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1940, 1941 and 1945 Cowls, grills, blisters, and trim

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  • #31
    Re: 1940, 1941 and 1945 Cowls, grills, blisters, and trim

    Murphy is absolutely hiding in the corners! ;-) Interesting to see how someone else attacked the same problems. Wish I had known what you were doing when we could have worked together.

    I think you hit the real problem we will have with resin. The FAA won't like it because it isn't the way it was always done. Before we get too far into it we need to know from some of the legal eagles here if they think we would be wasting our time. I think we could get approval for an NC machined one, but how do we prove the resin one is safe? Making a "plastic" one would be pretty easy and inexpensive (unless of course if it failed and tore up a prop!) If I was doing a plane for museaum display i would cast a plastic one in a heartbeat. There even paints that would fool someone even if they touched it.

    Hank

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    • #32
      Re: 1940, 1941 and 1945 Cowls, grills, blisters, and trim

      Its a minor, no real approval necessary...
      N29787
      '41 BC12-65

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      • #33
        Re: 1940, 1941 and 1945 Cowls, grills, blisters, and trim

        Which part would be a minor? If any of them failed they would go into the prop and cause major damage.

        I feel (just a feeling with no analysis to back it up) like they would have no problem with a machined part from a plate of aluminum because it would be stronger than the cast part; but if you were presented with a reinforced cast resin part or one that was 3-d printed, would YOU as an IA sign off on it and would the FAA be OK with your doing it?

        Hank

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        • #34
          Re: 1940, 1941 and 1945 Cowls, grills, blisters, and trim

          Part 21.303 owner produced part, non structural, installed per original, its a log book entry with proper documentation.

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          • #35
            Re: 1940, 1941 and 1945 Cowls, grills, blisters, and trim

            cnc yes 3d no
            N29787
            '41 BC12-65

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            • #36
              Re: 1940, 1941 and 1945 Cowls, grills, blisters, and trim

              OK, that is what I was thinking also. The reinforced resin to me would require some testing to insure any failure would NOT go into the prop. Maybe a welded frame encased in the resin or graphite fibers inside to insure it is at least stronger than the cast aluminum ones. Either way, I would want a lot more data before I would even present it to my A&P/IA. I think the CNC machined ones would be pretty easy to approve, problem is the high cost.

              Hank

              How many people out there are interested in getting grills? Main cooling and or case grill on the bottom?

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              • #37
                Re: 1940, 1941 and 1945 Cowls, grills, blisters, and trim

                Originally posted by Hank Jarrett View Post
                OK, that is what I was thinking also. The reinforced resin to me would require some testing to insure any failure would NOT go into the prop. Maybe a welded frame encased in the resin or graphite fibers inside to insure it is at least stronger than the cast aluminum ones. Either way, I would want a lot more data before I would even present it to my A&P/IA. I think the CNC machined ones would be pretty easy to approve, problem is the high cost.

                Hank

                How many people out there are interested in getting grills? Main cooling and or case grill on the bottom?
                You can 3d print some metals. I have some dimpling dies that are way stronger than the cast aluminum. Problem is the material is wrong so it will look wrong.

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                • #38
                  Re: 1940, 1941 and 1945 Cowls, grills, blisters, and trim

                  Hank,

                  To answer your question, I'm in for one lower cowl if someone figures out how to make them.

                  Peter

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                  • #39
                    Re: 1940, 1941 and 1945 Cowls, grills, blisters, and trim

                    Dad had a couple sets cast from his old grills. He looked at the lower grill, and thought about cleaning it up on his last restoration. He wound up using the old grill, but he thought the newly cast grill was going to fit OK. Maybe the shrinkage has to do with the alloy used for the casting. Also at Oshkosh there was someone who said their son was willing to do some casting for some of these older hard to find parts. There is already someone who is casting wheel pant brackets.

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