Propeller Choice

whpilot · #1 03-28-2022, 09:51 AM

I am getting ready to buy the prop for my RV-6A. Is there any performance difference between the 74" and the 72" prop? Any advantages either way?

Thanks

jneves · #2 03-28-2022, 10:07 AM

A little info on engine and if you are looking at FP or CS would help. Also are you looking for climb or cruise performance?

Walt · #3 03-28-2022, 10:56 AM

Ground clearance is the issue, definitely the 72".

wcalvert · #4 03-28-2022, 12:29 PM

Two blade? Three blade? Fixed or constant speed?

What's the mission you have in mind? CG considerations? Cost?

So many questions!

gregfuess · #5 03-28-2022, 03:47 PM

I asked the Van's representative this same question. They recommend the shorter diameter propeller for both the tricycle and taildragger. I don't recall why, but that's what they use.

BoydBirchler · #6 03-28-2022, 06:24 PM

I have 600 hours on a 74" Hartzell mounted to my RV7. So far clearance has not been an issue. I probably do 200; 3 points to every wheel landing.

Desert Rat · #7 03-28-2022, 07:19 PM

There is a spec in the FARs for normally certificated airplanes that prop clearance needs to be certain minimum distance from the ground.

Without looking it up, I believe it's in FAR23 and the rule is 10 inches? If I'm wrong about the details, somebody please correct me.

Anyway, the gist of it is that the 74" prop potentially blows that minimum on the tailwheel airplane during landing.

Personally, I don't thing that 10" vs. 9" prop clearance is a big deal, but Vans doesn't have different performance numbers for either one, so I'm going with the 72" just because that's what they recommend.

ChiefPilot · #8 03-28-2022, 08:01 PM

Quote:

Originally Posted by whpilot

I am getting ready to buy the prop for my RV-6A. Is there any performance difference between the 74" and the 72" prop? Any advantages either way?

Thanks

I have a 74" Hartzell on my -6A. I'm not sure there is any performance difference. I was told that a 74" can be repaired and shortened to a 72" if the tip is dinged somehow but that the 72" cannot be shortened further. Some prop shops might do it anyway since it's not a certified prop so it may not really matter.

Performance-wise, it's great. Video of my bird doing 164KTAS on 5.8GPH at 15,500. The prop certainly plays a part in this.
https://www.youtube.com/watch?v=Vt_Xduuc1QU

penguin · #9 03-29-2022, 10:19 AM

I had a 6A for 17 years, I would say 72" definitely. If you're going FP then Sensenich metal is the best compromise I found. Some have found a ground adjustable (Sensenich or Whirlwind) to be easier to tune to local or personal preference factors. If you plan CS then carbon blades save 25lb on the nose.
Pete