Composites and Water Absorbtion
Posted by: BPD on Feb-05-13 10:05 AM (EST)
On water absorption:
Composite boats do absorb water, but it is the resin, not the cloth that does the absorbing. This is a particular problem with polyester resin in thicker laminates--much less of a problem with the vinyl-ester resin that Wenonah uses in it's ultralight Kevlar boats.
In the sailboat industry people are aware of the problem of osmosis blisters in fiberglass hulls. These are formed when water is absorbed into the fiberglass laminate and undergoes a chemical reaction with polyester resin.
Here is a link to osmosis blister information: http://www.nauticalweb.com/info/maint/osmosi_e.htm
This is not a problem with any canoe, since the boats are stored out of the water and have a chance to dry between use. But composite canoes and kayaks can theoretically absorb water.
Usually it is composite kayaks that will show a slight increase in weight with a little bit of water absorption. The enclosed hull of the kayak allows water to be trapped and absorbed in a high-humidity environment. And almost all kayaks are made with polyester resin. Storing kayaks with hatches removed allows air to circulate inside the boats and keeps water absorption to a minimum.
But--the effect is pretty minimal overall one way or the other. Certainly not something that people have to worry about.
For all practical purposes it's probably safe to say that Kevlar boats don't absorb water and gain weight over time.
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