Byron Ward wrote:

The down side of low aspect ratio wings is induced drag.
This affects them during takeoff and climb. Most delta wings have
been over powered and design oriented towards top speed.
Just like ducted fans I might add.

The induced drag coefficient based on the wing area
is Cl^2/(Pi X Aspect Ratio).

Paul,

I don't have my textbook right in front of me, but I think that you are
missing the efficiency factor "e" in the denominator, which is only 1 for
an elliptical lift distribution. Also I think this formula assumes that
the wing can be represented by a single bound vortex (lifting line theory)
which is not the case for very low aspect ratio wings or for delta wings.
I think I have a chart somewhere that shows the error for low aspect ratio
wings. I'll send it if I can find it.

Byron

It is indeed the simple first order equation. e varies only over
a small range compared to Cl^2.

I agree on the delta wings. There are large vortices
generated at high angles of attack that produce lift by projecting
the low pressure in the interior of the vortex to the upper surface
of the wing. Unfortunately almost no intermittent combustion engine
is powerful enough to take advantage of this effect. Well perhaps
a pulse jet.

Swept back wings at subsonic speeds lose lift by spanwise flow.

Paul Lamar
 
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