Wing Attach Fitting Welded In Wrong Spot

[TonyG]

Marty, just for fun the plans don't actually tell you how the wings attach! However, the outside dimension of the fuselage tabs is called out as being (conveniently) the same as the inside spacing between each pair of spar straps. Spacing between front and back fittings is kind of ambiguous, as "by the numbers" the wings don't fit correctly. I noticed this while building my CAD model of the project to help visualize various bits of work. In any case, the idea seems to be to capture each spar fully without having to put any axial load on the bolt. The bolt holes are 5/16", so I assume an AN5 bolt is the tool for the job (the bolt is also not called out in the plans, unless I'm missing it).

I'm still open to the spacer idea since that's what I wanted to do in the first place due to ease, but since that wasn't met with resounding agreement my confidence in that method is kinda weak. Would it be fine? Probably. Is it worth me worrying about for the next XX hours of flight? Ehhh... I know I should probably just do it right to begin with and not think about it ever again.

-Tony

[TonyG]

Well, I'm committed now. I spent Saturday night out at the hangar cutting and grinding the offending wing fitting off. I started with a Dremel and an abrasive cut off wheel, but it proved to not be stout enough for the job. Mainly, I think the Dremel just didn't have the torque I really needed. A newer one might be better in that regard.

In any case, I moved to my angle grinder with cutoff and grinding wheels. The welds were (reassuringly) pretty stout, so it took some work. I never got that moment of satisfaction of pulling/peeling the fitting away, instead having to basically grind the whole thing down to the welds. But I did it, and now I have to fix it. There is still some cleanup to do before installing a new fitting, but it was past midnight and I had been grinding for over an hour. My hands were killing me. I might remove the upper portion of the strap still in place since it's attached to a non-critical piece of structure. The lower portion is welded to a critical member and will also be out of sight in the long run.

I was worried the angle grinder would be like trying to cut wing ribs with a chainsaw, but I was able to keep precise control for the most part. The fuselage gave me a good stable platform to rest against. I put a few shallow gouges in the neighboring tubing, but they're small and not worrying. If I change my mind, I might weld a 0.035" or thinner patch over the gouges and call it done. The patches would be hidden once the airplane is covered.


Original fitting.




And butchered.


-Tony

[Aaron Novak]

Well, I'm committed now. I spent Saturday night out at the hangar cutting and grinding the offending wing fitting off. I started with a Dremel and an abrasive cut off wheel, but it proved to not be stout enough for the job. Mainly, I think the Dremel just didn't have the torque I really needed. A newer one might be better in that regard.

In any case, I moved to my angle grinder with cutoff and grinding wheels. The welds were (reassuringly) pretty stout, so it took some work. I never got that moment of satisfaction of pulling/peeling the fitting away, instead having to basically grind the whole thing down to the welds. But I did it, and now I have to fix it. There is still some cleanup to do before installing a new fitting, but it was past midnight and I had been grinding for over an hour. My hands were killing me. I might remove the upper portion of the strap still in place since it's attached to a non-critical piece of structure. The lower portion is welded to a critical member and will also be out of sight in the long run.

I was worried the angle grinder would be like trying to cut wing ribs with a chainsaw, but I was able to keep precise control for the most part. The fuselage gave me a good stable platform to rest against. I put a few shallow gouges in the neighboring tubing, but they're small and not worrying. If I change my mind, I might weld a 0.035" or thinner patch over the gouges and call it done. The patches would be hidden once the airplane is covered.


Original fitting.




And butchered.


-Tony

Looking good. So how many people welded on the original fuselage?

[TonyG]

Looking good. So how many people welded on the original fuselage?

In my expert opinion (i.e. complete guess), it kind of looks like there were two welders on the project. One might have welded up the basic structure and another came in later to add fittings and other odds and ends. The wing fittings were a little rougher looking than the rest of the structure, which is beautifully gas welded. Then there's me, a monkey with a torch.

I actually have recently been able to track down the original builder (or at least AN original builder), who had signed his name and location on the front of one of the spars. He's up there in years, and this project is who knows how old, but he's still around. An EAA member in the area was able to provide me his phone number and I just need to pick up the phone. It's on my short list of things to do soon. I'm hoping he can give me some information about the project.

-Tony

[Aaron Novak]

In my expert opinion (i.e. complete guess), it kind of looks like there were two welders on the project. One might have welded up the basic structure and another came in later to add fittings and other odds and ends. The wing fittings were a little rougher looking than the rest of the structure, which is beautifully gas welded. Then there's me, a monkey with a torch.

I actually have recently been able to track down the original builder (or at least AN original builder), who had signed his name and location on the front of one of the spars. He's up there in years, and this project is who knows how old, but he's still around. An EAA member in the area was able to provide me his phone number and I just need to pick up the phone. It's on my short list of things to do soon. I'm hoping he can give me some information about the project.

-Tony

Kind of figured that, there are 2 very distinct “signatures”in the welding on that fuselage from the pictures you showed.

[mrbarry]

i would not call that butchered , i would say +offending fitting removed +

im no welder however as a retarded [excuse me i mean retired ] inspector
i think you need to work on that upper join until the +teeth + are gone

to quote the lemon heads .. i might be right but i might be wrong

and at the proper and correct angles to receive the new piece , taking care to remove minimum amounts of the longitudinal structure

[TonyG]

Aaron, you got that right. Learning to weld has taught me a sincere appreciation for really nice welds and really challenging welds. There are some very pretty welds on this project. Those straps were certainly more utilitarian, but still not bad.

Mrbarry, don't worry, I'm definitely going to do some more cleanup. The teeth you point out are on the short list to be cleaned up but survived to see another day on account of it being 12:30am by the time I reached the stage shown in the picture! What I cannot remove safely will probably become filler in the weld of the new fitting. I plan to work the lower half some more also, as I recall there was still some of the original fitting hidden in there. It at least needs to be removed to a point that the new fitting will fit correctly like you say.


-Tony

[mrbarry]

a wing to fuselage fitting ,,
here is an image from earlier in the string should not he area circled be filled with a very pretty weld bead
perhaps some one else remarked and i missed it , perhaps i am wrong ,,but my gut requires me to speak my piece
let the experienced weld tube builders step forth and make it clear.

[TonyG]

Ah, I see what you're saying. A valid concern and I would have wondered the same thing, but the plans actually specify welding only across the top and bottom of the fitting before forming and welding the strap over it.

-Tony

[nrpetersen]

Ah, I see what you're saying. A valid concern and I would have wondered the same thing, but the plans actually specify welding only across the top and bottom of the fitting before forming and welding the strap over it.

-Tony

Good point. The problem with a fillet weld is that it is already precracked on the invisible side. That crack will propagate if there is flexing from tension-compression. Worse, the cracked side can't be inspected.

A fillet weld backside crack however won't seriously propagate if the weld is loaded in pure shear.