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  #41  
Old 09-05-2021, 11:50 AM
David Z David Z is offline
 
Join Date: Aug 2010
Location: Thunder Bay Ontario
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Nickel or stainless steel leading edges are extremely common on other composite propellors. Just because there are issues with certain Catto props doesn't mean all nickel leading edges have problems.

In the attached picture, the leading edge took a large rock on the forward blade face. The nickel was scratched, but the composite material was blown out the back. Not an RV prop, but shows the level of protection a metal leading edge provides.
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  #42  
Old 09-05-2021, 11:52 AM
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Quote:
Originally Posted by lr172 View Post
NLE has many advantages, but is not the only optoion.

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  #43  
Old 09-05-2021, 07:01 PM
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rjcthree rjcthree is offline
 
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Default NLE Failure mode and root cause?

Has there been a root cause of NLE cracking identified? Is it prop blade bending fore and aft with thrust loads? Twisting? Radial rotational loads ( as in the stiffness of the NLE is carrying a large portion of the blade load due to higher modulus?) Even if there is a nick, the stress riser only drives to a fracture with significant unit loading. The pictures shown all seem to be nicely perpendicular to the blade axis, which seems like a clue.
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  #44  
Old 09-06-2021, 10:52 AM
PilotjohnS PilotjohnS is offline
 
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Default Maybe

So I stayed at a Holiday Inn Express last night. The bar girls got me drunk so I would give them my credit card. What a surprise when they discovered it was declined, I was happy thou. But I digress…..

Curious if the props that are showing NLE cracking lived a hard life? Like maybe the flyer habitually pulls and pushes the plane around using the prop? I could see a condition whereas the prop is getting tweaked because it is being used as a tow bar?

I think the Catto props have superior performance, but that may be coming at a price of needing to be babied a little.
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Last edited by PilotjohnS : 09-06-2021 at 10:55 AM.
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  #45  
Old 09-07-2021, 07:39 AM
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Snowflake Snowflake is offline
 
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Quote:
Originally Posted by PilotjohnS View Post
Curious if the props that are showing NLE cracking lived a hard life? Like maybe the flyer habitually pulls and pushes the plane around using the prop? I could see a condition whereas the prop is getting tweaked because it is being used as a tow bar?
They'd have to pull or push at the tip of the prop to even be likely to cause damage... Usually one pushes/pulls near the root, where you're unlikely to flex the blade.

Props experience much higher loads in flight than you are likely to put on one pushing it around on the ground.
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  #46  
Old 09-07-2021, 08:17 AM
PilotjohnS PilotjohnS is offline
 
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Default Actually

Quote:
Originally Posted by Snowflake View Post
They'd have to pull or push at the tip of the prop to even be likely to cause damage... Usually one pushes/pulls near the root, where you're unlikely to flex the blade.

Props experience much higher loads in flight than you are likely to put on one pushing it around on the ground.
Actually i did some quick math, and it appears there is greater bending loads on a prop when it is pushed or pulled on than at any time during flight. The g loading from the rotating blade is so high, that the thrust vector is insignificant on the blade stress as compared to the centrifugal force.
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  #47  
Old 09-07-2021, 03:41 PM
dtw_rv6 dtw_rv6 is offline
 
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I'd like to see the FBD for those calcs. I'm pretty certain that my prop at full throttle can pull harder on the frame than I can when the engine is off.
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  #48  
Old 09-07-2021, 04:27 PM
PilotjohnS PilotjohnS is offline
 
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Default math

Quote:
Originally Posted by dtw_rv6 View Post
I'd like to see the FBD for those calcs. I'm pretty certain that my prop at full throttle can pull harder on the frame than I can when the engine is off.
So like a helicopter blade is pretty floppy when it is sitting on the ground tied up, but yet is very straight and rigid when flying, so too is the prop. The bending moment on the blade from being pulled is really high as compared to flying. The centrifugal force is so high that the pull moving the airplane through the air does not contribute much bending to the prop. I think I calculated the acceleration of the prop blade as, like 10000 g's keeping the prop blade from bending while flying.
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  #49  
Old 09-07-2021, 05:03 PM
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Saber25 Saber25 is offline
 
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Knock on wood, but with over 320hrs of hard acro and gyro maneuvers using the Catto three blade, nickel leading edge, on a Pitts S1S, I have not observed any structural degradation of this prop. The prop is limited to 3200 RPM and frequently operates at 3000 rpm, neither it nor the engine show any distress with that RPM visited often. Nor has the Catto two blade, with far more time on the RV4 shown wear or tear. We don't fly in rain and the planes are babied in their own hangar. Perhaps that helps.
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Last edited by Saber25 : 09-07-2021 at 05:22 PM. Reason: incorrect rpm
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  #50  
Old 09-08-2021, 07:32 AM
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Quote:
Originally Posted by PilotjohnS View Post
Actually i did some quick math, and it appears there is greater bending loads on a prop when it is pushed or pulled on than at any time during flight. The g loading from the rotating blade is so high, that the thrust vector is insignificant on the blade stress as compared to the centrifugal force.
Pull into a vertical climb, and your prop is lifting your entire gross weight, half on each blade (for a two-bladed prop). I doubt you're pulling with that much force when you move it on the ramp.
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