Fiberglass filet question

Josh Schwenger

Josh Schwenger

Active member
So I am attempting to bond plywood inside a sunfish hull. I have to install bulk heads to existing fiberglass. If I want a structural bond between the plywood and the fiberglass using epoxy resin can I use wood flour or should I use a different material like micro balloons or something like that to create a structural filet.
 
Wood flour will be fine. Micro balloons are for fairing. Cabosil by itself is harder to sand than wood flour and can cause gouges in the softer wood when you attempt it. A mixture of wood flour and cabosil is often used to get a nice fillet compound yet sand well too.
 
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One other thing to keep in mind; The new epoxy will not chemically bond with the present fiberglass. Therefore the surface of the present fiberglass should be roughed up with coarse sandpaper to provide "tooth" for the fresh epoxy to latch onto.
 
Yeah my plan was to sand 6 inch wide or more area with 80 grit on both sides of bulkhead I sand the plywood as well though I?m not sure it?s necessary. I pre wet out the ply about ten minutes prior with epoxy and seal end grain.
 
Depending on what you are bonding, adding fiberglass fabric over the fillet and extending on to the wood and glass would be even stronger. I wouldn?t think that would be needed in many cases where you are adding plywood to an existing hull, but if you were adding a transom or something like that, it may be appropriate. Are you adding a structural support or just something to partition the hull?
 
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