Question about glide ratios (for the aerodynamically skilled)

On Sun, 16 Sep 2007 15:15:25 -0000, Tina wrote
in . com:

As best I can tell, it seems for a given configuration air speed for
best glide angle (I will define best as most shallow angle) changes
with weight, but the angle itself doesn't change much.

That's essentially correct. Parasitic drag increases with an increase
in air speed, so the effect of increased weight to increase the speed
at which maximum distance is achieved in still air does decrease the
Lift over Drag figure some.

Hi performance gliders carry water to increase penetration into headwinds,
dump it to increase time aloft, but still go down about foot for every 20
some they move thru the air, don't they?

That is approximately true. But any sailplane worthy of the name has
an L/D of thirty to one or greater with the highest performance
sailplanes today in the fifty or sixty to one range.

I need, for a fictional piece I'm writing, an efficient long range low
power consumption airplane and don't want it to fail because of
technical errors.

It is unclear exactly what sort of aircraft you need. Are you
referring to an actual aircraft that exists in today's world, or a
fictional aircraft? How many seats does your aircraft need to have?
Are you looking for a certified aircraft or will something excremental
do?

Here's the ultimate:
http://www.nasa.gov/centers/dryden/n...-068-DFRC.html
This aircraft is designed to remain aloft for months without requiring
any refueling, nor any fuel at all.

Thanks for your comments

You're welcome.

Thanks everyone.

The airplane we need for the story is a pilotless drone, a fictional
airplane, capable of carrying a few hundred pound payload long
distances -- think in terms of drones used by the DoD now.

The principal author will model it after some of the existing high
performance gliders, that will both save him from working at making
his airplane unique and will make it more believable -- don't you hate
stories that contain technical errors?

I loved one of the (God I hope it was) typos, where Larry asked if the
airplane should be "a certified aircraft or will something excremental
do".

Thanks again, you've offered the insights and verification I hope for.

"Tina" wrote in message
ups.com...

I loved one of the (God I hope it was) typos, where Larry asked if the
airplane should be "a certified aircraft or will something excremental
do".

If you spell "inconvenience" in a certain way, the first selection in
Office's spell check can turn out *VERY* ironic results:

(Actual email):

"I'm sorry for the incontinence, but I will be out of the office tomorrow
for a doctor's appointment."


--
Doug Semler, MCPD
a.a. #705, BAAWA. EAC Guardian of the Horn of the IPU (pbuhh).
The answer is 42; DNRC o-
Gur Hfrarg unf orpbzr fb shyy bs penc gurfr qnlf, abbar rira
erpbtavmrf fvzcyr guvatf yvxr ebg13 nalzber. Fnq, vfa'g vg?

Originally Posted by Tina

Thanks everyone.

The airplane we need for the story is a pilotless drone, a fictional
airplane, capable of carrying a few hundred pound payload long
distances -- think in terms of drones used by the DoD now.

The principal author will model it after some of the existing high
performance gliders,

Then you are looking for Dick Butler's Frankenglider (he calls it the Eta Biter). Dick is a real life rocket scientist or engineer and has highly modified an ASW-22. It probably performs well over 60:1 and can easily carry your payload if the shape will fit and the plane remains within CG limits.

V7