Polar with spoilers extended?

On Oct 23, 2:00 pm, Marc Ramsey wrote:
John Galloway wrote:
as an ex Duo owner I agree with Dave Nadler and Bill
Daniels; the Duo airbrakes are better than their reputation:

Well, clearly, not all current and former Duo owners agree.

My 2c: (Our club has a duo, so based on some experience.) The actual
glide angle of the duo, with full spoilers out and at a stable
approach speed, is decently steep. Looking at this angle at altitude
is instructive. The duo seems not to lose speed as quickly as other
gliders when you open the spoilers, especially in ground effect. "Too
high" really often means "too fast". I think a lot of the perception
that the duo has poor divebreakes is realy that it does not slow down
fast, rather than the actual steady state glide angle is shallow.

This all makes some aerodynamic sense. The duo is heavier than basic
trainers, and much heavier than the single seaters we are used to.
"Spoilers" work as much by "spoiling lift" as by "increasing drag",
and much of the latter is induced drag due to the gap in the lift
distribution anyway.


John Cochrane