Long time ago, because I had some, I used lightweight bonding plaster (with vermiculite. IIRC it may also be called "browning", or that might be the next layer) to fill a hole in the front inner wing on a Morris Marina (1930's British components held together temporarily with a series of Italianate rust-traps. Loved that car) to give me backing for a fibreglass patch.
Worked really well, much easier and cheaper than "bondo" or equivalent. Would probably absorb more moisture but sprayed with oil it didn't seem to. If I was using it again I might try mixing vegetable oil in with it, though that might stop it sticking.
Later, because I was in the (British) Army Reserve and they let me use the gas welder, I welded up the rotted out box sections. Super-strong job, quite satisfying experience, but a much bigger waste of time since something else killed the car a year or so later.
Don't bother with "proper" repairs unless you're committing to a full restoration.
Worked really well, much easier and cheaper than "bondo" or equivalent. Would probably absorb more moisture but sprayed with oil it didn't seem to. If I was using it again I might try mixing vegetable oil in with it, though that might stop it sticking.
Later, because I was in the (British) Army Reserve and they let me use the gas welder, I welded up the rotted out box sections. Super-strong job, quite satisfying experience, but a much bigger waste of time since something else killed the car a year or so later.
Don't bother with "proper" repairs unless you're committing to a full restoration.
