Seat rebuild recommendations

   So I spent the rainy day researching CCF and the web on tips and threads for seat rebuilds, which lead to many side tracks. In 2 weeks I plan on rebuilding my seats and reusing the same good upholstery. I guess exterior grade plywood is still the best choice? I'm thinking 5/8 but my dad says we used 3/4 20 years ago. I'm thinking 3/4 is overkill, no? I was going to CPES then epoxy over that. I know about as much in resin and glass as I do brain surgery so I'm just doing this as a practice. Of course Im using SS hardware and need to re-order SS staples and want to order everything so it'll be here when I need it.

No joints on a basic 70's interior, Pete.

I'm not convinced cpes and epoxy are a better way to go on seats vs. treated ply. One day I plan to put together a better solution than wood, but it will probably involve 2 different composite materials sandwiched together-
One for strength, one for staple retention. It seems there is no magical material that does both well (and doesn't rot).

Id be curious to know exactly what you used... got any scraps left that you can post a picture of? The 2 composite materials Ive seen suggested for seat base use are HDPE (high density polyethylene, like King Starboard) and XPCV (expanded polyvinyl chloride like Sintra Board). Correct Craft uses the latter in their seat bases. Both are supposed to accept staples.

The problem with XPVC is that its not all that strong... which is fine on a modern interior where the seat bases are well supported by the frames. Most times theyre 100% supported by glass structure, other times the spans are very small.

I have read numerous accounts online of HDPE bowing or warping due to age, temperature, or weight. I'd be a little nervous using it alone if the spans are large.

A 70's interior has large unsupported spans- most notably on the observer seat, where 2 aluminum frames (2" wide) carry the full load over a 30-36" wide seat. Lots of opportunity for flex.

Many structural composites, like coosa (which is foam and fiberglass based) will not hold staples well- making it a poor choice to wrap upholstery around. I think a hybrid seat base made of a 3/8" layer of coosa (glassed on both sides) plus a 3/8" layer of XPVC would be pretty much ideal from a strength and longevity standpoint. The downsides would be cost, and complexity.