FlyingMonkey Posted January 30, 2021 Report Share Posted January 30, 2021 So, I noticed this crack a while back. I *think* it's just a cosmetic crack in the paint, but it does run along the aft spar of my right wing and is quite long (maybe 18-24"). The composite area is slightly raised along the spar where the structure is, so I think the paint is more stressed there. There is not a good way to inspect the composite in that area, so I'm not sure what to do about this. I noticed it a few weeks ago and have flown without issues or it getting worse, but I guess it's time for more opinions... Quote Link to comment Share on other sites More sharing options...
Roger Lee Posted January 30, 2021 Report Share Posted January 30, 2021 No picture Quote Link to comment Share on other sites More sharing options...
GrassStripFlyBoy Posted January 30, 2021 Report Share Posted January 30, 2021 The pic was showing earlier. My thought is sand through the paint to confirm it's only paint, if only paint then you could dust it with some primer as a short term option until weather is more paint friendly climate. If it's more than paint you want to understand that ASAP. I'd be surprised if more than paint. Quote Link to comment Share on other sites More sharing options...
AGLyme Posted January 30, 2021 Report Share Posted January 30, 2021 Andy, I cannot see the pic either... don’t know if the crack is easy to get to... but you may want to contact FD USA... FD should be very interested to help you with this situation. there is an NDT penetrant for carbon fiber. I have never seen it used, but my old company performed NDT/ penetrant tests every day on all types of metals... it is a reliable way to find and diagnose material cracks. I suppose you have to grind the paint away from the area first ? Quote Link to comment Share on other sites More sharing options...
FlyingMonkey Posted January 31, 2021 Author Report Share Posted January 31, 2021 Try this pic: I sent this to FD for an opinion. Quote Link to comment Share on other sites More sharing options...
Warmi Posted January 31, 2021 Report Share Posted January 31, 2021 Would composite fail so neatly along a line unless it was at some kind of seam ( glued) ? I have a similar paint hairline crack in my Sting and had it inspected just to be sure but yours seems to be a bit more bubbly . Quote Link to comment Share on other sites More sharing options...
FlyingMonkey Posted January 31, 2021 Author Report Share Posted January 31, 2021 The "bubbling" you mentioned is the edges of the paint lifting/flaking on the crack line. Next time I'm at the hangar I'll try to get a better detail pic. Quote Link to comment Share on other sites More sharing options...
Animosity2k Posted May 11, 2021 Report Share Posted May 11, 2021 To me it looks similar to the paint cracks on my cowling from flexing. Quote Link to comment Share on other sites More sharing options...
Runtoeat Posted May 16, 2021 Report Share Posted May 16, 2021 Hi Andy. Hope your crack turns out to be cosmetic. It definitely appears to be running along the rear edge of the spar and the spar itself appears to be more pronounced and visible than I recall my spar being. Each CT is different from another though. One thing comes to mind is the CTLS's "living hinge" for the stabilator where the carbon skin is used for the trim tab hinge with no metal hinges. The area that flexes will show cracks in the paint. This looks bad but is only cosmetic and FD puts bolus tape over the flex area to hide the cracking. Not suggesting you cover your crack with tape but cracks which show up on our CT's normally turn out to be inconsequential like Animosity's cowl cracking. FWIW, Warmi's picture of his crack on the Sting aircraft wing looks very similar to yours. Quote Link to comment Share on other sites More sharing options...
FlyingMonkey Posted May 16, 2021 Author Report Share Posted May 16, 2021 2 hours ago, Runtoeat said: Hi Andy. Hope your crack turns out to be cosmetic. It definitely appears to be running along the rear edge of the spar and the spar itself appears to be more pronounced and visible than I recall my spar being. Each CT is different from another though. One thing comes to mind is the CTLS's "living hinge" for the stabilator where the carbon skin is used for the trim tab hinge with no metal hinges. The area that flexes will show cracks in the paint. This looks bad but is only cosmetic and FD puts bolus tape over the flex area to hide the cracking. Not suggesting you cover your crack with tape but cracks which show up on our CT's normally turn out to be inconsequential like Animosity's cowl cracking. FWIW, Warmi's picture of his crack on the Sting aircraft wing looks very similar to yours. Thanks Dick. I really don't think this is any big deal. The photos I posted make it look worse than it is because they are zoomed. In reality it's so tiny I can't even get an X-acto knife blade under it. It looks like the other small paint cracks I have all over the airplane, so I'm 95% sure it's non-structural. And honestly, I have been flying it for 9-12 months since I first noticed it and have seen no progression of it. I have a friend who is a composite expert and works on a lot of jets, and I'm trying to find some time to have him stop by the hangar and take a look. I'm willing to sand through a small section of the paint to the composite to inspect as FD suggested, but I'm hoping my guy will say that's not necessary. Quote Link to comment Share on other sites More sharing options...
Tom Baker Posted May 16, 2021 Report Share Posted May 16, 2021 2 hours ago, Runtoeat said: One thing comes to mind is the CTLS's "living hinge" for the stabilator where the carbon skin is used for the trim tab hinge with no metal hinges. The CTLS uses Kevlar in the stabilator hinge, not carbon fiber. I'm pretty sure that carbon fiber would break in that application. Quote Link to comment Share on other sites More sharing options...
Runtoeat Posted May 18, 2021 Report Share Posted May 18, 2021 Tom, thanks for the correction. Is the kevlar just applied in the hinge area or is the whole stabilator (top, bottom, both surfaces?) constructed with kevlar? Quote Link to comment Share on other sites More sharing options...
Skunkworks85 Posted May 18, 2021 Report Share Posted May 18, 2021 I don't know anything about the ctls stabalator, but it sounds like you're describing a "Flexure joint" - flexures provide consistent and predictable kinematic characteristics. Quote Link to comment Share on other sites More sharing options...
Tom Baker Posted May 18, 2021 Report Share Posted May 18, 2021 1 hour ago, Runtoeat said: Tom, thanks for the correction. Is the kevlar just applied in the hinge area or is the whole stabilator (top, bottom, both surfaces?) constructed with kevlar? I'm pretty sure it is just molded in the hingeline area. Quote Link to comment Share on other sites More sharing options...
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