noel.wade wrote:
On May 16, 12:59 pm, "jonathan"
PLEASE.REMOVE.THIS.PREFIX.jonathan.go...@ntlworld .com wrote:

Sort of visualise the difference between a wing (spoiler) on a racing car
creating downpressure and throwing a dirty great parachute out the back to
assist braking?

Jim.

Oh, boy - where to begin?

First: In the automobile world, the difference between a "spoiler"
and a "wing" is very important. A wing is a device that allows air to
flow over both top and bottom surfaces, and is typically used to
create down-force (just like the horizontal tail on your glider). A
spoiler actually has the leading edge fixed to the auto in such a way
that air flows over the top surface only. It, too, creates down-
force, but it also creates a lot more drag than a wing.

Second: Technically "spoilers" are supposed to be there to change the
airflow over the _wing_. By "spoiling" the airflow such that it
cannot follow the curves of the airfoil, it changes the glide-path and/
or drag of the aircraft. "Airbrakes" are technically a device
_anywhere_ on the aircraft that increases drag.

Now here's where most people fall down: They want to categorize every
device as one or the other type. But the plain truth is that most
devices on sailplanes do BOTH.

Have fun debating spoilers and airbrakes! I don't think this one will
ever be fully settled...

I think it's fair to say that the debate is of little significance, but
much concern. ;-)


Shawn