It's strange to not see in this thread the most basic information about
this problem. Airsickness is usually caused by the discordance between
what the body senses visually compared to what the inner ear is sensing in
terms of motion. If the inner ear signals movement but the eyes register
no movement then the result is sensory discord leading to nausea etc. The
problem becomes even more complex if the movement is not being created or
anticipated by the person experiencing it. This is why the rear seat
passenger of an automobile becomes carsick - but a driver almost never
does. The driver is looking outside and anticipating the movement. The
rear seat passenger has a very reduced outside view (or is usually looking
inside) and not creating the movement. Hence the p1 vs.p2 experience where
we become airsick as passengers but not as PICs.

The same occurs on a boat. On deck seasickness it is rarely a problem -
but below deck (where there is no visual movement) watch out!

For the pilot prone to airsickness this means at all times he should work
to keep his/her head still (to reduce inner ear movement) and keep eyes out
of the glider. Watching the instruments, looking at at the floor or a map
will bring on the nausea quickly.

If you disagree, try the following experiment that I use with my students
to teach the symptoms of vertigo: In a 2 place ship with a safety pilot
keeping a lookout, put the glider in a moderate bank and stare at the
outboard wing tip in the turn. Keep staring. Keep turning. The combination
of G force from the turn with no visual input is very physically upsetting.
Oh - and bring a barf bag.

Roy