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April 2021 Engineering Change Regarding Flap Hinge Drafting Error

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  • April 2021 Engineering Change Regarding Flap Hinge Drafting Error

    Bob has just sent an update relating to the way the flap hinge parts are drawn in the plans. This one applies to the 4-Place Model B, Patrol, Companion, and Five. flap-hinge.jpg
    http://bearhawksafety.com/Five/april2021.html

  • #2
    Thanks Jared.
    Would a similar change also apply to the center flap hinge and aileron hinges? They are dimensioned the same way.
    Mark
    Scratch building Patrol #275
    Hood River, OR

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    • #3
      It appears the center hinge and aileron hinge may have similar errors. On my model B plans the aileron hinge calls out 3-1/16" hole spacing and the spar calls out 3-1/8" spacing.

      I'm curious if this has any effect on the quick build kits. I'm sure Mark could answer that question. My wings are still in the crates.
      Model B quick build started 2021

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      • #4
        I just spoke with Bob about it. It really makes no difference. If that one hole is 1/16" from where he intended it there is no problem. I had trouble even seeing the difference in the old drawing versus this correction. Nothing to worry about. Mark

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        • #5
          Thanks Mark.
          Mark
          Scratch building Patrol #275
          Hood River, OR

          Comment


          • #6
            Are the circled dimensions the only change? Those are correct on my plans the only differences I see are that the thickness of the part on my plans is .050" not .063" and the space between the center of the holes is .98" on my plans, not 1.0" as depicted on the change. My thought was that the thickness difference is because I am building a Patrol which is lighter than the 4-Place or Model 5, so those would need thicker material. Is my thinking correct or do I need to be using thicker material?

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            • #7
              I think the controlling dimensions is on drawing 10 lower right corner for the patrol. The original 0.98 comes from the sum of 0.49+0.49.
              I do not know why the new drawing shows 1.0 inches since that part does not need a dimension call out for 1.0 since the bolt holes from drawing 10 are 0.98.

              The thickness of those parts on my patrol are listed as 0.050 not 0.063. I also wonder if the increased thickness applies to the larger airplanes.

              I thought the change was made so that the steel hinge parts had holes that would line up with drawing 10.

              Drawing 10 was the controlling reference for the 3 1/8 and the 3 7/8 bolt hole distance on the aluminum doubler plate.
              The drawing change was to make sure that the steel part would line up with those bolt holes in the aluminum doubler plate

              The original drawings would have had the 3 1/8 and 3 7/8 steel part holes off by 1/16. The original tick mark was at the pivot hole. The tick mark was changed to be the center to center distance of the bolt holes.
              Last edited by sjt; 08-15-2021, 11:47 AM.
              Stan
              Austin Tx

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              • #8
                When I redraw Bob's engineering revision to the flap hinges I arrive at the 3/16" bolt and washer being very close to the top of the hinge bracket in fact the AN960 washer will protrude beyond the end of the bracket. Can this revision be correct? That only places the top bolt one diameter away from the top of the hinge.
                FLAP INBOARD-OUTBOARD ASSEMBLY.JPG




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                • Sir Newton
                  Sir Newton commented
                  Editing a comment
                  R U a cad tech? Just being Nosy there spinning wrench ;-)

              • #9
                There is no harm in lowering the bolt's position down a little. If you like. Mark

                Comment


                • #10
                  I would call Bob, I haven't in a long time, and miss the conversation. His detailed memory of every hole in his designs is shocking. In a few places he violates norms, but because a fastener isn't loaded in that direction, it is OK. I leaned a lot building his design, and every single time I talked to him, which is prpbably only half a dozen times. He definitely knows how to beat every gram of weight out of his design.

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                  • #11
                    I have sent Maria a copy of my drawing for Bob to comment on.

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                    • #12

                      When I started I tried to make everything as light as possible. I would have made my angles exactly like the drawing. And if nothing went wrong I could drill the rivet holes without violating the hole to edge distance. Whenever I did get the hole to close I had to throw the part away.

                      I gave up trying to make it as light as possible. The picture below is how I make angle now. After match drilling everything I might be able to go back and trim - but I probably won't.

                      Make everything to big, then if you have time go back and remove extra material - or not.

                      halfinch.jpgangle.jpg
                      Attached Files
                      Stan
                      Austin Tx

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