RV-6, Aymar Demuth prop pitched too high?

[Neal@F14]

My new-to-me RV-6 has an O-320-D1A with an Aymar-Demuth 68-74 prop (the builder called it a 68-74+). I get maybe barely 2150 static RPM and solo, it climbs about 1700 fpm on a nice warm Texas summer day. Today I went flying with a friend and we got about 1200-1400 fpm climb. It eats up quite a bit of runway with two aboard, probably a bit more than it should. This was the first time I've really got to check out the cruise performance at altitude and at 7500 MSL I can get 2450 rpm max, and with the wheel pants still off the plane, it trued out at just about 182-183 MPH. My friend says the prop is pitched too high, he says it should be able to just almost hit 2700 rpm at 6500-7500'. It'll definitely make 2700 rpm at 2000-3000' but not at higher altitudes. The 180 mph cruise speed with the wheel pants removed seems to confirm this is definitely a cruise+ prop. The airplane reportedly (by the previous owner/builder) will do 190 mph with the wheel pants installed.

I understand Aymar Demuth is no longer in business with the passing of Mike Demuth, so it's probably not even possible to have this wood prop reduced in pitch a wee bit for better climb and more rpms at higher altitudes.

A hangar mate has a brand new Whirlwind ground adjustable GA200 series prop that he bought for his O-320-equipped Glasair tri-gear and took it off due to only having about 4" of ground clearance, and I might consider buying this prop from him, as it's a 72" diameter prop and should work pretty well on my RV-6. These props seem to have pretty good reviews here on the VAF forums. He's running a 3-blade Catto prop right now and he loves the climb but wishes for a bit better cruise, that's why he bought the Whirlwind in hopes of getting that, but then was afraid of the tight ground clearance.

Thoughts anyone? Should I just accept and be happy with my current prop? I'd really like to have a bit better climb and shorter takeoff roll, since with two aboard today, with the temperatures and density altitude up, the takeoff and climb felt like I was in my old Cherokee again.

[Kyle Boatright]

Your climb performance sounds good to me. I would reserve judgement on the cruise performance until you fly with the wheelpants installed. The 74" pitch prop is what I have. It is biased towards cruise.

[humptybump]

My 150hp RV-8 has an Aymar Demuth pitched at 68-71. At 8000' DA it will turn at 2725 rpm.

I've been happy with the prop and am only now swapping g it out because I want something that will handle a bit of rain without throttling way back.

[Neal@F14]

Well, my hangar mate decided he's not interested in selling his Whirlwind GA200L prop after all, but is possibly interested in swapping fixed-pitch props. I'm not exactly sure what pitch his 3-blade Catto is, but he says he can hit 2800 rpm with it in his Glasair-I with a 160hp O-320. It might be worth a try.


Speaking of ground adjustable props... has anyone here got any first-hand knowledge on the Sensenich ground-adjustable composite prop for the Lyc O-320 that was first announced a couple years ago? I know it was talked about a lot when first announced, but there seems to be almost a complete absence of any actual reviews or 1st-hand reports about it since then. It was also priced about $1K higher than the WW GA200L props.