Thread: Getting contour on plywood seats

Suggest also heating the casts before applying them.

Maybe heat the ply and casts loose but together, then spray hot water onto both and reheat.
Spray hot water again onto ply and then quickly apply and lightly clamp heated casts,
Avoid clamping down hard in the first instance.
I'd keep the clamped ply and casts hot and increase pressure every few minutes.
One way of keeping things hot is to use a couple of 100W incandescent light globes inside an insulated wooden box - add dimmers to control temp.

Thanks BobL - some good info. I was thinking of making the moulds with a 50 x 25mm surround - then placing them into a 30 x 25mm surround (same fit) when dry, to allow the moulds and ply room to have space to clamp together to form the depression. Do I need to seal the face of the moulds? With shellac or pva? Also will I need a releasing agent between the ply and the mould? Was also thinking of making the ply slightly larger than the template to allow for shrinkage. Tis all new ground for me so your thoughts are most welcome. Kind regards, Grahame M GM2

Originally Posted by GM2

Thanks BobL - some good info. I was thinking of making the moulds with a 50 x 25mm surround - then placing them into a 30 x 25mm surround (same fit) when dry, to allow the moulds and ply room to have space to clamp together to form the depression. Do I need to seal the face of the moulds? With shellac or pva?

I'd use 2 pack epoxy.

Also will I need a releasing agent between the ply and the mould?

Probably not needed if epoxy is used.

Was also thinking of making the ply slightly larger than the template to allow for shrinkage.

Yep - good idea.

Is 3mm ply strong enough for a seat? How does the seat fit to the frame?

Is this just curved or is there an actual 3D bum shape in the ply.
A photo would help.
Simple curve easy as, just single sided mould and a follow piece and vac bag or a lot of clamps.
3D in ply ‘interesting’, probably use veneer and lay up ply into mould as you go with epoxy and vac bag.
Something like patternstone might stand up to the pressure needed.
H.

start with 3mm ply cut to shape soak in hot water or steam if you can and shape it onto a mould, maybe an old tractor seat.
oh yeah lots of clamps!