I have a friend that is finishing a kit plane with a 0-360. He said he had actually ordered the std prop for the 0-360, a McCauley 1A200 I think, which weighs like 44 lbs? I tried to tell him he ought to change his order to a Catto 84 or 86 which weigh like 14 lbs or something. What is the difference in those two lengths and performance compared to the one he ordered; anyone know? The goods, bads and uglies too. I don't want to talk him into something he shouldn't really do but 30 lbs off the nose sounds good to me.
Catto 84 or 86?
- Thread starter The Kid
- Start date
DJ
MEMBER
Bolivia
I like the 86/38. I get 90 mph at 2500 with a draggy Cub. I think the total weight with hardware is closer to 20 lbs.
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PerryB
FRIEND
Chico, CA
Yeah, ditch that aluminum boat anchor. He'll be a lot happier with not only the CG, but lack of gyroscope. It kinda sucks to have to ballast the tail of an already heavy airplane.
FdxLou
BENEFACTOR
Canton, GA
I had a 1P235/8442 and replaced it with a Catto 8443. Picked up 7 mph at same rpm and actual scale weight savings were 19lbs. Those weights included the spinner and backing plate, etc. Not aware of any Catto for a O360 that weighs 14lbs. Mine was a hot rodded O360 and Craig Catto said unless I was willing to go with an 8638 to stick to 8443. Lost maybe 30-50' T/O roll but went from 88-90mph to 104mph. WB Smith Cub on 31" ABW's.
Lou
Lou
I think with an 84" prop, and not to exceed about 83% of the speed of sound, you'd want to have an RPM of about 2500 to 2525 at 60 MPH indicated in a climb. In the winter, with denser air, you'll be less than in the summer with thinner air. Fixed pitch is always a compromise. I'd like to know what that Catto 84/43 is reading in RPMs at 60 indicated in a climb and it would nice to know what the 1P235 84/42's rpm was at 60 too. Just my thoughts.
DJ
MEMBER
Bolivia
9.5:1 pistons but otherwise stock. The 86/38 turns just over 2300 static and about 2500 in a 60 mph climb. I would like more of both. To get 104mph in level flight it would be 2650+.
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FdxLou
BENEFACTOR
Canton, GA
Kid
When I switched from a 1P235 84/42 to the Catto at 84/43 yes, I did lose a wee bit of T/O ground roll, but the more efficient Catto really shined when in cruise. I could either take the extra speed at a given rpm or less fuel burn at a lower rpm at the old speed. I misquoted my speed above....should have been old speed was 98 and Catto speed was 105. Sorry for the confusion! When I pulled back to 98mph indicated I was burning 0.8 gph less!
Lou
When I switched from a 1P235 84/42 to the Catto at 84/43 yes, I did lose a wee bit of T/O ground roll, but the more efficient Catto really shined when in cruise. I could either take the extra speed at a given rpm or less fuel burn at a lower rpm at the old speed. I misquoted my speed above....should have been old speed was 98 and Catto speed was 105. Sorry for the confusion! When I pulled back to 98mph indicated I was burning 0.8 gph less!
Lou
I just noticed this. As the prop lengths get longer, the pitch gets flatter. The flatter the pitch, the less bite you take with every revolution which means you don't go as far which then decreases your cruise speed? Example; 76/56 vs say an 86/39. I do know that when I put my Borer 82/44 on over my old Sensenich 76/56, the take off distance was tremendously shorter but I think the cruise was less too at the same rpm; it would have had to have been. But the longer props seem to shorten take off distance a lot . So I wonder if there is a formula that one could use to calculate how much speed you would loose with a flatter pitch prop that gets you off better?
skywagon8a
MEMBER
SE Mass MA6
inches of pitch x 60 (minute) x 60 (hour) = inches per hour. You take it from here, include an efficiency factor for the prop.
Our engine power is related to RPM. Longer props require flatter pitch to maintain required RPM. The bigger disc of the long prop has better thrust at slow speeds but needs to spin at a rate where the engine is making adequate horsepower. For the sake of max power on the takeoff run (my old -12) I had a Borer prop pitched to 40 to get more RPM to accelerate to takeoff. It didn’t make a noticeable improvement and lost performance in climb and cruise. That plane worked best with a 42. Static RPM minimum 2400 and full power level flight 2700. That’s my target for a fixed pitch.
