Date: Tue, 21 Oct 1997 21:48:41 -0600
To: m-selig
Subject: Drela Airfoils


I have two I can think of right now... both from the
last version of the Decavitator hydrofoil wing system.

MRC-16   Used on the "big"   wing    span x c_avg  =  60" x 2.3"
MRC-20   Used on the "small" wing    span x c_avg  =  36" x 1.4"

MRC-16 design drivers:

Wide bucket, CL ~ 1.2 - 0.3,  7-14 knots
Re*sqrt(CL) = 180K
CD not important at CLmax = 1.2   (7 knot pontoon lift-off speed)
Low CD crucial   at CLmin = 0.3   (14 knot transition speed to "small" wing)
Strong bending strength requirement.

MRC-20 design drivers:

Moderate bucket, CL ~ 1.0 - 0.5,  14-20 knots
Re*sqrt(CL) = 170K
CD important throughout CL range
Extreme bending stiffness requirement.

The somewhat weird layout of the MRC-20 was indicated by LINDOP.
The bump on the bottom is not due to a local thickness constraint,
since there was no spar -- the wing was solid graphite.  Apparently
it was advantageous to "bunch" the thickness at 40% to take advantage
of the nonlinear  stiffness ~ \int t^3 ds  dependence on thickness.

- Mark