Cloth weave showing


Curious about Wooden Canoes
I built a canoe about 12 years ago and in the last few years there are areas where the fiberglass cloth weave is showing with an amber color. This is a blotchy pattern and as far as I can tell it doesn't appear the cloth or epoxy have separated from the wood. Has anyone experienced anything like this and is there any solution? I used System Three epoxy.
This is not on the surface. I have sanded a couple of areas and the problem appears to be the epoxy reacting to something that causes the weave of the glass to turn an amber color. The result is a blotch of amber cloth weave appearing in irregular spots from about 1/2 inch to several inches across. I had varnished the canoe with several coats of spar varnish, which appears to be holding up well. The canoe has been stored under shelter and out of direct sunlight. One other thing, the problem appears only on the outside of the canoe.
Odd. Never seen that before.

Sounds like the coating (Volan or the like) on the cloth may not have been compatible? Or contaminated somehow? I know that we like to avoid getting body oils on the fiberglass before coating as that can cause problems with poor saturation and generally handle the cloth with gloves. Body oils are known to leave brownish stains on other fabrics. (i.e. clothing.)
I'm not sure if this is the same thing you are describing but I've seen mild delamination from blunt impacts. The glass doesn't come all the way off the wood, but enough that it doesn't appear clear anymore. But it sounds like you haven't hit anything or vice versa so it probably is a chemical/ oil issue. Any photos?
I am currently on the road, but I will post a couple of pictures when I get back home. Thanks to you all for your interest and comments.
Cloth weave showing - photo

I think the photo of my problem is attached. I haven't had this around any oils, and this problem has only showed up in the last year; increasingly spreading across the outside of the hull. The canoe is about 12 years old, no big hits against anything.


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I'm gonna go with "impact failure" for $50. I notice curved scratches that are at the center of the problem areas. Just a guess, I'd like some of the pros to weigh in.
Give that man a prize! What you're looking at are small fractures in the fiberglass, most commonly from impacts. Before fiberglass rips or breaks, it can sustain lesser damage, leaving one of these "bruised" spots that's actually a patch of micro-fractures. The resin/cloth matrix has been pushed beyond its ability to stretch or flex (which doesn't take an awful lot). It hasn't lost all of its strength in those little spots, but it's lost some of its original strength.

The good news is that the boat probably isn't in much danger from them and they haven't delaminated, which would usually be indicated by the fracture sitting on top of a cloudy-looking "bubble" where the wood and glass were no longer connected (that would be much more serious). The bad news, is that there is no easy way to make these spots go clear again, aside from cutting them out and installing small patches of new fiberglass. You can sand them a little bit, add some resin and new varnish on top and they will go somewhat clearer, but they aren't going to completely disappear because you can't get the new resin down between the little fibers that make up the fiberglass yarns. As long as they haven't delaminated, most people would just live with them (but do re-varnish the boat on a fairly regular basis to prevent UV from degrading the resin).

There have been strippers built from different wood types, different weights and types of fiberglass, different types and brands of resin and with varying amounts of fiberglassing experience and skill by the builders. All of these things can contribute to how hard you can flex or smack a particular boat before the glass fractures or delaminates, so there isn't really any specific way to minimize this type of damage. Some canoes and some constructions will tend to be more prone to it than others, though as of yet, I haven't ever seen a "damage-proof" stripper..