Propeller EXPERIENCE

[Jim Herpst]

Ok so am going to replace the A65-8F with A C85-12. I have McCauley Clip Tip which is a 74/47. I would like to hear from folks with REAL experience if I were to repitch to a 43 or perhaps a little less? and use that as a 74/43 on the 85. Yes I have read here that some say it will not turn up 85 (usually the same person) however I have also seen it stated in these pages that it has worked well on 0200. If that is the case it should work on an 85 that has to turn up less rpm to develope its full hp power than an o200. Also I understand I would need to see about getting Terry Bowden to approve it. Climb is so very important here in the deep south .(summer..)the length should help.. I do not want to mess up the cruise either and would like to get all we can there also.

Real experience? Thanks!

Also as an aside not that it much matters it will be on the short mount with only a starter and a battery. No alternator /Gen. The Mrs does not want me hand propping any longer

[Ragwing nut]

I had a 74/43 on my O-200 deluxe. I liked the climb, but had to keep it wound up to have enough speed to keep it on step. I would fly it as is before repitching.

[Jim Herpst]

Mike, Thank you. That makes some sense. The 0200 does like Rpm...

[Woody]

7443 is listed on tcds for F19 with 0200

[Jim Herpst]

7443 is listed on tcds for F19 with 0200

Yes it is. Dorothy Ferris had that approved. . . with the thought for use with the float planes . Lots of variables involved.

[Ragwing nut]

7443 is listed on tcds for F19 with 0200

the 69-50 sucked. I tried both on my deluxe. it was easy to keep speed, but climb rate was horrible in summer for o200 tcart.

[Jim Herpst]

the 69-50 sucked. I tried both on my deluxe. it was easy to keep speed, but climb rate was horrible in summer for o200 tcart.

Yup . Crazy little tooth pic props. That belongs on spam can.

Any how I found good deal on a C75-12. Going to start out with my McCauley 74/47 "cliptip" and go from there. That prop is approved from McCauley for the C75 (again C) as in will have a starter to please the wife...will see bout final approval from Terry on the prop Enough to do outside this and later can bump up to a an 85 (the engine is the same .) Just need to turn it up ..not going into a long diatribe about how I would do that... big deal right now is to have everything set up...new cowel correct holes for the luscombe 8e exhaust etc.

[otrcman]

I ran a McCauley 1B90 (74/43) on the C-85-12 in my Taylorcraft L-2 for 40 years. Seemed just about perfect to me. Excellent takeoff & climb, quite good cruise with the RPM right about where I wanted it. The full throttle static RPM was about 2150, and a full throttle 80 MPH climb let the engine turn right around 2450. My typical "easy cruise" RPM was 2150 to 2200. At cruise power, I was burning right at 4.5 GPH, so it was only about 55% power.

Full throttle, flat out, the engine over-revved slightly. The official red line for the C-85 is 2575, whereas I was turning more like 2625. At that setting, the airspeed showed 118 MPH.

All these figures were taken at about 1000' MSL and air temp of 60°F

Now, I know people will say the L-2 and the side-by-side are different airplanes, but they are pretty close. The L-2 is a little heavier and a bit more draggy. So you can expect the 74/43 to rev a little bit more with a side-by-side. Fixed pitch props are always a bit of a compromise, becoming even more so as the speed range of the airplane increases. If you like a zippy take-off and good climb, and don't mind a slightly compromised cruise, the 43 pitch will serve you well. If you are working out of a longer runway and want more cruise, maybe at 45 pitch will serve you better.

Whatever you do, don't shorten the diameter. That diameter is golden. See Ragwing's note above regarding the 69/50. I don't know it for a fact, but suspect that Cessna called for the 69" diameter on the O-200 powered Model 150 for ground clearance. That's why the world is stuck with so many 69" props on O-200 motors.

[Jim Herpst]

I ran a McCauley 1B90 (74/43) on the C-85-12 in my Taylorcraft L-2 for 40 years. Seemed just about perfect to me. Excellent takeoff & climb, quite good cruise with the RPM right about where I wanted it. The full throttle static RPM was about 2150, and a full throttle 80 MPH climb let the engine turn right around 2450. My typical "easy cruise" RPM was 2150 to 2200. At cruise power, I was burning right at 4.5 GPH, so it was only about 55% power.

Full throttle, flat out, the engine over-revved slightly. The official red line for the C-85 is 2575, whereas I was turning more like 2625. At that setting, the airspeed showed 118 MPH.

All these figures were taken at about 1000' MSL and air temp of 60°F

Now, I know people will say the L-2 and the side-by-side are different airplanes, but they are pretty close. The L-2 is a little heavier and a bit more draggy. So you can expect the 74/43 to rev a little bit more with a side-by-side. Fixed pitch props are always a bit of a compromise, becoming even more so as the speed range of the airplane increases. If you like a zippy take-off and good climb, and don't mind a slightly compromised cruise, the 43 pitch will serve you well. If you are working out of a longer runway and want more cruise, maybe at 45 pitch will serve you better.

Whatever you do, don't shorten the diameter. That diameter is golden. See Ragwing's note above regarding the 69/50. I don't know it for a fact, but suspect that Cessna called for the 69" diameter on the O-200 powered Model 150 for ground clearance. That's why the world is stuck with so many 69" props on O-200 motors.

EXCELLENT !! I m going to start with the 47 pitch. Then work down ..

And no. No way would I cut that 74" clip top McCauley . If I ever sold it I pity a buyer trying to negotiate it.

[Ragwing nut]

Internally the c75 and 85 are the same. Change the spider and jets in the carb, and should be good to go, Its a log book entry to make those changes per continental service letter.

[Jim Herpst]

Internally the c75 and 85 are the same. Change the spider and jets in the carb, and should be good to go, Its a log book entry to make those changes per continental service letter.

That is my understanding also the venturi I believe.

[Ragwing nut]

That is my understanding also the venturi I believe.

yes, a c75 is an c85 with a65 carb and spider for the most part

[otrcman]

the 69-50 sucked. I tried both on my deluxe. it was easy to keep speed, but climb rate was horrible in summer for o200 tcart.

Yep, I agree. I have flown a number of Cubs, Champs, C-120's with O-200 conversions and the 69" prop and all were disappointments. Basically, the 50" pitch is too high for the RPM and airspeed range of those airplanes. In determining the optimum propellor pitch for any given airplane/engine combination, rated RPM and airspeed are the two primary determinants. Once the optimum pitch is determined, then the diameter is chosen to absorb the rated horsepower.

As an example, in the case of an airplane with a top speed of 110 MPH and an engine with a red line of 2575 (C-85), the optimum pitch would be right around 43". Then it would take a diameter of about 74 inches to absorb the horsepower and hold the RPM down to red line at full throttle flat out. If the rated RPM were 2750 (O-200) the optimum pitch would be more like 40 inches. The two examples given are just to illustrate the effect of changes in engine and airframe.

Unfortunately, none of us has an endless variety of props to try out. That's why it is good to calculate the desired dimensions so you don't have to keep buying different propellors just to see how they work.

[Jim Herpst]

That sums it all up. Based on the real world experience of the comments my bet is I will end up around 45 or 43 pitch.

[astjp2]

Why not a 75/38? approved for the c-150 seaplane...