Paul - I have a BASIC program that predicts performance pretty well
and it computes induced drag, uses prop diameter, airfoil tables
wing span,shape etc. The 2G is easily modeled by increasing
gross weight by twice. Weight is a minor player in top speed,
and the turns in the F1 class course are a larger factor than on
the unlimited course. It took F1 guys a long time to get the message
on aspect ratio. Acceleration is also a factor in F1, but not so much
in unlimited with the paced start.
If you like I could run some straw man cases for you. Vance
Figure 4000 HP and a R3350 Rare Bear or Corsair R4360 size airplane and
see
what you get. The unlimited guys are saying pretty much 2.5 G's continuos
at 500 MPH. If you are not going 500 you might not be pulling 2.5.
I think you will have to model the course.
Paul Lamar
Paul - the problem is definately not induced drag. I modelled a smaller
plane
than the big radials - sort of a stripped, clipped wing P51 class racer
probably a contender but not a gold. Input values were 4000lb race wt
200 sq ft wing 2500 sea level hp, fuse ACD 2.52 sq ft (pretty clean
but not "slick glass" - 10 ft prop. 2G was simulated by running a 8000lb
case. 3000ft eq alt. for both. The lift coeff above 400 mph is so low, that
with
anything but a symetrical airfoil, the light wt case backs out of the drag
bucket, and the loaded plane is actually slightly faster top speed. Putting
in a symetrical 66 series 12pct foil, and I get the curves shown on
the Excell plot. Thrust HP is after all the prop losses are factored
in. Top speed was 447mph true in both cases, with the increased load
only showing up at the lower speed - Interesting!! Vance
I still think you need to model the course. As you go faster on a given course
the G's go up. Do you have a map of the course? It takes over 500 MPH to win.
Centrifugal force is (mass x V^2)/turn radius
Also I think 4000 pounds is way too light for a P51. According to Crawford
an empty P51 is 7125 pounds. A Bear Cat is 7070 and a F4U is 8694. Hawker Sea
Fury is 9240. You will need to add fuel, water (ADF) and pilot and take out armor.
Paul Lamar
BTW Crawford gives 3 for the flat plate on the P51, 4 for the Bear Cat, 4.1 for
the Sea fury and 4.3 for the F4U.
Paul Lamar
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