Wooden propellers

[MXpilot1]

I have heard stories about wooden propellers being damaged from flying in rain. Any truth to it?

[Kyle Boatright]

Most wooden props have a urethane leading edge which helps reduce rain damage, but flying through anything other than a sprinkle without reducing RPM will result in prop damage.

Think of it this way. At 2700 RPM, the tips of the prop are moving at over 500 mph. When a 500 mph prop tip hits a raindrop, that's plenty of force to take a little chunk out of the prop.

My experience is that keeping RPM below 1900 or 2000, raindrops don't hurt the prop.

[osxuser]

Same reasons they use metal leading edges on some composite props. Even aluminum props get damage from rain, it's just much more subtile, and can be dressed out very easily.

[hevansrv7a]

I gave some thought to this and got a carbon fiber over wood prop. You can restore the leading edge on a composite prop, but all you can do when an aluminum prop's LE erodes is to even out the erosion to a larger portion of the prop so as to make is smooth again (dressed out).
h

[RV9AFlyer]

Originally Posted by hevansrv7a

I gave some thought to this and got a carbon fiber over wood prop. You can restore the leading edge on a composite prop, but all you can do when an aluminum prop's LE erodes is to even out the erosion to a larger portion of the prop so as to make is smooth again (dressed out).
h

Flying in the Pacific Northwest for nearly 20 years, a good aluminum prop does not seem to erode in normal rain conditions. We do apply a hard polymer coating (Nu Finish 2000) every 10 hours or so as recommended by FAA standards for prop maintenance. I also highly recommend an aluminum prop, and if you are not sure about composite props, just read about Van's experience in the First 2006 RVator. I don't like wood props for two reasons--they need to have the bolts re-tightened every condition inspection, and they don't allow your engine to idle well at lower RPM due to the lower mass, which applies to composite props, too.

John

[osxuser]

I respect the abilities and advantages on all types of props. For people who are doing day-VFR sport flying (more of the mission of the -3 and -4 flyers I suspect) the wood and especially composite props are ideal. For someone who wants to travel in the airplane, and may get into weather, aluminum is the only way to go.

[rvbuilder2002]

Originally Posted by RV9AFlyer

I don't like wood props for two reasons--they need to have the bolts re-tightened every condition inspection, and they don't allow your engine to idle well at lower RPM due to the lower mass, which applies to composite props, too.
John

Bolt torque on wood props should be checked more than just once each year.
Any major seasonal change in temp and humidity can cause a big change in the prop bolt torque because of swelling or shrinking of the prop due to weather changes.

I used a three blade wood prop on an RV-6A for many years and liked it. Wood props are very smooth and there is very low likelyhood of casing any engine damage if the unthinkable ever happens. But there is significantly more maintainance and upkeep work compared to a metal prop. Rain errosion is also more of an issue but with uralight leading edges and reduced power when flying in rain, it can be mostly avoided.

That said... my current project will have a fixed metal prop (same as it orig. had). The metal props provide a slight performance advantage since the blades can be a lot thinner in cross section (particularly at the root end) because of the higher strength and stiffness of the aluminum compared to wood.

Wood is a good choice for someone on a tight budget (though the prices of some of the popular wood props have gotten very near to the metal prop), but after adding up the cost of all the parts needed to install the less expensive wood prop (extension, crush plate, bolts) most RV builders find the cost difference between wood and the metal Sensenich (bolts and extension includede in purchase price) is not very big.

[Mel]

I've been flying for almost 40 years. I have flown behind metal, wood, and composite props. They each have their advantages and dissadvantages. Unfortunately many people who knock a particular type of prop haven't flown extensively behind them. The rain problem with wood props is extremely exagerated by most people. In the early days of aviation, that's all they had. But the mail still got delivered by air. If you get into heavy rain you should pull the throttle back (just as you should with any other prop). Yes, wood props have their maintenance needs. Idle smotheness? If your wood prop doesn't idle smoothly, you need to check into it. My wood props have always idled very smoothly. The argument is the same as the F/P vs. C/S. It's a choice for you to make. But your mission and likes need to be the determining factor, not those of others.
Mel...DAR

[gmcjetpilot]

Originally Posted by hevansrv7a

I gave some thought to this and got a carbon fiber over wood prop. You can restore the leading edge on a composite prop, but all you can do when an aluminum prop's LE erodes is to even out the erosion to a larger portion of the prop so as to make is smooth again (dressed out).

No disrespect to hevansrv7a, the erosion on a solid aluminum prop is a non-
issue. I guess at top speed and RPM there can be some erosion. Yes even
aluminum props wear down but we are talking 10,000-30,000 hours
of service life, extreme to normal. If you feel a well worn aluminum prop
leading edge it can feel a little rough, like it was sand blasted but the erosion
is just not an issue with solid metal props at normal cruise RPM's.

Also the "dressing" of a metal prop is really only needed if you get a rock
ding, not rain erosion. The good news is if a nick needs to be blended it can
be done on the plane. With wood/urethane leading edges or bonded metal
strips they need to be removed to be repaired. These strips have and do
continue to come off in flight on occasion. I have had two friends which had erosion
protection spit off their prop, one metal strip, one urethane strip. In both
cases it shook the plane like crazy. In the case of the urethane it only partly
came off but did do some damage to the plane when it flew off and hit the
plane. The metal strip was off a composite constant speed prop.

Nothing wrong with wood but prefer metal. Wood's advantage over metal is
light weight, smoother operations and low cost. However the cost of
some "wood props", especially ones wrapped in composites are not cheap.
They cost as much as a certified Sensenich. Wood was much more popular
15 years ago because there was just not any good fixed pitch metal props.
Fixed metal props off of slow planes, repitched and cut down, turned out to
be a bad Idea. Also one side advantage of wood is if it hits the dirt while
spinning the chance is the prop will splinter and be less likely to damage the
crank.

Now with the Sensenich available it's almost a no brain-er, almost no
maintenance, no rain issues and in my opinion will out perform any wood prop.
I know this performance issue is fighting words, but I believe it is true from
the flight test Van has done and honest performance estimates from wood
prop fly'ers The fact, metal props have an advantage with much thinner
blade thickness, making them more efficient. The advantage of a metal props
is better performance, less maintenance and rain erosion. With Sensenich
costing just over 2 bills with all the hardware they are a bargain.

I appreciate the wood prop, they are light and pretty (the ones you can see
the wood). If I was building a Day/VFR only RV-3/4/6 I would look for a used
wood prop on the cheap. However for overall value and performance the
Sensenich is the way to go IMHO.

George

[hevansrv7a]

George's points are always well worth the time to read them. However, I reluctantly have to disagree about erosion on aluminum. My C-150 has the normal, certified (Sensenich?) metal prop. It keeps on getting rough and I don't fly in rain nor from gravel strips. The roughness makes a noticeable difference in performance. Total time on the airframe is <4100 hours.
h