I'm in the process of completely refurbishing a 72 (and then a 73) Decathlon. I've got the fuselage completely stripped down to the bare frame. I've found one of the longerons and two of the cross tubes have extensive pitting. The joint in between the sections of pitting on the longeron has a reinforcing patch welded on. There is no documentation for this repair. Dale at ACA told me to do a punch test on it. I've never done a punch test on a tube and I can't find any data for doing one. Is anyone familiar with this process? I also asked Dale about pitting limits and he didn't give me any numbers. I've been an A&P since 84 but this is my first tube and fabric project. I would welcome any suggestions before I start replacing tubes.
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Corrosion pitting on longeron on both sides of old repair
- Thread starter jamey
- Start date
I believe there is a recommendation of 10% of the wall thickness somewhere. (not ACA documentation)
Basically take an awl or something else sharp and see if you can punch through the wall with your hand. Its really a common sense test and not some calibrated procedure. You are basically hoping that its not pitted on the inside as well and collapses with hand pressure on something as sharp as maybe a dulled drill center punch.
I will repeat that its a common sense test. Its also something you want to monitor in the future. Personally, if its a bare frame, I would just replace or reinforce the segment. Finding frame flaws is one of the big reasons you strip her down so far.
Basically take an awl or something else sharp and see if you can punch through the wall with your hand. Its really a common sense test and not some calibrated procedure. You are basically hoping that its not pitted on the inside as well and collapses with hand pressure on something as sharp as maybe a dulled drill center punch.
I will repeat that its a common sense test. Its also something you want to monitor in the future. Personally, if its a bare frame, I would just replace or reinforce the segment. Finding frame flaws is one of the big reasons you strip her down so far.
Thanks for the info. It makes sense. I was thinking way to hard on this one. I was thinking that if you punched it with something to make an indention, you'd just be inducing a stress riser if it was actually OK. Being that I don't know anything about why the repair was made in the first place, I've pretty much decided to cut out the joint and replace or splice in new tubes. I want this to be a pristine airplane from every aspect. I think you're right on target with your comments about that being why its down to this level anyway.
My next big subject to tackle are the spars. I've decided to replace the wood spars with new wood spars. Mainly for financial reasons, but also, just to get the experience doing it. Where is the best place to purchase my spar stock?
My next big subject to tackle are the spars. I've decided to replace the wood spars with new wood spars. Mainly for financial reasons, but also, just to get the experience doing it. Where is the best place to purchase my spar stock?
Just my opinion, but I would use the Millman metal spar conversion, if cost is the big issue. If you go to all the work of replacing the spars, why put wood back in? If you do want wood, the best choice is the Rainbow spars. http://www.rainbowflying.com . I bought the new wings from ACA for my 8KCAB rebuild, and they are great, cost a lot but saved a lot of time, I got them un covered and covered them mysellf. Very happy with them. Bill Becker
I called Millman about two months ago and they told me that they didn't have a replacement spar STC for the 8KCAB. Do you kow if they have produced one recently?. I'll check out rainbow.
I may be crazy and regret it, but I want to get into this type of work (refurbishment) full time. There's a lot of challenge and satisfaction in restoring things to original or better quality. I worked as an A&P for a FED-EX commuter carrier for 11 years and everything had to be done right. I liked it that way. Since then I've worked for a few general aviation FBO's and I'd have a really hard time signing off some of the airplanes that get "annualled". I just can't get comfortable working in that environment. Too many corners get cut. I think refurbishment work will bring me the self satisfaction and gratification I'm looking for. I've just got a lot to learn.
I may be crazy and regret it, but I want to get into this type of work (refurbishment) full time. There's a lot of challenge and satisfaction in restoring things to original or better quality. I worked as an A&P for a FED-EX commuter carrier for 11 years and everything had to be done right. I liked it that way. Since then I've worked for a few general aviation FBO's and I'd have a really hard time signing off some of the airplanes that get "annualled". I just can't get comfortable working in that environment. Too many corners get cut. I think refurbishment work will bring me the self satisfaction and gratification I'm looking for. I've just got a lot to learn.