Nope!
Once the sail gets wet the reflectance goes down.... Just like a radar
reflector cant be seen (attenuated radar-wise) if its shadowed by or
behind a wet sail.

Parallax wrote:
A back issue of Practical Sailor said that radar returns from
sailboats are very weak without a radar reflector. So.....Useless
idea #3724

Have sailmakers put a few electrically conducting threads in the sail
every few cm so the whole thing reflects. It isnt as good as the
corner cube reflectors and will vary a lot with point of sail but, its
probably waaaaaay better than no refelctor.