wide wingspan and good lift to drag ratios

In article .com,
"Tony" wrote:

I suspected most "lift" or at least delta momentum was generated near
the leading edge, so having a long chord didn't contribute much at low
airspeeds.

I do appreciate the effects of the burble or vortex at the wing ends
and the advantages of winglets, at least at higher air speeds.


High aspect ratio reduces induced drag, which helps aircraft flying at
slow indicated airspeed.

The formula is: CDi = CL**2/(pi*A*e), whe

CDi = induced drag coefficient
CL = lift coefficient
pi = 3.141759..........
A = aspect ratio = wingspan**2/wing area
e = wing shape efficiency (elliptical lift distribution is best;
constant chord is least)

If I'm reading this right induced lift for constant area is inversely
proportional to span, and goes up linearly with area.

At more or less constant chord, area is linear with span, so the idea
would be to have chord go down as span goes up. I'd guess e starts
changing as the wing grows too slender.

That pretty much gives me what I wanted to know. I'd guess higher order
terms have to come into play with increasing airspeed.

Thanks

Tony

In article .com,
"Tony" wrote:

If I'm reading this right induced lift for constant area is inversely
proportional to span, and goes up linearly with area.

At more or less constant chord, area is linear with span, so the idea
would be to have chord go down as span goes up. I'd guess e starts
changing as the wing grows too slender.

That pretty much gives me what I wanted to know. I'd guess higher order
terms have to come into play with increasing airspeed.

Thanks

Tony

Only partially correct. Induced drag goes up inversely with the square
of span, and directly with area.

The efficiency factor, e, is a lift distribution (wing shape) factor,
being, theoretically, 1.0 for a wing with elliptical lift distribution
and reducing in magnitude for tapered distributions and constant chord.

Bear in mind, e can be tricked into higher efficiencies by varying the
angle of incidence or changing the airfoil shape from root to tip, so it
*may* not represent an elliptical planform.

Flutter problems may arise with wings that have long spans and narrow
chord, so everything you do is a compromise.