Gelcoat over Raka Epoxy?

[TomS]

Just a quick post to confirm the bit of research I did today -- it is not recommended to gelcoat over epoxy, correct?

I'm sure that there are ways that it can be done, adding another filler/buffer layer of some sort, chemical or otherwise.. but just to keep it simple, lets ignore those options for now.

I am re-repairing a crack in the lip of my transom near the engine mount. I have already dremeled it out, filled with thinned epoxy and then topped off with an epoxy/cabosil mix. There was a bit of shrinkage during the cure, so I'm left with a thin crack that needs to be filled, just to keep water from collecting.

I was planning to try and gelcoat over it as the last step, but now think I am better off mixing up another small batch of epoxy, thickened pretty heavily to make it more opaque and applying proud of the remaining crack to dry - then sanding flush.

I'm not so concerned about color matching, etc..

-- Tom

 

[TimC2520]

If you are sure the core is sufficiently protected with the already applied epoxy, I have used formula 27 followed by gelcoat on top with success. I had to fill some old ducer screw holes in my transom and for my first time, I can't even find the repair now some 5+ years later.

 

[DaleH]

FWIW the base of both the Parker gelcoat and Formula 27 is a polyester resin. Technically, one shouldn't or isn't supposed to gelcoat directly over epoxy, but with the right techniquevit can be done.

What I do is use both products above and ensure the epoxy protects only the core where needed and is wickedly roughened up, to at least ensure a mechanical bond with the F27. F27 will also adhere both chemically and mechanically to the glass edge of the area to be repaired. The F27 should almost, but not quite fill the 'divot' remaining to be filled.

Then I gelcoat the divot and wet sand, rinsing the wet/dry paper in water so it is in the water more than on the gelcoat.

FYI, I repaired (30) 5/16" holes PER SIDE, from my old bow rail, in a such a 3-step manner ... and I defy anyone to find any evidence of the repairs in less than 5-minutes of careful looking.