DIY pocket foil board buoyancy

[Matthijs94]

Last weekend I made a pocket foil board. Two plates of 6mm poplar plywood with reinforcement (meranti plywood 18mm thick) at the baseplate. Dimensions 90x45x1.2cm (with reinforcement 2.4cm thick). In between the poplar and meranti I placed 4 inserts with a big plate (80x30mm). Total weight of the board 2.4kg. Planning to give it 4 layers of fiberglass 200g, 2 on top, 2 at the bottom. Which gives it a roughly total weight of 3.4kg. The structure is strong enough in my opinion. Only thing I am not sure about is the buoyancy. I am riding a Slingshot hover glide NF2, which is not light at all (5.4kg - 11.9lbs). Still need to add deck grip, which also adds some extra volume.

Any experience with adding some volume? I saw spherecore, which adds volume, any experience with that material?

[TomW]

Best way is to put eps or 30 kg PU foam between. 10-20mm thick. Then embed the reinforcement for foil in between the ply skins. That core you show will suck up a ton of resin and add almost no flotation.
You can buy 10mm PU foam in smaller pieces and have it in several pieces, it doesn't have to be in one sheet. Easycomposites.co.uk

[merl]

I can't see why you would need so much glass on a plywood board. Can you test the stiffness? I recon it will be stiff enough without any glass. If stiff enough then just coat it with epoxy for waterproofing. If not, just stiffen the center with some 200g and then coar the whole thing in the lightest cloth you can get. If you add low density foam to both sides then you will need glass for impact resistance, but the amount you need will depend on how soft the foam is.

(I'm no expert but have messed around with plenty of plywood, foam, epoxy etc.)