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-   -   Need Advice on Prop Pitch RV-9A, 160HP (https://vansairforce.net/community/showthread.php?t=180227)

Av8torTom 03-07-2020 07:58 AM

Need Advice on Prop Pitch RV-9A, 160HP
 
I'm trying to decide on a fixed pitch propeller for my RV-9A, 160HP.

I know the 9 tends to be a little tail heavy, so an aluminum prop might be advantageous there. However, the Sensenich props are RPM limited to 2600.

My other choice is a Whirlwind ground adjustable. I believe the composite props have a higher RPM rating, but are significantly lighter.
I have 3/8" bolts, and the Sensenich ground adjustable apparently only comes 7/16" bolt compatible.

Please chime-in with thoughts and experiences for the 9A.

Thanks,

Tom

Steve Melton 03-07-2020 08:03 AM

why would you consider a prop limited to 2600 RPM?

Av8torTom 03-07-2020 08:06 AM

Steve,

So you're saying the higher RPM limit is more important than the extra weight up front?

Thanks

pa38112 03-07-2020 08:06 AM

Whirlwind 100%. Fantastic props with better performance than the Sensenich. I would not add extra weight just for the **** of it unless you have already calculated that you need to, and in that case only add what is necessary - far better to move the battery a little forward over having all of that extra spinning weight. Pluss, with the ground adjustable feature you can tune the prop in to your exact plane and flying.

cojaken 03-07-2020 08:24 AM

I have a Sensenich fixed pitch 70CM7S9-0 (79), which is limited to 2600 RPM, on my RV-9A that has an O-320.

I have never seen 2600 RPM and think I would have to be in a very purposeful dive at full throttle to hit that. 75% power in cruise is something like 2450 RPM and 160 knts TAS. Climb is >1500 fpm.

I do not experience CG problems within MTOW.

I was not the builder and therefore did not choose this prop. Some of the composite 3 bladed props would be tempting if this one wasn't performing so well!

Kyle Boatright 03-07-2020 08:28 AM

I'd be tempted to get the metal Sensi. No rain worries, no degradation worries, probably a more useful CG. Having a thinner blade section should lead to the metal prop being more efficient, so what you give up in ultimate RPM, you get back in efficiency.

Av8torTom 03-07-2020 08:30 AM

Correct me if I'm wrong, but the metal Sensenich prop is pitched so you cannot exceed (at least not easily) the 2600 RPM limit. With a composite prop you can select a pitch that will allow you to use the full RPM range of the engine. That's a advantage of a composite prop as I see it.

Joe Parish 03-07-2020 08:39 AM

I have the whirlwind ground adjustable on my 9 and have no cg issues. I for one would not use a rpm limited prop. I personally don’t understand why anyone would but maybe I’m missing something. My empty weight was 1087 I believe. My weight and balance info is in the plane but I could get you numbers if that would help. Whirlwind lists 3/8, 7/16 or 1/2 bolts for the 0320 or 0360.

N941WR 03-07-2020 09:06 AM

Keep in mind that all the prop manufacturers calculate their pitch slightly differently. This makes comparison by pitch number alone very difficult.

I have had a Catto on both my engines and wouldn't run anything else!

Av8torTom 03-07-2020 10:01 AM

Quote:

Originally Posted by N941WR (Post 1412870)
Keep in mind that all the prop manufacturers calculate their pitch slightly differently. This makes comparison by pitch number alone very difficult.

Another reason for a ground adjustable???


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