Those are really good looking blades guys - good show!
Acouple of questions- What pitch setting is the twist
optimized for? and I presume it is set for clockwise
(reversed from most us engines) rotation. I am sure
you will keep us up to date on the testing, and I am
looking forward to the results - Vance J
Here is an old message from Bill, the actual chord and airfoils differ
from this slightly because I had to do some "smoothing" to make the
blade look better. But the angles are correct.
Perry,
Here is the latest. I think I gave you what I call "twist 03", this is
"twist 04", twist 05 didn't pan out. The computer says this is good for
1 lb extra thrust at 200 mph, 2 lbs at 100 mph and the sme at 50 mph for
2800RPM/200 hp/sea level with a 1.25 chord factor. It is supposed to put
out 1 extra lb thrust at 200mph, and (again) 2 lb at 100, but 17 lb less
at 50 mph at 2500 RPM/150 hp/8K MSL/1.25 chord factor. Since this
second case is a cruise at altitude condition, the slight loss of thrust
at 50 mph seems tolerable.
SO ---- "TWIST 04" with a chord factor of 1.25:
Radius angle chord airfoil
6 84 3.13 2424
9 71 5.00 2421
12 62 7.60 2418
15 56.5 8.00 2415
18 53.5 8.21 2415
21 50.5 8.25 2412
24 48 8.11 2412
27 46 7.80 2412
30 43 7.31 2412
33 40 6.65 2409
36 38.5 6.11 2409
The angles are arbitrary in a absolute sense, but the relative angles
are (of course) critical. This blade has min pitch of about 7 degrees at
the tip, so you can index it that way using Butch's index jig design.
Subtract 31.5 from all of the angles to get the
"as built" angle.
Bill Freeman
Long EZ builder & pilot
BSME, MSME
EAA Technical Counselor
This is a four blade Rhino rendering so you can get more of an idea
of what the blades look like. The actual prop is only two blade
of course.
Paul Lamar
The AirCraft Rotary Engine NewsLetter. Powered by Linux.
ACRE NL web site. http://home.earthlink.net/~rotaryeng/
Copyright 1998-2002 All world wide rights reserved.
