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In a message dated 04/14/2003 12:38:14 AM Eastern Daylight Time, LHenney@dellepro.com writes:
I turn the Hartzell 68" prop at 2920 RPM
Larry,
Thanks for publishing your speed 'tricks'. It was very interesting reading.
A few years ago, Lancair did compartive flight testing between the 68" and the 72" props (I have the 72") and various altitudes and power settings. For those interested in the results, here it is:
72-inch 68-inch
Cruise@7,500 Ft (mph) (knots) (mph) (knots)
2500rpm/23.9" Hg 233 203 237 206
2500rpm/21.8" Hg 221 192 228 198
2500rpm/19.5" Hg 210 183 211 183
Cruise@12,500 Ft
2500rpm/19.5" Hg 227 197 233 203
2400rpm/19.5" Hg 223 194 227 197
2300rpm/19.5" Hg 221 192 228 198
2200rpm/19.5" Hg - 224 195
Climb: (1,000' climb from 4000 MSL)
IAS 72-Inch 68-Inch
(mph) (Knots) (fpm)
80 70 1670 1430
95 83 1760 1460
120 104 1880 1670
140 122 1765 1670
As the results above indicate, the 68-inch prop has a 3 to 6 knot advantage over the 72-inch, but shows a lower climb rate.
Hmmm, let's see now, if I switch to the 68-inch prop (3 knots), run at 2,900 rpm (2 knots), get hi-comp pistons (3 knots), that make my speed number (209 to 217 knots) a bit less of a 'minimal' racer, eh?
-grease
PS Are the Sun 100 race results published anywhere on the internet?
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