Does a glider pilot with a PC canopy need to protect himself from UV radiation?
I assume that you mean polycarbonate by "PC". Polycarbonate plastics block nearly all UV radiation. Here is a typical transmission spectrum:



UV is the light below 400nm. As you can see, the curve shows 0% transmission in that range. In general, the risk of damage by radiation is greatly reduced by elimination of sub-400nm wavelengths.

Nevertheless, high energy visible light from 400-500nm should not be ignored and long exposure to such light can be damaging, especially to the eyes and is implicated in macular degeneration, and I know sailplane pilots with high hours who have suffered macular degeneration.

Also, if you are flying, you know that most pilots spend many hours out on the field waiting to launch or doing other chores, so there is plenty of time when you are not protected by a canopy at all.