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Biggest possible prop for RV3?

Lufthans

Well Known Member
Hi guys,

I'm on the fence with my RV-3B resurrection project - either keep my (150 hp, conical mount) O-320, or turn it into a real hotrod with a Subaru and constant speed MT.

Not wanting to turn this into a Lycoming versus Subaru discussion - I've done several Subaru-powered aircraft and the aircraft I am flying most often at this moment (my Jodel) has one on it. I've put in the required engineering to make this REALLY work. Perfect cooling, runs smooth like a sewing machine and it hauls. If I am fair to myself, I'd love to have this on my -3B as well.

On my Jodel, I cruise my prop at 1750 rpm (4000 on the engine), and the engine with that steep reduction ration has loads of torque. And so I need all the prop I can get. On the Jodel this means 3 blades and 74".

I'm pretty sure that 74" is more than the RV-3 could handle. But would it handle 70"? Or is the typical 68" the limit of what can be bolted on without risking prop strike? I've searched all over this forum but haven't been able to find any answers...

Anyone know?

Thanks!

Hans

jodel_subaru.jpeg
 
If I remember correctly, a friend has a 72" prop on his RV-3 and with the airplane level, reported 5 inches of ground clearance. I don't know if he has the oversize tires or the pneumatic tailwheel, though.

Dave
 
Any more props

I am interested in picking up some speed and am currently spinning a Sterba 68 x 72. This spins up to 2800 RPM at 180mph and I think I could get a little better speed from something with a little more bite. I like the simplicity of the wood and am considering just asking Ed to try to repitch this prop.
 
Mine originally had a 72" Hartzel prop. When it failed inspection, I replaced it with a 72" Whirlwind 3-blade. I put about 17 incident free hours on the 72" Whirlwind followed by about 3 seconds worth of "incident." :-/ I now have about 25 hours on a new 70" Whirlwind 3-bladed prop [and an overhauled engine].

I wouldn't hesitate to run a 72" on the RV-3. There is plenty of ground clearance unless you plan to operate out of a wheat field or something like that. Mine had 850+ hours with a 72" without a problem.

I can say from firsthand experience that if you ding a 72" prop, your pitch attitude is very scary tail high. I can't imagine EVER getting to that point unless something goes very wrong.

For what it's worth, Jim Rust suggested the 70" blade was more appropriate for my IO-320 engine so that's what I went with on the most recent prop. Otherwise, I wouldn't have had any issue with buying another 72" prop. The 70" blades weren't available on their 300RV prop when I ordered my first one last fall, but they are now.

Just another data point.
 
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