Pitch on Sensenich

I'm hoping to benefit from the advice of those who have gone before.... I'm about to spring for a prop for my 9A, with an IO-360 (I know, not advised by Van, but I generally operate at high density altitude and wanted the bit of extra potential power). My main use will be cross-country; I don't have to have the bigger engine, but would rather have the reserve if needed to get out of a tight spot, and can always throttle back. Standard FP prop that Vans sells for the IO-360 (on an RV-7A) is with 85" of pitch. Can anybody give me a reason to go with more or less than the one Van's sells? I notice that Sensenich can make the same model with pitches between 77 and 88.

Thanks,
greg

Alternative

I am not sure if you have considered the Catto but it is definately worth looking at. A friend just replaced his sensinich on his 4 and has an average speed gain of 9 knots and his take off is close to 600' even at our airport which is at 4700' to start with. He said just yesterday that it is much smoother than his Sensi and that he is getting 2600 rpm at altitude. He is very very hapy with his choice. He runs neck and neck with another 4 that has a three blade on it. One poster here just reported that his Catto is averaging around 200 mph i thnk it was. This was on his 7A.

FP Sensenich

Hi Greg, First of all, my plane is still in pieces, so I can't tell you how it flies. I have the Sensenich with 83" pitch instead of the usual 85" that Van sells. Ken, one of the guys that worked with Sensenich developing these props lives not too far from me and he said that there seems to be little difference in performance between the 83" and 85" props. What he noticed is that he burned a bit less fuel with the 83" vs 85". Perhaps the 85" is just a bit over pitched? Good luck.

Consider C/S...

With that much power on tap, Constant speed might be a better call. Having flown 1500 hours in my fixed pitch RV4 and another 275 behind the IO540 in my Rocket, I have seen just a bit of performance with a few different (7) props and the big Hartzell paddle on my HR2. The beauty of the big motor in the Rocket is amazing takeoff and climb along with economy cruise at very low power settings. You packing an IO-360 in your 9A, you could climb like an elevator and throttle back to 20/20 and still be very efficient. With the high cost of gas, every little bit helps. An MT or Whirlwind would be worth the price and might pay for itself in the long run...

My Dos Centavos..

Rob Ray

I have installed the 83 inch pitch sensenich on a 7 and it is way under pitched. You will punch thru the red line on the engine very easily. The last 7 I used a 85 inch and it still would go easily thru the redline esp. at high altitudes. This latest 7 will have a 87 inch pitch I will let you know next month what it does. But it will be hard to relate the figures to a 9 because it is a different plane. Even if it has the same engine as the 7.

Thanks for the input. Rob, I can't go to a CS prop at this point because of the solid crank in my engine (except possibly an electric CS?). I also wanted to keep this thing as simple as possible when originally designing, but... Anyway, I will look into the other alternatives out there. Norman, I will look forward to hearing what you find with the 87 prop.

cheers,
greg

Norman's right.. 83" is WAY underpitched on a -7... since 85" is slightly underpitched.. so math says 87" would work best.. I have it (87) on mine but don't have numbers yet (no fairings)

85' was a good year...

Greg,
My buddy Rascal(Sensenich poster boy) has an 0-360/Sensy metal on his RV8 with 85 pitch and at 8500' he could get 2850 RPM flat out and passed any C/S 180HP RV8. He re-pitched to 87 and lost some climb, but burns less gas at the same cruise speed...
85 might be your best bet for climbing out of high airstrips...
BTW, I visited Sensenich's Plant City FL shop yesterday to look at ground adjustable composite props for a friends float equipped R-912 ultralight. While there the Engineer (Charley) told me they are now working on getting them into the RV world of 0-320's and 360's. They've been running them on airboats with IO-540's for a long time and they work great.

Maybe later...

RR
www.sensenichprop.com