Masking Gel Coat on GRP Repair?

Joined
20 Jun 2007
Messages
16,234
Location
Live in Kent, boat in Canary Islands
www.bavariayacht.info
I'm removing a 100mm diameter speaker from a GRP instrument panel, blanking off and fitting a smaller display. The plan is to lay up gel coat then GRP on a sheet of glass, cut a circle slightly under-size, then place in the hole and mask the gap from the front. Finally fill the gap from the rear with gel coat, then laminate over. With a bit of luck there will be little filling to do afterwards, he said hopefully.

Ideally I'd use some wide "sticky backed plastic" to hold the infill and mask the front edge, but it obviously needs to be resistant to styrene.

Suggestions?
 

laika

Well-known member
Joined
6 Apr 2011
Messages
8,173
Location
London / Gosport
Visit site
Can you build your infill in situ? Bevel the edges of the hole, cut glass mat circles in increasing sizes from the diameter of the hole to the diameter of your (shallow in the inside) bevelled edge, find some formica or other suitably shiny substance to stick over the front of the hole, coat with release wax, screw around the hole, paint on a few layers of gelcoat (I found I had to "stipple" more than "paint" the first coat due to the wax) from behind, laminate with your mat circles, grind smooth, remove shiny thing from front, touch up front gelcoat as necessary (grinding out with a dremel and filling as necessary, including the screw holes you just made), then sand through the grades and polish?
 

lw395

Well-known member
Joined
16 May 2007
Messages
41,951
Visit site
I've found clear or brown parcel tape, the nasty thin 50mm wide stuff to be OK with polyester resin.
But I'd check, because the stuff you have may not be the same as what I had last year.....
I like it for masking because it is so thin, it leaves a smaller ridge to polish out.
 

maby

Well-known member
Joined
12 Jun 2009
Messages
12,783
Visit site
I've never done a repair in the way the OP describes, but I've always found that standard masking tape works perfectly well. The proposed solution is ingenious - I would love to hear how it works out. I don't think I would bother with the step of infilling the join with gelcoat from the rear - I doubt that you will be able to get the bubbles out well enough to leave an invisible join, so you may as well fill it from the front after you have glassed the patch in from the back.
 

capsco

New member
Joined
20 Nov 2001
Messages
1,619
Location
North
Visit site
No it is important to apply gel coat first otherwise you will need to grind the matting back before you can apply the finish gellcoat, it is possible to get a very good finish the way laika describes, not usually perfect 1st time but a very sound start.
 
Top