Bearhawk Aircraft Bearhawk Tailwheels LLC Eric Newton's Builder Manuals Bearhawk Plans Bearhawk Store

Announcement

Collapse
No announcement yet.

Wing Strut Attach Straps

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Wing Strut Attach Straps

    I just finished riveting my rear spars and getting ready to re-assemble and rivet the main spars.

    I hate to ask questions that highlight my lack of knowledge...but here goes: regarding the wing strut attach strap fittings that bolt onto the spar, the plans call for 0.190 thick 4130 N steel. Does the N stand for 'normalized' as opposed to 'annealed'? Does Wicks and/or Aircraft Spruce provide 4130 N steel?

    As a follow-up question to the type and source of the appropriate steel to make these parts...would it make more sense to just buy these ready-made parts form Mark for ~$120 ?

    Also, how hard is it to accurately match drill 1/4-inch holes through the steel straps into the thick stack of aluminum at the splice.
    Karl
    Bearhawk Bravo #1508B - Scratch Build (wings)
    Northern Idaho

  • #2
    Yes 'N" is normalized. Do not use "A". If in doubt, ask for a cert. A mill mark is the best identification but you might not get one on such a small piece of plate. The problem with raw stock is that the part is longer then 12". Raw stock is generally sold by the foot. A 1'x2' plate of .190 is pretty heavy and costly to ship. Plus you have to be able to cut, shape and accurately drill the .190. And you end up with a lot of matl you'll have to sell to another builder. The prefab parts are good value. I went at the holes a little at a time, enlarging the steel off the assembly and using a drill press and the strap as a drill bushing to drill the AL. Use LOTS of clamps and T or L pins. Have a plan and work the plan. Try not to drag big steel chips through an AL hole bore. Reaming can't hurt. Learn about MS bolt diameter tolerances. This is a part of the airplane that demands your full attention.
    Gerry
    Patrol #30

    Comment


    • kilohotel
      kilohotel commented
      Editing a comment
      Thank Gerald! ... but....what are 'T' and 'L' pins ?

  • #3
    N is for normalized which is different than annealed. Most of what Wicks and ACS sells is normalized unless noted differently.

    Comment


    • #4
      If I were to do these again I'd buy prefab, but I would still do the drilling and reaming myself.
      Mark
      Scratch building Patrol #275
      Hood River, OR

      Comment


      • #5
        Thanks! I ordered the parts today!
        Karl
        Bearhawk Bravo #1508B - Scratch Build (wings)
        Northern Idaho

        Comment


        • #6
          Google Carr Lane for the full story on L and T alignment pins.
          Gerry
          Patrol #30

          Comment


          • kilohotel
            kilohotel commented
            Editing a comment
            That worked! Thanks!
        Working...
        X