R

rrd1_99

Active Member
Sometimes I think making these decisions is more mentally taxing than building an airplane....

RV-9A with a 160 HP O-320. I have definitely decided to go fixed pitch, but I haven't made the metal versus wood decision. I like the aesthetics of a wood prop, as well as the "smoothness". But I have very little experience flying one and no experience maintaining one.

I live in semi-arid eastern Oregon and don't plan to find myself in rain very often. I will have a home strip, likely dirt treated with dust control agent. The ground is very loamy, with very little natural gravel.

Are there any other considerations I should be mindful of?

Thanks,
Roger Barnes
slow QB -9A
 
MT fixed pitch

I live in northwest Washington State which is rain soaked compared to beautiful La Grande. I purchased an F/P MT prop because it has a stainless steel leading edge. The prop is supposed to be somewhat weather resistant. Wood core with composite shell, steel leading edge. I have not flown it yet but it looks pretty sound. You might want to check it out.
 
If you have your plane hangered wood should be fine, although you will have to always check torque on your prop bolts on wood, whereas metal does not change its size. I personally would look into the composites as the outside composite material protects the wood core. You still get the smoothness and light weight of wood, but it will stand a little more weather.
 
I have been checking my prop bolt torque every 50 hrs as part of my oil change routine. Never an issue so far with 300 hrs on the Hobbs. I have a Sterba wood prop on my 160 hp O320.
 
With wood there are no RPM restrictions that I am aware of anyway, and they are a tad bit smoother. Personally, I like to see the wood, I think they look better...kinda retro old school.
 
I like wood

Roger: I have an Aymar Demuth wood propeller on my second hand RV-4. I like it. They are inexpensive compared to metal propellers. Smooth as can be. Makes it real easy to lean using the engine roughness technique. When I fly in the rain I run at 21-2200 rpm and I have not seen any errosion. Checking the prop torque is a must but it takes only 20-30 minutes and is a good excuse to really inspect the prop and spinner. Even better, wood propellers are light. A light RV4 with 180 hp and a wood prop is very nimble. And fast. I can cruise 200 mph TAS at 75%, but I usually run about 60% and get about 185 mph. WOT down low will bust Vne in level flight. This is my first wood propeller in about 35 years and I think wood is a winner for the kind of flying I like. If I build a second airplane, it would be an RV3 with 160 hp and a wood prop, bare bones. (Just idle daydreaming, that's all, Mary.)
 
Basic wood prop rules

I've been running wood props on my aircraft for over 25 years. I like them. they are cheaper, lighter, smoother, quieter, and in my opinion prettier. I don't like flying in heavy rain. When I get in heavy rain, I throttle back and go toward the light spot. I've never had any serious erosion problems.
Rules for wood props: 1/Leave them parked horizontally, 2/Keep them clean, 3/Re-torque periodically depending on the local environment, 4/Keep the finish intact. 5/Remove and inspect the bolts at annual condition inspection for stretching at the base of the threads.
 
Thanks everybody!

I actually expected to hear more in favor of the metal prop. Thanks everybody for the input, and I am definitely going to check out some wood props!

Roger
 
Roger:
I went with sensenitch wood, but I?m a wood kinda guy to begin with. Price was a big factor for me at the time, I think I paid $1,100 for it. Considerabley cheaper than the metal. Rv-9A, N625DK out of KS12 Albany ore, O-320 160hp. No complaints to date other than watching my buddies with constant speed props dance circles around me come take off or landing. If your home strip is under 2000? I would perhaps re-consider the fixed pitch vs constant speed thing, but that is just my opinion based on my experience and skill level (or lack of). Go to ?http://terry.disorderlywitches.net/photos/flying/ ? for some photos and trips from this past summer, maybe a pic or two of the prop. On the Burns trip we took off at gross wt (1800lb) with two of us, full fuel and density altitude of around 5500?. It took a good 1800? of paved runway to get us into the air. I don?t have the specs on the prop here (they are at airport) but it was middle of the road between cruise and climb pitch reccomended by the factory(I can get it for you if you like). I did not have any flaps down for increased lift (ie. short field).


A buddy of mine owns the Pine-Eagle strip in Halfway, a little more gravel there than I would like but I will be going in and out of there some this next summer helping him do the electrical on a new hanger he is building. I think I may take my wheel pants off before going in there to keep them from getting chipped up. Just a hop-skip and jump to La Grande. Let me know if you need a look-see and a ride next summer. I gotta fuel up over there somewhere, heck might as well be La Grande as long as the price is right. Gotta be cheaper than Baker City last spring @ $5.79/gal !! Ouch!

Cheers
doug
 
metal prop

ok, I'll throw in a word for the metal prop. I am running a catto two blade now but I had a Sensencih metal on my -4 for about 350 hours. I would not hesitate to use the metal prop again. It performed well and it was certified. At 9500msl and 2600 rpm ( 0-320 160 hp ) it would true out at 165 kts average. The weight up front made for better handling with passengers in back. The only reason I switched was to get max performance for xc air racing. By the time you buy spacer, crushplate, bolts etc. you will have the same money in a wood or a metal prop. Certified engine, certified prop... 25 hour test period!

Chris Murphy RV-4
 
Christopher Murphy said:
By the time you buy spacer, crushplate, bolts etc. you will have the same money in a wood or a metal prop.
Chris Murphy RV-4
Click to expand...

I do not believe this is accurate. Not in my case anyway. My $700 prop plus another $400 or so with the bolts, crush plate, spacer, etc... still does not come close to the cost of a metal prop.
 
some numbers

I have a Sensenich metal on my 9A now, and I must say it performs well. Great climb, good cruise, trouble free, and smooth. Tracked to within .030", and Certified too. For grins, I just got a quote on an MT fixed 2 blade composite from the guys in Florida. 2250.00 for the fan, and 1500.00 for the installation kit which includes the prefitted spinner. I really like the light weight and smoothness of a wood or composite prop, but ...Cha Ching!!!.....Think I'll run the metal one for a while. Guess that Euro buck is doing well here recently.

Regards....Chris
 
Of course I need a ride!

dougknight said:
If your home strip is under 2000? I would perhaps re-consider the fixed pitch vs constant speed thing,


A buddy of mine owns the Pine-Eagle strip in Halfway, a little more gravel there than I would like but I will be going in and out of there some this next summer helping him do the electrical on a new hanger he is building. I think I may take my wheel pants off before going in there to keep them from getting chipped up. Just a hop-skip and jump to La Grande. Let me know if you need a look-see and a ride next summer. I gotta fuel up over there somewhere, heck might as well be La Grande as long as the price is right. Gotta be cheaper than Baker City last spring @ $5.79/gal !! Ouch!

Cheers
doug
Click to expand...

Heck, I will pay for the fuel! Very few RV's over here, and rides don't come along every day. I will PM you my contact info!

As for the home strip (right now just a pipe dream), it will be about 1600'. However, I will only fly out of it solo and under good conditions. The local airport (LGD) is only five miles south, so I will hop there for fuel and passenger. I will also have available hangar space at LGD for those times when landing at home is sketchy. No obstacle clearance issues at either end, so all things considered I think fixed pitch will be perfectly ok.
 
dougknight said:
If your home strip is under 2000? I would perhaps re-consider the fixed pitch vs constant speed thing, but that is just my opinion based on my experience and skill level (or lack of).
Click to expand...

My strip is 1500' and I fly out at almost gross most of the time. F/P Catto. No problems at all. If you're seeing an 1800' take-off roll on ANY RV, I'd look for a problem.
 
Mel said:
My strip is 1500' and I fly out at almost gross most of the time. F/P Catto. No problems at all. If you're seeing an 1800' take-off roll on ANY RV, I'd look for a problem.
Click to expand...


5500' density altitude at Burns is probably lower than average in the summer months. And the runway choices for winds are not always optimal. I took off there in a 172 well under gross and I'll bet I almost doubled that 1800' takeoff roll.

Roger
 
Propeller bolt inspection

Mel said:
I've been running wood props on my aircraft for over 25 years.... 5/Remove and inspect the bolts at annual condition inspection for stretching at the base of the threads.
Click to expand...

Mel: How is a propeller bolt inspected for stretch? Mic'ed? What locations on the bolt? What are the tolerances, and where does one find that data for the bolts? Thanks.
 
RV-6 w/ O-320 160HP. I switched from a Sterba to an MT this summer. Took the time to carefully run tests on both for thrust, climb and cruise. The MT outperformed the Sterba on all segments.
Most important is the MT is a certified prop and protects from wx and damage with a kevlar wrap and stainless steel leading edge. It bolted on with no mods needed to the spinner. Price is $2250 plus shipping from Germany. 8 wks to delivery. I sell them. Call or write if you want to order.
John Nielsen
www.MTProps.com
-----------------------------
Here are the test results:
Static Thrust
Wide Open Throttle, Full Rich Mixture

Sterba 68-78
RPM 2400
MP 16
Thrust (lbs) 360

MT-170-R/180-3E
RPM 2350
MP 16
Thrust (lbs) 422
--------------------------
Cruise Speed
Sterba 68 - 78
TAS 3000' MSL 177mph
TAS 6000' MSL 188mph
TAS 8000' MSL 181mph
MT-179-R/180-3E
TAS 3000' MSL 199mph
TAS 6000' MSL 191mph
TAS 8000' MSL 180mph
 
Stretched bolts are somewhat rare, but....

Stephen Lindberg said:
Mel: How is a propeller bolt inspected for stretch? Mic'ed? What locations on the bolt? What are the tolerances, and where does one find that data for the bolts? Thanks.
Click to expand...
they can happen. If for instance you torque the bolts when the prop is extremely dry, then the humidity comes up considerably, the wood will swell and can stretch the bolts. I have seen them break under these circumstances. If you have a "stretched" bolt it will be obvious upon visual inspection. It will begin to stretch at the base of the threads. If you find one stretched bolt, you should replace them all.

I once presented a program at an EAA meeting on propellers and talked about this phenomena. The next week I had a fellow call me and told me that upon inspection of his wood prop, he found 2 broken bolts and the other 4 were obviously stretched.
 
BloomerJohn said:
RV-6 w/ O-320 160HP. I switched from a Sterba to an MT this summer. Took the time to carefully run tests on both for thrust, climb and cruise. The MT outperformed the Sterba on all segments.
Most important is the MT is a certified prop and protects from wx and damage with a kevlar wrap and stainless steel leading edge. It bolted on with no mods needed to the spinner. Price is $2250 plus shipping from Germany. 8 wks to delivery. I sell them. Call or write if you want to order.
John Nielsen
www.MTProps.com
-----------------------------
Here are the test results:
Static Thrust
Wide Open Throttle, Full Rich Mixture

Sterba 68-78
RPM 2400
MP 16
Thrust (lbs) 360

MT-170-R/180-3E
RPM 2350
MP 16
Thrust (lbs) 422
--------------------------
Cruise Speed
Sterba 68 - 78
TAS 3000' MSL 177mph
TAS 6000' MSL 188mph
TAS 8000' MSL 181mph
MT-179-R/180-3E
TAS 3000' MSL 199mph
TAS 6000' MSL 191mph
TAS 8000' MSL 180mph
Click to expand...

These numbers don't make sense to me. The Sterba is 20+ mph slower at 3000', but slightly faster at 8000'. What could cause this relative disparity between two fixed pitch props? The prop's helix?


Also, I will point out that static thrust figures are nearly meaningless. Our airplanes are only static at the beginning of the takeoff roll, and after that, static thrust figures don't translate well.
 
wanted prop for sale

Due to a damaged metal prop (previous owner) I to am in the market and trying to decide wood or metal. I would like to replace with the Sensenich cm77 and remove the old one. anyone out there gone to wood and have a sensenich they want to part with?

Chuck
 
Metal prop.

I echo the comments of Ron "Smokey" Schrek. If you use a wood prop on an RV and It begins to rain then you fly at Piper Cub speeds. To the Guy from Oregon does it ever rain there? Go with metal and forget you own a prop.
Tad Sargent
7A (had wood switched to metal)
 
What kind of Piper Cub do you fly?

tadsargent said:
I echo the comments of Ron "Smokey" Schrek. If you use a wood prop on an RV and It begins to rain then you fly at Piper Cub speeds. To the Guy from Oregon does it ever rain there? Go with metal and forget you own a prop.
Tad Sargent
7A (had wood switched to metal)
Click to expand...
Not sure what kind of Piper Cub you fly, but when I get in rain I throttle back to about 130-140 mph. I never flew a Cub that would make those speeds.
 
tadsargent said:
I echo the comments of Ron "Smokey" Schrek. If you use a wood prop on an RV and It begins to rain then you fly at Piper Cub speeds. To the Guy from Oregon does it ever rain there? Go with metal and forget you own a prop.
Tad Sargent
7A (had wood switched to metal)
Click to expand...

There you go... Taking my name in vain again! OK, I never said Piper Cub speeds, but when the rest of the formation is ripping through the rain at 160+ knots and you have to throttle back to 2100 RPM, you will "feel" like you are in a Piper Cub. Ask "Radar" how we all know this. ;)
 
I have had the FP MT on my RV-6 for one rainy season. I have never let rain stop my planned flights, so it saw several hours of sometimes heavy pounding. There is no signs of wear. I have also sen MT used on several area float planes and after many years of water use, no erosion, only bits of paint begin to wear away.
John
 
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