Prop Choice

[DPKII]

My 46 BC12D was converted to a BC12d-85 in 1948. When the c-85 was worn out it was replaced with a A-65 years ago. It is time to do a top end on the 65 so I used this as an excuse to put a zero time c-85-8 on.

I ran a McCauly 74/45 on the a-65 and it performed well. Best climb seemed about 70mph and was positive but sedate. Cruise was 90-95 @2150.

I have a borrowed McCauly 71/44 on the c-85 as the 74/45 is not certified for the 85. With this combination the Taylorcraft is a completely differnt airplane. All I can say is wow! Best climb seems about 65mph and is very positive. It now climbs on the prop instead of the wing. Cruise @2400 is about 100mph. I can redline in level flight if I run wide open so I think I may need more pitch. Static is 2300.

I will have to buy a new prop so I can return the one I have. From the research I have done I think the standard prop for the c-85 is a 71/46. That is 2 degrees more pitch than I have now. This should give more cruise speed.

Has anyone had experience using a 44 and 45 or 46 pitch props with the c-85? How much climb performance will I loose going up one or two degrees in pitch. Higher cruise at lower throttle settings would be great if climb doesn't suffer too drastically. Will it climb at a shallower angle (more airspeed) but at about the same rate?

I have searched this site for prop selection but still have not really found a definate answer. Found a lot of info on seaplane and non-certified setups.

I really hate to buy a new prop without knowing exactly what I want and I don't have a 71/45 or 71/46 to try.

Thanks for any help you can offer,

David

[crispy critter]

Re: Prop Choice

David,
I have 2 McCauley props and I will trade either to your 74/45. One is a 70/48 and the other is a 71/50(the last one is off a C90). Both props look new,one is new.

[DPKII]

Re: Prop Choice

Kevin,

Thanks for the offer in trade. I plan to keep the 74/45. It still looks new as well. I still have the a-65 and plan to overhaul it for a later project.

thanks,
David

[Forrest Barber]

Re: Prop Choice

71-48 is the prop for you.

[PT13Pilot]

Re: Prop Choice

I stuck a brand new McCauley 71-48 on the 85 BC I did the wings on. 3 previous IA's didn't notice/care that it had a 65 HP wood Sensenich on it. One even jerked it off, sent it to Sensenich for overhaul, and stuck it back on. So telling the owner it had to go wasn't easy. I've never seen a Champ, Chief, Luscombe, whatever little continental powered airplane I've flown, that is as happy with a prop as that 71-48 on that 85HP BC12. I thought it might be a little overpitched, but having the wrong prop on it, and I hadn't found this site yet for recommendations. So I went with the recommendation from McCauley. First run it didn't turn any more static than the wrong wood prop did, which made me wonder again. One flight dispelled any doubts I had. It gets off and climbs like it's scared of the ground, and cruise was equally as impressive. And it won't bury the tach at WOT in level flight either. Seems as good as a fixed pitch prop gets for a good all around prop on that airplane. And 2 years later the owner still raves about it.
CJ

[DPKII]

Re: Prop Choice

Forrest and CJ,

Thanks for the reply. Exactly tne advise I was looking for.

71/48 it is.

Thanks,

David

[mohawktipi]

Re: Prop Choice

I have a 1943 T-craft L-2B with A-65 aand Flottorp 72/48 wooden prop. I am currently overhauling a C-85-12F that I hope to install over the winter. I wouild like to use the same prop. Anyone have any comments?

Thanks

[PT13Pilot]

Re: Prop Choice

Tom,
These are just my opinions, but I would think it would work well. Might want a little less pitch for better climb with that airplane, but that would be up to you. Being that airframe isn't gonna go as fast with the 85 as a BC12. I'm sure someone here has more info. My friends L-2B had a field approved 75 with Sensenich metal prop that flat didn't work worth a darn, but that's what it had been approved with. It would flail away RPM wise, but didn't move much air. The afore mentioned wood prop on the BC12 I installed the 7148 on, ended up going on the L-2B for a while, and was on it when he sold it a few months ago. I flew it before and after the same day. It performed identically poorly, just turned about 300 RPM's less with the wood prop.
I was dieing to hang an 85 on that airplane, he even had a 0 time 85 hanging on the wall to do it, but he sold it. The L-2 needs an 85 badly. Too much fun scaring people with spoiler approaches, then 10 minutes to climb back up to do it again with the 65/75 on it. Makes me wonder if whoever bought it in North Carolina has found their way to this site yet. Good luck with your 85 swap, I'm sure you'll like it better whatever prop you end up sticking on it. To get maximum gains, a good metal McCauley will outperform a comperable wood prop any day.
CJ

[mohawktipi]

Re: Prop Choice

Thansk CJ

I was going to keep the same prop for economic reasons. Climb right now is poor but I get good cruise. The extra horsepower should help the climb enough for my purposes.

[Forrest Barber]

Re: Prop Choice

Try it, if you hit red line FT in cruise and a good static then keep it.
RPM is the answer , I have been away a bit getting two guys going in their 140 Cessna's ; one a 1946 w/wheel extensions and the 85 hp ; the other is the 1948, forward swept gear and a 90HP ; they have fine pitched props and they haul my big butt and the owner into the air just fine . I am now 248 lbs, going down as we speak.

[NY86]

Re: Prop Choice

...140 Cessna's ; one a 1946 w/wheel extensions...

Training wheels...

[Forrest Barber]

Re: Prop Choice

The extensions put the wheels forward to where the other has its located from the factory. I agree they are not necessary. Kind of like the Goodyear cross-wind landing gear. Another of my favorites was the Gyro Copter with a retracable landing gear.