I have been fooling around with the 3D again and I decided
to change the Reno racer design. I always worried about those belt
drives taking 1000 HP. This design uses two Bell 47 final drive
gear cases just like Dave Garber's airplane. According to Bell they
are
good for 1000 HP at 6000 RPM input revs.
Sort of a half or 3/4 scale P38. The liquid to air intercoolers
are fed with acetone and dry ice. The pilot will sit behind the
spar.
Paul Lamar
Paul - I think the references to the Pond racer were well taken. I think
that is a design
that Burt would like to forget. It had more problems than just the hand
grenade engine
(tho that is exactly what did it in). As you recall, the P38 was a big
disapointment
to the air racers - being a big horsepower hog. You cant fool mother
nature,
the
frontal area and interference drag exists to steal your horsepower away
from
you. As I mentioned, I put that V8 pusher with the vegimatic prop into
my
performance model (originally written in BASIC and skilfully converted
to
VBASIC/EXCELL by fellow ACRE member Les Orosz) and it is better
than it looks at first glance - the 48 inch prop is better than it seems
(The fastest prop driven plane in the world - Russiab Bear- has
supersonic
props). It has an easy 400mph potential (as you say 500 is required),
and
the tiny wing has no problems at 3 G turn loads with induced drag. When
you go that fast the lift coeff is so low that induced drag is a non
issue.
If they kit it and get some customers it could really raise the bar in
the
sport racer class - tho the noise level from that prop is probably
cruel and unusual punishment.
If you want to challange unlimiteds you've got to get your rotors in a
row!
I have some more numbers on that airplane. They state a prop efficiency
of 74%. Did you run the numbers on the prop? Also gross weight is close
to 3000 pounds. Is that the number you used on induced drag? Of course
the V8 at 1100 HP and 14:1 is more of an over grown hand grenade than
the Nissans were.
So you don't think we can overwhelm the drag with three 3 rotor engines
and 3000 to 3600 HP?
Paul Lamar
Paul
My model program uses the prop disk area in its calcs for thrust, and has an
eff curve for
fixed pitch props that roughly simulates the reduced eff and hp at low
speeds (but no
Mach No effects) . Classic prop eff is more a function of aircraft speed
than prop
design, and 74 % at that speed is quite possible. I used the gross weeight
at 3G for
the top speed calc and it only loses about 5mph - weight is a very weak
function
for top speed.
The V8 at 6800 rpm and 1100 hp is almost the same specific power and stress
as the NASCAR "stock car" engines which run about 800hp and over 8000rpm
for 500 mile races witn almost no "blow ups". How long has anyone run a
3 rotor at 1000 hp ?? The Nissans in the Pond were trying to pull 1000hp
with about 180 cubes!! - bad scene!
If you can get 3000hp you will be allowed about the same frontal area
as a clean unlimited P51, and no excess interference drag.(and that
includes the radiators to cool those 3 pressure cookers). Remember
the P38 racers probably had over 3000 hp and were only "back
markers" in the races. - Vance
I was thinking 3000 pounds in a 3G turn. the wing loading goes from 50 pounds
per square foot to 150 pounds per square foot. Hard to buy the induced drag
does not have more of an effect. What formula are you using for induced
drag Coef. Mine is Cl^2/pi*aspect ratio. The aspect on that wing looks like 2:)
That is nine times the induced drag.
What wing form drag coef are you using? What over all flat plate equivalent
drag are you assuming?
Paul Lamar
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