Simple string used as artificial horizon?

I had a very interesting conversation yesterday with a very
experienced pilot (older) who has spent a lot of time in some amazing
aircraft starting with the P51 Mustang and going up to jets including
the SR-71 blackbird and as we were looking over my glider we started
talking about the yaw string on the canopy.

He then mentioned that way back in the early days of flying they would
simply tape a string hanging from the ceiling to act as an artificial
horizon. I've never heard this one before! Next person who reads
this who goes up tape a string hanging from the inside of the canopy
and tell us how it works. Now you have another reason to take off
work and go soaring.

Bruno -B4
http://www.youtube.com/user/bviv