Bad fiberglass job on seam

Hi all:

I've got a problem and I need help.

I fiberglassed the exterior seam with 4oz glass. Unfortunately the job didn't go well and I ended up with air bubbles under the tape because the glass didn't adhere to the boat.  The glass adhered all along the tape on the deck and hull, but just not on the hull side of the seam.

I contacted CLC and they recommended that I cut out the offending spots and repair it from there.  My problem is now I have fairly deep cratersall along the edge where I have removed those pieces of fiberglass (see pictures).

The areas to be repaired are 1/4 wide at the largest and some are several inches in length.  

What is the best way to fill these holes and repair this problem?

Thanks in advance!

4 replies:

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RE: Bad fiberglass job on seam

not to really have done half the work and it's not going to be that hard to get it all right.

now that you have 'dug' out the bubble, you need to carefully sand around the edges of the bubble so you have a relatively flat surface you can lay a new piece of glass on.  re-do the wet out and fair it back in.

think of it like the approach you would take to repairing a deep scratch that went into the glass.

your hole is too deep/large to simply fill with epoxy.  so you have to sand the area around the crater back down in a way that you have no sharp edge of the crater.  so you are not going to make it any deeper than the bottom of the are just going to reslope the sides so you can actually get a glass patch in and rebuild it up.  after you have built it up a couple flicks with a sanding block or a cabinet scraper will bring it back fair with the rest of the surface that was not a problem.

the immediate effect of prepp sanding prior to re-glassing will make the sharp holes bigger/wider.  but you need to do that to be able to lay cloth in.

see this you tube video starting at about 2 minutes on.  even though its not a kayak....its a great illustration of the concept.

keep up the good work

RE: Bad fiberglass job on seam

Thanks for the reply Howard. This makes me feel a bit better. I had visions of having to look at that ugly seam forever.

If I am following correctly, you're suggesting that I put a patch in place that is the same size as each hole to build up to the thickness of the surrounding cloth. Some of those holes are pretty small yet fairly deep and it doesn't seem that there's enough space for a patch. Maybe the size of a pencil eraser in diameter.

How would you suggest handling those spots?

Also, I've only done the starboard side. Any suggestions on how to avoid this on the port side?



RE: Bad fiberglass job on seam


Bubbles like those are caused either by trying to bend the glass too much, applying glass to a bumpy surface or poorly wet out glass. To avoid the problem, first make sure that you sand a nice smooth radius onto the seam. The transition from deck to hull should be round enough and smooth enough so that the glass doesn't have to do any extreme bending or have any dips to fill. Then, when you lay the glass, be sure to thoroughly wet it, but not so much that it floats.

One easy way to fill the holes is to angle the boat so the epoxy won't run out and just pour epoxy into the holes. Once the hole is as filled as it can be, cover it with 2-inch wide clear packing tape to smooth and shape it and to keep it from running out. You may have to do this more than once per hole and you may have to do each hole individually, depending on their locations. Once the holes are filled, you can sand the filling smooth to match the rest of the boat,

This method works for bright finishes, ends up invisible and keeps you from having to play with small glass patches. I've used it very successfully on my own boats to fix trailer and dock rash on a bright finish.

Good luck,




RE: Bad fiberglass job on seam

Thanks Laszlo.

I filled and smoothed the seam with thickened epoxy prior to glassing.  It looked fantastic and at this point I wish I could have left it alone without glassing but I wanted the added strength and protection of glass.

The edge is nearly a 90 degree bend, based on the design of the boat.  I think that sharp angle combined with excess epoxy contributed to the problem.  I didn't roll the glass either, I just brushed it out, so I think those three things combined to cause the issue.

I thought about cutting cloth on a bias for the other side, but I'm concerned about having too many seams along the edge since that would cause me to use several shorter strips of glass.

This forum has been very valuable to me and I hope to be able to give back to others as you and Howard and many others have done.


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