C85-8F seaplane prop pitch

[Dano"T"]

Re: C85-8F seaplane prop pitch

I do have a Sensenich 76AK-2-40 on my C90....my C85 has a McCauley IA90 71-42....I guess what brand we use makes a difference as well. Thanks for responding and straightening me out. I wonder why McCauley and Sensenich have different oinions on this? are they different other than rounded tips on the Sensenich and square tips on the McCauley? Anyways...the point remains...if you get ramped and they find you have the wrong prop or is not properly logged etc...they [FAA] can make life difficult for you.

Also, don't be too dissappointed if the O-200 doesn't give you as much extra ooompf as you are seeking. A very good friend of mine has an O-200 (no electrics)on his BC12D and my C-85 powered BC12D outperforms him...on takeoff and climb. Same pitch prop...his is 2" shorter I think. He gets me at cruise though. Just a thought...anyone else have an opinion on this? I know my new C90 powered plane out does the C85 also...especially loaded....both on skis. Again, It has a 74" 40 Sensenich.

[gcgilpin]

Re: C85-8F seaplane prop pitch

I think the whole issue is ridiculous and mainly due to manufacturers chosing to certify a few props and stopping there. It may be somewhat relevent for land plane installations (due to clearance), but not seaplanes.

Sensenich 76AK-2-40, 76AK-2-42 and 76AK-2-44 (all 74 inches in diameter) are all approved for Cessna 120 / 140 airplanes with C85 engines.

I wouldn't hesitate to put a 74" prop on a C85 engine installed in a Taylorcraft or Aeronca.

From this discussion alone it's clear that C85 powered planes haven't started dropping out of the sky because of 74" props.

Feel free to slap my hands for having this attitude :-) I'd be happy if someone could enlighten me.

[matsuthunder200]

Re: C85-8F seaplane prop pitch

Im not shure why but the sens ak props have always out preformed the mc props i have a ak 76- 38 prop on a c90 that was approved with a 337 when i had the c90 installed. and it dose real well but i only cruse at 80 to 85.
for what i do i like it alot. Flew it the other day on skes me a frind and about 18 gallons of fuel took off from a slick runway was dead calm was off the ground in about 100 ft. climed out at about 800 ft per min at 60 mph. was about 0 deg they shure fly well in the cold air.

[gcgilpin]

Re: C85-8F seaplane prop pitch

I wander how the sensensich 76-AK-2-38 would work on my C85? I'm thinking I should try that before buying a C90.

[Dan Mahalak]

Re: C85-8F seaplane prop pitch

I can understand, and appreciate the vibration thing, in fact, I had the same Idea, sorta...P=MV.......(p being rowe) or some derivation therofe.....but stillll nonetheless.......
Im not buying why a sen vrs a mac are not the same thing...I guess I am ingorant but isnt a moment a moment, no mattter how is gets its distance from a measured point, the center of the hub in this instance? .........
74 is 74 no matter how I creatively measure it....

So are there any other reasons? What makes a Sen a different animal in your opinion? is it better than a mac?

See, I am going to floats for the first time this summer, and am scouring the earth for the largest prop I can put on. I do care about my life however. Where I live, i must certainly climb like mad, 3000ft plus to go anywhere, as I live in in FJORD......cruise, what is that|?Oh yeah, that where one uses that thing in the top of the window that does not work half the time..., but throwing a larger or smaller t.w. on does.... and putting the emergency brick elsewhere in the baggage compartment.

[Dano"T"]

Re: C85-8F seaplane prop pitch

I swapped props on my planes this weekend....put the 76AK-2-40 from the C90 T-Craft to the C85 T-craft...It made a difference. Got off quicker and climbed better...Lost 5 MPH only. I think I'll try it like this on floats this spring. The new prop measures 75" on the tape...the old one 71" on the tape. Turns up to 2550 Rpm Static. Still on skis here in the U.P. of Michigan....the snow really crusted up this weekend and made for spectacular short take offs on skis...my neighbors on the lake said they really enjoyed watching this weekend with the nice sunny weathey...many on the lake were out and about...gave lots of rides.

[NY86]

Re: C85-8F seaplane prop pitch

So are there any other reasons? What makes a Sen a different animal in your opinion? is it better than a mac?

The Sensenich and the McCauley are different castings with different resonant properties. So is the McCauley 1A100, etc. They all have different resonant properties and thus different restrictions.

[gcgilpin]

Re: C85-8F seaplane prop pitch

Wow, you got 2550 rpm static with that long prop? I guess you have to throttle back quite a bit in cruise?

This long AK prop sounds like the answer then. I'm not looking for a huge improvment just a bit more performance for those glassy water conditions.

Anyone have a 76ak 40 or 38 for sale?

I swapped props on my planes this weekend....put the 76AK-2-40 from the C90 T-Craft to the C85 T-craft...It made a difference. Got off quicker and climbed better...Lost 5 MPH only. I think I'll try it like this on floats this spring. The new prop measures 75" on the tape...the old one 71" on the tape. Turns up to 2550 Rpm Static. Still on skis here in the U.P. of Michigan....the snow really crusted up this weekend and made for spectacular short take offs on skis...my neighbors on the lake said they really enjoyed watching this weekend with the nice sunny weathey...many on the lake were out and about...gave lots of rides.

[N96337]

Re: C85-8F seaplane prop pitch

"The Sensenich and the McCauley are different castings with different resonant properties. So is the McCauley 1A100, etc. They all have different resonant properties and thus different restrictions."

The thing about resonant vibrations is also that we may not feel them... We had a brand new 400HP Piper Brave (IO-720 LYC) one time that would shed an alternator in about 10 hours of flight. We threw the Chadwick on and did everything else we could think of, and finally Lycoming sent someone out, and they did a bunch of testing, and decided that it was a hidden resonant vibration somewhere in the engine/prop combo, and replaced both. The aircraft flew for years and never had another problem. The whole time we were chasing this, the guys were all swearing by how smooth the thing ran and flew.

I'm hoping this long prop setup gets some time on it... I'd like one myself!!!
JH

[Dano"T"]

Re: C85-8F seaplane prop pitch

Wow, you got 2550 rpm static with that long prop? I guess you have to throttle back quite a bit in cruise?

This long AK prop sounds like the answer then. I'm not looking for a huge improvment just a bit more performance for those glassy water conditions.

Anyone have a 76ak 40 or 38 for sale?

That's assuming the tach is accurate...the 74" prop has a 40 pitch...the one I took off has a 42 pitch....I have gotten anywhere from 2450 to 2550 with the one I took off...pretty much the same as the new one. Do atmospheric conditions affect static RPM? Just wondering why I get 2450 in summer and 2550 in winter....maybe my tach is not totally accurate. I can redline it in cruise with either prop....around 2600.