fiberglass cowling cracks

dakota-cowboy

dakota-cowboy

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dakota-cowboy
18 months ago I purchased a Piper Dakota that had fiberglass surface cracks in the top cowling and fine fan like cracks in the bottom section.
I had the fiberglass repaired and both sections repainted. The cracks have returned.:( This is my first Piper to have a fiberglass cowling. Is this a common occurring problem with Piper fiberglass?
Suggestions on repairing this so that it doesn't just keep reoccurring?
 

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Properly repaired, the fiberglass shouldn't crack. Did the repair shop sand off the paint, then add layers of fiberglass cloth over the cracked areas, or did they just smear the cowling with filler?

Additional plies of glass would eliminate cracks for years and years. If they just filled the cracks with bondo or some other filler, they stole your money.
 
The repair was just short of $1900. I've been feeling like there was not fair exchange.
 
How long ago was it? Have you tried talking to the repair shop about this?
 
dakota-cowboy said:
18 months ago I purchased a Piper Dakota that had fiberglass surface cracks in the top cowling and fine fan like cracks in the bottom section.
I had the fiberglass repaired and both sections repainted. The cracks have returned.:( This is my first Piper to have a fiberglass cowling. Is this a common occurring problem with Piper fiberglass?
Suggestions on repairing this so that it doesn't just keep reoccurring?
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It looks like the cracks are in the paint, not the fiberglass.

You have one, some, or all conditions present: the fiberglass is too thin, you have a loose latching mechanism, the paint is aged/improperly maintained, the plane is/was based at poorly maintained asphalt.

Was cowlings repainted before the most recent work? It's possible the wrong paint was used.
 
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We have the same issue in our Dakota ... hey, wait a minute - are you flying out of KBJC?
 
Could you tell me more about your Dakota paint/fiberglass issues? These reoccurring cracks are on top not by the latches. The fine spider web cracks are near the exhaust pipes.
 
Arvada Greg, I was directing my last post toward your remark that you have a Dakota with a similar issue.
 
dakota-cowboy said:
Could you tell me more about your Dakota paint/fiberglass issues? These reoccurring cracks are on top not by the latches. The fine spider web cracks are near the exhaust pipes.
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Cracks due to flexion don't need to be near the latches. Flexural cracks result from near linear cracks which may fan out when the structure is secured in two locations in different planes. The flexion results along the plane of each secure point. Spider cracks are signs of stress risers. These are highly localized. More info is required to know the source of the stress. However, in the OP it seems there is a concern of abnormal stress. One abnormality may be an insecure latch and that would result in increased movement/vibration of the fiberglass cowling. Radial cracks are due to impact.

While you will never eliminate the vibration and flexion which causes cracking, you can minimize it's effect through secure and effective latching/mechanical fastening/stiffening and by choice of coating. The paint needs to be sufficiently elastic to overcome the stress.
 
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There be cracks and there be cracks.

Are these cracks in the glass structure due to stress? Or is this crazing of the gel coat? Different problems with different fixes.

If it's the gel coat crazing, then the fix is to grind all the gel coat off - down to bare laminate, fair it up, and paint. If the gel coat isn't removed, cracks will come back.

If it's cracks in the laminate, then either reinforce with more glass or throw it away.

Neither is a "Piper" thing - check out the glass at the local boat yard...
 
Had the same thing happen when I repaired the fiberglass on our Warrior's lower cowl. The cracks were back in a year.

I've learned to live with them on our Pathfinder's cowl.
 
The cracks are due to the paint not being able to expand and contract as well as the fiberglass structure.

Sand the entire cowl, and refinish with Air-Tech system. it will last about 10 years before the cracks show up again.
 
dakota-cowboy said:
18 months ago I purchased a Piper Dakota that had fiberglass surface cracks in the top cowling and fine fan like cracks in the bottom section.
I had the fiberglass repaired and both sections repainted. The cracks have returned.:( This is my first Piper to have a fiberglass cowling. Is this a common occurring problem with Piper fiberglass?
Suggestions on repairing this so that it doesn't just keep reoccurring?
Click to expand...
Any chance of posting pictures of the cracks?
Capt. Geoffrey Thorpe said:
There be cracks and there be cracks.

Are these cracks in the glass structure due to stress? Or is this crazing of the gel coat? Different problems with different fixes.

If it's the gel coat crazing, then the fix is to grind all the gel coat off - down to bare laminate, fair it up, and paint. If the gel coat isn't removed, cracks will come back.

If it's cracks in the laminate, then either reinforce with more glass or throw it away.

Neither is a "Piper" thing - check out the glass at the local boat yard...
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This is the reason why I ask.
 
Our club's Dakota will be back in the hangar on Wednesday. If my and it's schedule cooperate, I'll post pictures. Our cracks are on the upper center of the cowl, near the oil dipstick door. We had it re-finished last year and the cracks reappeared within weeks.

I'll see if I can get the details on what exactly was done during the "re-finish"

I only asked where you're based because I thought "wouldn't that be funny if it was another club member who just found POA and we were talking about the same plane?"
 
The Top cowling cracks start at the oil dipstick door and radiate forward toward the blade.
I will try and post a couple of photos. I will first have to learn how to attach photos. Thank you to everyone for imput today on this problem. I just signed up for Pilots of America today in hope that someone would have suggestions as to what the underlying problem could be. I have been pleasantly surprised with the number of pilots commenting on this aggrevating fiberglass/paint problem. Thank you for your imput.
 
"near the dipstick door" translates to, "'oil caning' of the fiberglass". It needn't be a huge movement but done many times. Funny thing about oil caning, you have an otherwise rigid structure suddenly 'popping' (deformed) out of plane. Repeat that a minimum twice per flight.

Of course, a crack begats a crack. I guess you could stop drill just the paint.:rofl:
 
Jay Honeck said:
Had the same thing happen when I repaired the fiberglass on our Warrior's lower cowl. The cracks were back in a year.

I've learned to live with them on our Pathfinder's cowl.
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Cracks aren't necessarily a bad thing but when they are in a protective coating they sure can be. But I wonder, of all the owners who decry surface cracks and crazing, just how many say, regularly wipe the road dust from the wheels on their vehicles?
 
I don't believe the Piper cowlings have a gelcoat finish, Paint gets brittle as it ages, and will not flex with the substructure. Airtech top coats are formulated with a plasticizer to allow flexing with fabric covers, it will age, but a lot slower than regular paint finishes.
 
Richard said:
Cracks aren't necessarily a bad thing but when they are in a protective coating they sure can be. But I wonder, of all the owners who decry surface cracks and crazing, just how many say, regularly wipe the road dust from the wheels on their vehicles?
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The fiberglass cowl on Cherokees is subject to all sorts of vibration and flexing. Since we're all flying antiques now, they are all cracking -- and fixing them is much harder than your local auto body shop appreciates.

I had mine professionally done, by a body shop that was owned by a pilot -- and the cracks still returned within a year. It's just not an easy fix, and is terribly labor intensive.

I wish someone would come out with a cowl that was either made out of a different material, or perhaps stiffened so that it doesn't flex and break the paint. Of course, given the FAA, that cowl would cost $10K, and no one would/could buy it. So, we put up with cracks.
 
Jay Honeck said:
The fiberglass cowl on Cherokees is subject to all sorts of vibration and flexing. Since we're all flying antiques now, they are all cracking -- and fixing them is much harder than your local auto body shop appreciates.

I had mine professionally done, by a body shop that was owned by a pilot -- and the cracks still returned within a year. It's just not an easy fix, and is terribly labor intensive.

I wish someone would come out with a cowl that was either made out of a different material, or perhaps stiffened so that it doesn't flex and break the paint. Of course, given the FAA, that cowl would cost $10K, and no one would/could buy it. So, we put up with cracks.
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As a non-structural item, I believe the owner is allowed to make cosmetic repairs. Why not overlay a layer or two of fiberglass on the inside and the outside of the cowl, fill it, then sand/blend the repair and repaint? I had cracks on my old Tomahawk cowling, made repairs as described, and the cracks never returned (At least until the aircraft was involved in a fatal crash several years later.).
 
I have been wondering if the cowl baffle seal material could be a factor in the cracks? I dont have this product but there is a video on the McFarlane Aviation site that is impressive for showing how the "cowl saver" material reduces cowling vibrations. http://mcfarlaneaviation.com/Details.aspx?ID=7503613&Article=187
I asked the IA last month during the annual about the possiblity the cracks being induced by the battling but he completely dismissed the idea. Thoughts?
 
dakota-cowboy said:
I have been wondering if the cowl baffle seal material could be a factor in the cracks? I dont have this product but there is a video on the McFarlane Aviation site that is impressive for showing how the "cowl saver" material reduces cowling vibrations. http://mcfarlaneaviation.com/Details.aspx?ID=7503613&Article=187
I asked the IA last month during the annual about the possiblity the cracks being induced by the battling but he completely dismissed the idea. Thoughts?
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Hmm, I'm skeptical. If you need new cowl seals, then I guess there's probably no harm in trying these.
I doubt that they'll solve your cracking though. The cowl lives a very hard life, and I think it is probably asking a lot for a finish to stand up to the heat and flexing. I don't think you can blame any one thing like cowl seals, oil door, or vents. Even just removing and reinstalling a Piper cowl flexes the heck out of it. Its hard to expect the paint to last forever given all that movement.
 
Some under catalysed epoxy paint will solve your problem. If you did it right we won't be hearing about ripples in the paint or how the paint now flows towards the windscreen.:goofy:
 
With the help of a couple of POA mentors, I have added 3 photos to the first post. The first is at the oil door, the second is just above the exhaust pipes and the third is down from the oil door toward the blade.
 
Are those pics after the most recent repair work?

Boy, all I'm gonna say is you have paint issues. That includes prep or lack thereof.
 
COFlyBoy said:
Hmm, I'm skeptical. If you need new cowl seals, then I guess there's probably no harm in trying these.
I doubt that they'll solve your cracking though. The cowl lives a very hard life, and I think it is probably asking a lot for a finish to stand up to the heat and flexing. I don't think you can blame any one thing like cowl seals, oil door, or vents. Even just removing and reinstalling a Piper cowl flexes the heck out of it. Its hard to expect the paint to last forever given all that movement.
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As with all designs, it's a compromise. I am, quite frankly, amazed that the thing is held on by just four latches. If you think about the titanic force of 160 mph air being slammed through the engine, you start to wonder why it hasn't blown off in flight.

When we remove the cowl, we ALWAYS use two people to minimize the flexing. We started this practice after I watched my mechanic (not being one to care about such things as cosmetics) whip the thing off by the pilot's side edge. The damned thing flexed a full 20 degrees when he did that!

I suspect every mechanic in America does something similar -- at least when they think no one is watching. You might think back to when you noticed the new cracks. I'll bet they appeared (or worsened) after the plane was in for maintenance.
 
dakota-cowboy said:
18 months ago I purchased a Piper Dakota that had fiberglass surface cracks in the top cowling and fine fan like cracks in the bottom section.
I had the fiberglass repaired and both sections repainted. The cracks have returned.:( This is my first Piper to have a fiberglass cowling. Is this a common occurring problem with Piper fiberglass?
Suggestions on repairing this so that it doesn't just keep reoccurring?
Click to expand...

Based on my boat experience, I would think you need another layer of glass for the areas in the first and third pictures. The middle almost looks like a gel coat issue, but someone said that Piper doesn't use gel coat (good for them, if true). Is this area right where you have an exhaust leak?

In any case you want to get back to bare laminate before adding another layer.
 
Posted by Jay Honeck : "You might think back to when you noticed the new cracks. I'll bet they appeared (or worsened) after the plane was in for maintenance."

The cracks started to reappear within 6 months of the repair work which done in Feb 2010. But when the plane came out of annual in June 2011, the cracks were more noticeable after the annual. So the handling by the annual crew may have added to the stress of the cowling. The fellow who did the cowling repair has years experience doing airplane paint work. When I talked to him recently about how the cracks and crazing had returned he did not have much to say other than the airplane is 30+ years old and things happen.
 
dakota-cowboy said:
Posted by Jay Honeck : "You might think back to when you noticed the new cracks. I'll bet they appeared (or worsened) after the plane was in for maintenance."

The cracks started to reappear within 6 months of the repair work which done in Feb 2010. But when the plane came out of annual in June 2011, the cracks were more noticeable after the annual. So the handling by the annual crew may have added to the stress of the cowling. The fellow who did the cowling repair has years experience doing airplane paint work. When I talked to him recently about how the cracks and crazing had returned he did not have much to say other than the airplane is 30+ years old and things happen.
Click to expand...

The problem is ,, most A&Ps don't know the difference between a paint with a plastizer and one with out.

UV light makes paint brittle, and without a plastizer it will crack when flexed. Paints and top coasts that are formulated for fabric covers will flex for a lot longer than regular automotive paints.

ever see "ring Worm" on a fabric covered aircraft? that is what you have on your cowling, when you push on a fabric cover and the paint cracks in a circle that is ring worm. your cowl has been flexed in 1 direction thus the cracks are straight not curved, its the same thing, the paint is adhered but won't flex.

here is where to order the paint, you will need a qt of top coat color, catalyst for it, a pt of reducer and your equipment will clean up with acetone.

http://www.airtechcoatings.com/
 
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