sailboard designs have and are inspiring a new look at main only rigs particularly on very fast boats.
I've experimented a bit recently on a small camber induced rig for an rc model but it doesn't work well yet- it IS ,however, an area very much worth working in for fast rc boats particularly when combined with a square top planform and modified wishbone that allows a practical deck sealing main.
Are you considering a sailboard type rig on your new model?
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Here is the aeroSKIFF14 sailplan-note that the boom appears to be a normal boom but the forward part of the sail actually comes down thru a wishbone boom; on the proto,the F100 and my personal boat the portion of sail that comes thru the boom down to the deck would be about double(back end twice as far aft) what is shown here:
Address:http://www.boatdesign.net/forums/att...7&d=1141571544 Changed:10:12 AM on Sunday, March 5, 2006

[messabout]

Question;

I have been persuaded that wing sails have a very narrow range of ideal trim. An experienced sailor could deal with this on a full sized (people) boat. A model is a whole other deal. The skipper can not feel the gusts or shifts that the boat feels because it is out there somewhere. That means that the skipper will always be behind the curve. One of the things that makes models interesting and/or frustrating perhaps. My limited experience is with an EC12 and a bunch of experimental RC boats of my own devising. Also RC land yachts which are a hoot but very difficult to drive competantly as acceleration is eye popping and trim response time is very short. Wing sails on a land yacht are probably the only way to go because the vehicle is so fast. Not necessarily so with a boat. Can superior RC sailors deal with the wing sail well enough to make it a good choice ?

Messabout, my view is that a wing sail would be very ,very difficult for an rc sailor to trim no matter how good he or she is. I think significant improvements in rc sailpower can be had with things like a square top rig with upper and lower out haul. The gust response and planform contribute to noticeble improvements.
I have very little confidence in significant improvements being made on miniature boats with solid wind sails...

[AleX`G]

We shall see in due course. If it does fail I could alwasy make a computer controlled system. And use a conventional sail.
I see no reason why it should fail. Surely the wing would maintain the correct angle of attack itself and you adjust the flap to change lift/drag ratio.


Alex

[AleX`G]

Hey guys hat to bring up this question again but i am getting to the point were i am actually making the sails.
The wing sail turned out to be just too heavy and i dont think i could get the weight down enough. So now i would like to concentrate on a square top main and a jib probably running to the top of the mast.

I have one question though im hoping you guys can help with. For the gaff extension doesnt it need to be able to rotate with the boom when adjusting the main sheet. If this is so it will not automatically return to its neutral position so to say so how do you adjust the tension in the gaff and the top of the sail. Can you use leech tension to work this or would a seperate control line be required.

I will be making the mast out of aluminium. I thought about using a spring attatched to the gaff so the head of the sail could let air out in large gusts. Would this work?

What ratio of main to jib for sail area would you guys recomend assuming max mast height 90cm.

The image below represents kind of what i am thinking of but i am unsure about battons and exactly how the gaff works. To i need something that will tension the boom?

Alex

[b_rodwell]

Hi

I am very close to launching my 4.7m x 1.5m dinghy with a sailboard rig. The rig is a second hand ($600) 10.4sqm formula windsurfer sailboard rig. It is stayed to the point where the wishbone boom clamps on the mast. The mainsheet is off the end of the wishbone.

I bought this rig aware that it would not have the optimal drive characteristics for my application. This has been confirmed when trying out the rig on dry land. It is very flat at the top.

I now want to add more shape. My inclination is to do this by stiffening the top mast half with carbon tows. I would be interested in your views on this approach. And is there any science to work out the amount of carbon tows that would do the job?

Brian Rodwell

[Hansen Aerosprt]

Brian:
As you have surmised, Formula windsurfing rigs are highly refined for a particular set of dynamic problems rarely encountered by small boats and not the best choice. Not knowing which sail and mast combination you have, it is a little hard to give specific advice but in general, Formula sails have rather stiff battens and flat twisty sections in the top of the sail.

There are a few things you can do to add shape: less downhaul (which may cause problems,) softer upper battens, stiffer mast or re-cut the head of the sail. If you have access to a local sail repair station or are handy with it yourself, the best way to add shape is to peel up the top 2-3 batten pockets and take a 2-3cm wedge out of the leech running forward to the 1/4 chord point under each pocket. Then replace the pocket and soften the battens in the front half before replacing them. This will tighten up the leech and add shape using the same mast. If you wish to stiffen the mast, it will be 'trial and error' but you can set up a spread sheet to predict the added material needed by using the inverse of the fourth power of the outside diameter minus the fourth power of the inside diameter to predict the deflection change. That is, for a given diameter, wall thickness and material, increasing the wall thickness will stiffen the mast accordingly and the deflection will be less. Even with a stiffer mast, you should more than likely do the sail re-cut as well. Otherwise you will probably never get the desired shape.
Good Luck!
Bill Hansen
Hansen Design
Hansen Sails, LLc
Current 'chop top' boat projects
Hoot Dinghy
Laser Turbo
Antrim Wing Dinghy
Cal-20+ Uni-rig
Wyliecat 17
Wyliecat 30
Commodore Tompkins Wylie yacht tender

[b_rodwell]

Hi,

Thanks for your detailed information.

The sail is a Sailworks NX2 10.4. The mast is a Fibrespar Reflex 4600 QT 520/26/32.

Does that change any of your recommendations?

I would like to use a sailmaker to make the changes to the sail. Who in Sydney OZ would be the best to do this sort of work?

Brian Rodwell

[Hansen Aerosprt]

Brian:
That sail doesn't have many battens in the top third so my recommendations won't help as much as you will probably want. The top batten is too high to do much but should be done anyway to tighten the leech. Another method would be to remove the upper sleeve and 'luff adjust' it by adding luff curve in the top 1/3 of the sail. All-in-all, you won't get far towards an effective dinghy sail with the kit you have. I can't help with sail repair in Sydney, sorry.

[CT 249]

Bill, can you tell me the relevance of the number of top battens? Are they relevant simply because they are a convenient seam to use when introducing the seam taper?

I'm thinking of modifying older FW sails for use on a Lechner and IMCO, and the un-modified FW sails don't seem to be all that good on a longboard, in terms of speed for size.

[Hansen Aerosprt]

CT:
Yes.
In my experience, adding built-in shape works best at the battens. If you are just trying to tighten the leech, you can take a straight wedge all the way to the sleeve 1/2 way between battens. This is effectively an increase in luff curve and easier than removing the sleeve. You may have some slight distortion at the sleeve if the wedge is large. If you do this, you will need to reinforce the area along the luff to prevent it from pulling apart under downhaul. The other option is a stiffer mast. A combination of all three should get you there, i.e., batten re-cut, leech tightening and mast selection.