What to use for floor?

Just removed a rotten 1/4 ply floor out of a mid eighties mod-v boat. I was going to replace it with plywood again, but have been told to use klegecell or divinylcell to keep from rotting again and to save weight. Sounds good to me, now what thickness do I need? I plan on building ribs on the walking area for added support.

1/2" would be the best. The manufacturer will tell you exactly what you need in terms of density and thickness if you give them the spans. The only problem you may have is with the cost vs. plywood, but rot-free is a good thing.

[getyouone]

I have a allison mod v to replace the stringers and floor and the owner dose`nt want wood. He said that allison uses fiberglass reinforced pvc? I would be interested in what you decide to use. mike

[tgundberg]

If you are replacing 1/4" plywood, I would reccommend using at least 3/8" 5 lb/ft^3 foam (Divinycell H80, Klegecell R75, or any other equivalent density). On the walking side of the deck, you should have around 0.080" thick fiberglass for puncture resistance, and around 0.040" on the backside. Just a quick analysis.

[getyouone]

thanks for the recomend, first I have to get to the floor, top deck is glass to the hull,oh what fun!!!