Derek Copeland wrote:
I have had an ASI failure in flight. A few hundred
feet up on an aerotow launch, I glanced at the instruments
and noticed that the ASI was reading 20 knots and slowly
falling. Realising that neither the tug nor the glider
were capable of flying at this speed, although they
were clearly doing so quite happily, I knew that it
had to be an instrument failure.

snip story

I know of at least two other occasions where pilots
have suffered instrument failures and have managed
to cope with it.

My first flight in a 1-34 had an ASI failure. I radioed the tow pilot
to fly along next to me at a reasonable pattern speed to get a feel for
the proper attitude to fly the pattern. Seemed to help. Did a few
stalls to see how far up the nose needed to be before I got into
trouble. I also recalled Tom Knauf's comment about how very few gliders
will stall under normal flight conditions (i.e. not accelerated stalls)
with the nose below the horizon. Probably landed a little hot, but
all's well...

Shawn