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)