Crack on the leading edge

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astaib
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Crack on the leading edge

Post by astaib »

Hello,

My club has a old DV20 Katana from 1993 (that will go to 6000hr visit is some weeks) and they noticed a crack that is 1,2m long on the leading edge of the right wing.

The tap test is not revealing any difference in the sound.

Do you know if this can be something that has to be investigated deeper or if it’s only a surface crack.
192C7F37-0109-426A-849F-3AABA8021063.jpeg
38A3982F-BEB9-427A-81A4-A4BB4E9ECD0D.jpeg
E085592D-1A97-4709-BA05-29C89F4B244B.jpeg
E87645A1-ABF2-48A6-AF2B-4DA458D516AF.jpeg
Thank you.

Arnaud.
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Rich
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Re: Crack on the leading edge

Post by Rich »

It kind of looks like some sort of a "wrinkle" in the upper shell layup. It's not my money, of course, but it probably merits further investigation.

I assume these wings are like the other Diamonds - the actual seam is right at the most forward part of the leading edge, so it would not be a separation of a natural seam. Is there any possibility this plane has had a repair in this area in the past?
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Steve
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Re: Crack on the leading edge

Post by Steve »

Based on your photos, that looks like more than a superficial crack to me. I have had a very fine crack on the aft pilot's side fuselage wing root. It has been there without change for 20 years. My mech and I were able to inspect the other side of the skin via the flap recess, and the crack does not penetrate.
Superficial wing crack
Superficial wing crack
I sent photos to Diamond when I first discovered it, and they said that it was in the paint coat only, no repair needed. I would want to see the underside of your wing skin, irrespective of a negative "tap" test. You might be able to visualize that area via one of the access panels on the underside of the wing, using a borescope...
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vnehess
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Re: Crack on the leading edge

Post by vnehess »

These do look like paint coat cracks to me also.
My only qualification for this observation is owning several older sailplanes, some of which did exhibit paint cracking like this and were eventually refinished to remain airworthy. While the paint cracks are not structural, they can, if left unchecked, expose the underlying structure/layup to harmful UV damage.
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Re: Crack on the leading edge

Post by astaib »

Rich wrote: Thu Apr 21, 2022 9:32 pm It kind of looks like some sort of a "wrinkle" in the upper shell layup. It's not my money, of course, but it probably merits further investigation.

I assume these wings are like the other Diamonds - the actual seam is right at the most forward part of the leading edge, so it would not be a separation of a natural seam. Is there any possibility this plane has had a repair in this area in the past?
I don't know if this plane was repaired in the past, I will look in the documents, but I don't think so.
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briankelly327
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Re: Crack on the leading edge

Post by briankelly327 »

I had an epoxy surfboard that delaminated in the sun and developed a few cracks over time. One day I was surprised as the entire bottom peeled off in one sheet as I was surfing.

The diamonds composite wing skin, material and design is no doubt stronger than a surfboard, but I’d want engineering to bless or repair that crack. I shudder to think of the top wing skin peeling off in 130mph wind forces.
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Rich
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Re: Crack on the leading edge

Post by Rich »

In any case, I wouldn't take any of our opinions, based on a couple of pictures, that it's superficial as a definitive answer. Check with Diamond and get an expert hands-on inspection to figure out how to proceed.
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soarer20
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Re: Crack on the leading edge

Post by soarer20 »

It appears to be superficial paint cracking. Most likely your best option is to find a glider repair center who is an expert with composites to determine how deep the crack is. Almost all glider repair shops deal with issues like this all the time and will probably know way more than a regular mechanic or even diamond for that matter.
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Re: Crack on the leading edge

Post by Spinner »

I would echo to check with Diamond. We have had leading edge cracks similar to what your pictures show. I was told by Diamond that they are caused by the shrinking of filler that they use to mold the leading edges. Temperature changes shrink the filler to give cracks like that. It usually (and I say usually so don't take my word for it) requires a removal by sanding of the paint and sometimes an addition of filler but normally a touchup of paint will cure this issue.
A quick discussion with Neil will probably steer you to the right solution. It is not a major issue but does not look pretty.
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