My ply tub is looking rather tired its had a lot of use and its also been hacked about with experiments to get the balance right so I am now looking at replacing it with a GRP tub, I have done quite a lot on small GRP projects but not as big as a yacht tub so I would appreciate any comments and pointers on what I am hoping to do. Intention would be to build a foam/timber/ plaster plug around my chassis, when finished double sided thin sections would keep a foam inner, flat single sided sections would be released from the plug. I have used 300gm CSM in the past and thought about using 3 layers with extra reinforcement for mainsheet mountings etc, then topcoat for a finish. I am building it primarily to get a better shape than my ply tub and more durability but it would be nice to save some weight if poss, can anyone suggest what weights/layers of woven or combination mat might be an alternative?

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Bynorthsea said..
My ply tub is looking rather tired its had a lot of use and its also been hacked about with experiments to get the balance right so I am now looking at replacing it with a GRP tub, I have done quite a lot on small GRP projects but not as big as a yacht tub so I would appreciate any comments and pointers on what I am hoping to do. Intention would be to build a foam/timber/ plaster plug around my chassis, when finished double sided thin sections would keep a foam inner, flat single sided sections would be released from the plug. I have used 300gm CSM in the past and thought about using 3 layers with extra reinforcement for mainsheet mountings etc, then topcoat for a finish. I am building it primarily to get a better shape than my ply tub and more durability but it would be nice to save some weight if poss, can anyone suggest what weights/layers of woven or combination mat might be an alternative?

Do a search for Lindahl LR4 A Class catamaran home build. Perfect for you. Foam strips and glass/carbon cloth, male moulded with wet lay up. Very achievable for the home builder.

if its a one off , considermaking a mold with smooth surface on the inside ,then glass,2 3 layers in places and some coremat for stiffening,where required. then break off the oute mold. i used anything at hand,chipboard,corflute,carbog, all waxed and sealed with PVA mold release before glassing

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landyacht said..
if its a one off , considermaking a mold with smooth surface on the inside ,then glass,2 3 layers in places and some coremat for stiffening,where required. then break off the oute mold. i used anything at hand,chipboard,corflute,carbog, all waxed and sealed with PVA mold release before glassing

This was my original intention and the work has begun, the basic mould is made from building insulation foam and timber.





This has been refined and filled with plaster, trouble was that with the low winter temperature it had to go inside to dry out and to seal


Was I in trouble for the dirty marks on the carpet but work progressed and its been sealed and a coating of PVA release agent.



It now ready to go back to the workshop for three layers of 450gm CSM and then a top coat, hopefully this week but I need to get the temperature above 5deg so its very much weather dependent

did you wax onto the layer of bog or just PVA?. you are gonna make a hell of a mess digging the foam out afterwards

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landyacht said..
did you wax onto the layer of bog or just PVA?. you are gonna make a hell of a mess digging the foam out afterwards

The mould was finished with polyurethane varnish to quite a good finish before the PVA and then waxed for good measure, I expect to have to dig out the plug. Weather has been good this week so I have managed to make some progress with the layup.




layup seemed to go quite well, left it overnight before dismantling and digging out the mould.




Very pleased that the major parts came away easily and the rest dug out ok.




A few areas will need a bit of remedial work but so far so good.




The surface now needs shearing back, filling and rubbing down before top coating.

Excellent job, really impressed. thanks for sharing. That is a great way to make a one off seat.

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aus230 said..
Excellent job, really impressed. thanks for sharing. That is a great way to make a one off seat.

I have given it a few more hours now, first it was rubbed down and filled to refine the surface.




It then had a couple of coats of flow coat and more rubbing down to get a finish. I have not gone overboard only finishing the outer surfaces and then only just I have not got a power mop and anyway as soon as it gets rigged on the beach its going to get scratched, but overall I am pleased with the result it has given me a clean simplified layout compared to what I had. Can't wait to try it but it should sail just like the old one, just look better

Great Job
A kindred spirit also ! Battleship grey yacht and ski axles

And a matching broom......

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Gizmo said..
And a matching broom......

Not only a matching broom but a matching front mudguard. Had some resin and mat left so decided to have another go at a guard to keep some of the wet off. sacrificial plug from foam first.




Then the layup.

how did you resist the dark side of the force when you painted the wheel cover