Need Advice on Prop Pitch RV-9A, 160HP

Av8torTom · #1 03-07-2020, 07:58 AM

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 · #2 03-07-2020, 08:03 AM

why would you consider a prop limited to 2600 RPM?

Av8torTom · #3 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 · #4 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 · #5 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 · #6 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 · #7 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 · #8 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 · #9 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 · #10 03-07-2020, 10:01 AM

Quote:

Originally Posted by N941WR

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???