Quote:
Originally Posted by NZtyphoon
Where did you assume the propeller efficiency was 0.8?
De H 55409 B 0.930
Rotol RA 611 0.924
Rotol RA 621 0.920
Rotol RA 600 0.911
Rotol RA 640 0.940
Take your pick, which propeller did you claim had an efficiency of 0.8?
http://www.spitfireperformance.com/spit2prop-b.jpg |
Apparantly, you can't even read your own tables..
Column 12, "Airscrew effiency" from flight results, at 18 000 feet:
Rotol RA 611 0.924 = 0,800
Rotol RA 621 0.920 = 0,805
Rotol RA 600 0.911 = 0,785
Rotol RA 640 0.940 = 0,800
... besides the fact that NZTypoon has reading comprehension problems, there's also the fact that the above values are only true for 18 000 feet altitude and max. speed level flight of about 365 mph.
Quote:
Originally Posted by MiG-3U
Well IvanK, had RAE chosen the lowest available speed and max lift coefficient values for the Spitfire and the highest available speed and max lift coefficient values for the 109, at the altitude which is most favorable for the 109, their results would have agreed with Crumpp's  |
Instead, RAE has picked the lowest available speed and max lift coefficient values for the 109 and the highest available speed and max lift coefficient values for the Spitfire, and so they have arrived at the results they did.
What all people seem to forget that the results in all these calculations are deeply rooted in the source base data, and since there is a great deal incertainity in those, the results tend to diverge quite a bit.