The design of soft wing sails for cruising

[David Tyler]

In your main hinge assembly drawing --

main hinge assembly.dxf

-- I'm curious how you will cover the green hinge portion with sailcloth? Since the triangular hinge component is rather long (475mm), if you use the sailcloth which covers the wishbone to also cover the triangular hinge, then there could be a lot of sliding motion between the wishbone sailcloth and the batten sailcloth. But if you use the batten sailcloth to cover the triangular hinge then you might have a more complex batten sail configuration, plus possible problems connecting the wishbone sailcloth to the batten sailcloth.

There's no problem here. So long as the parts of the sail come together as near to the vertical pivot as is practicable, there is little movement relative to the batten.

There must be a good reason why you don't use a single universal joint right where the batten enters the end of the wishbone assembly? It appears you plan to assemble the wishbones around the mast by sliding them aft-end first over the mast. Are there other piece(s) to the wishbone assembly to be used to position the wishbone on the mast?

There are indeed other configurations of joint that could be used, but they all have disadvantages. The joint must be strong, when the limit of articulation is reached, and that implies a certain size. It can be long fore and aft, or it can be wide, side to side. The latter implies the use of a double after half to the sail, and although I can design a very nice joint, I haven't been able to solve all the problems associated with the doubled sail. The former is what I am going with. The hinge that I have drawn is such a universal joint, with the degrees of freedom that are required, the strength that is required, and with the meeting of the two sail parts in the best place.

Are you actually involved in designing and making rigs, or are you an interested onlooker? I regret that I have little time for fielding queries from such, and must concentrate on collaboration with others who are working in this field.

 

[David Tyler]

Did you look at the camber inducers used by Windsurfer sails?

Yes, and I think I've already explained how they are unsuitable for large sails on a cruising vessel. They just don't scale up to become an all-weather, all size, automatically-operating proposition. What works on 4 sq m doesn't necessarily work on 40 sq m. If they did, Omer wouldn't need hydraulic rams to operate their rig.

 

[Baltic Bandit]

I was thinking more about deriving from that mechanism the idea of an inboard floating end of the batten. that solves some of the articulation limit problems you are challenged by.

 

[Cat2Fold]

Ohhh great! How timely. I have a 36' biplane rigged, freestanding masts (that can rotate 360), that is in desperate need of new sails. I have dreamed for a while now of doing something just like what David has done. I really like the idea of being able to fabricate something up myself, sewing flat pieces of fabric together.
My current Marconi sails work great, but if I can get better performance and have something I can do myself (saving $), I'd love it! Plus I'm a builder of things...
Anyhow a couple of thoughts/questions.
Who here could help me develop/design the proper shape/size wing for my boat?
And, although it wouldn't be of flat panel fabric, how about the idea of a wishbone leading edge with a tensioned batten trailing edge sail? Sure one may need to "pop" the battens around between tacks, but it would be a smaller "sail" that a sailmaker would have to custom build for me. Work the extra long battens into the hinge and voila!
Thanks for pioneering and actually using this type of sails David.
I applaud you're effort.
If I should start a separate thread, I'd be happy to.

 

[David Tyler]

Cat2Fold,
With Cad, it's easy to scale the batten design to any desired chord, and there is latitude in the spacing and number of battens, so you should be able to get any desired sail area starting from my design.

But I think you have to take the whole design, including the stiff battens and chinese sheeting, as I have no idea what would happen if you introduce other features. I do know that the upper battens where the leech is curved exhibit the kind of action that you describe, as they are under compression, and this is a problem that has to be resolved, not a benefit. If they don't flip between tacks readily in light airs, it's hard to encourage them to do so.

 

[David Tyler]

For the past week, we've been beavering away at making moulds for the components, but there's not yet anything to show you.
Soon.

 

[David Tyler]

At last, we seem to have a good moulding procedure for the carbon components, with the first piece out of the mould, and the second now curing in our “oven”, a plywood box with a thermostatically controlled fan heater set to 30C. I can now devise a method for making the mould, somewhat better than our first effort, which was a bit of a compromise allowing for different moulding procedures.

 

[Cat2Fold]

Cat2Fold,
With Cad, it's easy to scale the batten design to any desired chord, and there is latitude in the spacing and number of battens, so you should be able to get any desired sail area starting from my design.

But I think you have to take the whole design, including the stiff battens and chinese sheeting, as I have no idea what would happen if you introduce other features. I do know that the upper battens where the leech is curved exhibit the kind of action that you describe, as they are under compression, and this is a problem that has to be resolved, not a benefit. If they don't flip between tacks readily in light airs, it's hard to encourage them to do so.

Thanks David,
Well...with absolutely NO CAD experience, I'm afraid the time to figure all that out is just not available. If anyone on here has the time to help design a simple batten pattern and size (I'm liking the single layer batten aft) for a small fee, let me know. I'm open to different ideas as long as it follows the KISS principle.
I have (or can get) measurements from the boat in reference to mast height, distance between masts, etc...
Cheers!

 

[David Tyler]

If you tell me the chord of sail you need (parallel luff and leech for the lower two thirds), I can scale my batten shape to that, very easily. But then you need to be able to print out the drawing at 1:1 scale in dxf or pdf format. To do that, you really need to get a CAD reader program at least. The noses and hinges can be made in carbon (difficult, expensive, strongest), laminated wood (easier, perfectly OK for smaller sails), or sheet material (easy, OK for small sails but heavy).

 

[Cat2Fold]

Hi David,
Wow, Thanks for responding. I know you have your own work to do...
Anyhow, I'm not exactly sure what you are asking for. My masts are 17' 1/2" apart center to center. So, if you are asking for the measurement of my current sail parallel to the luff it is approximately 14'6". Whatever distance the new wingsail would project in front of the mast would need to be taken into account so that when broad reaching, the two sails would clear each other. I also need to have the forward wishbone thick enough inside to be able to lift the masts out from within. The thickest part of my masts are approximately 10". If this is unattainable, I need to be able to take apart the forward section of the sail so I can remove the sails from the masts before trying to step them.
I do have a friend with CAD experience and a large scale printer with a roll of paper for any length printout needed.
Thanks for any and all your help!
Again I applaud your real life effort in figuring all this out!

 

[David Tyler]

That's fine. The battens we are currently making were designed to fit around a 10" dia mast, and the chord is 14' 9".

I'll update the drawings to take account of the things we've improved during the tooling manufacture, and post the dxf file here.

 

[Cat2Fold]

That's fine. The battens we are currently making were designed to fit around a 10" dia mast, and the chord is 14' 9".

I'll update the drawings to take account of the things we've improved during the tooling manufacture, and post the dxf file here.

Thanks David!!!

 

[Cat2Fold]

And what do you all think about using a type of Tyvek as the cloth? Doubled, tripled, and quadrupled as necessary? Glues nicely. Strong. Looks a lot like the sailcloth I see on small dinghies...

 

[David Tyler]

Tyvek and polytarp have been used for junk sails, so you could try. My feeling is that you would be putting so much time and labour into making battens that a better cloth would be a good investment. With well-made laminated wood battens, I'd recommend Odyssey III. I'm using Mustang, for serious ocean-going.

 

[Mark Thomasson]

Dear David,
Excellent forum, so full of useful information. I see you have built / sailed even more interesting sail types than I realised. Perhaps, in that mythical time, when you have nothing better to do, you could produce a book (e-book?), which I am sure many would enjoy.

I can see that for the ordinary folk (in my case, rather too much of an armchair sailor of late) testing our 'good' ideas by asking you first, is rather tempting, so trust that you will not mind a few simple questions.

A sail with a single sided 'flap' involves a lot of work with making a good connection to the wing section. Although a full double sided sail would involve more sail cloth, would it not be much easier to construct, and being simpler, perhaps no more expensive?

You mention that a hinged wing cannot point as high a double sided sail where the camber is locked in on each tack. For the most part this is of no significance, unless you are fortunate enough to sail a very slippery craft. Whilst I dream of building a very slippery proa, the reality may a fat cruising catamaran (Heavenly Twins giving so much for your ££s), the fat-cat may need the help of the engine to work to windward on occasion. In this case a sail that can motor-sail and point high will be of use. The thought is that a light line (ok lots - 2 per batten) could be used to lock in the camber. Would it work / be worth while?

Is your mizzen going to be a full soft wing?