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FlyingMonkey

Prop Issue -- Cosmetic or Serious?

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Today after flying I was wiping down my Neuform prop, and noticed a number of fine parallel cracks just below the black edge protector, running lengthwise on all three blades.  They can be felt with a fingernail.  Can those with the knowledge to make a determination please take a look at the pics below and tell me if this looks to be a serious issue or just cosmetic damage to the gelcoat?  The prop has right at 600hrs on it and has spent its entire life hangared.  I'm supposed to make a flight tomorrow morning, but I'm a bit hesitant now until I get more info.

Thanks.

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Andy, good definition on your pictures.  I'll be waiting to hear from the experts on this.  I'm also going to take a good look at my prop.  It's similar vintage as yours.  How about sending your pics to Arian at FD with follow up phone call to him?

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2 minutes ago, Runtoeat said:

Andy, good definition on your pictures.  I'll be waiting to hear from the experts on this.  I'm also going to take a good look at my prop.  It's similar vintage as yours.  How about sending your pics to Arian at FD with follow up phone call to him?

I was hoping for a quick “it’s fine” answer, since I have a lot of flying to do this weekend.  But I guess I will have to wait for the experts to weigh in.  Asking Arian is a good idea.

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I have more experience with glass then carbon. That said, that looks like stress related cracks. Stacked hair cracks like these usually come from the layup flexing or “moving” in a way that’s incompatible with the paint system or gel coat above it. its hard to say if the flexure underneath which caused the hairline fractures was in or out of spec; it would depend on the paint system and underlying layup. 

It’s also interesting that the cracks are the entire length. Stress cracks have reasoning behind them; they follow load paths, or they propagate in areas where quality layup is difficult etc. On the other hand, “cosmetic only” is usually much more random. 

Now with all that blah blah said........if it were me I’d be ordering a new prop.

 Its pretty important to me that all pieces of my propulsion system are in unquestionably good order. It makes me nervous that it’s the whole blade length on all blades. 

Maybe not the answer you want but i won’t sugarcoat, -not with something this important! 

Ymmv

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Any chance someone was cleaning the leading edge while wearing a ring with something sharp on it?  They look like they could be tool marks rather than cracks. 

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4 minutes ago, John Vance said:

Any chance someone was cleaning the leading edge while wearing a ring with something sharp on it?  They look like they could be tool marks rather than cracks. 

Negative, I don’t wear jewelry.  I only use a microfiber cloth and water with Composiclean bucket wash on it.  I find it weird that the marks are on all three blades in the same general areas.  

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34 minutes ago, CTMI said:

I have more experience with glass then carbon. That said, that looks like stress related cracks. Stacked hair cracks like these usually come from the layup flexing or “moving” in a way that’s incompatible with the paint system or gel coat above it. its hard to say if the flexure underneath which caused the hairline fractures was in or out of spec; it would depend on the paint system and underlying layup. 

It’s also interesting that the cracks are the entire length. Stress cracks have reasoning behind them; they follow load paths, or they propagate in areas where quality layup is difficult etc. On the other hand, “cosmetic only” is usually much more random. 

Now with all that blah blah said........if it were me I’d be ordering a new prop.

 Its pretty important to me that all pieces of my propulsion system are in unquestionably good order. It makes me nervous that it’s the whole blade length on all blades. 

Maybe not the answer you want but i won’t sugarcoat, -not with something this important! 

Ymmv

That’s why I’m asking, it is important!  It seems bizarre to me that the prop would have stress-related cracking at 600hrs when it has been taken good care of and never had any issues previously.  The last time I looked it over it looked great, now maybe 5-10 hours later it’s got cracking on all three blades.

I will tell you this:  if I need a new prop, it will not be a Neuform.  Probably a Sensenich.

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One thing I just noticed in the last picture.  There are a few short “cracks” that go almost exactly perpendicular to the direction of the main cracks.  That is weird and does look like kind of a stress pattern to me.

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I don't have the knowledge or experience to give you an answer or even a guess as to the integrity of the prop.

I do know that a prop coming apart once airborne is often deadly so were it me I would ground the aircraft until cleared by someone with experience specific to Neuform or similar. Arian has been suggested. Maybe he has a contact at Neuform.

To me, it's not worth the risk. I suspect you feel the same way. If there were any doubts I would spend the $$ for a new prop rather than worry about it going forward. 

Not too many years ago at the Albany, OR airport the local EAA chapter was conducting Young Eagle flights. The airplane involved in this incident was one of the RV series, the prop may have been one of the MT models that most if not all have removed from their planes, and the Young Eagle was on his very first flight in a small plane. Apparently a blade was thrown but the pilot got the plane safely on the ground. No injuries but the plane was damaged beyond repair. Among other damage, the fuselage was twisted. I think the seat cushions may have also been stained. Anyway, that incident is the only one I know of where there were survivors. Most of the time the planes occupants are not as lucky.

Hopefully this will turn out to be cosmetic.

 

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They are in fact stress cracks. I have seen these cracks in a few Neuform's. The only sure way to tell is to send it up to FD and let their prop guy take a look. 

If you have to put another prop on put a Sensenich 68" 3 blade.

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Send it to flight design for inspection.

 If I recall correctly, on the neuforms, there is a leading edge fence to protect the blade. The glue might be coming apart.

Your blades themselves could also be coming apart. Neuforms are two blade halves put together around a core.

The part that catches my attention most is the perpendicular cracks. This makes me think it's twisting and flexing more than it should be.

@CTMI there's not a whole lot of difference between fiberglass and carbon fiber. They act in much the same way, your assessment is still quite valid.

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Thanks Corey and Roger, I guess it's inspection time.  I can remove the prop today, is there any real trick to it other than just unbolting it?

Roger, you say you have seen this on a few Neuforms...any reason why?  It seems crazy that a prop would start to shred itself at 600 hours without any event to cause it.  I'm just trying to think it there is anything I did wrong or could have done to prevent this...

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Composites are sensitive to age. Unfortunately, composite aircraft are very likely not going to last as long as an aluminum aircraft. If your prop is old, it may just be breaking down.

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You live in Georgia. That's enough to cause anything to crack. :rolleyes::D

Usually when I see this it's from being stored outside. I know that isn't the case here. How about before you bought the aircraft? I would also bet that vibration has played a part. Vibration which you can only feel bad vibration may still be there and you can't feel it. Things like this usually come from owners not syncing carbs, props out of balance and gearbox's that need shimming. I know these may not be an issue on yours, but should be ruled out.

Then there is it just may be a bad prop and you had nothing to do with it.

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This makes me think that I demand a lot, every flight to 14,000' these days and I make top cruise speed numbers high of 125kts.

My 2nd hand warp drive with a big chip in one blade looks pretty bullet proof like it could last 100 years.

I think the construction is so simple that it lacks transitions to fail like Andy's here.

 

 

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Carbs synced regularly, including two weeks ago.  Prop dynamically balanced a couple of years ago.  Airplane always hangared, including previous owner.  I'm at a loss here unless the gearbox or prop hub have a problem.  Other than that I'd have say it's a bad prop.

 

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Because your experimental I bet you could just bolt on a new Warp Drive for something like $650.  My experience is the performance is good. You might hate the look.

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4 hours ago, Ed Cesnalis said:

This makes me think that I demand a lot, every flight to 14,000' these days and I make top cruise speed numbers high of 125kts.

My 2nd hand warp drive with a big chip in one blade looks pretty bullet proof like it could last 100 years.

I think the construction is so simple that it lacks transitions to fail like Andy's here.

Ed,

Why did you replace your Neuform prop with the Warpdrive?

Did you ever consider the Sensenich?

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2 minutes ago, WmInce said:

Ed,

Why did you replace your Neuform prop with the Warpdrive?

Did you ever consider the Sensenich?

I din't I did replace my Warp with a Warp. The Warp was original equipment and was damaged by a mechanic and Roger sold me a cheap replacement.

I've had Warps and similar before and don't see the need to move to such a fancy / expensive blade design if it doesn't perform a lot better.  

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I will evaluating all prop options if it comes to that.  The only downside of the Warp is weight.  I don't want to add an additional 5-10lb way out at the farthest forward point if I can avoid it.  Though the price is certainly right.

 

15 hours ago, Anticept said:

If I recall correctly, on the neuforms, there is a leading edge fence to protect the blade. The glue might be coming apart.

Corey might have it right with this.  The cracks are all under and around the edge protector, and stop where it stops.  I'm wondering if there might be excessive flex in the bond between the protector and the body of the blade, causing the gelcoat to crack.

In any event, the prop is off the airplane now, and I'll send it to FD as soon as I talk to them, probably Monday.    

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Does anybody know if there is a fleetwide LOA for the 3-bladed and/or 2-bladed prop?

I like that stainless steel protective leading edge on them.

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You can get an LOA for a Sensenich 68" 3 blade for an LS or SW.

If you want a Sensenich prop I'm and OEM and can get you a discount. 

Model: 3B0R5R68C

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I had cracks on my Neuform a little different than yours and I wasn't too sure if it was just the paint.   I decided it was not worth worrying about and went for the Sensenich props.  (Note; it was going to cost me almost the same to have it sent in, examined and repaired so it clearly wasn't a tough decision)   and the Neuform didn't go to waste. Hanging happily on bedroom wall. 

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