What Prop?

[mohawktipi]

Last year I used Terry Bowdens STC to upgrade my L2-B from an A-65 to C-85. I kept the same prop (7248 wood) and was very satisfied with the overall performance. I picked up about 7 mph cruise with an improved climb performance.

Over the winter, I am rebuilding the C-85 with the O200 STC. I should pick up another 10 to 15 horsepower and was wondering what would be the best prop. I would like to go to a metal prop and I am interested in improved cruise performance without sacrificing climb. Any suggestions?

[Mark Julicher]

Re: What Prop?

Well, the F-19 with the O-200 will swing a McCauley 1B90 , 74-43 or a McCauley 1A 105SCM, 69-50. I believe the L-2 will look better with the longer prop.

The L-2 has a little bit more drag, but a little less weight - so I figure that for a wash as far as prop selection goes. You may want to keep the round tip prop - then select a McCauley 1A90.

[jim cooper]

Re: What Prop?

Last week I changed from a Sensich wooden prop (72-40) in VERY nice condition to a McCauley METAL prop B90 series 74-43. It made a BIG difference in the takeoff ! Cruise remains the same, 90mph. The tail comes up almost immed. and it takes off much quicker. I bought it from East Coast Propeller in Lancaster, Penna. They gave me 600 bucks trade in. I am very satisfied with the new prop. Bob Dart, who used to run Dart Airport in Mayville N.Y. said that wooden props belong over the mantelpiece. He was right. (I have a BC12D with a 65hp.) with good comp. and 600 hours SMOH. JC

[N95645]

Re: What Prop?

Jim,

I've got the same McCauley B90 prop and pitch on my BC12D with 65 hp and the change was phenominal from the wood prop. In the cold dense air of this time of year, my cruise when up to 92 mph (GPS confirmed) but I only get about an 86 mph cruise on an average summer day. Gross weight also plays with the airspeed cruise numbers by a few mph as well as rate of climb. I have gotten as much as 750 ftm with just me in it and about 10 gals of gas. I also get a solid 500 ftm with a pax and 8 gals of gas on a 70 degree day. The prop seems like it added 10 horsepower.

Best,

Tim

[barnstmr]

Re: What Prop?

Tom,
They are on the right track with the 1B90CM7443 recommendation.

[crispy critter]

Re: What Prop?

Borrow and try the 74/45 McCauley....you'll gain some speen and won't notice much if any climb performance.

[flyguy]

Re: What Prop?

Are we talking about using a full length (not a dash whatever) 74 inch prop on an O-200? What transpired out there while I wasn't paying attention?
DC

[crispy critter]

Re: What Prop?

yep....it worked great.

[astjp2]

Re: What Prop?

Long and flat for great climb. The Seaplane prop is a 75/38. Tim

[T-Rex]

Re: What Prop?

Does the O200 crank STC specify a different prop than the C85? After the mod can you run the same props as the O200? Please explain.

[Ragwing nut]

Re: What Prop?

read your tcds, longest is 72" on L-2.

[Ragwing nut]

Re: What Prop?

Does the O200 crank STC specify a different prop than the C85? After the mod can you run the same props as the O200? Please explain.

no it does not. mod is not "suppose" to add hp but does due to increase displacement. Engine remains legally an 85 and operated as an 85. Prop options is determined by a/c tcds not engine tcds

[T-Rex]

Re: What Prop?

But you can not go off of an ac TCDS that was certified with a 65 and go to an 85 or 85 stroker and use the same prop as the 65. When you go from a 65 to an 85 you need to cut the Mac 1A90 or 1B90 prop to a max length of 71". If you want to go longer you will probably have to use the Sen M76AK-2 prop. That is the only 74" metal prop approved on a c85. Unless the STC specifies that you can use the Mac props at longer lengths.
You cant use them with the straight 85 because of harmonic vibration, weather or not this changes with the O200 innards i do not know.
What does the STC for the install of the 85 say to use for a prop? There is your answer.

[astjp2]

Re: What Prop?

In seaplane configuration, the longer props are approved.

[Ragwing nut]

Re: What Prop?

But you can not go off of an ac TCDS that was certified with a 65 and go to an 85 or 85 stroker and use the same prop as the 65. When you go from a 65 to an 85 you need to cut the Mac 1A90 or 1B90 prop to a max length of 71". If you want to go longer you will probably have to use the Sen M76AK-2 prop. That is the only 74" metal prop approved on a c85. Unless the STC specifies that you can use the Mac props at longer lengths.
You cant use them with the straight 85 because of harmonic vibration, weather or not this changes with the O200 innards i do not know.
What does the STC for the install of the 85 say to use for a prop? There is your answer.

Sure you can. TCDS for the 1A90 says they are hp eligble for 85 and above depending on model. L-2 TCDS states only 1a90 is the only legal metal prop. Interesting part is that is states max 72", until you get down to specific prop requirements and then it mentions 74" is legal on DCO-65, so which do you believe? All this means nothing if Terry's STC lists applicable prop models, and then you must use one on his list.