problems@gmail wrote in message ...
J a c k wrote:

I think the Duo's airbrakes are better than many people think. The Duo
is a
big heavy glider with lots of inertia. It doesn't like to change
direction
quickly. That includes its behavior on sudden airbrake deployment. You
don't get a lot of sink right away.

My first reaction was that the airbrakes were weak but a little more
experience showed me that with a little patience, the brakes took effect
and
produced a respectable decent rate. The Duo just makes you plan ahead a
little more than with a light single seater.

I don't understand the physics here.
Consider an analogy:
when the VW-beetle came out it had a reputation of 'turning over easily',
based on the false logic that you need less men to 'turn it over' than to
'pick up & turn over a bigger car'. Of course the forces while driving,
that
tended to 'turn it over' were less for a VW, but so too were the forces
that
resisted 'turn it over'.
A heavy pendulum is 'eqivalent' to a lighter pendulum.

So too for the BIG glider.
What doesn't scale up is the pilots strength.
Or is reynolds number significant ?

== Chris Glur.

OK, the first post above wasn't too clear and, since it is just speculation,
may not even be correct. Maybe, what the pilot 'feels' when typical air
brakes are deployed is the sudden onset of deceleration. The increase in
sink isn't great enough to feel.

The Duo is heavy, clean and accelerates like a rocket when the nose is down.
The airbrakes don't reduce this much so the deceleration is smaller than
lighter gliders giving the first impression that the brakes are weak. The
rate of sink with air brakes extended is within the normal range gicving a
~7:1 glide which will get you down but won't do a lot to control airspeed.
You still have to control airspeed with pitch.

Bill Daniels