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Wood Prop Question

Mr Charles

Well Known Member
I have a RV-4 that I purchased a few years ago...has a IO-360, inverted oil, Vetterman exhaust, fluid balancer, old style cowl, and a Berne Warneke wood prop...I developed a small trailing edge crack in the prop that I found when I removed it to refinish the clear coat. I called a prop guy in California and am repairing/refinishing, but thinking about getting another prop. The Berne is stamped 68 X 76...a couple of people I have talked to can't believe these numbers...I measured the length and it is 68" long. Does anyone have experience in this area? Is this an uncommon setup? What is recommended length and pitch for my setup/flying? I do some aerobatic flying with it, but not competition...cruise flight probably more important to me for performance. How about the fluid balancer? Good thing or no??
Appreciate any feedback
Charles
 
You cannot compare pitch information on wood props between manufacturers. There are too many differences in planforms, airfoils and measuring techniques.
You need to determine who you want to build your new prop, give him hp, and speed range of your airplane and let him/her determine what pitch to use.
 
Charles-
Mel is correct.
I usually make a 71X76 for an 180 HP RV4. The older props were a bit smaller in diameter. Feel free to call me and I'll be glad to answer any questions you have.
Frank
713-417-2519
 
Thanks

Thanks for the feedback...I have been able to research and talk to a few people, and you guys are right on. Any ideas on the fluid balancer/dampener? In theory I think the idea is great, but the fact that no one seems to know anything about them and no one seems to be using them makes me wonder if I should leave it on or take it off? Comments appreciated!
Charles
 
You will find a few threads here on VAF. (I've been searching on the same subject). Most of the installs of the dampeners were two fold - vibration control and weight. You will find some of the threads by searching "inertia ring" or "mark landoll".

For RV's with wood propellers, there was a tendency to be nose light. The ring adds about 12 lbs to the hub. It also helps with the inertia of the prop druring starting.
 
Take it off

I would not use the dampner. If you need weight call Saber Mfg, http://www.sabermfg.com/ and get a heavy crush plate. Of the few people I knew who had the dampner they did not like them. If you have a wood prop that is causing vibration then it needs rebalancing. Hope this helps.



Thanks for the feedback...I have been able to research and talk to a few people, and you guys are right on. Any ideas on the fluid balancer/dampener? In theory I think the idea is great, but the fact that no one seems to know anything about them and no one seems to be using them makes me wonder if I should leave it on or take it off? Comments appreciated!
Charles
 
Frank, wood props require retorquing with "significant climate change" which in many parts of the country is twice a year. The prescribed instructions call for loosening the bolts for at least 30 minutes then torquing.

Would that not require rebalancing twice a year?
 
Frank, wood props require retorquing with "significant climate change" which in many parts of the country is twice a year. The prescribed instructions call for loosening the bolts for at least 30 minutes then torquing.

Would that not require rebalancing twice a year?

Glen- I recommend refinishing(balancing is done at this time) a wood prop every 2-5 years, depending on use and enviornment(IFR in rain is usually 2 yr intervals). Climate change dosent effect the Multi-Laminate like it will the Plank Props. The torque values are much higher for the Multi-Laminate -35-40ft lbs for 1/2" bolts-
and it dosen't crush like the planks. As long as the finish is intact you have a vapor barrier and moisture content will not change, the major problem with wood propellers is lack of Maintenance/Refinish. I recommend retorquing at Condition Inspection for my propellers.

One very important thing to check If you have the long bolts which go thru the extension into the crank drive lugs. Sometimes the bolt thread will bottom out and give you a false torque reading, leaving the prop loose-Very Bad things happen.
 
Frank, thanks for the info. I just keep learning!

I do keep a close eye on the finish and have only encountered rain once. (throttled way back but still a little paint abrasion at the tips. Did maintenance before the very next flight.)

My prop is the Aymir DeMuth and the documentation says to torque the 3/8" bolts to 22-24 ft-lb.

(O320-E2A 150hp with Aymir DeMuth 68-71)
 
I have a question about metal props. we have all heard about not trying to
cut down a metal prop to use on a RV. What if you find a metal prop whose
manufacture's specs allow a small length reduction that remains within its
published limits and likewise a repitch done within spes? For my 0235
in a RV3 it seems possible to find such a prop. Can you safely go any longer than 68" on a RV3. I have a good metal prop than can operate at 69.5"
length for example. When it comes to pitch is there any rule of thumb on
metal versus wood? Does a 60" pitch metal relate to a 60" pitch wood?
The prop I have is from a American yankee powered by the same engine
i will be using in my RV3. It is a 71 X 53 but the manufacture says it can
be reduced to 69.5". If it was reduced from 71 to 69.5 and the pitch increased a few degrees what could i expect in the way of performance?

Thanks
Jim Miller
 
When all else fails...

Jim,

All the RV builders manuals clearly state that Van's Aircraft only gives one Metal FP prop their seal of approval, the Sensenich props specifically designed for RV's. The RV's develop an inflight harmonic vibration unique to a wide speed range high speed cruise airplane. The Thorp guys figured this out long ago when several guys were killed when their props shed a blade inflight. Take my advice, don't do it.

I tested Nine props on my RV4 over the years including Bernie and Margie Warnke's wonderful almost C/S masterpieces. Additionally, I put 1000 hours on a Landoll dampener, and liked it. Bernie died many years ago and Margie is currently retired in AK last I heard.

There are some wonderful wood or composite props available out there. Craig Catto,www.cattoprops.com"composite props" Gary Hertzler [email protected] "Silver Bullet" wood/composite and Margie's props performed far and away better than the rest. Craigs new props with Nickel leading edge are very impressive, great climb, cruise and aerobatics and bulletproof in rain. Frank "propman" is currently doing some nice work with performance props down in Tejas...Gary Hertzler makes the best performing prop I ever flew on my RV4 but requires throttling back in rain.

Give Craig or Frank a call or drop Gary an email, they pretty much have every RV engine/HP pitch desire dialed in.

V/R
Smokey




New Catto prop on my RVX
 
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