To add to Bill's explanation, control rods through
belcranks is the simplest. Some older gliders used
cables and pulleys. Some early glass gliders used complex
gearboxes to convert linear into rotary movement and
modern gliders with flaperons have mixer arrangements.
All have one thing in common they are directly mechanical.
In most modern gliders the stick forces are very light,
frightening so in something like a Discus. Some of
the older gliders did get heavy at speed, for instance
at 80kts the ailerons on a Sedbergh (Slingsby T21)
are set in concrete requiring two hands or even four
if available, not to mention the foot behind the stick
to relieve the need for forward pressure on the stick.

DJ

At 15:30 25 February 2005, Bill Daniels wrote:

wrote in message
roups.com...

I note that some gliders are controlle with a joystick
which
makes me curious as to how the control surfaces are
powered.

Assuming these are useable by people who lack the
forearms of
a truck driver, how are they powered?

Do these systems use electric servos with a battery
recharged
on the ground? Do they use vaccumm assist from a
venturi?

Just asking?

--

FF


You really need to visit the nearest gliderport and
take a ride. Assuming
you are in the USA, check www.ssa.org and click the
button 'Where to fly' to
find the nearest location.

One of the great beauties of gliders is their simplicity.
Usually, the only
'power' in the glider is a small battery to power the
radio and a few
instruments. Everything else is powered by the pilot.

The control forces in modern gliders are small enough
that pilots can fly
with their finger tips most of the time. If you see
a glider pilot with
'truck driver forearms', it's from assembling the glider,
not flying it.

Bill Daniels