Bob Denton wrote: > > If I am not mistaken, the fact that a gelcoat is clear does not affect it's > uv properties. Window glass has excellent UV properties and the UV coatings > on sunglasses are completely transparent, as is 303. Depends. Stuff that is clear to our eyes may or may not be "clear" to UV. Also, "clear" for UV comes in a range of sizes. So that even a piece of window glass allows SOME UV through. If you are thinking that "98 % opaque to UV" is pretty close to "99% opaque to UV," consider that the former *lets in* TWICE as much UV as the latter does. So, a "clear" gel coat "opaque" to UV (if it is the 98% version), compared to the filled ("unclear") gelcoat (if is is the 99% version), will allow your kayak to die from UV exposure in HALF the time. Filled (pigmented) gel coat must be almost completely opaque to UV (probably at the 99.999% level, I'd guess). I suspect that clear gel coat, even if it has a UV absorber in it, is no more opaque than the 99% level (another guess -- somebody else may have authoritative numbers). Let's see, that would be 1 % divided by .001% -- hmmm -- the filled gel coat would protect your kayak's underlayers for 1000 times longer! Something else to think about: the UV which is absorbed by the gel coat has to dissipate its energy into something -- guess what that something is? Yeah, the gel coat. So, don't be surprised if a boat with a gel coat (clear or unclear) needs to have its gel coat restored if you leave it outside in the sun all year for a couple years. Even my boats show "oxidation" of the gel coat -- and they are stored indoors out of any sunlight all but about 30 days a year. This is where the statement about free lunches goes. -- Dave Kruger Astoria, OR *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************Received on Wed Dec 16 1998 - 14:14:44 PST
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