Originally Posted by Forward Look
Thanks to all who have added to this thread-- it's a great resource as I tackle the same project.
I'm hesitant to use any kind of plywood, OSB, waferboard etc. for this small but structurally important piece. I'm worried that should it ever leak again, we'll be going down the same road twice.
For around $10-$15, I can get a piece of solid pine, poplar or oak -- but I'm also thinking that a piece of PVC (plastic) board might also be an awesome, completely rot-resistant option for roughly the same price. Any thoughts on the PVC to fiberglass bond, or its suitability for this application?
It took me a while to re-bed the window with butyl tape, and clear the weep holes that prev. owner sealed so that wood was exposed to water several times by window leaks
before I finished work (this spring I go the last drip) BUT the plywood is completely coated with fiberglass resin before I installed. Wood can't get wet. End grain three coats, top, bottom a good solid two coats.
Then after installing tabbing it in with fiberglass and resin to attach to camper puts some more fiberglass between wood and outside world. My guess is it wouldn't rot in a bucket of water.
Plywood is generally stronger in most uses than same thickness of solid wood. Grain in each layer of plywood runs opposite ones it is between. Alternating grain lines + glue + massive pressure yield more strength than wood alone. Might consider marine plywood but if all is sealed in fiberglass resin all the extra cost of marine ply buys you is fewer voids and waterproof glue.
Attaching to wall would be biggest headache I would see to non wood solution. With wood you just "tab" strips of FG cloth or matting and resin like tape. Using thickened resin or epoxy as a filler in the wall to wood join. That bonds to the properly prepped wall and the properly prepped wood with a great deal of strength. You walls are attached to the scamp
floor with tabbing and it holds until the wood rots out. Which usually take a long time because the wood is coated with fiberglass resin.