GRP Inflated Tarp Mold - How to Achive Look Like a Yrvind 4mt Boat

I bought large tarp and want to cut , tape and inflate it for use as male mold for polyester glass. How should I cut and tape it to achieve a look like a proper yrvind 4 meter boat ? I am thinking 2 long aluminum tube to keep the shear line and cut the tarp as circumference long as each post.

 

Not so easy. You are going to need a much more taut female mould. When FG cures, it distorts fabric. Even tightly stretched material will bend and ripple as the FG cures.
Unless you want a rippled, bulging result, you should go to the trouble of a solid mould.

 

Perhaps somewhere in between can work if he can find a bit of timber and make a skeleton mould and cover it tightly with the tarp and staples..

Certainly not going to win any awards, but I've seen people make a boat with a skeleton frame of woodland timber and a tarp.

 

Try a small test section. I think you are going to be very disappointed. I am talking 1-2 centimetre ripples here.

 

What do you intend to do with this 4 metre long Yrvind type of boat once you have built it?
Do you want to cross oceans and try to beat Sven's records, or just potter along the coast of Turkey, or something in between?

If you list your Statement of Requirements here, that will help a lot in your decision as to what type of boat to build.

 

I've made more complex shapes out of an exercise ball heavy wall tube... local guy up here produced a complex shape with thin balsa slats and aircraft cloth. Someday when the ground dries I need to crawl up under that thing and take a Pic of that tunnel.

 

True. Definitely needs to be more than just an inflated floppy Tarp, especially if you are laying up hull thickness number of layers, in Bi-Axial

 

Build a wooden frame, cover it with a tarp and go to sea.

 

The closest I have seen to what you are trying to do is one of Kim Fisher's experiments. He made a mold for a 1 metre long model hull out of lycra stretched over a few stringers and stapled to the gunwale. If I remember correctly, he then used epoxy to give the lycra a bit of stiffness, let that set, and only then laminated some Parabeam over that. Parabeam is two layers of glass woven together so that fibres between the layers give some compressive and shear strength to make a sandwich. I don't know how compressive and shear strength compare to foam sandwich. Perhaps you can find some information at Parabeam https://parabeam.com/

Kim's hull looked fair. He thinks the method would scale up if the spacing between stringers is no more than what he used, about 30 cm if I remember correctly. However, building a boat from Parabeam would be an experiment, and carry the risk of losing your money and work to a failed experiment.

Are second-hand glass fibre canoes available cheaply in Turkey? If yes, you could buy a pair, ideally identical, cut the decks off exactly horizontally, put one hull bottom upside down on top of the other, and glass them together, perhaps after putting in some ring frames and stringers. Cut a hatch into the one you designate the deck. Use your tarp to make a sail.