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What is best CRUISE prop and pitch for a PA12/PA18 with a 160hp O320-A2B on wheels to give the best cruise speed on long X/C trips?

Colin

MEMBER
I currently have a Sensenich 74DM6-052 on my PA12 for float ops but I want to do a 6000 mile trip on wheels and would like to get better cruise performance on a long trip to keep up to my buddy in his faster plane?
Any suggestions?
Thank you
Colin
 
Hi guys, thank you for your reply.
So do you think the 74-56 pitch is ideal or what about a 74-58 or -61 ? pitch so that I have a cruise prop that is significantly different than my float flying prop.
If 74-56 is the best prop for best cruise performance then that is what I would get.
 
Hi guys, thank you for your reply.
So do you think the 74-56 pitch is ideal or what about a 74-58 or -61 ? pitch so that I have a cruise prop that is significantly different than my float flying prop.
If 74-56 is the best prop for best cruise performance then that is what I would get.
The ground adjustable one in 10 minutes would do both and everything in-between. And save 15lbs off of your nose

Glenn
 
See what your static rpm is with the prop pitch you have, assuming the pitch marked on the prop is correct. You can figure 50 rpm change in static per inch. A 58" pitch prop will theoretically go forward 58" for every revolution. Someone can figure the difference in speed between props with that knowledge.
 
I kinda thought you might do the math Pete. ;) I was too lazy. Thanks.
Colin should be ordering a new ground adjustable Sensenich from you. Not just for this planned trip, but to get better performance when he goes back on floats. That 7452 which he is using now is leaving a lot of his horsepower wasted.
 
FWIW i used to own a C150/150 taildragger.
I discovered that a 74x54 sensenich was the sweet spot.
If you're looking for speed, just turn up the rpm.
It'll be working just about as hard as a 74x58 or whatever does at lower rpm, due to the lower manifold pressure.
And you won't have to deal with doggy takeoff & climb performance when you get where you're going.
 
I used a 43 degree Borer on N3788M driven by a 160 hp B2B. It worked very well for me on wheels, wheelskis, and EDO 2000 floats.
 
With increased pitch comes the need for added engine torque and more fuel burn if you want to go faster. That can affect range - miles per gallon, etc., in still air. Same for driving the rpms up on a lower pitch prop.....there's an rpm and airspeed above which thrust and engine efficiency deteriorates at that pitch, and MPG declines. The engine's optimum specific fuel consumption at RPM can also be noted (it's in the engine ops manual see Section 3). Cessna does the math and makes range and endurance profile charts at various power settings for that info.

I'd try a different pitch as suggested then keep track of RPM, airspeed, and fuel burn to determine MPG. If you still have fuel when your buddy and you arrive together then that's good.

Edit: For me the choice would be between minimizing the time flying, or maximizing range on load of fuel while avoiding undesirable airspace and weather. One's fast, the other's MPG (or range). Piper via prop pitch offered the pitch range in Post #8. Good enough.

Gary
 
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The ground adjustable one in 10 minutes would do both and everything in-between. And save 15lbs off of your nose

Glenn
I currently have a Sensenich 74DM6-052 on my PA12 for float ops but I want to do a 6000 mile trip on wheels and would like to get better cruise performance on a long trip to keep up to my buddy in his faster plane?
Any suggestions?
Thank you
Colin
I have a Sensenich 76-56--O-320 ( PA-12_ Kenmore STC) that puts out closer to 160 HP. I have 26" Goodyears. I have a very short T/O run on tarmac. during cool/cold weather I have to throttle back to 2300 or the prop will pull the wings off. The ASI and GPS agree that cruise is at 115 MPH. I do keep the plane clean and waxed---it makes a difference. Fuel burn is 8.5- 9 but on trips to Oshkosh/ New Holstein from MA I have gotten it down to 7.8. I've done many 1000 mile plus X country and the numbers are consistent.
 
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