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Anyone doing a recovering project?
On Oct 12, 11:51*am, "Peter Dohm" wrote:
"Stealth Pilot" wrote in message ... On Sat, 11 Oct 2008 03:30:59 -0700 (PDT), Lou wrote: On Oct 10, 9:28 am, "Mike" nospam@ microsoft.com wrote: "Lou" wrote in message .... Depending on where you live EAA may have a workshop in your area from time to time on the subject and they also do those workshops at Oshkosh.. I think it costs a little north of $200, but it is well worth it. Thanks Mike, but thats not why I'm looking for it. I want to see and feel the texture and the underside, the weight and flexibility. I want to study an already used piece. * * * * *Lou If that's the case, then you should still check with your local EAA chapter. There will almost certainly be one or more members with some left over material. I have, It seems that nobody is recovering these days. * * * *Lou that is actually a common issue with Stits (polyfiber) when I bought the tailwind I thought maybe 5 years and it would need replacing. 9 years on I can discern no deterioration. Stealth Pilot I haven't heard much about it lately, possibly because I haven't been hanging around in the right places, but I can recall a lot of concern expressed years ago about structural deterioration hidden under the newer and more durable fabrics. *As I recall, the theory was that the need to recover was also an opportunity to thoroughly inspect the underlying structure and the newer fabrics drastically extended the time interval. *The question was whether the extended time might be excessive... Peter- Hide quoted text - - Show quoted text - I have wondered about that too. There were issues with the Citabria/ Decathlon aircraft with wooden wings some years ago. The current factory changed to metal wings as a result. (I wonder about fatigue in a few years unless the wings are life limited.) Another thing I have noticed is that most fabric covered aircraft I have seen in recent years, (Pitts, Decathlon) have never had the inspection rings cut open. I was taught in A&P school that you left them covered only till the first annual. Otherwise you could not properly inspect the wings. I saw a Decathlon that was at least 15 years old that had never had the panels opened. The owner mentioned that the little covers tended to come off during aerobatics but I know I wouldn't annual a fabric covered aircraft unless all the rings were in place per the parts or maintenance manual and that I could open them all for a proper inspection. I suppose that Decathlon mechanics could use other means to inspect the wings, i.e. borescope but I have never confirmed that. John Dupre' |
#12
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Anyone doing a recovering project?
On Oct 17, 10:25 am, John wrote:
I have wondered about that too. There were issues with the Citabria/ Decathlon aircraft with wooden wings some years ago. The current factory changed to metal wings as a result. (I wonder about fatigue in a few years unless the wings are life limited.) Another thing I have noticed is that most fabric covered aircraft I have seen in recent years, (Pitts, Decathlon) have never had the inspection rings cut open. I was taught in A&P school that you left them covered only till the first annual. Otherwise you could not properly inspect the wings. I saw a Decathlon that was at least 15 years old that had never had the panels opened. The old Champ/Citabria wood spars had issues with several areas of the spars, including cracking from the root attach fitting holes, the areas at the ends of the strut attach doubler plywood (where the stiffness imparted by the doubler caused stress concentrations in the spar at the ends of the doubler) and at every rib. The aluminum ribs, which do not shrink with age, were nailed (in three places) to the wooden spar, which does shrink across the grain with age, so that the nails forced the grains apart and cracked the spars spanwise. The AD demanded a bunch of extra inspection holes and covers, all of which were a pain to install, especially in the underlying aluminum leading edge. Some owners opted to do a recover to get a better look at the spars and some of them found a lot of cracks. These were cracks that were just about impossible to find unless the fabric was torn right off. Those aluminum ribs have corrosion issues at the trailing edge, where condensation collects and rots them out. The aluminum-spar wings, retrofittable to older aircraft, might be cheaper than replacing cracked wooden spars and rotten ribs and leaky fuel tanks and so on. I think they're heavier, though, something not very welcome on these airplanes that tend to have small useful loads already. The front strut attach fittings have an airworthiness limitation on them, requiring NDT every 1000 hours to look for cracks. I've never found any cracks in ours, but one of our fittings had a small flaw in the metal that appeared to have been put there when the aluminum bar was rolled. The factory milled the fitting but apparently they don't NDI them after manufacture. I'm recovering our 7GCBC now. Found cracked flap/aileron cove skins on factory retrofit wings with 700 hours on them. Dan |
#13
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Anyone doing a recovering project?
On Oct 17, 7:06*pm, wrote:
On Oct 17, 10:25 am, John wrote: I have wondered about that too. *There were issues with the Citabria/ Decathlon aircraft with wooden wings some years ago. *The current factory changed to metal wings as a result. *(I wonder about fatigue in a few years unless the wings are life limited.) *Another thing I have noticed is that most fabric covered aircraft I have seen in recent years, (Pitts, Decathlon) have never had the inspection rings cut open. *I was taught in A&P school that you left them covered only till the first annual. *Otherwise you could not properly inspect the wings. *I saw a Decathlon that was at least 15 years old that had never had the panels opened. * * * *The old Champ/Citabria wood spars had issues with several areas of the spars, including cracking from the root attach fitting holes, the areas at the ends of the strut attach doubler plywood (where the stiffness imparted by the doubler caused stress concentrations in the spar at the ends of the doubler) and at every rib. The aluminum ribs, which do not shrink with age, were nailed (in three places) to the wooden spar, which does shrink across the grain with age, so that the nails forced the grains apart and cracked the spars spanwise. The AD demanded a bunch of extra inspection holes and covers, all of which were a pain to install, especially in the underlying aluminum leading edge. Some owners opted to do a recover to get a better look at the spars and some of them found a lot of cracks. These were cracks that were just about impossible to find unless the fabric was torn right off. * * * Those aluminum ribs have corrosion issues at the trailing edge, where condensation collects and rots them out. * * * The aluminum-spar wings, retrofittable to older aircraft, might be cheaper than replacing cracked wooden spars and rotten ribs and leaky fuel tanks and so on. I think they're heavier, though, something not very welcome on these airplanes that tend to have small useful loads already. The front strut attach fittings have an airworthiness limitation on them, requiring NDT every 1000 hours to look for cracks. I've never found any cracks in ours, but one of our fittings had a small flaw in the metal that appeared to have been put there when the aluminum bar was rolled. The factory milled the fitting but apparently they don't NDI them after manufacture. * * * * I'm recovering our 7GCBC now. Found cracked flap/aileron cove skins on factory retrofit wings with 700 hours on them. * * * * *Dan Forgot to mention: Steel-tube airframes often rust out where the fabric touches the tubing, especially along the lower longerons. Condensation or rainwater (or mel****er from snow that has blown in through cable openings and so on) will run down the inside of the fabric and collect along the tube and start the corrosion. The old cotton was bad for that, absorbing the water and holding it there. I've seen rudder and elevator tubing rotted clean through. My old Auster had a corroded longeron right behind the battery box, where some acid had gotten free and lay along the tube. More good reasons to recover. And some wings use rib lacing to attach the fabric. The lace is (or often was) usually waxed linen, and since linen comes from flax it's something mice find edible if there's nothing better on the menu. Missing riblacing means fabric that will pull off the upper side of the ribs and will flutter, causing loss of control. And mouse pee will rot aluminum structure so fast it's not funny. Not having adequate inspection holes is just asking for trouble. Dan |
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