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I was able to fly both props back to back today and get some comparison data. Craig Catto makes a couple props standard for a 180hp Pitts S-1S - a 72x56 and 72x58, both 3-blade...though he can make pretty much any diameter/pitch combo. I ordered a 72x56 and received it mid-May after a 5 month wait. I've been running a metal Sensenich 76x59. My main reason for buying the Catto was to get rid of most of the stress on my light crank flange. I was not expecting additional performance, but was hoping not to lose any.
Test runs were done with the same fuel load and from the same altitudes. I tested the Catto first. Density altitude at the start of the first test was 1,348' (72 deg, 50 deg. dewpoint, 29.86"Hg) At the start of the Sensenich test, DA was 1,485' (73 deg. 52 deg. dewpoint, 29.85"Hg). Here are the numbers:
Rate of Climb @ 100mph IAS from 1000'-2000' MSL:
1,818 fpm @ 2,350 rpm (Catto)
1,935 fpm @ 2,525 rpm (Sensenich)
Level flight, full-throttle IAS (1000' MSL):
160 mph @ 2,850 rpm (Catto)
162 mph @ 3,000 rpm (Sensenich)
Cruise IAS @ 2500 rpm (1000' MSL):
139 mph @ 10.5 gph (Catto)
130 mph @ 9 gph (Sensenich)
Cruise IAS @ 9 gph full rich:
130 mph @ 2400 rpm (Catto)
130 mph @ 2500 rpm (Sensenich)
IAS @ 3,000 rpm, full-throttle (WOT):
180 mph (Catto)
162 mph (Sensenich)
Max altitude gain, 45 degree pitch up from level flight, WOT:
1,200' (Catto)
1,300' (Sensenich)
Max altitude gain, 4.5G pull to vertical from level flight, WOT:
900' (Catto)
1,020' (Sensenich)
So it's a little overpropped for my liking and I may send it back to Craig for re-pitch. But based on the numbers, it appears that the metal blade is more efficient, regardless of pitch. No surprise really, S-2's with metal Hartzell's outperform the MT a little. Aside from the performance numbers, these are the positives to the prop, as expected simply due to the construction (laminated maple w/ CF and glass outer layups). The Catto is much smoother in flight through all RPM ranges than the Sensenich. Much less vibration, and no red arc. It weighs about 20 lbs. less than the Sensenich. There is no prop bark at 3,000 rpm (noise friendly). There is MUCH less gyroscopic/torque effect. Hammerheads require much less forward stick, and don't have a tendency to torque nearly as bad. Can fly over the top of a humpty much slower without uncontrollable torque rolling. Spins are much cleaner...no hesitations in the spin rate while under 2-turns, and the nose doesn't oscillate up and down before the spin fully develops. Snaps and spins seem to stop more quickly and crisply. Elevator stick force is lighter due to less gyroscopic resistance. Oh yeah, and it looks pretty cool.
Test runs were done with the same fuel load and from the same altitudes. I tested the Catto first. Density altitude at the start of the first test was 1,348' (72 deg, 50 deg. dewpoint, 29.86"Hg) At the start of the Sensenich test, DA was 1,485' (73 deg. 52 deg. dewpoint, 29.85"Hg). Here are the numbers:
Rate of Climb @ 100mph IAS from 1000'-2000' MSL:
1,818 fpm @ 2,350 rpm (Catto)
1,935 fpm @ 2,525 rpm (Sensenich)
Level flight, full-throttle IAS (1000' MSL):
160 mph @ 2,850 rpm (Catto)
162 mph @ 3,000 rpm (Sensenich)
Cruise IAS @ 2500 rpm (1000' MSL):
139 mph @ 10.5 gph (Catto)
130 mph @ 9 gph (Sensenich)
Cruise IAS @ 9 gph full rich:
130 mph @ 2400 rpm (Catto)
130 mph @ 2500 rpm (Sensenich)
IAS @ 3,000 rpm, full-throttle (WOT):
180 mph (Catto)
162 mph (Sensenich)
Max altitude gain, 45 degree pitch up from level flight, WOT:
1,200' (Catto)
1,300' (Sensenich)
Max altitude gain, 4.5G pull to vertical from level flight, WOT:
900' (Catto)
1,020' (Sensenich)
So it's a little overpropped for my liking and I may send it back to Craig for re-pitch. But based on the numbers, it appears that the metal blade is more efficient, regardless of pitch. No surprise really, S-2's with metal Hartzell's outperform the MT a little. Aside from the performance numbers, these are the positives to the prop, as expected simply due to the construction (laminated maple w/ CF and glass outer layups). The Catto is much smoother in flight through all RPM ranges than the Sensenich. Much less vibration, and no red arc. It weighs about 20 lbs. less than the Sensenich. There is no prop bark at 3,000 rpm (noise friendly). There is MUCH less gyroscopic/torque effect. Hammerheads require much less forward stick, and don't have a tendency to torque nearly as bad. Can fly over the top of a humpty much slower without uncontrollable torque rolling. Spins are much cleaner...no hesitations in the spin rate while under 2-turns, and the nose doesn't oscillate up and down before the spin fully develops. Snaps and spins seem to stop more quickly and crisply. Elevator stick force is lighter due to less gyroscopic resistance. Oh yeah, and it looks pretty cool.
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