tommayer wrote:

Paul,
    As usual, I think you are right on when you say there are a bunch of
factors.  I don't know much about RVs.
Tracy might find Kent Paser, who is also an engineer, and who made a

150 Lyc

Mustang with a fixed pitch wood prop go 239 mph, interesting on wing root
fairings. Paser put really big wing root fairings on his Mustang and got
7-8mph increase in top speed--p.92 of his book, documented in many

races and

contests. (RV fans should remember Sailor [Saylor] is running a

constant speed

and an IO-360 tweaked so he gets TSIO-540 hp out of it.)

  I'm not sure I understand your point in mentioning Tracy Saylor's HP (I
think he's in the 220 -230 HP range). The issue is drag reduction
attributable to wingroot fairings - whats Saylor's HP got to do with it?

   I tried to duplicate Paser's fairing on my Mustang.  No detectable
improvement in top or cruise speed.  There was a 3 mph or so decrease in
stall speed, which was very welcome.

  So even your own personal experience fits with what the RV guys have
experienced (in the best of cases) with wingroot fairings.

 Probably the following won't mean much because of the difference in
operating speeds, but the P-63 had really good drag coefficients, according
to NASA TN C-8206, in which it was within a whisker of as clean as a
51Bravo.

Mike Wills wrote:

  I agree, it probably doesnt mean much in the context of the original
discussion - the applicability of wingroot fairings to RVs.

   Tracy mentioned wingroot fairings as an example of a classic drag
reduction technique that on RVs has been proven to not work. I think his
point was to not lock onto all of the engineering theory while ignoring the
practical experiences of guys that are flying similar airplanes. Wingroot
fairings clearly have a place on other airframes or they wouldnt be used.
But none of the fastest RVs (with the exception of Steve Barnard) uses them
because in the best cases they havent increased speed at all and and in the
worst cases they have actually slowed the airplanes down. I think Steve
Barnard may have mentioned that he saw a slight reduction in stall speed
and maybe thats why the fairings are still there on his plane. Or maybe he
just didnt want to repaint. :-)

Mike Wills

BTW I just talked with Tracy Saylor and he now claims well over 200 HP.
He has made some improvements in his engine and will run in next years Sun 100
at Sun&Fun. He is also replacing the tail on his RV6 as it is a mass of cracks.
Dave Anders has been through two tails on his RV4 so far. Some say it only happens
with a constant speed metal prop and other say it is higher HP on the O and IO 360
engines running over 2700 RPM and or airplanes going well over Van's VNE specs.

With four smaller power pulse per prop rev rather than just two  we are in 
much better shape vibration wise than the O and IO 360 four cylinder engines.
 
Paul Lamar
 
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