If you fiberglass both sides of a strip of wood, and then bend it, that is exactly what happens to the fiberglass on the compression side. The fibers buckle and delaminate. Looks to me like it was some how over-stressed on that side.

: Occaisionally builders contact me offline with questions. Here is one that I
: thought the Group could answer better than I. I thought it looked like
: some type of stress fracture. Here is the original text of the question:
: Hi Chip,
: I am getting ready to start a kayak....I finished a Bob's Special canoe in
: November but just like everyone else I can't wait to start the next
: project. However, I have a problem with the glass on my canoe and don't
: want to have the same problem on my kayak. so I'm hoping that you can give
: me some advice. I had no problems with it in 15 half day trips. The
: weather was on the cooler side (65-75 degrees) when it got hotter (85
: degrees plus) is when I first noticed the problem. It seems that gas
: bubbles or something has appeared under the cloth from pinhole size to
: several inch lines that follow the wood joints. First, I am wondering your
: opinion on sanding off the glass and re-doing it or do you have any other
: thoughts?

: Second, I am wondering what I need to do that is different on the next
: project. Do you think that pre-epoxying would help? I used Raka 1-2 mix. I
: included two pics of the problem.

: http://www.chipsandresky.com/cedarstrip/images/conoeprob.jpeg
: http://www.chipsandresky.com/cedarstrip/images/canoeprob2.jpg