Another borer question

[High Country]

The time has come for me to purchase my first borer prop. I have went back and reread many of the old posts about which borer prop would work best for me. I have a PA-18-150 and like most Alaskan pilots a short take off roll is important to me. However it seems that no one can agree on which prop is the best for that. And if you can gain 5- 10 mph with an 82/42 over an 82/41 and have nearly the same take off roll then that seems the way to go. But I have read some posts that a 150 won't pull a 82/42 that well. I will have Merrel Field Propellers check over my prop before installation, but I sure hate to spend the money on prop that is not right. It seems to me that you have to buy a prop and then keep trying different pitches until you get what you want. I don't know how much it costs to re pitch a prop, but the whole thing seems like alot of money to me. Help (said in a weak high pitched tone).

Shane

 

[Dave Calkins]

I believe the last one that George 'tweaked' for me cost 153 bucks.

I'd buy a -42 and have him check it for pitch, balance, etc., then run it. If you need more static RPM, have him tweak it to a 41. If you run it at a -42 and are happy with the static rev.'s, but end up eventually getting a 160 HP, you'll be tweaking from a -42, not a -41. (I guess it's not a big deal either way, but I'm interested in seeing what a -42 would do for me)

.....personal opinion.

PS, I'm running a -41 on a 150Horse.

...aaaannndddd, I will always take a new-from-the-factory fixed-pitch McCauley to the prop shop for a check-over before I even take it out of the box.

 

[RedEye]

82-41 for 0-320 150hp. It'll turn the rpms you want for take-off performance. If you feel the need for a bit more cruise speed, just run a a bit more rpms in cruise(at the expense of fuel economy of course). You wont be disappointed!

 

[cubunltd]

82-41 for an 0-320, 150hp. going to a 42 pitch will not give you more than 1or 2 mph at cruise and the takeoff roll will suffer a bit.

John

 

[I Fly the River]

another borer question

I used a 82-41 for several years. Bought a new 82-43 and honestly gained 5mph at 2450. As good or better take off roll. Don't know why. My Super Cub goes 95mph ground speed with no help from the wind. I have a 160 horse with 500 hrs on it. I routinely work out of very tight places during hunting seasons and love this prop.

Jim

 

[JayH]

What would be the recommendation for an O360-A1A 180hp. I've heard that you can over rev them pitched flatter than 45. Suggestions???

Thanks,
Jay

 

[Alex Clark]

When I had a 0-290 powered 12, I had a prop that was a 82 cut back to 78 inches after a boo-boo.

When I first installed it, I think it was a 46 pitch. So I did not get squat for static RPM. BUT over 3,000 feet the cruise speed really kicked in...and climb. I took that thing up to 10,000 ft.

But it was still pulling you on landings and it made me float. So I went to Dominion and they re-pitched it to what THEY said was 42. (later claimed to be 41 by another shop.)

Now I could get off a little faster and land MUCH shorter since it was now braking and not producing thrust.

Unfortunately it would not do much in the way of climbing above 5,000 ft. At least not in the summer. It would go that high and no higher...unless I inched up a tiny bit at a time.



xx

 

[High Country]

So too flat means no high altitude sheep strips?

 

[polarpete]

82 with a 41 pitch for my 150hp has worked for 25 years. If you want the shortest takeoff roll and aren't concerned with cruise the 41 is the way to go. I have always had the 41 pitch and like it.

What do you mean about too flat no high altitude sheep strips? Are you saying the air is too thin and you will over-speed?
I don't follow that one, that's when you have to turn the extra rpm to get any hp back due to altitude.

As far as cruise speed I heard-
a 41 pitch at 2450 rpm
a 43 pitch at 2350 rpm
the cruise speed will be about the same.
Anyone else heard this or experienced it?

 

[westwind]

we have a 44,82 on our cub 0-320, 160hp seems to bite better at higher altitudes than an acquaintance's 42 does, 150 hp though... not sure if the 150hp would swing a 44 very well?? have not tried that combination.... we weren't concerned with cruise just takeoff performance........ my buddy went to a 41 pitch prop "cannot recall the length" from a 38 pitch on his J3 cub 80hp and noticed a difference in takeoff at higher altitudes also.....

 

[Luke_theDrifter]

A propeller diameter is measured in inches, a propellers' "pitch" is also measured in inches.
Propeller "rake", which basically explained is the "angle the blades are relation to the hub" is measured in degree's.

Standard in the industry when talking about, or writing about, a propeller you name the diameter first, followed by the pitch. Like 82 x 41.

Pitch, which is measured in inches, means the theoretical distance the plane would move per revoltuion of the propeller.
For example, a prop that has a pitch of 41 would move the plane [forward] 41 inches every time it completed one revolution, based on 100% efficency. Not many things in this world are 100% efficent, including propellers.

As a practical FACT, the Propeller is the single most important link between "power" and actually making the most effcient use of the power. In other words, you could have the "best" plane in the world, with the "best" engine, rigged better than all other airplanes, but if your propeller is not performing as good as it could you're not getting maximum performance from the plane. I realize the word "performance" is arguably to different people, it means different things to different people, you might consider it as "effiency".

By doing a little math and applying some basic formula's, such as: revolutions per minute (RPM), gear ratio (1:1 direct drive for this application), convert 41 pitch inches into feet = 3.42 feet, 60 seconds per minute, 60 minutes per hour, 5,280 feet in each mile, you can calculate your theoretical speed...based on 100% effiency. If the ACTUAL true speed is know, such as from a GPS, you can compare to theory and find your true efficeny, and/or "slip" percentage.

I have fooled around with quite a few different props on a Cub, of course I run one that is best for my application. I've seen them vary from around 67% effiency to as high as 86-89% effiency.

For a standard out-of-the-box prop, 150hp Cub, its hard to beat an 82 x 41 prop STC'd by Roger Borer.

 

[cubflier]

The 82/41 is the most common that I've seen used on a 150 horse cub. I originally had a 43 and flattened it to a 41. I did a lot of sheep hunting and it served me well. Now that my engine is 160 horse I use a 42 and have even contemplated a 43. I get conflicting reviews on the subject and wish I could just collect them like they were cheap ball caps and put a different one on depending on what I was doing that day.

Not to distract, but did you ever resolve your high stall speed issue? It was an intriguing problem that I hope you got resolved.

Good luck,

Jerry

 

[redrooster]

I've seen this formula used to calculate airspeed versus prop pitch. Generally used for estimating cruise speed, I don't know what percent efficiency it's based on.
RPM X Pitch / 1,056 = MPH
Cub examples:
2400 X 42 = 100,800 / 1056 = 95
2450 X 41 = 100,450 / 1,056 = 95
2350 X 43 = 101,050 / 1056 = 96
Does that seem about right?
Works out pretty close for my 170:
2500 X 51 / 1056 = 120
2400 X 51 / 1056 = 116
2300 X 51 / 1056 = 111

Rooster