Quote:
Originally Posted by drgondog
One is that he calculated a Cd0 for the Mustang rather than use one or more of the much lower referenced values.
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Using different Cd0 does not make large difference on speed reduction. You can of course do the calculation with different Cd0 and see.
Quote:
Originally Posted by drgondog
Two he used the Hp to Thrust conversion as if it was a law of physics and seemed to not fully understand the full context of all the forces acting on the Mustang, including Thrust of the airplane at rest.
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The method I used is good enough for Hamilton Standard, Hoerner, NACA... should be good enough for internet discussions as well, particularly when the speed change is so small.
And it really is related to the laws of physics.
Quote:
Originally Posted by drgondog
I wanted Harri to walk through this to show that the relationship between (Tprop1- Dprop1)=Thrustnet holds true for both velocites (and weights) in order to use the equation Thp=thrust x V/375 in mph or Thp=thrust x V/326 in kts and hold THp constant
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You can take that mentioned Hamilton Standard Red Book and walk through it your self. However, the speed change is so small that there is no any practical difference. Same is true also for compressibility effects.
Quote:
Originally Posted by drgondog
Harri - I respect your approach - but don't think it is adequate for precision for the reasons I have stated.
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I don't claim that my calculation is a precision model, as example Holtzauge has far more sophisticated model; still, we got similar results for this particular problem. However, I do claim that it is good enough for testing the scale of the effect, to test Graham's statement in other words. Small errors in n, e, compressibility effects, Cd0 etc. do not cause large difference.