Paint Failure / De-bonding

[generalaviationguru]

When we purchased our aircraft, we noted that there were minor pieces of missing paint around the meeting area of the fuselage and cowl.  Now we are noticing accelerated flaking of the paint, and more severely, severe cracks and complete separation of the paint layers from the underlying aluminum.  

What would cause this to happen and what should we do while we build the paint job fund?  The cash account took a big hit from an annual that was nearly 2x the expected cost   Is it better to leave it alone, and let the paint continue to fail on its own?  Or physically remove it until we get to strong paint, prep the bare aluminum and rattle can (this is not a control surface obviously).

 

This paint job is not original to the plane.  Though we have original logs, I cannot find when and where it was done.  In 3000 hours I have seen many planes (including airliners) with ABYSMAL paint, but I’ve never seen it start to come off in sheets.  
 

The first picture vs. the picture with no cowl are a few weeks and about 10 hours flight time apart.  The problem is getting worse…

[Fly Boomer]

22 minutes ago, generalaviationguru said:

What would cause this to happen and what should we do while we build the paint job fund?

Short answer is bad prep before the last paint job.  Usually a good idea to keep the aluminum protected (with appropriate prep work).  Rattle can is okay, but bare aluminum is not usually a good idea.  It's unfortunate, but you'll just have to keep fixing it as fast as it peels off until it can be repainted.

[EricJ]

The first pic looks like there was 1/16" or so (maybe more) of bondo/filler on there that is starting to come off.    That's not going to get better, and it'll come off in a chunk or more at some point.    That'll have to be addressed eventually.    If you have a local aviation paint shop you might try calling them and see if they have a best practice for dealing with such things.    You might need to do a little sheet metal work around there, maybe just involving some simple dent removal or reshaping techniques before repainting that area.

[PT20J]

You can see shims placed on the edge where the cowling attaches presumably to make it match up with the thicker bondo’d skin. This in not a good repair and it’s concerning if not described in the logbooks because the extent of the repair (and thus the damage) is not known.

[EricJ]

2 minutes ago, PT20J said:

You can see shims placed on the edge where the cowling attaches presumably to make it match up with the thicker bondo’d skin. This in not a good repair and it’s concerning if not described in the logbooks because the extent of the repair (and thus the damage) is not known.

Yes, I think the best thing to do would be to remove all the loose filler and the paint around it and see if there's hidden damage or just a bend that got filled in.    Inspection of the firewall around the same area may help indicate whether this had to do with significant damage or not.   If it can be pulled out back to shape that might be a good solution.   Since Mooneys have tube frames the sheet metal around the fuselage is generally not structural, so there's more liberty on how to perform such repairs.    If the logbook isn't revealing, a consultation with a good airframe shop or the factory could be useful if it's more than a simple repair.    Not the end of the world in any case if the tubes are all straight.

[Pinecone]

I would be asking the seller if they knew when it was painted and where.

Maybe talk to your paint shop and they can just do the cowl to get it to the full repaint.

[generalaviationguru]

1 minute ago, Pinecone said:

I would be asking the seller if they knew when it was painted and where.

Maybe talk to your paint shop and they can just do the cowl to get it to the full repaint.

The previous couple of owners only had it for a few years.  Google picture history shows that this paint job has been on prior to them.  I just can’t find the logbook entry for it (if it’s there)

I am currently looking around for a shop to get on the list for a full repaint.  Would be open to looking for a local place for a minor repair like your describing - a long trip for a touch up seems excessive.   Any suggestions in the ATL region?

[Pinecone]

Remember, this is a Mooney.  So "long trip" is not the same as if you were flying a 172.

@jetdriven and my airplanes were painted by Hawk in FL.  Both are very well done and holding up great.

[ArtVandelay]

That looks like the original paint scheme, I agree, touch up with a rattle can until you can get a full paint job.

[generalaviationguru]

16 minutes ago, ArtVandelay said:

That looks like the original paint scheme, I agree, touch up with a rattle can until you can get a full paint job.

From 1967?  I haven’t seen any original F’s with this scheme….

[LANCECASPER]

18 minutes ago, ArtVandelay said:

That looks like the original paint scheme, I agree, touch up with a rattle can until you can get a full paint job.

Definitely not original paint with bondo underneath and shims under the cowling.

[generalaviationguru]

44 minutes ago, Pinecone said:

Remember, this is a Mooney.  So "long trip" is not the same as if you were flying a 172.

@jetdriven and my airplanes were painted by Hawk in FL.  Both are very well done and holding up great.

I agree.   I’m just thinking ROI.  Each incremental mile of travel for a temporary fix adds sunk cost.  It’s more so the expense of travel taking away from the long term goal of a full paint job.  
 

Hawk is on the short list for our full job.

[kortopates]

I agree.   I’m just thinking ROI.  Each incremental mile of travel for a temporary fix adds sunk cost.  It’s more so the expense of travel taking away from the long term goal of a full paint.

True, but if you’re worried or concerned about ROI you’re going to be a very short term owner. The reality is that the acquisition cost of the aircraft is very small compared to the yearly operational expenses over the years. General maintenance doesn’t add to the aircraft value but lack of it will certainly detract from it. A nice quality paint job will add resale value but even its value will depreciate with age.
As a long term owner, my personal enjoyment trumps any other priorities.

That said, sorry to read about the paint delaminating but my chief concern would be unknown damage. But getting a full strip and new paint will give you the best visibility into the extent of any damage. Hopefully only very minor cosmetic damage.


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[generalaviationguru]

2 minutes ago, kortopates said:

 

True, but if you’re worried or concerned about ROI you’re going to be a very short term owner. The reality is that the acquisition cost of the aircraft is very small compared to the yearly operational expenses over the years. General maintenance doesn’t add to the aircraft value but lack of it will certainly detract from it. A nice quality paint job will add resale value but even its value will depreciate with age.
As a long term owner, my personal enjoyment trumps any other priorities.


Sent from my iPhone using Tapatalk

 

I agree whole-heartedly.  That’s why we want to use our resources wisely and target the full paint job while protecting the metal in the meantime.  

[LANCECASPER]

2 hours ago, generalaviationguru said:

I agree whole-heartedly.  That’s why we want to use our resources wisely and target the full paint job while protecting the metal in the meantime.  

If you're just looking to protect the metal in the meantime a good primer should do that.

[1980Mooney]

On 9/19/2023 at 4:32 PM, generalaviationguru said:

When we purchased our aircraft, we noted that there were minor pieces of missing paint around the meeting area of the fuselage and cowl.  Now we are noticing accelerated flaking of the paint, and more severely, severe cracks and complete separation of the paint layers from the underlying aluminum.  

What would cause this to happen and what should we do while we build the paint job fund?  The cash account took a big hit from an annual that was nearly 2x the expected cost   Is it better to leave it alone, and let the paint continue to fail on its own?  Or physically remove it until we get to strong paint, prep the bare aluminum and rattle can (this is not a control surface obviously).

 

This paint job is not original to the plane.  Though we have original logs, I cannot find when and where it was done.  In 3000 hours I have seen many planes (including airliners) with ABYSMAL paint, but I’ve never seen it start to come off in sheets.  
 

The first picture vs. the picture with no cowl are a few weeks and about 10 hours flight time apart.  The problem is getting worse…

From your post and pics your plane appears to be a 1967 M20F Executive 21 that was for sale not too long ago.

When I take what I think your N number is and search on the Aircraft.com site I find three (3) advertisements.  The oldest from about 1999-2000 claims that it was painted in 1990 in "a Mooney ‘252’ Scheme".  Perhaps a second narrowed look at the logs may turn it up in the 1990 section.

As @LANCECASPER and @PT20J noted, there is bondo and there are shims where the cowling mates.  As your pic shows, your plane has been modified.  I can see the "201" windshield. The ads say that the F cowling was replaced with a full "201" cowling.  The original Cowling mounting flanges on the F did not have the offset or step down for the J fiberglass cowling.  Somehow these cowling flanges on your plane were added/modified.  These Mooneys are handmade planes to begin with.  When you add in the numerous bespoke modifications I am not surprised that you are finding bondo where things didn't quite match up.  I would look in the logs for the date of the "201" cowling modification.  There may be additional painting that was done immediately after.  The second advertisement on Aircraft.com for what I think your N number is, circa 2005-2006, says that the plane was painted in 1999 (again? or typo?).

Also I see from AviationDB.com that there was a gear-up landing in 1984 that involved a flapping oil fill door and loss of a spinner in flight.  When you strip the plane you may find there is some bondo covering/smoothing out vestiges of that fubar.

 @EricJ suggested "the best thing to do would be to remove all the loose filler and the paint around it and see if there's hidden damage or just a bend that got filled in.",   Once you start pulling on that bondo you don't know where it will end.  You will probably wind up peeling off a lot more bondo/paint than you expected. 

The problem is that water will get in those open cracks and cervices. In addition accelerating oxidation of what might be exposed aluminum underneath, when the water freezes it will keep lifting more bondo and opening the cracks wider.

It's a dilemma.  As Eric suggested "If you have a local aviation paint shop you might try calling them and see if they have a best practice for dealing with such things."   I personally would be cautions about physically opening the cracks further and peeling the bondo off.  I would try to patch/fill the cracks and spot paint until the time of the full strip/repaint.  But that is just my opinion.  If you don't mind (large?) areas of primer visible around your cowl, then start peeling with a thin plastic putty knife.

 

Edited September 21, 2023 by 1980Mooney

[generalaviationguru]

10 minutes ago, 1980Mooney said:

From your post and pics your plane appears to be a 1967 M20F Executive 21 that was for sale not too long ago.

When I take what I think your N number is and search on the Aircraft.com site I find three (3) advertisements.  The oldest from about 1999-2000 claims that it was painted in 1990 in "a Mooney ‘252’ Scheme".  Perhaps a second narrowed look at the logs may turn it up in the 1990 section.

As @LANCECASPER and @PT20J noted, there is bondo and there are shims where the cowling mates.  As your pic shows, your plane has been modified.  I can see the "201" windshield. The ads say that the F cowling was replaced with a full "201" cowling.  The original Cowling mounting flanges on the F did not have the offset or step down for the J fiberglass cowling.  Somehow these cowling flanges on your plane were added/modified.  These Mooneys are handmade planes to begin with.  When you add in the numerous bespoke modifications I am not surprised that you are finding bondo where things didn't quite match up.  I would look in the logs for the date of the "201" cowling modification.  There may be additional painting that was done immediately after.  The second advertisement on Aircraft.com for what I think your N number is, circa 2005-2006, says that the plane was painted in 1999 (again? or typo?).

Also I see from AviationDB.com that there was a gear-up landing in 1984 that involved a flapping oil fill door and loss of a spinner in flight.  When you strip the plane you may find there is some bondo covering/smoothing out vestiges of that fubar.

 @EricJ suggested "the best thing to do would be to remove all the loose filler and the paint around it and see if there's hidden damage or just a bend that got filled in.",   Once you start pulling on that bondo you don't know where it will end.  You will probably wind up peeling off a lot more bondo/paint than you expected. 

The problem is that water will get in those open cracks and cervices. In addition accelerating oxidation of what might be exposed aluminum underneath, when the water freezes it will keep lifting more bondo and opening the cracks wider.

It's a dilemma.  As Eric suggested "If you have a local aviation paint shop you might try calling them and see if they have a best practice for dealing with such things."   I personally would be cautions about physically opening the cracks further and peeling the bondo off.  I would try to patch/fill the cracks and spot paint until the time of the full strip/repaint.  But that is just my opinion.  If you don't mind (large?) areas of primer visible around your cowl, then start peeling with a thin plastic putty knife.

 

Thank you for your detailed response!  I spent lots of time in that range, as the engine overhaul was done in 1999.  The primary upgrade to “J” was done in the late 1970s, per the STC paperwork included.  I see the same regarding 1984.  I’ll dive back into the logs once my day flying job allows me back home.  
 

Given the bondo (I didn’t initially recognize it, as I’ve never worked with the material), I agree with you on the risk of working with it.  Further agree on the risk of trapped water - I won’t belabor my previous gripes about being on the ramp despite being promised a hangar - big dilemma.  
 

We’ll have to think this one through until we can get this thing repainted.  
 

Frustrating - the gentlemen who parks next to us has a 1967 E with ORIGINAL paint and it looks fabulous.  Airframe is lower TT though.  But similar number of hours on the paint.  I wish this paint wasn’t showing so much failure.  

[tony]

On 9/20/2023 at 8:17 AM, Pinecone said:

Remember, this is a Mooney.  So "long trip" is not the same as if you were flying a 172.

@jetdriven and my airplanes were painted by Hawk in FL.  Both are very well done and holding up great.

I had mine down at Hawk as well.  They did a fantastic job.

[M20F-1968]

I would be careful with this.  Bare aluminum is not a good idea.  Corrosion sets in rather rapidly on bare aluminum and progresses from there.  Cracks in paint and bondo, allow water to get in and accelerates the corrosion process.  You will need to remove the paint and Bondo down to bare metal and good paint, clean the underlying metal well and use allodine and paint or an etching primer just to protect it.  This should be done particularly in light of the fact that you are flying it and it will be exposed to weather and the element.  Don't concern yourself about what it looks like. You need to protect the metal. 

It may turn out that there is sufficient damage to warrant changing the involved skins.  Don't be surprised that if the work is sufficiently substandard given the history, changing the skins would be a good choice.

John Breda

[glbtrottr]

“Bad prep” is too general and subjective and doesn’t cover all sins committed included crappy product. Some people use “essentials” or “delfleet” and while a fine and pretty paint, durability is questionable. But hey! It look good when it left the shop…riiiiight? What about many of those lacquered jobs or those that were thinned too much or people who didn’t use the right amount of hardener or they used too much accelerator or…

Piper did a crappy job in some lower end models we paint regularly and an outstanding job in others. I recently painted a Twin Comanche with original paint where all of it had all but fallen off …and though close to the ocean, it has virtually no corrosion because of how well zinc- chromated it was. Mooney didn’t do a fantastic job with our birds - I’d say middle of the road. I had a job done on my am model during the Gretchen years that didn’t even last 5 years before the Jetglo clear coat rotted….

We see airplanes that were alodined , we see airplanes that were chromated, we see airplanes with neither….

Often times factories and shops will take the bare aluminum, sometimes etch it / brighten it and sometimes not, immediately followed by a thin coat of “sealer” (a wet on wet primer)…sometimes the sealer is low quality or allowed to dry for too long and no real cross linking occurs with the paint- and not long after results in some awesome delamination, “crows feet” from sitting out in the sun for too long and destroyed all the way down to the bottom but hey - people think it will be fine if you just spray a little primer and paint on it.

Full strip and paint jobs uncover many old sins and give us a chance to right many wrongs.

We use paint from Axalta (imron), jetglo, skyscapes, awl grip, akzo and even Hentzen.

By far the most durable system we see in GA is Imron. We standardize on Imron. If you want paint to stick and be guaranteed for 10 years, you gotta follow the TDS….

We are in Southern California….