On Mon, 05 Jan 2004 09:04:20 -0800, David Lednicer
wrote:

:
:
:Ed Wischmeyer wrote:
:To get
:low induced drag, you need the sum of all lifting surfaces to have an
:elliptical lift distribution.
:
: Lemme display my ignorance here. I always thought that the elliptical
: lift distribution minimized wingtiptip effects. That being the case
: (ignoring the wake of the canard for the moment), then each wing should
: have an elliptical lift distribution. When you toss in the wake effects,
: is having the sum of all lifting surfaces give you an elliptical
: distribution a handy approximation, or is it what you really want from
: first prinicples?
:
:The canard usually has a much smaller span than the main wing. Subtract
:its elliptical load from the overall elliptical sum and you end up with
:a really wierd load distribution on the aft wing.

It's much worse than that. The winglets create much more lift at the
wingtips than you'd normally get, while serving double duty as
vertical stabs. And you have to add up all the lift into a single
system, and see how the entire thing is loaded.

It's true that if you fly a perfectly point designed canard off it's
point, it will be worse than a perfectly point designed conventional
configuration flown the same amount off it's point. For example, the
Solitare has a terrific L/D - if it's flying in a straight line. Load
up the canard to thermal and it's a dog. But if we're trying to make
sweeping statements about one configuration always being better than
another, the difference is small enough to be overwhelmed by the
details of the execution.

Besides, I don't like looking through a prop.