"Byrd, Ray" wrote:

Paul - I understand your affection for the rate-of-climb chart.
Outstanding!

How can I contact ACS to purchase a copy of the book?

I think AirCaft Spruce may have a wb site. Yes here is is.
 http://www.aircraftspruce.com/main.html

Does anyone know how/where to purchase Hoerner's "Fluid Drag" book? I saw an
ad recently, but lost track of it.

HOERNER FLUID DYNAMICS
                                               P.O. Box 21992
                                            Bakersfield, CA 93390
                                           Phone/Fax: (661)665-1065
                                               Hfdy@aol.com

Yes, drag is a beast at low speeds.  Max Munk wrote NACA Report 221, in
about 1923, with test data from the variable density wind tunnel (Rn 6E6) on
a series of related airfoils at aspect ratio 6. Plotted L/D/Moment data very
thoughtfully included a calculated curve of the induced drag. One of the
most useful/practical/conventional foils was M-6. Very interestingly at a
lift coefficient of 0.4...induced drag was fully half of the airfoil
(finite-span model wing) drag.

AND interstingly, the M-6 (12% thick) had small, forward-loaded camber
(about 2-1/2%, max thickness at 30% chord) with a small reflex camber (0.5%)
from about 85% aft.  Pitching moment was very small and slightly positive!!
The overall profile looks interestingly much like the "much newer" NACA
747A315 (max t at 40%).

I focus here on pitching moment in observation that the Questair Venture
used the "old" NACA 23xxx airfoils that have nearly zero pitching moment;
and is reputed to be (with less horsepower) noticeably faster than the
Glasair. The Glasair LS(1)-0413 has a pitching moment 8.5 times greater than
the 23xxx (-0.11 vs -0.013). Yes, the old 23xxx's also have noticeably lower
drag coefficients at similar Cls  (gad!...25-30% less at Cl = 0.1! [12% vs
13% thickness])

In line with your observation re highspeed flat plate area/drag
relationship...Munk's early, simple equation was lift-squared divided by
span-squared x dynamic pressure x pi.  Rather insightful to note the induced
drag beast is diminished by the square of weight reduction AND the square of
wing span extension (ie aspect ratio).

Ray Byrd

 
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