Sailing a new small twinhull (Help!)

Hello to all sailing experts!
I recently invented a new type of twinhull personal watercraft.
So far it's been used only as a paddling boat, and now I'm looking to find out how to sail this thing.
I'd like to cooperate with an expert sailor (canoe, hobie cat, dinghy or any small boat) and/or windsurfer, preferably from around Boston, MA.
The basic idea is to have fun while developing something new and of possible interest to others.
Creative ideas are most welcome, preferably those that I can understand

Yoav

 

'W boat' sail

Hi Icetrader

I went to your web site and looked at your boat.
I found two possible problems:

One. The height of the rig would have to start at about the skipper's neck. That means it would have to be at least 30in above the seat. This is already a height greater than the 25in beam. This combined with a high center of gravity is bad news for sail carrying ability.

Two. There has to be a way to attatch the mast to the boat which is quite sturdy. It has to withstand 2160inlbs of torsion moment. I thought of stepping the mast in one of the hulls, but worried whether it could stand the torsion.

I thought about these two problems and came up with a solution for both of them.

For problem one, I came up with a rig with a very low Vertical Center of Area (VCA). I chose a boomed lateen sail with equal spars. Its numbers are as follows:

Boom = 105in
Yard = 105in
Tria. ht. = 72in
VCA total = 64in
HCA = 22in behind mast
Mast ht. = 86in

Sail Area = 25sft.

For problem two, I came up with a weird mast scheme. I thought of a bipod mast with a crosspiece joining the two butts together. The two heads would be joined together at the top, so the whole structure would become a triangle. Instead of being a triangle with two equal sides, it would be one with one vertical side and one slopeing side. A right triangle instead. The reason for this is so the yard and boom could be against one side of the triangle, the vertical side, and the two shrouds (needed to hold the mast up and take the forward loads) would be attatched to the slopein side and the hull it leads to.
This structure would be as wide as the boat.
Now. All you need to attatch this to the boat are: two chain plates (for the two srouds), A notch on each hull (to keep the cross piece in place), and a tie down for the vertical side of the mast. I think that all of this would be relatively easy to engineer and relatively inexpensive. the original torsion moments of 2160inlbs is now reduced to 86inlbs. The notches could either be moulded into the standard hull, or they could be added later eith fasteners.

For latteral area and steering, I decided to use the slim, relatively deep, hulls themselves. Because this boat has a very long seat, it is relatively easy to drasticly change the trim of the boat. By doing this, it is possible to make the boat round up into the wind or fall off it without a rudder. The skipper would, of course, carry a paddle. The hope is that the hulls themselves would provide the lateral (side slip) resistance.

I know the sail area is small. It would only be usefull in winds of 10kts or better. The reason for this is so that just when its getting windy enough to make paddling uncomfortable, the sail rig could be set up. With a 200lb skipper on board it should be able to handle winds up to 19kts without trouble and without hiking.

I am now going to try to attatch a picture of this sail.

I hope you like it.

Bob

 

I took a look at the WaveWalk. It's great and appears to perform nicely, but if you were to consider sailing it, I'd have to say, with the current width and length, you'd be crazy. MAybe extend it a foot or two in length and another 2 feet in width? I dunno. Definately make it larger!

 

Wow!

Bob,

This is great! -Thank you!

You managed to understand this little boat so well, and solve so many problems - It's truely amazing!

I'll start working on this thing as soon as the weather here allows me...(soon I hope)

Thank you very much!

Yoav

 

Hi Icetrader.

Thank you for your kind words.

I wish you the best of luck with your project.
Please let us all know how it turns out. This will be the most unusul sailing cat since the Gougeon Brother's 8 x 32ft Gougeon 32, which did, by the way, actually sail.

Bob

 

First test: good

Bob,

We tested the first sailing rig (24 sq ft) and everything went well.
After we test it some more under various conditions we'll go for a bigger sail, maybe 36 sq ft?
As you can see your initial idea metamorphosed -I hope you like it the way it is now.

Yoav

 

Glad I was some help.

Seems like you found an even more clever way to get around the torsion problem.

If you keep the triangle the same length and only increase its width, you should have no ballance problems.

This will mean, of course, a taller mast. But with a kite sail (for lack of a better term) this should be of little problem. Because of its upward lift vector it can be considerably larger than one with just a side ways vector.

How much larger is anyones guess. 36sft does not seem unreasonable.

Best Regards.


Bob

 

Expectations

Bob,

What you said about the boat being stable, and that it won't require a rudder was very important.

Yoav

 

sharpii2: with a kite sail (for lack of a better term)

It's a crab claw! Low CE probably helps too. The only issue I can see is you might have to get the tack up higher when you tack in a strong breeze.

 

Nice pictures, Yoav! Congrats. By the way, is(are) there rudder(s)?

 

Rudder

Thanks
No rudder - just the paddle to assist in making sharp turns, on occasion.

Interesting question though -Did the original Polynesian catamarans equipped with crab claw sails have rudders? -I suppose they did, or at least steering was assisted by paddles.

Yoav

 

Crab Claw

Yoav, I'm sure you know Marchaj considered the crab claw rig to be superior to a standard marconi(corr: Bermuda rig, main only) rig. Your method of flying it is simply brilliant! Great job!

 

Marchaj

Thanks Doug,

As a matter of fact I know little about sailing, but now I know Marchaj is a sailing guru and I'd better start reading things he wrote!

I thought that thing looked friendly enough after my wife told me: -"OK, now it's my turn to try it!"

Yoav

 

Marchaj

He goes into the crab claw rig a bit in Chapter 11 of "Sail Performance". See the correction on my previous post: he compared the crab claw with a triangular(Bermudan) main only-no jib; he also talks about other rigs as well.

 

Why this sort of rig? Why not a gaff, bermudan or other common sail? Maybe for a larger WaveWalk, have a Hobie Cat style rudder, with a main tiller, two rudders branching off into a single tiller in the cockpit.