On 2/13/2011 8:41 AM, Bob Whelan wrote:
On 2/13/2011 8:41 AM, db_sonic wrote:

I got an amazing sun tan under that old ASW19 canopy. But nothing of
the sort with my DG800.
Anecdotal evidence may be indicating the canopy material of the 80's
and earlier simply let this radiation through?

Here's some more anecdotal information: I put 3000 hours on sailplanes
built between 1969 and 1984, and did not get sunburned doing it.


Anecdotal evidence can be the best kind sometimes...it's from the real
world!

Only if you assume it's reported accurately and completely, which it
rarely is - not even mine.

I remember in 1972 or 1973 Wil Schuemann coming into the office one
Monday looking like a negative raccoon: pale around the eyes with thin
pale stripes from eyeball corners to his ears, and considerably redder
everywhere else on his face. He'd gotten that way soaring his ASW-12 (in
MD, but I don't remember whether in wave) wearing glass sunglasses and
the usual goofy hat.

How long was he in the sun before and after the flight? An hour rigging
the glider, and an hour waiting in the line for a tow, can be ten times
the exposure you get under a canopy during a 5 hour flight.

While there might seem to be a pattern of old canopies passing UV and
new ones don't, I'm skeptical until I read a report, with transmission
vs wavelength charts, of measurements on a number of old and new
canopies; alternatively, a report from the manufacturer of canopies back
then that the plastic used did transmit more UVB and a chart showing it.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)