Filling old screw holes in the deck

[maddmike]

Ahoy.



We are changing deck hardware for running rigging. Took off all the old stuff and filled the holes with thickened epoxy. To improve the cosmetics, we'd like to cover the patched holes with gelcoat and fake the non-skid texture.


My question: how thick should the gelcoat be? Right now some of the filled holes are slightly concave. Should we add more epoxy to the underfilled ones or just use more gelcoat?



Yes, I understand we also need to clean off the dirt that was under the old hardware.

[tkeithlu]

Faking the non-skid surface is going to be very difficult. Consider instead a goal of matching the color of the existing gelcoat with the stuff you top the plugs with. Then, the old holes largely disappear. You'll want some depression, such that the stuff you put in is a real plug rather than a thin layer on top, just for adhesion. I would be tempted to drill down a 16th of an inch or so just to make sure that the plugs won't break loose.

[rwidman]

I believe gelcoat is incompatible with epoxy. I plugged some holes with wood and epoxy and later had a gelcoat guy cover them with gelcoat. It all flaked off after a few months.

Perhaps there is some sort of primer that could be used between the epoxy and the gelcoat, I don't know.

Duplicating non-skid is very difficult. You might try making a mold from the existing surface with silicone RTV (and a release agent) and use that on your patch.

[Flatswing]

[QUOTE=rwidman;3392825]I believe gelcoat is incompatible with epoxy. I plugged some holes with wood and epoxy and later had a gelcoat guy cover them with gelcoat. It all flaked off after a few months.

This is not entirely correct-watch Andy’s vids (Boatworks today) he ran a series of tests (admittedly not scientific) bonding polyester (gelcoat) to epoxy. Way stronger than everyone says - but you must get rid of the amine blush & properly prep the surface because it’s a mechanical bond, not a chemical bond.
For your situation, wash carefully, then drill out 0.5 mm more depth, then you are good to go with with gelcoat. Overfill slightly as it will shrink slight on curing. Matching the non skid is really hard, but small-medium holes with decent color match will look fine. Only you will notice.

[xxxxx]

Originally Posted by rwidman

I believe gelcoat is incompatible with epoxy.

Right. Polyester (gel coat) over epoxy is generally a not advisable but for the size of a screw hole he's probably fine.

[shimari]

Gel coat over epoxy is a no-go as others have said. I learned that the hard way. I was able to recover by covering the epoxy repair with 3m premium filler (green can), and then gel coating. It saved the time of sanding off the entire epoxy repair. Based on your picture, you should be able to put a coat of 3m over the epoxy and then gelcoat.

Andy from Boat Works today has a video on spot repairs in non-skid areas. I haven't watched it for a while, but it might help you out.

https://www.youtube.com/watch?v=2eZLorXTNys

[xxxxx]

Originally Posted by Flatswing

This is not entirely correct-watch Andy’s vids (Boatworks today) he ran a series of tests (admittedly not scientific) bonding polyester (gelcoat) to epoxy. Way stronger than everyone says - but you must get rid of the amine blush & properly prep the surface because it’s a mechanical bond, not a chemical bond.

Interesting. I haven't seen that video yet but I'll look into it. A perfect polyester resin mechanical bond is in the area of 500psi if I recall correctly.