BllFs6 wrote:
Hi all...

I know this is somewhat off topic perhaps...but maybe somebody here has the
tidbit of info I need....

As Im sure you all know....the Lift to drag ratio of a wing goes way up once it
gets close to ground.....and roughly speaking the effect becomes pronounced
when the wing has an altitude on the same order as the span of the wing or
less.....

What I was looking for was:

1..... a graph that shows the L/D ratio as the wing gets closer and closer to
the ground......anything rough will do...I found such a rough graph once a year
or 2 ago on the internet....but I cant find it again......

I'll give you the equation for drag in terms of altitude above ground.

D = drag
D0 = zero lift drag (parasitic)
DL = drag due to lift, proportional to lift^2, equl to K x L^2, where K
is some constant.

D = D0 + K x L^2

Now, K gets adjusted as you get closer to the ground by...

K' = K x (33 (h/b)^1.5 )/(1+33(h/b)^1.5)

Where h is height, b is wingspan.

As h/b goes to zero, K' goes to zero too, leaving only parasitic drag D0