botttom fairing

[phil416]

When I returned to the boat after her first winter on the hard I noticed a greenish liquid oozing out at several locations thru the bottom paint.  How bad was the damage?  The hull sounded out as solid, but I had to accept the visual evidence.  To make a long story short the previous owner had faired out gouges on the hull with Bondo.  I sanded down to the hull  and covered the faired spots with several layers of 7 oz cloth applied with epoxy.  Problem solved.  Amazingly the same problem was encountered on a Moody being purchased by a Portuguese friend in Povoa de Varzim.  Even the surveyor was baffled for a while.  The bottom line is that Bondo has no place below the waterline, and probably no place on yours or anyone elses boat.     Fair Winds Phil 

[Oldrig]

The bottom line is that Bondo has no place below the waterline, and probably no place on yours or anyone elses boat.

I always thought Marine Tex was the nautical equivalent of Bondo.

;D

[CharlieJ]

Bondo is polyester based. Marine-Tex is an epoxy. Huge difference.

[s/v Faith]

Bondo is polyester based. Marine-Tex is an epoxy. Huge difference.

Yes, and Bondo would be ok... if not for the choosen filler.

You can thin bondo with fiberglass resin (even the Bondo tech support will say so).

The catalyst for bondo is the same as fiberglass... the problem with marine use of bondo
is that the filler is talc.

  It will absorb water over time... just like talc...

I HAVE found one suitable use for it on a boat though.  It makes a reasonable bedding compound for backing plates.
(on the inside of the hull).  So your flat backing plate (like under a cleat) does not rest on a curved or irregular surface inside the boat... but can transfer force evenly)... I believe that I gave a better explanation in the 'deck hardware' thread.

[JWalker]

I think what oldrig may have meant is that if you were going to use bondo on a car, you would use marinetex on a boat for a similar application.

Which I admittedly have done.  ;D