05/29/2001 08:53:21 AM
Graham Singleton wrote............
"I believe that a 3 blade composite prop will always be better than 2 blade
wood on an efficient airplane like the Europa. The intrinsic yaw vibration
cause by any 2 blade prop will damage the laminar flow over the wings and
result in a drag increase."
I am not an engineer and won't try to be one, however I do have some real
world experiences. Yesterday my good friend Bill Stewart and I took to the
air in our Europa's for the purpose of comparing air speeds at comparable
power settings. Bill has a monowheel with an electrical driven 3 blade
constant speed prop - Warp blades, while I have a trigear with a 2 blade
Whirlwind hydraulic constant speed prop. We both run 914's.
We leveled off at roughly 1300 ft elevation and set our power at 30" MP and
5,000 RPM, which is our usual cruise power setting. We both indicated 130
kts and flew dead even, side by side. Our actual speeds were identical
with neither plane gaining on the other.
Conventional wisdom would tend to favor a higher speed in the mono due to
less aerodynamic drag, and in our case the mono is roughly 100 lbs lighter
than the trigear. One might therefore conclude that the 2 blade prop on
the trigear is more efficient, making up for the weight and drag penalty.
That's all I can figure out. Anybody out there have any other explanations
for what we experienced?
Regards
Garry
N4220S
(813) 878-3929
FAX (813) 878-5651, Internet ID Garrys@att.com
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