Sealing in fuel tank

[Jeklund]

I've been working on restoring a boat that was gifted to me. The fuel tank was pulled and cleaned and now I need to seal it back up. I have cut a piece of marine grade plywood to fit over the tank and was planning on glassing over it. Would I be able to just lay some fiberglass mat over the screwed in a piece of plywood? I don't really care about the finish as the boat will be getting carpeted but I just want to make sure the patch over is rigid and strong enough to have people walk over it. If it's fine to just use CSM in a few layers (versus using say something woven as a middle layer) how much overlap do I need onto the existing deck? Attached is the best picture of the deck for reference (sorry about the shop vac in the way).

I don't really have much experience or knowledge about fiberglass so if you need any clarification I'll do my best to provide it.

 

[Baylinerchuck]

How thick is the plywood? Are you planning on leaving this as an access or permanently sealing the tank in?

 

[Jeklund]

I plan to have it permanently sealed in and the plywood is 1/2 inch thick.

 

[dingbat]

Permantly glassing the floor panel would be a mistake.

Things can and do go wrong with permantly installed tanks. Fuel senders and anti-shipon valves go bad. Not to mention semi annual inspections that should be done.

Build an angle iron support to recess you panel. Glass the panel and screw it to the frame. Lay your carpet over that.

Worse case, have to remove carpet to access the tank

 

[Jeklund]

With the way the engine cover sits I still have access to all the ports on the tank to do annual inspections. I would only not have access to the sender.

I did not think to just support the tank, glass the cover then mount it. I feel that was probably how it was prior to being gutted and the better solution. It doesn't appear though that there was anything underneath the old cover to support it. The cutout just has a lip 1/2 inch depth from the deck. Would I have to chisel out part of that to recess the supports so the deck stays level? Or could I just get away with glassing my cutout and mounting it down?