Subwoofer Box out of Fiberglass

pyrotek

Petty Officer 2nd Class
Joined
Nov 19, 2011
Messages
183
Previous owner of boat installed basic 10" subwoofer under the back-to-back seat where there is small storage. It is not sealed. Woofer was cheap and light and needs to be replaced. I have an older very heavy woofer that needs to be enclosed in a small sealed enclosure. The current seat base is made out of pure fiberglass which is about 3/16" thick. The weight of this unit would likely crack the gelcoat, due to the large 10" hole cut out (not much other support). I would like to re-inforce the enclosure and seal off the back and top (under the seat cushion).

This does not need to look pretty since you will only see the new fiberglass inside the storage closet. I think I should use 3/8" plywood to re-inforce the current front and create the backing. But due to the complex rounded shapes, the plywood would be very rough cut. In fact for the front, maybe only one to two inches of plywood would be around the 10" hole. For the other joints the fiberglass would have to fill large 1" or larger joints where the plywood doesn't meet up. Can I expect any issue with this? Should I just slather it up with PB, or start layering up woven cloths? I'll be using Poly or VE (may be ordering for a different repair). I don't want to spend too much time getting exact cuts since I know its impossible. Maybe I don't need the plywood at all for the re-inforcements parts?

If I could double the stiffness of the current fiberglass I would be happy. I'm not looking for acoustic perfection or to have neighbors hear this (I'm not on a lake anyways).

Any tips, appreciated. This will be my fiberglass practice before I attempt to rip up a portion of my floor that is soft.
 
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