Hi everybody
The stressform system (tortured plywood) is a quick and easy system to build very slim round bilge boats out of two identical hullsides cut out of two pieces of plywood. I had made some models (in that system you need to) and wanted to try to build that hull in a size I could build alone for the lake of Zurich. Also I wanted to see how it works in a bigger scale than a model before I would go to Thailand and build it in 12 meters length. The interior is very simple, just a floor of 3 meters 60cm wide, so I can sleep inside, 4 bulkheads and 4 ribs.
She weights 125kg and has 14m2 sail aerea in one jib. The throat of the jib is sliding along a wire from bow to bow. The rudders are retractable inside the hull and are only movable when completly out. So near the beach I use a yuloh for propulsion and steering.
She sails well ballanced and easy. I only was once on the water in light winds. The next week I had a motorcycle accident and it took me a year to recover. Then it was time to go to Thailand and build a bigger version. One day returning to Switzerland I will sail her again. The name Nixe means mermaid. Kleinnixe is the small mermaid.

Hi Alexander, and welcome to the forum. Thanks for posting the pics of this beautiful little proa! I LOVE the shapes you have developed from the plywood. How long is she? Surely more that 2 sheets of ply? What a shame you had only sailed her once before the accident!

Hi Michael

Thanks for your comment. She is 6 meters long, the ama is 5 meters, she weights 125 kg, what I think is not a lot. I uses 4 mm ply sheated with one layer of 165 g/qm glassfiber. All epoxied. As I love bamboo I used it for the platform lengthwise and have woven into brown nylonbelts abeam. That looks quite nice, is good to sit on and is a bit flexible but not hanging down where you sit. The beams are a squar box and have a hinge about in the middle so I can easily transport her on a 1.80m trailer and spread her out floating in the water. The keel of the ama and the keel of the mainhull come close together when folded.
The mast is 9 meters made of 1mm plywood wrapped in 165 g/qm glass and epoxied. So I can have a 14qm sail (cut like a foresail) what is a limit for boats without insurance in Switzerland. For very light winds I have a Genoa of 18 qm. To shift the sail there is a wire leading the throat from bow to bow.
The rudders are retracting inside the hull. As I don’t like the sight of upward protruding daggerboard rudders I made them as you can see in the drawing below. They work very nice, only that they are only movable when completely run out. Otherwise they are fixed daggerboards. There is a leading block with a round pipe inside that holds the rudder in place and goes up and down when lowering or taking up the rudder. The rudderblade has a square pipe inside all going down where the thinner rudder shaft sits in. So the rudder together with the block can move up and down and the ruddershaft and tiller stay in place. That works very well only I never touched the ground. The rudder shaft is quite strong (stainless 1mm wall) but if it bends the whole thing would have to be taken out, what is easy possible by opening a square top (visible in the fotos).
When I have finished my Nixe project here and being back in Switzerland I will take her out again and see what tere is to make better.
Cheers
Alexander

Hello Alexander,

what a wonderful boat!!! I know its a naughty question ... but would you share the design with us and give us the panel offsets and keel angles for reproduction? I think this is a very fast and cheap way to get a beautiful proa. I’am interested espeacially in the design and costruction of the mast. Some scetches and a little more detailed scantlings would be nice.

Many thanks in advance, Michel

Hi Michel

Yes, I like to do that. It just will take some days, because I am in Thailand now and all papers are in Switzerland, but my wife can scan and email the sketches to me so I can post them here.

Have a nice day
Alexander

Not a critisism, but:

I read somewhere that plywood does not actually torture that much.  What looks like a 2 way curve is in fact due to a conical section.

How much do you find is managed, for Nixe especially?

Mark

Hi Mark
Plywood can be bent in three dimensions. On the high sided hulls of Nixe and Kleinnixe it seems to be less than in the lower outriggerhull of Nixe. The higher part of the sides can not be bent inward, lower siedes can. If you follow the line of the scarfings on Kleinnixe or the end of the fiberglass on the outriggerhull of Nixe you see that there is a curve vertically. The other curve horizontally is the bulwark.

Alexander