Hole in Airframe

[Hank Jarrett]

Re: Hole in Airframe

That is kind of my question. Considering the size of the hole it would seem that if a welding a rosette would reduce the strength then a patch would actually be WORSE. That's why I would want to see a stress report for the part. Looks like the cure could be worse than the desease.
Hank

[Dennis Keels]

Re: Hole in Airframe

I hope I don't show my stupidity here but your talking about a very small hole....why can't it simply be spot filled with 4130 rod using a gas welder?

I'am with Kevin don't look like that big of a deal.

[Pearson]

Re: Hole in Airframe

I didn't see anything in AC43.13 that addresses patching such a small hole. Seems like everything is to replace tubes, or repair dents and rust. The problem with putting a patch over this hole is that it is so close to the weld at the upper longeron. If you look at the picture posted earlier, it is only about 1/4" from the edge of the hole to where the weld starts for the longeron. It sounds like several others here are thinking the same as I am that just a a tiny little rosette weld would do the trick.

[Guest]

Re: Hole in Airframe

I did a closer examination of the hole in the tube. It is within 3/16" of the hole in the wood that goes on top of the tube. I bought this plane as a project that had already had the airframe blasted and primed. The wood was already temporarily screwed on. I didn't discover the hole until I removed the wood to prep the airframe for a top coat. I could not detect any sign of rust inside the tube. If the hole was drilled by the guy I bought the project from, it has not been outside to get any water in it since it was drilled. I have not checked with my copy of AC 43.13, but I suspect that a small diamond patch might be the way to go. I don't have access to TIG. But I can either gas weld it, or MIG weld it and then relieve the stresses with the gas.

Hi Richard,

Its good to hear of your findings. Sounds like you just have nuisance hole.

I have been using MIG since about 1989. It is really good for fast production type of welding (I know body guys use it too).

I use it on thick cross sections where the bead is curvy or short. In fact I made the bungee tools out of thicker metal than needed just so I could use the MIG machine to cut down on welding time.

I don't think that I would be able to fill that hole with a MIG machine. For short beads its all over before you even get to see what happened.

Migs are constant voltage supplies and pump out up to max current to achieve that. Things vaporize fast for me!

I suspect that I would blow it thru before I knew what happened. If I do anything that is a short bead with MIG I like having a nice thick piece of metal so that the process of bringing it up to temp asap doesn't blow it away.

I use MIG in the long straight bead of the split sleeve repairs. Its thick and has a long run. That works for me and its fast.

TIG would fill the hole easily.

If I was doing it with gas I would get the smallest tip I could (I have a Smith) and try filling it with that. Get a piece of scrap 1" tube or something close to that with a similar wall and drill a hole about the same amount from the end an practice on that.

My first choice would be to fill the hole. If the owner insisted I would consider doing the diamond patch but probably not for too long. Looks to me like there is not room for it. If the owner was really insistent one could consider welding a very small diamond like a diamond shaped washer. I think in the long run that will be a mistake though. The more you do here the longer your bead gets and its is closer to teh fitting. More bead means more chances for problems and possible burn throughs that are farther from the hole and closer to the fitting and are catstrophic to repair. ie a big mess!

I would just weld it up with gas after a few practices on scrap. I would just use a standard rod. A double or triple deoxidizing rod. I would not use a 4130rod, I think that you need the deoxidizers and allow that control you puddle content with a gas flame.

I suspect that if it was in my garage that the hole would have been filled in less time than it took me to write this.

Dave

[Pearson]

Re: Hole in Airframe

Dave,

I was thinking of just using gas to weld it up. It is a very small hole. Thanks!

[N96337]

Re: Hole in Airframe

Good God yes...just gas weld it full and forget it!!! Take a step back and look at where it is......there are WELDS (gas welds!) literaly surrounding it! I say clean the surrounding area, shoot a bit of Polyfiber's tube oil in very carefully with a syringe, weld it (I use gas...guess it was good enough for Taylorcraft, so why worry about it???), and re-prime it. AC43 is great for reference to repair...this is a minor nuisance, not a repair.
John

[Ray36048]

Re: Hole in Airframe

The Poly Fiber tube oil is great stuff. But, I would not use it before you weld the tube. It will burn and cause pressure in the tube that will blow back throught the weld.

Funny thing about the tube oil, they do not caution you about what tubes you can drill and those you can not. After you inject the oil, you use a blind rivet to seal the hole. They are not welded.

I welded a crack on the step on my Cherokee 180. When I had it off years ago, I had injected it with some tube oil. I drilled the rivet to drain the oil. When I hit it with the torch, it started to burn the oil coating the inside of the tubing. It went off like a roman candle. Thick smoke and hissing for several minutes. The step tube is streamline about 2 inches by 10 inches.

[TonyL]

Re: Hole in Airframe

You can do whatever you want. The repair as per the FAA is specified. When you start welding into 4130 as thin as that, I hope you don't wind up replacing the whole area. Applying heat to the tubing itself causes certain effects. a 3/16 hole in that tubing, is not as small as may be thought. Then again, I'm not that bright, so why not look at the AC and come up with your own approved fix. Good Luck and Merry Christmas

[crispy critter]

Re: Hole in Airframe

You can do whatever you want. The repair as per the FAA is specified. When you start welding into 4130 as thin as that, I hope you don't wind up replacing the whole area. Applying heat to the tubing itself causes certain effects. a 3/16 hole in that tubing, is not as small as may be thought. Then again, I'm not that bright, so why not look at the AC and come up with your own approved fix. Good Luck and Merry Christmas

I thought it was a 3/32 hole(#40). In the pic it doesn't look much bigger then that,1/8th at the most. If it's a 3/16 hole then I do agree that it should be patched rather then filled.

[Pearson]

Re: Hole in Airframe

The hole is about 1/8" in diameter. I have done all the other welding required by the Harer STC, so I don't see why filling such a small hole would be anymore detrimental to the tubing. I agree that a patch would help spread the stresses over a larger area. But that would require a lot more welding and heat. It is such a tiny hole, I think I am just going to put a small rosette weld on it and be done with it. I appreciate everyone's input. Thank you all! Now if I can just see that eclipse tonight it will have been a great day!

[Hank Jarrett]

Re: Hole in Airframe

Just remember, no matter WHAT you decide to do, get your IA to agree BEFORE you do it! We may all be making a mountain out of a mole hill here (or maybe we are trying to make a pimple out of a bullet hole). Whatever you do, your IA will be the one who decides if you can fly it when you are done. A lot cheaper to ask ahead of time.
Hank

[Forrest Barber]

Re: Hole in Airframe

Whew! what a discussion. That tube is under compression ( unless flying upside down and the diagonals are to prevent "kick-out" somebody drilled it for some reason, probably as a slip up as mentioned. I will not override the IA signing it off. However I too think a proper gas welding to fill the hole would be fine, normalize when done and away you go. YES check the tubing for any corrosion, the whole fuselage should be checked. Wish she was here in my shop.

[N96337]

Re: Hole in Airframe

The Poly Fiber tube oil is great stuff. But, I would not use it before you weld the tube. It will burn and cause pressure in the tube that will blow back throught the weld.

Funny thing about the tube oil, they do not caution you about what tubes you can drill and those you can not. After you inject the oil, you use a blind rivet to seal the hole. They are not welded.

I welded a crack on the step on my Cherokee 180. When I had it off years ago, I had injected it with some tube oil. I drilled the rivet to drain the oil. When I hit it with the torch, it started to burn the oil coating the inside of the tubing. It went off like a roman candle. Thick smoke and hissing for several minutes. The step tube is streamline about 2 inches by 10 inches.

Ray, that's why I said to put the tubeseal in there by the use of a syringe... then you don't get the oil near where you're welding. Roll the fuselage to move the oil to the downhill side, away from the weld, and there will be no problem. The only time I've had the "roman candle" effect is when I was sloppy putting the oil in. If you're getting that whole tube hot enough to boil the oil and create pressure, you need to change tips for sure! We're dealing with old tubing and structures here, and a little "preventative" may go a long ways! Maybe I'm doing it wrong, but after 25 years of doing it that way, I've never seen a problem...and some of the airframes I work on get used HARD! A blind rivet in a tube changes the whole stress load as was mentioned in an above post, much like a screw.
John

[Ray36048]

Re: Hole in Airframe

I don't know how much oil was in the step, not much. It was in there for several years. I drained it. The crack I was welding was no where near the rivet hole. When the weld started, so did the fire inside the tube. I know Poly Fiber says it is "special oil", but it sure smells like Linseed oil.

Just saying what happened.

[Guest]

Re: Hole in Airframe

I don't know how much oil was in the step, not much. It was in there for several years. I drained it. The crack I was welding was no where near the rivet hole. When the weld started, so did the fire inside the tube. I know Poly Fiber says it is "special oil", but it sure smells like Linseed oil.

Just saying what happened.

Hi Ray,

Yeah I noticed that smell too.

Maybe it has drying agents added??

Or maybe it is special because you can get much more for it?

Dave