disappointed in McCauley prop

[astjp2]

I took off the M74ck-0-46 Sensenich prop and swapped it with the McCauley, both were 74-43, I lost 150 RPM at static going to the McCauley. I may have to get the McCauley flattened to 40 or 41 to replace the climb performance I had. Tim

[Ragwing nut]

how is the mac a 43 pitch when you listed a 46 pitch? Did you have it repitched?

[astjp2]

The sensenich was repiteched to a 43, the mac was a 43 from the factory

[Ragwing nut]

I would double check the mac. I had one on my deluxe and it preformed to book numbers, my airport is 1100 asl. I liked the climb performance, I didn't like I had to run higher rpms to keep in on step and not feel sluggish. she was on a chubby side being a deluxe with o-200

[astjp2]

What is your static? I am barely getting 2200 with an o-200 with the Mac.

[Ragwing nut]

What is your static? I am barely getting 2200 with an o-200 with the Mac.

It was closer to 2400. it would turn redline in level flight

[PA1195]

See if the pitch is equal between props. I've heard Macs can vary from the factory and Gerry at Dominion use to check them closely. Call him and ask. Macs probably have a different airfoil.

Calculating prop pitch: https://www.sensenich.com/wp-content...1297966148.pdf

Gary

[astjp2]

Static is required to be 2300-2400 per f-19 tcds for the same prop and engine.

[PA1195]

I run a Sen M76AK-2-40 static is 2440 at +70F with the C85 Stroker. Cessna exhaust and Donaldson air filter. Timed per C-85 specs. WFO 2600.

Gary

[Edwin Otha]

When you make a propeller, the pitch will be basically constant at all blade stations, one rotation moves the prop forward 43 inches at all locations. A re-pitched prop is twisted from this condition and measured at the 70-75% blade station, so the pitch can be a gradual change from the 43 inches as manufactured. Re-pitched props can be a tough to compare. I have had better luck with McCauley 1B90 props, but with Sensenich making them too I don't know what's going to happen. I have a 1B105 I'm going to use on the current project.

[PA1195]

Well I guess one could say that Tim's Sen prop was puny in engine loading at the same 74/43 pitch compared to an equivalent Mac. If the Mac loads the engine at the same pitch more...lower static rom...is that cause for disappointment?

Before I'd start changing anything I'd tie a big weigh scale to the tail and have a tug test for pounds of static pull for both then adjust.

Gary

[astjp2]

Well it’s going out to the prop shop to get checked and repitched. 300 is not a bad price. Tim

[PA1195]

According to TCDS 1A9 for aircraft S/N F-154 and up using an O-200: Maximum Normal Operating Power: 2500 rpm (73 HP) For all operations: 2750 rpm (100 HP) to comply with FAR 36.501 (noise abatement). I suspect Taylorcraft spec'd the Item 5 1B90 CM7443 based upon that limitation while meeting at least a minimum static of 2300. Yours is closer to that than 2400.

Before the prop shop twists the blade ask them to check the angles of each blade at the various stations used for that to see if it meets factory specs. Then for plus 30-50 rpm per inch pitch decrease. I'd want redline in flight unless cross-country ops are preferred.

Gary

[astjp2]

To what end Gary? If I can get a 2350 static, that should give me great overall climb with an acceptable cruise. I may see if they can do a before and after report and dimensions check because I don’t have a history for this prop, I also have a new Sensenich prop to play with. There may also be a few restrictions basted on the engine stc so we will see what happens. Tim

[PA1195]

To what end Tim?..for the same reason you achieved your PhD...because you were curious and in the end it meant something to others. When one object behaves unexpectedly versus another when using a common source for the drive power plus common sense (Alaskan interviews remember?) dictates a "why?. Is the Mac correct before twist or not? If you let this comparison go we will have learned nothing about Sen vs Mac vs factory pitch distribution. Are you willing to learn and share?
Gary