Mike Wills wrote:

  Rare Bear holds the absolute piston engine record but hasnt won at Reno
in about a decade, losing to the Mustangs Dago Red and Strega. Neither of
the Mustangs conform to your "blimp" model and I'd also note that the
Mustangs equal Bear's speed on the course while using considerably less
displacement and less HP.

  Might also point out that in several years of trying the Ventures havent
managed to beat the Lancair at Reno and clearly the Lancair doesnt conform
to your blimp model. Though I suspect that has more to do with the dynamics
of $ than with aerodynamics.

  I'm not qualified to dispute your claim Paul, but I suspect that as with
most things practical realities make this a less simple issue than it
appears on the surface. I'd say the pointy P51 isnt a bad example to copy
if you utilize the TLAR (that looks about right) method of engineering.

Mike Wills

I do agree with you on displacement however as Rare Bear uses 3350 ci
and the Mustangs are probably 1600 to 2000 ci.

I am not sure I agree with you on the HP what with boost and nitrous.

Hey we are talking theory here and not practice. All I am saying is
if the P51 was reshaped into a blimp shape with the same frontal area
or the same interior volume and mid wings it would be faster. The pilot may 
not be able to sit upright or see as well. Visibility is one of the over 
riding considerations for fighter planes. The frontal area of a P51
is probably less than the frontal area of an F8F Bear Cat. That of course
has to do with the choice of engine type. V12's have less frontal area 
then two row radials of equivalent HP. 

I am not sure that would be true however if a four row radial was built 
with the same HP. The four row would have a big advantage in the number 
of cylinders with 36 instead of only 12. More cylinders more RPM more 
HP all other things being equal. I think a blimp  shaped airplane with
a "small" R-1800 four row radial, all other things being equal and that 
includes the wing airfoil, would easily beat a P51 in top speed.

I also think two turbo 3 rotors with less frontal area and much less weight
than a P51 would give it a run for its money. Two turbo four rotors
would win hands down.
 
Now Reno of course is an entirely different matter. What counts
a lot at Reno is the HP to span loading ratio. When in a high G turn
the induced drag can multiply. A two G turn gives four times the induced
drag. A three G turn would be nine times the induced drag.
Therefor low weight and high span are very very important in pylon 
air racing. One of the secret reasons that Nemesis is almost unbeatably 
with almost exactly the same power compared to all other Formula 
One airplanes.

Paul Lamar
 
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