Mt Propeller Paint Delamination

[Bob]

Yesterday I had an IFR flight thru mist and very light rain for a couple minutes.  After the flight I observed the blade paint was delaminating.  It looks like the poor adhesion is only over the stainless insert.  The prop is less than a year old and 45 hours since new.  Any similar experiences from Mt Prop owners?

My flightaware gives you an idea of how light the precipitation was.  http://flightaware.com/live/flight/N231PZ

[KSMooniac]

File a warranty claim ASAP.  I had a similar problem and got mine repainted at my local MT shop under warranty and it happened again the first time in IMC.  Then they replaced the blades with their standard paint vs. the custom I originally ordered.  I'm guessing you have a custom color as well.  My replacement blades used black.

The problem is nothing sticks to stainless, generally speaking,  The only design detail on their prop that is bad IMO is the way they handle the paint and stainless edge.  The edge is bonded on, and then body-worked so that the aft edge is faired in to the contour and then the paint is brought over the stainless up to the leading edge.  This leaves an exposed paint edge to the slipstream which is the worst idea ever.  I wish they would put the stainless on *over* the paint and then it would last forever, but leave more stainless showing and I think they want more paint visible for aesthetic reasons.  I requested my replacement blades put the stainless over the paint but they wouldn't do it.  I then requested they make the paint edge sit as far aft on the blade as possible and they did do that, and it has stayed put pretty well.

So, file a warranty claim and ask that the stainless go over the paint instead of the other way around.  Maybe after enough requests and warranty claims they'll fix it.

I still like the prop, though, after getting this worked out. 

[Bob]

I did file a claim this morning and got a quick response to process a warranty repair to repaint the blades. 

KS-I appreciate the information on your experience!  Any pics of your prop when it was done?  When I ordered my prop, I was told to pick the spinner color, blade color and tip color from black, red, white, blue, yellow and a few more.  I just picked their white blades with blue tips.  Don't think anything with the paint was custom, but different colors may have different adhesions.  When I talked to MT this morning, I asked about not painting the stainless and was told that it would just move the edge farther back and erode in a different spot.

If I am restricted to VMC just to not damage a 13K prop, that would be pretty messed up!

A guy in my hangar is just finishing an RV and I noticed that it has a Catto Prop on it.  Looks like the stainless is over the paint, or at least not painted on, like the pic below.  Is this how yours looks?

 

[KSMooniac]

Unfortunately I don't have any pics handy.  I ordered mine with custom maroon tips to match my paint scheme (white base).  They repainted in maroon and it shed on the first flight.  Then they made me pick a standard color and sent new blades with it, but the paint was stopped much further after...maybe 3/4" vs. 1/4" before (guessing).  That has helped tremendously.  Nothing sticks to stainless over time.

That pic of the Catto prop with stainless over the paint is ideal IMO, and that is what I wanted.  It doesn't look as nice (in MT's opinion) but it should be exceptionally durable.  Having a paint edge exposed to the airstream is stupid, yet MT does it.  

[Bob]

18 hours ago, KSMooniac said:

That pic of the Catto prop with stainless over the paint is ideal IMO, and that is what I wanted.  It doesn't look as nice (in MT's opinion) but it should be exceptionally durable.  Having a paint edge exposed to the airstream is stupid, yet MT does it.  

Unfortunately It sounds like MT floats material up to make a seam free line between the composite and stainless pieces. So the option to polish the paint off the entire stainless insert is not an option.  That would leave a high paint edge at the stainless insert. 

When I looked close at the Catto, It looked like they actually floated the blade resin down just before it came to the stainless edge. Not only did they remove any sharp paint edge at the stainless, but also formed a little valley floating up into the blade. This transition looks like it may reduce the paint erosion possibility.  Hard to explain but tried my best.

Any thought on leading edge tape or helicopter tape?

[aviatoreb]

Just now, Bob said:

Unfortunately It sounds like MT floats material up to make a seam free line between the composite and stainless pieces. So the option to polish the paint off the entire stainless insert is not an option.  That would leave a high paint edge at the stainless insert. 

When I looked close at the Catto, It looked like they actually floated the blade resin down just before it came to the stainless edge. Not only did they remove any sharp paint edge at the stainless, but also formed a little valley floating up into the blade. This transition looks like it may reduce the paint erosion possibility.  Hard to explain but tried my best.

Any thought on leading edge tape or helicopter tape?

Is it possible to change the leading edge treatment?  I got the nickel leading edge treatment which is a significantly deeper sheath covering the leading edge of the blades, specifically because it is designed to make the leading edges more durable to dings.  Can it be added after the fact?  Have you seen what it looks like?

If not, then I bet leading edge tape might do the trick.

[KSMooniac]

I can't imagine any tape product holding up on a propeller blade, and like I said earlier, nothing sticks to stainless.   

I don't think they can change the leading edge design on our blades as it is part of the type design, so it would need to go thru a release/analysis/approval cycle, possibly including the FAA or a DER.  Maybe someday they'll fix what I consider the only weakness in their design and offer us the chance to update during an overhaul.

[Andy95W]

http://www.mcfarlaneaviation.com/Details.aspx?ID=4841286&Article=476

[Bob]

34 minutes ago, KSMooniac said:

I can't imagine any tape product holding up on a propeller blade, and like I said earlier, nothing sticks to stainless.   

I don't think they can change the leading edge design on our blades as it is part of the type design, so it would need to go thru a release/analysis/approval cycle, possibly including the FAA or a DER.  Maybe someday they'll fix what I consider the only weakness in their design and offer us the chance to update during an overhaul.

This is what gave me the idea of leading edge tape.  Was thinking that if the tape extender past the stainless insert, it could work.  Just trying to explore all options to find the best for long term.  I have a FISDO on my home field, so would be EZ to talk to them.  Looks like it some do use it for Experimental. 

I wonder is it comes in a band aid print?

http://www.eaavideo.org/video.aspx?v=2616988676001

http://www.aircraftspruce.com/menus/cs/tape_leadingedge.html

[KSMooniac]

You would have to see if the tape extends past the stainless insert, but to me at a quick glance I don't think it does.  It would also have the possibility of damaging the composite face sheet of the blades if/when you try to remove the tape.  The pulling/peeling strength of composites is relatively low and you could cause some damage.  No problem putting it on a metal blade of course.  I'd also be wary of the "no performance loss" claim...remember that a propeller blade is an airfoil and now you're changing the shape of it.

[aviatoreb]

If you get either a hot prop or a tks STC, then one of the things that is done is they glue a thick rubber boot to the near-hub side of each blade.  And it is pretty big.  Not saying that would cure your problem, but just that this suggests that gluing stuff to your prop is perhaps not as surprising a thing as all that.

[KSMooniac]

True, but they glue the boots to the composite portion of the blade, and the stainless starts outboard of the boots.  They are present on the non-deice/hot models too like I have, although they're not very thick.  The stainless edges do not run the full length of the blade.

[wpbarnar]

I am a big fan of MT propellers but rain seems to be their Achilles heal.  The paint edge behind the erosion strip has to be perfect or it will erode just like the photos.

At the first sign of visible moisture, I pull the RPM way down between 2000 to 2100 RPM.  It seems to help some.

Bill

 

[Cody Stallings]

That's just paint chipping off, not delamination.

Painting stainless is like painting glass, it won't hang on very well.

I have seen several MT props that have that same issue, not just the custom painted propellers.

My opinion, the leading edge strip needs to go inboard all the way to the De-ice boot. An don't paint it.....its stainless.

[aviatoreb]

Why are they painting stainless steel?  I would think they would tape off the stainless steel and then paint right up to it. Would that help?

In any case would a leading edge tape help?  Yes it would not stick to the stainless steel but it would stick to the part of the blade past the stainless steel and the steel treatment is very shallow.

 

[Bob]

1 hour ago, Cody Stallings said:

That's just paint chipping off, not delamination.

I was thinking paint coming off due to poor adhesion and chose the word delamination so it would fit in the title block.  But technically, yes you're correct, a paint layer does not contribute to the strength of the part and not part of the lamination.

1 hour ago, wpbarnar said:

At the first sign of visible moisture, I pull the RPM way down between 2000 to 2100 RPM.  It seems to help some.

Yes, 2000 RPM does help a lot.  At 2700 RPM the tip is moving at 594 MPH.  Only 440 MPH at 2000 RPM.  Unfortunately while departing full power is the only option.

[KSMooniac]

The stainless goes aft 3/4-1".

Sent from my VS985 4G using Tapatalk

[Bob]

14 minutes ago, KSMooniac said:

The stainless goes aft 3/4-1"

Thanks!  This link, even though it is a line drawing, gives a bit of perspective.  http://www.mt-propeller.com/en/entw/blades.htm

The other interesting thing on the page is that MT states that the blade is "all weather operable".  Then they add additional effort to highlight the statement.

[carusoam]

Wondering out loud...

The surface characteristics of SS can be altered by washing/rinsing with an acid solution.  If paint is going to stick to the SS, I would bet there is a preparation for it that works best.  Finding a guy that paints/coats metals might be the way to find an answer.

Of course, finding a guy that can paint SS that alters the microscopic layer of the steel and can then log it properly...

Seek a paint chemist first, the paint manufacturer probably has a guy.

Best regards,

-a-

[kortopates]

I've used the McFarlane prop tape. It work very well. I'd have to measure it's width but it's near 2" wide and thus about 1" on each side. Their documentation from there website should tell you right off if it's approved for stainless- if not a quick call. However I bet it would work fine on a freshly painted prop - but the issue may be when you go to pull it off it may very well pull the paint up with it if the paint doesn't adhere well to the stainless. It can do that with aluminum painted props that weren't primed and painted properly. Given you'd likely need to replace the tape annually or similar you probably won't like seeing the paint come off.

And absolutely the tape must adhere well to entire span of its application as it would likely come off at the tip first. But an unpainted leading edge is probably okay as long as it had good adhesion right past the LE. But really calling McFarlane is the right answer.

Sent from my iPhone using Tapatalk

[wpbarnar]

There seems to be a misconception that the paint erodes off of the leading edge on a MT prop because of it's inability to adhere to SS.  This is not accurate in a large majority of the cases.  Most stock MT propellers are not painted on the SS or Nickel erosion edges.  The blades are painted after the metal leading edges are applied.  The chipping or erosion occurs because the paint is slightly proud behind the metal leading edge forming a ridge or edge for the high velocity air across the prop to catch.  Rain only exacerbates this.

If you look closely at the OP's photos, the paint is chipping off the composite material, not the metal leading edge. 

The exception to this is at the tips.  The metal leading edge extends further aft at the tips and sometimes the paint is applied to it in tip area.

Bill

[Bob]

1 hour ago, wpbarnar said:

If you look closely at the OP's photos, the paint is chipping off the composite material, not the metal leading edge. 

The exception to this is at the tips.  The metal leading edge extends further aft at the tips and sometimes the paint is applied to it in tip area.

Bill

I did not see any paint chipped off of the composite material.  I don't have the prop in front of me, so I'm going by pics like everyone else.  In the image below, it looks like the stainless runs to approximately the green line (just a guess). They then fill to float the composite into the stainless to remove seams and sand up to the blue line. Last they run the paint up to the red line that includes 1/4 inch of un-sanded (maybe scuffed) stainless.

That gives 3 levels of adhesion with the composite material having the strongest adhesion and the leading edge of the paint having the least amount of adhesion.

If you notice all the blades have paint chipping in different areas.  On this one the tip had better adhesion than other areas that were traveling at a slower speed.  Besides the poor system of laying paint over stainless, I think in my case here, there is an additional problem like poor surface preparation, dust, oil, moisture, etc.

[aviatoreb]

Like I said the MT nickel treatment is significantly deeper metal sheath covering the blade for this very reason.  But it costs a lot more and I see no reason it should or why they would not simply make that stainless steel sheath deeper because this is clearly a problem as they themselves know by having decided to develop the nickel cover.

[Bob]

1 hour ago, aviatoreb said:

Like I said the MT nickel treatment is significantly deeper metal sheath covering the blade for this very reason.  But it costs a lot more and I see no reason it should or why they would not simply make that stainless steel sheath deeper because this is clearly a problem as they themselves know by having decided to develop the nickel cover.

Erik- When I read your first post about the nickel, I appreciated the information, since I was not aware of the option.  

It may make sense to swap out overhauled blades rather than pull all the stainless off of mine. I'm waiting on more information from MT on this.  Any pics to share of your nickel blades?  Do you remember the up charge for the nickel?  At the time of purchase, for what benefit did you justify the upcharge for the option?

Looks like I do everything for the warranty claim and then figure out my final direction while at Oshkosh.

[wpbarnar]

Bob.   You are correct.   I incorrectly tried to compare my paint erosion to yours. After looking  more carefully at your photos the paint failures look different.  Mine appeared to be chips that turn into narrow streaks versus the broader chips on your blades.   I have a different blade and the SS only appears to wrap back only about an 1/2" except at the tips.   If I lose just a little paint it is quickly back to the edge where the composite starts.