Corner and Edge Voids

[Blwalker105]

I've been watching Dan's (RM1SepEx) thread with particular interest concerning his gelcoat problems and decided to post a new thread so more people might see it. Long story short, he has lots of corner and edge voids between the gelcoat and fiberglass. These areas are very weak and when they are low enough on the car to see active conflict with rocks and road debris, they lose the battle very quickly. Body flex alone can pop off large pieces. Better layup technique would solve a lot of these issues but that doesn't help us much.

I usually assume most edges and every 3-plane corner will have voids. A flashlight from behind can help spot them, as can tapping around with a quarter or large washer. Tap on an area where you know there is no void, then tap on a suspect corner or edge...you will hear and feel a big difference. Now for those of you who aren't planning on paint or wrap might not like the thought of drilling through your gelcoat, rest assured that filling 30 or 40 little uniform holes now will be much more preferable than doing large-scale 3D body repair down the road.

Get some disposable icing (cake decorating) bags WITH TIPS! Find a drill bit the same diameter as the smallest tip and drill hole a just through the gelcoat to expose the void. Take a piece of safety wire about 6" long and Sharpie a mark 1" from one end. Now use that end to probe around the inside of the void. If your 1" mark disappears into the void in any direction, drill another hole and repeat as necessary until you find the void's lateral limits. Mix up some resin thickened to a peanut butter consistency with glass bubbles or Cabosil and scoop it into the bag. Squeeze it into each hole until you're confident you have filled the void. The reason for so many holes is that in tight spaces, the mixture doesn't want to travel very far without trying to squeeze back out of the hole you are squeezing into. After leveling with a squeegee to the surrounding area, let cure and proceed with normal paint prep techniques. For the bare gelcoat crowd, you have a couple choices: either use the 3/16" bit to clear out a smidge of resin before it cures then use gelcoat repair into the indentation after it cures. Or, wait till after it cures and use a slightly larger drill bit to make your indentation then proceed to fill with gelcoat.

[Blwalker105]

Oops, near the end of the above post, instead of "use the 3/16" bit" it should read "use the same drill bit to clear out a smidge of resin".

[UnhipPopano]

There are a few ways to do this. while I have not tried this, most of the photos show outside edges and corners. If the fiberglass part is flipped over, and the holes drilled from the back, gravity will allow the resin to flow in and fill the void. No gel-coat work needed.

[flynntuna]

Excellent tips. :cool:

[Blwalker105]

Excellent tip, UnhipPopano! I didn't think of letting gravity take the smart work.

[RM1SepEx]

Great tips from all! I tried the light method but many had too much fiberglass to show through well, caught some before driving missed too many. A bigger issue is areas where there just isn't enough gel coat to fill the mold and the edge has exposed fiberglass or is a caked mess of what appears to be some sort of clay.

[Frank818]

Even Kurk's scoops have voids on the edges.

I don't understand how to put resin or gel coat through those holes if they are very small, even 3/16 is too small if you make a paste out of your resin.

[Blwalker105]

When I try this last method, I plan to keep the drill bit diameter VERY small and drill more holes: The larger the bit the more likely it is to "grab" the relatively thick fiberglass and pop right though the gelcoat.

[Blwalker105]

Yeah Frank, I hear you on the viscosity issue. Probably going to have to stay on the thinner side of peanut butter...thin enough to flow in but thick enough to stay put, at least till you can put a piece of painter's tape over the hole.

[Wayne Presley]

I tap all the corners with the shaft of the screwdriver and chip out all the voids before I give the panels to the body shop

[RM1SepEx]

Wayne, that's not acceptable if you are trying for the no paint finish we were sold

[UnhipPopano]

If the Gel Coat void is not too big, Clean the area with acetone, fill with gel and cover with cellophane. The gel coat does not stick to cellophane and it keeps air and moisture out. If you get the amount of gel correct, all that is needed is a light wet sanding to finish it off. By taping the cellophane tight over the area, the repair will follow the contour of the body.

[Frank818]

Yeah, not fair Wayne, you're not even doing the job yourself. :)

Unhip, I was effectively wondering on what surface gel coat does not stick. Is it ok with wax paper as well? Is it the same if you use resin instead of gel coat?

[UnhipPopano]

Cellophane is so easy to find, as when you purchase stuff it is usually wrapped in it. Nice thick stiff cellophane just waiting to be reused for something. Wax paper does work, but not as well. Cellophane, wax paper and modeling clay do not stick to gel, clear cast resins, epoxy resins, polyester resins and so forth. also, if you seal with Cellophane, you do not need to add wax.

Also, cabinet scrapers work to take gel down.

[Frank818]

Yeah that's the thing, cellophane is thick. We're talking about the bubble wrap here or the very thin plastic you wrap fruits and food into? The latter, that's fine, yes, but the former is too thick for some work. For voids yeah it'd be ok, but for example when I fit a side marker or a light and I want to add gel or resin in order to change the shape of the body and follow the contour of the part, then bubble wrap is too thick to put between the part and added gel/resin to fill the gap between the part and body. Know what I mean...?

[UnhipPopano]

If you are repairing an edge, find one just like it and using modeling clay and plaster, make a mold. Then put the cellophane between the gel and the mold.