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New Plans building with a few questions

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  • New Plans building with a few questions

    Hello fellow Bearhawk LSA builders. I just started on my plans built LSA this weekend. I have my master template done and am ready to start doing my form blocks. I have watched a lot of videos and read several build threads for the 4 seat and patrol on how they do it. My questions is this, I notice on the plans that the rib at the wing tip is a full rib instead of three pieces like the others. Most builders videos I see people are making their form blocks and cut blocks right up to the center line of the spar noted on the full size rib template. If I do that for the LSA the tip rib will be shorter since it doesn't have the spar thickness correct? Does this mean that on my nose, center, and rear ribs need to be made shorter than the plans by how ever much the spar and other support plates are thick? I would assume so but it seems as if everyone just goes off the center line of the full size rib template.

    A little about me. I live in Statesville NC and fly out of 8A7 (Twin Lakes). I have a Grumman Yankee AA1 and a Questair Venture that I keep there. Look forward to sharing my progress as well as watching others.

  • #2
    There are a couple different approaches to the rib lengths.

    Either all can be made to match and then trimmed as required for the various cap strip buildups on the spars or they can be made in varying lengths to fit at the start.

    I made all mine match and then trimmed as required at assembly

    Also, I made my tip ribs full length but it is my understanding that the kits just use the same "forward/center/trailing edge three piece approach.

    If you look back through the forum you should find a link to a PDF of my wing build.

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    • #3
      Welcome Grum.man. Good to have another Bearhawk LSA in the Carolinas!
      Stephen B. Murphey
      Bearhawk LSA
      Building #L-089

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      • #4
        Originally posted by BTAZ View Post
        There are a couple different approaches to the rib lengths.

        Either all can be made to match and then trimmed as required for the various cap strip buildups on the spars or they can be made in varying lengths to fit at the start.

        I made all mine match and then trimmed as required at assembly

        Also, I made my tip ribs full length but it is my understanding that the kits just use the same "forward/center/trailing edge three piece approach.

        If you look back through the forum you should find a link to a PDF of my wing build.
        I have already downloaded your PDFs and scanned through them which confirmed that the tip rib is 1 piece. So did you have to trim every single rib or did you make them slightly undersize to account for the spar thickness? Also, was it hard to trim the ribs once you already had them formed?

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        • #5
          Originally posted by sbmurphey View Post
          Welcome Grum.man. Good to have another Bearhawk LSA in the Carolinas!
          Thank you, where are you located?

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          • sbmurphey
            sbmurphey commented
            Editing a comment
            I am south of Florence SC. I travel NC quite often with my job though.

        • #6
          I made the tip rib full size(ignoring the spar web thickness).

          Once you set the spars up to start putting in ribs, you set the root end so the spar separation is correct. You then set the tip ends so that the spars are level root to tip which means they are also parallel. You then position the tip rib where it belongs based on the spar locations. You then start filling in the center ribs, which I trimmed to length as required. Theoretically, were the center ribs were built full length, at the few positions the ribs actually go to the spar web instead of being trimmed to fit against cap strips, one would need to take half the spar thickness off the front and half off the rear.(IIRC, a total of about .030").

          Reality is you won't be working to that tolerance and, If needed, minor variations are taken up by the attach angles.

          That's one of the things that becomes apparent as you go, that the design allows you to correct for tolerance build up(within reason).

          It took me a bit to overcome my +/- .001" machining background and accept "pencil line" accuracy.

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          • #7
            Regarding the ease of trimming, I was lucky and had a small corner notcher that I could set up to "nibble" as required.

            I would guess one could also use a router table or a bandsaw with a fence.

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            • #8
              Thanks BTAZ! I re-read your pdf last night in greater detail. Thanks for putting all of that together for us.

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              • #9
                I made all my form blocks to account for the spar thickness and cap strip thickness. In the end, the center and nose ribs will have to be adjusted to get the dimensions correct and they will match the tip rib. In the end I had to slightly adjust all the center and nose ribs because I tried to be too tight on the tolerances. If I had it to do all over again I would make my blanks to the expected size accounting for the spar web and cap strips then take another 1/10 of an inch off so that I did not have to do a small amount of trimming. As BTAZ also states you can make it up in the attach angles. I did make my attach angles a little bigger so that I could make up the difference and not have to worry about edge margin.
                John Snapp (Started build in Denver, CO) Now KAWO -Arlington Washington Bearhawk Patrol - Plans #255 Working on skinning the left wing! -Ribs : DONE -Spars: DONE, Left wing assembly's: DONE., Top skins : DONE YouTube Videos on my building of patrol :https://m.youtube.com/user/n3uw

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                • #10
                  Welcome! Glad to have another LSA builder on board.

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