Most art museums use some version of the Littlemore Scientific
Engineering Co (ELSEC) Crawford 760 or 763 UV meter. I've got one that
I use to evaluate window glazing and tinting systems. For instance,
there is a belief that all glazing that's laminated will stop UV, but
I've found that sometimes a glazing unit made with .030 laminating
interlayer won't stop quite enough so we have to spec it up to .060
interlayer which so far has always made the cut. 100% of the materials
that pass or fail the UV test are branded "stops 99.9% UV" so that
claim doesn't mean much.

My understanding is that most plastics are heavily doped with UV
inhibitors to prevent failure of the plastic and not out of any desire
to protect the end user from skin cancer. All the plastic I've bought
from the local plastic store has been well within the accepted limits.
Anyway, one day I took the meter out to the line and started checking
canopies with the expectation that all the canopies would stop enough
UV to make it a non-issue. All of the DG canopies I checked were 100%
good. On an LS1, the fixed section was good and the removable section
very poor. In general most of the older canopies were not that great.

Now the meter is designed to measure all of the UV, not just the
cancer causing part of the spectrum, so using this meter for this use
seems likely to cause a lot of false negatives. All I take from it is
that newer canopies, in particular DG canopies are probably blocking
enough UV.


On Aug 1, 7:05 am, sisu1a wrote:
On Aug 1, 5:55 am, Ed Downham wrote:

Having flown with a variety of tinted/non-tinted canopies, I would say that
on an average soaring day they seem to make very little difference to
vision and/or heating. In very low light levels (twilight/dark) I'd
prefer to be under a clear lid but practically it wouldn't make a huge
difference.

IMHO you're probably better off with a clear canopy + cover + a decent
pair of sunglasses: at least you can change/remove the sunglasses...

The "Perspex" normally used for glider canopies is transparent from
about 350nm and longer wavelengths, which includes part of the UVA band.
There is enough energy in the photons there to cause skin/tissue damage,
so although you might not visibly "burn" as much as in direct sunlight,
it's not at all good for you. I'm a bit sensitive in this respect so for
me high-factor sunblock is a must in a glider. You can get "UV 400"
Perspex which only lets in visible light but I've never heard of a canopy
being made with it (maybe I should ask!)

Well, you didn't really ask, but here is is anyhow...http://www.thermotecusa.com/
Ray Poquette has been making 98% UV blocker canopies of ALL flavors
for along time. Here is a link to his UV canopy chart:http://www.thermotecusa.com/ThermoTe...opy%20Info.htm

-Paul