Filling Holes in Fiberglass Boats – Project Gemini

Project Gemini is coming along nicely but sometimes even with new paint you realize some things didn’t come out quite right and they need to be retouched.

We noticed several issues with pitting and holes that should have been fixed and filled but due to me attempting to be cheap they presented new problems. These problems have now become your benefit!

Most of the pitting could have been fixed with a high-build primer thought he holes can only really be repaired using a fiberglass repair product.


  • Pack of Bondo Scrapers
  • Fiberglass Primer
  • 100grit Sand Paper
  • Acetone

You will want to start by sanding around the holes and pits to ensure the Bondo will have something to “bite” into, 100grit sand paper seams to offer the best compromise with this between cutting power and controllability.

Once you have the paint and surface around the hole(s) roughed up and cleaned with acetone then you can begin to prepare to  mix your Bondo. It is important to ensure your hull or whatever else you are repairing is at least 50 degrees, the warmer the better usually. I prefer my Bondo mix to have a slight redish tint, this makes it easier to work though it does take considerably longer to set.

Here you will be using the scrapers to fill the holes, depending on the holes you may have to go over it multiple times, sometimes you may even need to lay fiberglass mat for the resin to grab over the hole. The general idea is you want to fill the holes without getting too much all over the place though it does sand down.

Once it dries and hardens you can then sand it down, wipe it down with acetone and prime. From there painting is next!



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