On Sun, 16 Nov 2003 13:07:23 +0000, karel adams wrote:
"Fred in Florida" schreef in bericht
om...
You're missing the point of the modern canard. They were developed to
be a
stall/spin-proof alternitave to the conventional wing-tail layout. An
example: two friends built glass airplanes, one a Glasair with a 150
hp Lyc
and the other a Long-EZ with a 150 hp Lyc, both with fixed-pitch wood
props.. Flat out, the Glasair was faster, but only slightly -- 215
vs. 210
mph.
Even this surprises me, I had been led to understand that the canard
design is inherently more efficient because the canard wing, besides its
basic function as a stabiliser, also helps to generate lift; wheras the
stabiliser in a conventional design must push down. So that for every
100 lbs of weight, the main wing in a conventional design carries 110
lbs, in a canard only 90.
Have I misunderstood?
Or have the Glasir designers found a very clever trick?
Thanks for explaining!
KA
(rest snipped)
With a canard, you need to have the design details and CG such that the
main wing can never, ever stall. If you screw up and have a design such
that the main wing can stall, the aircraft will pitch up at the stall, and
will almost certainly come down in an unrecoverable deep stall. The
original Velocity design had this problem, but they made some design
changes to fix it. But there was a fatal Velocity deep stall accident
recently, and the working theory seems to be that the builder did not
incorporate the design updates.
If you need to be sure the main wing never, ever gets close to the stall,
that means that you cannot use all the lift that the wing is capable of
producing. So, if you have two aircraft that weigh the same - a
"conventional aircraft" and a canard aircraft, and you want the same stall
speed, the canard aircraft will need a much larger wing. That larger wing
has more drag, so you need a very clean design in all other respects in
order to get the desired performance.
--
Kevin Horton RV-8 (finishing kit)
Ottawa, Canada
http://go.phpwebhosting.com/~khorton/rv8/
e-mail: khorton02(_at_)rogers(_dot_)com