I’ll be performing a repair with Marine-tex epoxy. Unfortunately the instructions say that my gel-coat paint will not adhere well to the Marine-tex. Does this mean that I should just buy some other paint or is there some prep work that I could do to make the gel-coat work to some degree? I’ll be using the gel-coat to touch up other minor dings, so it would be nice to stick with just the one paint. Any advice/comments would be appreciated.
Gelcoat repairs are meant to be …
...... filled proud of the surrounding surfaces (and a thin coating also allowed to go beyond the actual chipped out Gel onto the existing good Gel which has been sanded also) ... then allowed to cure (24 hrs.) , then sanded down progressively using lighter papers each time (80-600) to a fair surface blend (OOOO steel wool can be used prior to buff out also) ... then buffed out with a fiberglass buffing compound (Wa La becomes invisible if you have a good color blend) .
It is best to use an air-cured type Gelcoat (waxed) "for repairs" so it's surface will harden and not remain tacky (but a non-waxed or non-air cured Gelcoat can be used if covered from the air as it cures) .
The new Gelcoat you fill the into the repair area should be "at least" as thick as the existing Gelcoat (which means if you are pre-filling with another material , "do not" fill that material to the surface , but keep it to the underside of the existing Gelcoat)
Prep work performed properly is important before beginning the fill . This is the sanding proceedure used to etch the existing surfaces for good Gelcoat adhesion purchase , and the sanding also sterilizes the repair area ... also the perimeter of the chipped out gelcoat should be beveled inward at a long shallow angle , dremel is a good tool for this (again better purchase and contact area for new gelcoat fill) .
Best to blow out all dust before filling ... some use an alcohol wipe off also (not me) .
Fillers should be vinylester or polyester under a polyester Gelcoat (not epoxy) .
Structural repairs are a case by case bases .
Marine-Tex (an epoxy) is meant to be a stand alone fill and sand out , or paint over .
Got help from the neighbor
Thanks for all the suggestions. My neighbor (who is an ex body shop guy) offered to help with the repair so we fiberglassed it. The hard part was not building it up too high as we had to glass from the outside (air chamber on inside prevented access). Anyways that part went ok. The gel-coat no so well. I spread it on and then covered with wax-paper. When I removed (or rather tried to) the wax-paper a few hours later much of it remained. Also it was very difficult to smooth out when initially covering the gel.
Not sure where to go from here. My neighbor suggested we sand it down and spray it. He’s not familiar with gel-coat so he’s not sure what to add to the paint to make it sprayable. Any suggestions as to where to go from here would be appreciated.
Sand it down and apply another coat of gel coat. I’d use mylar or saran wrap instead of wax paper though. Also depending on how big the area is, you might want to do it in two parts. I’ve had better luck doing a smaller section, say 6x6 inches max, than a larger area.
What should be used to thin the gel for spraying? Also since I don’t want to grind the wax paper into the paint, any suggestions for removing the wax paper another way?
it’s Gelcoat not paint …
....... air cured Gelcoat is made to be sanded , faired and buffed with a compound (rouge) . It's hard stuff not soft .
Did you know you can sand and polish out a piece of plastic to a high shine in similar manner ... Gelcoat is way much harder than plastic .
There are essentially two types of Gelcoat , one is a tooling Gelcoat , the other is general purpose . General purpose is what is used in the construction of boats , autos etc. ... tooling is used for molds and other things . Tooling Gelcoat is far to hard and much less flexable .
Can't see your stuck wax paper but I would do one of two things , burn it off with a flame and scrapper or sand it off (or both) .
Acetone is used at 10% (max.) by volumn to reduce Gelcoats for spraying . The reducer must have a very high evaporation rate (as does acetone) to allow it to evaporate between spray passes ... when spraying do not lay thick coats on but only ghost passes so the acetone can mostly evaporate before the Gelcoats' surface begins to skin over (a thick coat of spray will trap the reducer below the surface skin and cause problems) ... ghost passes and 10% acetone .
Since you layed in a fiberglass cloth patch over the existing skin (Gelcoat) surface you have two choices (well ,there are others choices but they go downhill from there) , #1., ... grind the patch away and re-do it properly by applying the fiberglass material and mixed resin to the existing construction fiberglass (this means remove enough Gelcoat for the new patch area and don't put the patch on the Gelcoat but the glass only .... or @2., ... fair out the patch you just applied over the existing Gelcoat as best you can do by sanding , and apply new Gelcoat over it all and fair that out as best you can (it will not be in plane with the existing surrounding surface but maybe you can at least make it look smooth and faired enough to suit you) .
Yes that's right , remove original existing Gelcaot to lay in a sub-surface patch !!