Support Backing during cure for Fiberglass Patch

[76SeaRay]

As the old saying goes, make sure you know what is behind the hole you are cutting. The previous owner decided to cut speaker holes in the dash just behind the windshield frame. Fortunately, the guy apparently realized what he was doing after cutting into the member a little bit. He stopped and then cut irregular holes for 4 x 6 speakers but they wouldn't fit so he just covered the holes with speaker grills.. Since I have my hardtop and both windshield levels off the boat, I have free room to fill those holes. I plan to use polyester resin and CSM to fill the holes and then gelcoat over that. I will be grinding out around the holes to fair them out about 1 1/2 inches. There is no structural support at these locations so these are simple patches that won't see any weight or stress.

My question is, what is the best backing to support the fiberglass while it cures that won't end up stuck to it.??. I don't think it is necessary to leave the backing in place long term. I have room to put a brace support underneath the backing from inside the V berth temporarily....

Thanks...

 

[chevymaher]

Whatever you want to use with saran wrap on it. It wont stick to that.

 

[76SeaRay]

Great, thanks....

 

[Chris1956]

You could lay the first few pieces of cloth on the faired out area and wait for the resin to cure. It will then be strong enough to putty and gelcoat.

 

[Grub54891]

I've seen it done with an old piece of Formica, wrapped with saran wrap.

 

[JASinIL2006]

Cardboard covered in parchment paper will work, too.