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.)

Its more than stock but I don't think it is as much as 230 HP.
I would say closer to 200 HP. It is an O-360 parallel valve and not the
200 HP IO-360 angled valve version. It has been modified by adding fuel 
injection among other things. BTW he had to do a complete top overhaul at around
500 hours and is now reluctant to run long cross country races where he has
to run flat out for 300 miles. Klause is backing off long distance air racing
too.... ever since he dropped an exhaust valve on his O-200. When things like 
that happen over the mountains it can make you see eternity :-) Tracy Saylor is a 
hangar neighbor of mine as is Klause at Santa Paula. The air racing capitol 
of the world. Dave Anders runs the angled valve version of the IO-360 and 
gets probably closer to 245 HP and goes 256 MPH in an RV4. The rotary will 
eventually blow these guys into the weeds and last longer in the bargain
if more of us get serious about drag reduction.

   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.
 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.   It is slab sided and flat bellied, like Mustangs and RVs.  Bell
put a very large expanding radius fillet on it. tommayer

YES! RIGHT ON! That is right in line with the theory of the wing fuselage
interference drag being a square law function of the lift coefficient. Lift 
coeff is a max at around 1.2 near stall speed.

If I were flying short races near sea level I would take root fairings
off. If I were flying long distance races with a turbo charger up
real high I would put them on.

Paul Lamar
 
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