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On Mar 25, 9:10*pm, Eric Greenwell wrote:
Bob wrote: Most sun screen on the market does not filter out all UV, so buyer beware. * Handily, there are now some clothing products like long sleeve shirts on the market that are claiming an SPF of 35 that should help protect much of your upper torso, and gloves and hats, too. * Consumer Reports and many other reputable sources says it does an excellent job if it's spf 30 and higher, and properly applied, even it it doesn't get "all" of it. You didn't mention what kind of UV meter you used, and "lighting up like a light bulb" doesn't tell us anything. Was it measuring UVB, or UVA, both? and what fraction of each? What percentage reduction did the canopy provide? The type of plastic and it's tinting can make an important difference: for example, the canopy on my previous glider blocked all the UVB and over 70% of the UVA as measured with a spectrophotometer, but not all canopies are not that good. I have a "sports" UV meter that is calibrated in UV index. It shows essentially zero UV coming through the canopy on my ASH 26 E. While it's not a calibrated spectrophotometer, it suggests sitting inside the cockpit is a lot safer than standing around outside it. Practically speaking, I think if you are properly protected with clothing and sunscreen for the rigging and waiting in the towline, you have more than sufficient protection while flying. -- Eric Greenwell - Washington State, USA (netto to net to email me) I use a Littlemore Scientific UV meter that was developed at Oxford University to measure UV transmission through different materials and in spaces where art is displayed and I believe it to be very accurate. It reads out in mW/M² or µW/lumen and it is mW/M² we are concerned with here. I once took it out to the airport and expected to see very little UV transmission through the canopies, based on past experience with UV through plastic. What I found was that mostly the nicer newer gliders had canopies that stopped almost all UV, but some of the older gliders had canopies that let in more than seemed safe, there was an LS1 with a replacement section that was transparent to UV. The spectrum of UV you want to block is everything above 420nm or so if possible. Tinting can be misleading as I have seen tinted glass before that reduced visible light without affecting the UV and that is a worst case situation, as the tinting leads you to think there is protection when there isn't. However in glider canopies I suspect tinting means a higher quality product and that would tend to have more UV doping. I don't think the manufacturers are primarily concerned with human health as much as the life span of the plastic, the addition of UV doping agents protects the plastic from the sunlight and blocks UV as a side benefit. As has been stated the problem is going to be while rigging and not flying for most of us in newer gliders. Brian Brian Brian |
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