I've posted this before and hope I'm not boring everyone.

Using an excellent and expensive Crawford UV meter and testing a whole
line-up of gliders one day there was a distinct pattern of older
gliders passing UV and newer gliders not. *Eric, one of these days
I'll be out at EPH the same time as you are and we can do some
research on the line-up out there, but we won't get wavelength charts


Now we're talking evidence instead of anecdote! Can the meter quantify
the difference in transmission?

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

Well, the meter reads out total UV/sq.meter and UV as a % of total
light energy measured in microwatts per lumen ( –µW/ l) so if the
source of UV remains constant you could get a sense of the comparable
values, yes. Usually the source is daylight and it's changing from
moment to moment so an exact measurement would be tricky. In reality
what happens is that you stand next to a glider with the meter reading
huge amounts of UV and when you put the meter under the canopy of a
newer glider there is a radical drop in the reading. Because this is
indicating UV as a % of available light the tinting is not a factor at
all unless the tinting is reducing visible light but not blocking UV,
which I have seen in some residential glazing products. Anyway, DG
gliders for example have UV reduction to the point that I don't think
it's a factor at all. I still get sunburned but it's while I'm
rigging and not while I'm flying and I think that is going to be true
for many (most) other gliders and their owners. In museums there is
this blue fabric that they scatter around that fades at a given rate
in the presence of UV and works as a warning, it would be nice if
there was something like that for this application.

Brian


Brian