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Aerobatic Prop

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Wanted:prop for aerobatic monoplane 1100lbs gross IO320 150 hp with 68x72 prop
WOT 160mph at 2700 rpm at 4000' msl. Static 2050 rpm at 1150' msl, climb 2100 rpm at 100mph, 2200 rpm at 120 mph. Eventually straight and level it will wind up to 2700 rpm. Climb is lethargic. I would like 25-2600 rpm climb and 2800 level. I am in the market for another prop better suited. Cost is always an object.
Ideas?

Thanks,
Mike Warbington
 

cwilliamrose

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You may want to see more like 3000rpm WOT in level flight. That may not even be enough to make the airplane happy at low speeds.
 

EAABipe40FF

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You seem way over propped? I'm not familiar with monoplanes but most 150 hp Lycoming powered biplanes will use a Sensenich 74DM pitched at 56" for aerobatics. That's what I had on my Pitts S1C.

I have a IO320/160 HP on my Acroduster 2 with a 74DM6 X 58". Static is 2350-2400 rpm. It turns 2500 rpm in a 90 mph climb. Level flight @ 2000', 2400 rpm= 120mph, 2500 rpm= 130 mph IAS, 2600= 140 mph, 2700= 150 mph, WOT 2950 rpm= 160mph. (or so?)

Hope this helps,

Jack
 
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Thank you very much for the information,
the speed/rpm numbers you guys have seen seem more like what I need.
I am in the market for a wood/composite prop in that range.
 

race38

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Just a comparison, I have a Prince 68x71 on a 150Lyc that gave these numbers: 2350 static 2850 wot 155-160 ias on a Smith Mini. Cold air induction, 4into1 exh, and aggressive timing. Accelerated well at 1000-1050 gross.
Don't know who's prop your working with, but they measure at different locations. I liked the Prince.
 
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Race88:
Thanks for the comments, Your Prince prop on the Smith sounds about right for me. I have a Smith Miniplane I used to fly. I think my Zenith CH 150 Acro is a little sleeker than the Smith, your prop might pull my airplane a little faster at a little higher rpm. That pitch sounds about right. Prince will make me one for $2.6k roughly, which would buy a lot of mogas.
 

race38

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Keep your eyes open, saw one recently on Barnstormers for reasonable.
I think the carbon prop is that expensive, but fiberglass is less. Call and speak to Lonnie if you have questions, great guy and very helpful.
Mine is glass and paid about $600 for it. Old design, but works well.
I would bet you'd be quite a bit faster at 2800+.
 
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An update to my search for the correct prop:
I found a 74DM61 Sensenich aluminum prop and spinner, and put it on my airplane.
Static and climb rpm are sluggish, but it winds up to 2900+ rpm at 3k msl and 150+ kts.
It is heavy and the pitch and gyroscopic loads are heavy. Too heavy. There is an rpm restriction to 2600 for this prop, I believe.
The performance of this prop is very good. I think a little finer pitch, perhaps the 7458 recommended would be a better fit.
I tried today a 7456 wood Sensenich. Rpm at climb speed is higher, rate of climb is higher at 1300 fpm, WOT rpm is almost 3100, WOT IAS IS ABOUT 20 kts less than the 7461. It is smooth. Pitch forces are much lighter. They seem about right. I don't really like this prop, mainly because I know the 7461 aluminum has much higher top speed.
A couple weeks ago I put a 6872 Prince P-tip prop on my airplane. Flew it for one flight. Prince told me it was too coarse, He is right.
The prop is smooth. Take-off and climb lethargic, as predicted. Max rpm 2550 at 180mph. Would probably be a decent cruise prop for 160hp. I like the prop, it and the pitch forces are light, but it is too coarse for an aerobatic machine.
I have had a couple other wood props on it, and they seem to run into a wall at 2700 rpm and about 160 mph ias.
What I find interesting is that the 7461 Sensenich and the 6872 Prince both outperformed the 7456 wood Sensenich, the former at 100 rpm less, the latter at 550 rpm less. I think these results say those two props convert power into thrust much better that the wood props I tried. They effectively have spoiled me.
I plan to change pistons from 150 to 160 hp soon.
I think what I want is a prop that weighs like the Prince and performs like I think a 7458 aluminum Sensenich will.
Any and all ideas and comments are appreciated.
 

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