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Wing strut attach fitting

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  • Wing strut attach fitting

    Hi everyone, ran into some trouble Sunday night while drilling the pilot holes for the wing strut attach fittings. Basically what happened was a combination of several stupid mistakes, not clamping the drill vice down well enough, using too short of a bit, not keeping the bit cool with lube, and attempting to continue on even though the aluminum was getting sticky due to a hot bit and the bit hanging up when pulling out due to the vice not being clamped down well enough. Anyway, after the other pilot holes were drilled in the other fittings, I came back to this one and attempted to drill the hole from the back side so I could use a punch to knock the broken bit out. I managed to get within about a half a bit or so (1/8" bit broken off) so I tried to knock the bit out with a punch, which broke in the process. I then used a 3/16" bit to open up both holes so I could use a bigger punch and get a better hit on the broken bit. After extracting the broken bit, I ran the 3/16" bit down the hole and then ran a 1/4" bit to open the hole up to finished size. The second shows the little "step" I was left with since the two holes were off just a bit...about 1/32 - 1/16" or so.

    So...to those who have been here, can this part be salvaged to does it become the most expensive chuck of aluminum in my scrap bin to date? My gut is telling me one thing but my brain is telling me to exhaust all options before ordering another foot of bar. If I up size to the next bolt size I am scared that I will have edge distance issues and then their is the "looks" once it is complete. Being a crucial structural component, I would like it to be as close to perfection as realistically possible. Am I getting too crazy worrying about that little step or will it open up and allow the bolt to move starting a chain of events that we wouldn't like to experience?

    Thanks in advance.
    Joe
    Scratch-building 4-place #1231
    Almost Wyoming region of Nebraska

  • #2
    Why not just order a set from Mark? At $160 for a set of four ($40 each, nicely milled), that is a lot of work you don't have to do and very cheap by comparison.

    Comment


    • #3
      Paul, the journey is as meaningful as the destination. I enjoy taking raw material and making part from them, if I wasn't building an airplane I would be building something else. It is a hobby and I don't put a value on my time that I spend with my hobbies since I enjoy them and it is relaxing for me. Part of the challenge for me is making parts using the limited tooling I have available. I also enjoy the look on people's faces when they see what can be made from basic shop tools. Mark wants $160 for the 4 parts which is a fair price, I can buy the raw material for $70 +shipping for the 4 parts which leaves me around $70 difference figuring $20 shipping. That covers the electric bill at my shop for 2 months. Even if you factor in the messed up part and the fact I have to buy a foot of material ($35+shipping) I still have enough to almost cover a months electric bill and have enough material to screw up a second part before it would have been cheaper to buy the pre-made parts. If I would put a value on my time I would have just bought the pre-made parts and been done with it.

      So...about that hole...
      Joe
      Scratch-building 4-place #1231
      Almost Wyoming region of Nebraska

      Comment


      • #4
        If it were me, I would make a new part. Since these bolts are in shear, it moves the shear point inward and basically makes a lever (albeit a small lever) at that bolt location.

        That lever increases in size exponentially to the amount of turbulence you may experience. In other words, you probably don't want to be wondering about strut fittings when the airplane is being tossed around in the sky. But, that's just me, YMMV.

        Comment


        • #5
          That is the way I have been leaning Paul. Thanks for your opinion. The bolt is snug in the hole currently, but after repeated abuse from turbulance I could see the metal moving and filling in that hole which would cause a loose bolt and things snowballing from there. If I had active builders or an active technical counselor in my chapter I would run it past them but sadly my chapter is full of individuals in their 70s and 80s who have never built, were never involved in the maintenance of aircraft and many have never had a pilot's license. This forum is as good as it gets for me. Thanks again.
          Joe
          Scratch-building 4-place #1231
          Almost Wyoming region of Nebraska

          Comment


          • #6
            You might not know it, but Bob Barrows is one of the most frugal guys you'll meet in aviation. It is also good fortune that he is the most qualified person to talk about the structure of the airplane. Call him and tell him what you've got, and if there is any way your existing part can safely be salvaged, he'll be able to tell you. My experience has been that if Bob says something is "probably worth spending money on" or replacing, then I know it's worth spending without question.

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            • #7
              Thanks Jared, if I get a chance to call him this weekend I will. Do you have his phone # and a best time to get a hold of him?
              Joe
              Scratch-building 4-place #1231
              Almost Wyoming region of Nebraska

              Comment


              • #8
                Hi guys, just an update. When I got to the shop today I checked the depth and how far to the side the "step" was... 0.135" deep and 0.257" across top side was 0.250". Friction held the bolts in place when the part was turned upside down. Not as bad as I originally thought but I called Bob about it anyway and explained what i had going on. He said that that little hiccup would not be a problem and that the design would support that mistake so I could use the part safely. Feel kinda bad about calling during his supper time though, forgot about the 2 hour time difference.
                Joe
                Scratch-building 4-place #1231
                Almost Wyoming region of Nebraska

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                • #9
                  Thanks for the update. To often we never find out the outcome of a discussed problem, so we can't learn.

                  Doug
                  Scratch building Patrol #254

                  Comment


                  • #10
                    Hi guys, this is an old thread, but I'll try to relaunch it with a new question.

                    (4-place A quickbuild kit)

                    My strut fittings don't match my wing spar attachment fittings.
                    The two steel lugs from the wing spar are about 1/16th inch too wide to fit in the slots of the fitting.

                    If anyone else has encountered this problem - did you just squeeze the spar lugs together with a G-clamp or something?

                    Did you remove material from one / both of the lugs?
                    Obviously I don't want to be removing material from the aluminium fitting, or have it jammed on there with side loading on the lugs.

                    Or... (drumroll please) - is this a dumb question, and I'm missing something really obvious?

                    Thanks again,

                    James
                    Nowra, Australia
                    The Bob Barrows Bearhawk: "It's big like a Boeing... but better built."

                    Comment


                    • svyolo
                      svyolo commented
                      Editing a comment
                      Mine fit very tight.

                    • James
                      James commented
                      Editing a comment
                      Did you remove any material, or tweek them a litte SV?

                      James
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