86" pitch sensenich

Paul Austin · #1 02-24-2010, 09:15 AM

For all of you running RV7a,s with a IO-360 i am after your thoughts on what pitch best suits the RV7a. I have heard quite a few people say that the standard 85" is under pitched. I want to still have pretty good take off performance as i fly out of a resonably short grass strip 1500FT approx. Do you think 86" would change the take off much while giving me that little more at the top end. Look forward to your comments so i can get a prop on the way.

jsharkey · #2 02-24-2010, 03:21 PM

My RV-6 has a Sensenich 72/85 on a YO360-A1A. Static rpm is only 2200 and take off while brisk still feels like starting in 3rd gear. It certainly isn't a kick in the tail. I still don't have leg fairings or wheel pants fitted and have to throttle back very slightly at top speed to avoid red lining. Short of a constant speed prop I think that the 85 is a good compromise.

Jim Sharkey
RV-6 Phase 1

Greg Arehart · #3 02-24-2010, 10:26 PM

Paul,

Not exactly the same, but I have an 87" pitch on my 9 with an IO-360. I got the higher pitch for better cruise performance (and can still get 2750 RPM at WOT at 8000 elevation), but still have no problem getting off the ground in less than 1000 ft at gross weight, and I'm operating at a field elevation of 5000 ft. Not the same climb performance as a climb prop or CS prop would be, but WAY better than most spam cans.

Just another data point.

greg

turbo · #4 03-01-2010, 01:59 PM

question. if sensi is building that pitch for the 7 then i think you will be happy with that prop. being light would be nice going out of the short strip, a cs prop would be better if a short strip was used a lot. i have been running a 85 on a 6 with 0-360 and love it. being light with the fp is key. it will get off no problem.

elippse · #5 03-01-2010, 09:06 PM

Here's a formula which tells you the effective or actual pitch of a propeller as it screws its way through the air. This is not the geometric pitch which some obtain from some surface on the blade, but the actual amount that the propeller advances, in inches, each revolution. For this to be correct you must have a calibrated pitot-static system from which you or your instrument will give true airspeed. EP = TAS, mph X 1056 / rpm. So if you are going 200 mph TAS and turning 2700 rpm your true or actual pitch is 78.2". The same propeller on two of the same type of planes with different drag or power will give different results, so its not always possible to compare what will be obtained with the same prop.