Plywood on top of cf foam core panel, will it warp?

4mm plywood is attached to a 6mm cf foam core panel. Used as flooring in a boat. Will the ply warp the cf due to the combination of moist, dryness, heat & cold?

 

This is a cored GRP panel, with ply overlaying that ?

 

Yes, the idea is to get a "warm wooden feeling" but at the same time be very lightweight. We would rather have chosen veneer but we can't find any that is striped as in classic decking.

 

The ply will be attached to the sandwich panel, how ? Certainly would stiffen things up appreciably if bonded, and if the sandwich panel is firmly attached, to the sub-floor, I can't see much of a problem with warping. If the sandwich panel is stiff enough underfoot, as is, you could use loose-lay vinyl, instead of ply, plenty of wood patterns available in that.

 

It works as long as the plywood is totally sealed. Any moisture entering the plywood could cause it to warp. If the bond between plywood and sub-floor is strong, the worpage could include the sub-floor. If the bond is weak, then the plywood will lift away from the sub-floor.

Effectively sealed plywood is slippery when wet.

I whole heartily endorse MrE's recumendation of vinyl or or pergo style flooring.

 

Thx for your insights. Ultimately we don't want to attach it to the subfloor, but rather have it floating as in this picture

This is veneer on top of foam cored carbon with no attachments.
But as we can't get hold of that striped veneer and timber is strong I'll revert to ply and screws.

 

May I ask why you don't do the obvious thing and veneer the floorboards yourself? That "striped veneer" does not grow in a tree like that, it is made out of strips of different woods. Just buy some contrasting woods you like, cut to size and glue to the panel.

 

Good question. Since I posted the question I've actually been looking into exactly what you're suggesting. Seems like you still would have a bottom layer of veneer to compensate for warping. Cf is already quite expensive and veneer is actually more expensive than I thought. But I'll give it a shot.

 

No need for any bottom layer, just glue the veneer on with epoxy. A vacuum press would be usefull. 3mm thickness is enough. Use knife cut or sawn veneer with a vertical grain face.
As for expensive that depends on the species you want to use. Pine and birch are not expensive.

 

Labor intensive but cheaper to buy solid stock and rip it into 4mm strips. Then plain to 3.5, flip and plain to 3mm. If you have a good table saw and a great plainer.

 

With laminates of either composites or timber it is generally regarded as good practice to have a balanced laminate with similar amounts of material above and below the core. I can see the risk with the proposed construction but would think it is fairly minimal if the ply is well sealed.

The teak and holy faced boards do look nice.You can buy them by the sheet and Bruynzeel do a good one.Making your own gets expensive if you take into account wastage of at least 50% by sawing and then you have the time and effort of gluing and finishing after you have made the panel with good glue lines between the strips.If you can buy veneer thats thicker than the usual furniture thickness of 0.6mm it makes a bit more sense.You could use any old veneer on the reverse as a balance.Again it starts to get expensive if you factor in the time taken and it might have been better just to buy 12mm decorative ply in the first instance.