Air Pockets under Fiberglass

I am working on my first S&G kayak build and fiberglassed the inside of the hull yesterday. Unfortunately, I didn't do the best job laying the cloth and now I have some air pockets along the keel/stem seam. I tried to correct the problem before the epoxy kicked but I was not fast enough.

There are 4 air pockets, all about 1 inch long. The air pockets don't really bother me.

Are there any negative impacts to leaving them. e.g. trap water/moisture, etc. Can anyone suggest any remedies? Leave alone? Cut out the air pockets? Inject epoxy into the air pockets?

Any and all advice would be greatly appreciated.

3 replies:

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RE: Air Pockets under Fiberglass

An airpocket can look like any number of things so its hard to give a set pat answer.  They usually are raised higher than the surrounding cloth so sanding the area will remove the pockets entirely and leave fresh unprotected wood underneath.  In this case you need to apply a patch that overlaps about an inch in all directions, apply epoxy and sand the patch smooth so it transitions well with the rest of the cloth.


You have made a very very very common error.  Ive always wanted to have a hyperdermic needle for these purposes to selectively inject epoxy into the bubble.  Im not diabetic though so needles are hard to come by :)

 Good Luck and relax.


RE: Air Pockets under Fiberglass

Most medical syringes come with plastic needles that go small enough to inject into a 1/16 drilled hole. You may have to drill a second or third hole to let the air escape as the resin flows from the first one, otherwise some resin will be forced back out the same hole as air escapes. Another way is make a cut with a sharp knife to pry the cloth apart long enough to get the glue in.

Check under Boatbuilding supplies on the right side of this page.

I had the same thing happen on my first S&G build too.


RE: Air Pockets under Fiberglass

I recognize that this is old, but new reader like myself may benefit. Epoxy syringes are available from West Marine. I bought mine at Hamilton Marine in Maine. It is best to thicken the epoxy a little or it will simply seep back out. You can then be suck the epoxy into the syringge for the least amount of mess. I used an awl to open small holes in the epoxy and in many cases there were enough air gaps that a second hole was not necessary to let the air out as the epoxy flows in.   

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