wooden propeller

[VIP337]

Has anyone had experience flying behind a wooden propeller. At some point (soon) my metal prop will have to go in for overhaul and I'm not sure it will pass inspection. The cost is dooable but there is not much practical information out there. Ideally I would like a cruise prop but I don't think that pitch is approved. With the c-85/O200 engine I think that would work better.

Bill

[6643]

Bill:

I'm not sure exactly what you're asking. So, at the risk of looking foolish, here goes:

I have flown behind several wooden props. They are smoother running and less efficient. You cannot leave them outside all the time and I wouldn't want to do a lot of flying with one in any kind of precipitation.

The approval requirements are pretty lax. If you look at the Aircraft specification, you will see it states:
Propeller - Sensenich 74FC-47, 74FC-49, 74FK-47 or 74FK-49 or any other
approved fixed pitch wood propeller which is eligible for the engine power [and]
speed and which meets the following limits:
Static rpm at max. permissible throttle setting:
Not over 2160, not under 1885.
No additional tolerance permitted.
Diameter: Not over 74 in., not under 72 in.

So, any certified wooden prop that can handle the power and RPM, that is between 72 and 74 inches long, and nets you static RPM between 1885 and 2160 will work. For cruise, of course, and given that you have the O200 crank, you'd want to aim for the lower limit. For reference, note that the RPM limits for the C90 are not over 2160, not under 1835. I'd also aim for the longer length as longer props tend to develop more thrust than shorter ones at the same RPM.

HTH,

[VIP337]

John,

Thank you for the information. My knowledge of wooden propellers is zero but I think I would like to try one. Unfortunately if you get the wrong pitch you can't take it to the local propeller shop to have it repitched. I don't have a lot of hours on the new engine but the 120 is noticeable faster but I don't know (yet) the rpm range I need. I guess a good question to ask is the rpm range on a 48 pitch on a wooden prop the same as a 48 pitch on a metal prop.

Thanks again

Bill

[6643]

Yes, it is sort of hit and miss. Maybe someone else will chime in with some real world numbers. One place to start is the Sensenich listings in the Univair Catalog. They are showing 72-48 for the C85 and 74-48 for the C90. I expect the 74-48 would be a pretty good choice for your engine, too, unless you want to favor climb performance.

Of course, there is also some variation between props of the same dimensions from different manufacturers, as well.

The best thing would be if you could borrow someone's and try it out...

[1307]

Bill, John is spot on. I've had a Sensenich wood prop on my '46 C-140 periodically. Performance is definitely not as good as the metal prop, but it does absorb engine vibrations much better. And definitely do not fly in the rain with it, or leave it outside without being covered to protect it from moisture. With mine, climb performance was degraded about 6-8%, and cruise was 5 mph slower. But it sure looks nice on there. Mine is a 76-48. Installation and bolt torque is critical, and must be routinely checked as the wood compresses. Mine is no longer serviceable. Loaned it to a friend while his metal prop was in the shop. He was in the local pattern one afternoon doing touch and goes, and the top cowling right side hinge pin began snaking forward. Ate about 1/32 into the wood near the prop hub before he could get it down and shut off the engine.

https://youtu.be/ax0yaHi4acc

[VIP337]

Chuck,

With that loss of performance it doesn't look like the wooden prop is the way to go. Maybe I can find a cheap used one just to try out.

Thanks for the information.

Bill

[4290]

Hi Everyone – I’m trying to learn a little about Sensenich wood propellers, as I might put one on my 1947 C120 with a C85 engine (and 0-200 crank) with a flanged crankshaft. A couple of questions:

The approved flight manual stipulates a prop with a diameter of between 72.5 and 74 inches, but Sensenich stipulates a W72GK-48(46) prop for our airplanes. Sensenich does say that the “72” is just the “basic” dimension of the prop – so, can someone confirm that a W72GK-48 is actually 72.5 inches in diameter? Also, Figure 1 in the parts book calls for an FK not a GK hub and drill combination. Just trying to clarify the difference. Perhaps the old FK required bushings around the bolts and the GK doesn't?

Also, I assume there is a ‘compression plate’ or a ‘faceplate’ that goes forward of the propeller for a wooden propeller installation, but maybe I’m wrong here? Either way, can someone confirm or point me in the direction of the proper bolt lengths, compression plate part number (if there is one), etc.

Thanks in advance!
- John

[6643]

Ignore the flight manual. Look at the type certificate for the airframe and for the prop.

For C-85 Engine Installation
1. Propeller - Sensenich 74FC-47, 74FC-49, 74FK-47 or 74FK-49 or any other
approved fixed pitch wood propeller which is eligible for the engine power
speed and which meets the following limits:
Static rpm at max. permissible throttle setting:
Not over 2160, not under 1885.
No additional tolerance permitted.
Diameter: Not over 74 in., not under 72 in.
Not eligible on seaplane models.

The propeller manufacturer will specify any plates and bushings required for the installation.