Interesting 'exposed epoxy' test results - so far

[Thorne]

http://www.oneoceankayaks.com/Epoxyhtm/epox12m.htm

I'm not claiming this test is uber-scientific or the last word on what to buy, but the guy is sure going about it the right way and not taking anyone's word on epoxy quality and weathering.

[Todd Bradshaw]

His assumption that whitening of the fiberglass fibers is due to moisture penetration is most likely wrong - especially when he notes that it was happening deep down inside the laminations and telegraphing on the surface. It's much more likely that the whitening is actually micro-fracturing of the glass layers from the wood expanding and contracting from heat/cold cycles. Different brands of resin with different heat tolerance and different levels of brittleness will react differently to this - some worse than others. Those which are superior in this aspect may not be in other critical aspects, so it's not something that would automatically denote a superior resin. If you want to prove that this happens, just build a really nice stripper canoe and hang it up in the rafters of your garage (where there is little or no UV or moisture and it gets really toasty in the summer). You'll soon see telegraphing and whitish patches of micro-fractured fiberglass (don't ask me how I know this).

The test is interesting, but in some ways it seems pretty worthless to test bare epoxy for UV damage when leaving unprotected epoxy out in the sun is one of the first things that the manufacturers warn you about. Nobody seems to be trying to hide from the fact that you either protect it or it will fail.

[Howard Sharp]

I always assumed that whitening of epoxy is actually sun damage. Normally the resin remains slightly elastic. UV makes it brittle - hence the microfracturing. I also assume that the process starts immediately it's exposed to sunlight.

[Thorne]

Actually I've seen a few boats that have an epoxy and glass coating where the varnish has come off -- and the new owners don't know enough to re-varnish it. And they usually aren't happy to hear that they need to scrape and coat the boat, when to their eyes it has a nice shiny coating already.

So **some** boats will experience much what this this test shows...depending on many various factors, of cours.