Acceptable Propellor Nick Size

[John Vance]

I discovered a nick in one of my Nueform prop blades. Approx 1/4" diameter, about the thickness of a fingernail clipping, located at the trailing edge, mid-blade. Is this blade still airworthy?

[Anticept]

The neuform manual has this information. You need to read the manual for your prop.

Since I am not certain of your prop model, and I need pictures, I will not comment at this time on airworthiness. For the model I am familiar with, as long as only the gelcoat is damaged, it's fine.

Neuform manuals: http://www.neuform-propellers.com/en/propellers/service-and-consultation/downloads

[John Vance]

I should clarify that this is on the rear face of the blade, so the fingernail thickness described above is into the surface of the rear face of the blade. 

[John Vance]

It's model CR3-65-47-101.6. I'll get photos tomorrow. 

[John Vance]

Here are photos. It's a little smaller than I thought, about 3/16" diameter (I was feeling around in low light when first discovered it). To my untrained eye, this looks like gel coat. The white appears to be the gel coat from the front face of the prop. The first photo is the rear face of the prop, and the second is looking at the trailing edge. 

[Anticept]

Is that fabric in the white area? If it's damaged, it's no good.

[John Vance]

It looked like the white gelcoat from the front side rather than fabric.  This is an area where the white and black coatings would be very close together. I'll try to get a better look at it tomorrow. 

[Anticept]

If the fabric is undamaged, the prop is good.

A prop is one of the "red zones" of composites. Any damage at all to the composite is cause for rejection of the part unless the manufacturer says otherwise.

You can get the resin from flight design/neuform to fill that in if it's all good.

[FlyingMonkey]

I had a similar chip in the leading edge, through the plastic edge protector and down to the fibers but with no damage to them.  I filled it in with JB Weld and smoothed in to the contours of the prop with 400 grit sandpaper.  I shot some semi-gloss Rustoleum on it to color match, and you literally can't tell which blade was repaired, even if you look closely.  It has run like this for over 250 hours.  I inspect it regularly but it's never had any issues.

This is the repair method Warp Drive recommends for their all carbon fiber props.  Neuform will tell you to send the entire prop to them, so they can not only repair the damaged blade, but recheck the whole thing for balance.  This will cost $1000 or more plus bidirectional shipping.

[Anticept]

Neuform allows you to fill the prop nicks just like warp drive.

[John Vance]

Thanks everyone for your responses. I'm convinced that the damage is limited to the gelcoat. I don't see anything that looks like woven material or broken fibers. The white area shown in the photo all lies within 1/16" of the trailing edge, and actually extends all the way TO the trailing edge.  It's hard to believe Neuform would put structural fabric at the very surface. Also, the depth corresponds to the black/white gelcoat interface at the trailing edge, so I think it's the white gelcoat showing.  If I repair the damage, I'm wondering what happens if I send the prop in for inspection/overhaul at some point. Are they going to tell me that I have an obvious repair of damage that is now not inspectable, and therefore I have a non-airworthy blade?  Other than cosmetics, is there a reason to repair?

[Anticept]

It's in the neuform manual as an acceptable field repair. Follow those instructions and don't worry.

[FlyingMonkey]

10 hours ago, Anticept said:

It's in the neuform manual as an acceptable field repair. Don't worry.

Does the manual have limits describing at what point this kind of repair is no longer considered acceptable?  Just curious.

[Tom Baker]

11 hours ago, Anticept said:

It's in the neuform manual as an acceptable field repair. Don't worry.

Assuming you use the proper materials for the repair.

[Anticept]

It's one of those "should go without saying" things but... maybe it should!

[Tom Baker]

1 hour ago, Anticept said:

It's one of those "should go without saying" things but... maybe it should!

I only said because of simple epoxy and JB Weld being mentioned in the thread.

[FlyingMonkey]

1 hour ago, Tom Baker said:

I only said because of simple epoxy and JB Weld being mentioned in the thread.

I used JB Weld because that is what the Warp Drive factory recommends, and at the time as far as I knew there was no similar procedure for Neurform for cosmetic repair.  In fact, the EAA has a video called "composite prop repair" showing exactly this:

http://www.eaavideo.org/detail/video/2111048001/composite-propeller-repair?autoStart=true&page=2&q=propeller

I didn't just come up with this on my own as some kind of hillbilly, half-assed repair idea.  

[Anticept]

Always check the manufacturer manual first :-)

JB weld is also known as a "steel epoxy".

[Tom Baker]

2 hours ago, FlyingMonkey said:

I used JB Weld because that is what the Warp Drive factory recommends, and at the time as far as I knew there was no similar procedure for Neurform for cosmetic repair.  In fact, the EAA has a video called "composite prop repair" showing exactly this:

http://www.eaavideo.org/detail/video/2111048001/composite-propeller-repair?autoStart=true&page=2&q=propeller

I didn't just come up with this on my own as some kind of hillbilly, half-assed repair idea.  

Andy, I wasn't implying that yours repair was half assed. The thought I was trying to put across was, if he follows the Neuform manual for his repair he should have no worries about them rejecting the blade at a later date because of the repair.

[FlyingMonkey]

1 hour ago, Tom Baker said:

Andy, I wasn't implying that yours repair was half assed. The thought I was trying to put across was, if he follows the Neuform manual for his repair he should have no worries about them rejecting the blade at a later date because of the repair.

I didn't think you were implying my repair was substandard, only that you thought maybe the use of JB Weld might be a little sketchy.  So I wanted to make clear that that product is used by some manufacturers as their standard for repairs.  Of course, that only applies, as the video says, to nicks 1/8" deep or less. 

 

[CT4ME]

I've used that stuff that hardens when hit with a UV light.  Bondic, RapidFix, etc.  Definitely a hillbilly, half-assed repair idea... that has worked well.

[John Vance]

I haven't yet found Neuform's guidance on repairs. I have the operator's manual, which mentions repairs but provides no details.  Is there a maintenance manual?  

[Anticept]

It's not going to give details because there is nothing to detail. It's basically a touch up. It says you can order the resin, and no damage to the composite structure is allowed. Just try to keep the blade profile.