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One piece spar cap strips

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  • One piece spar cap strips

    During the internet "virtual get together" I mentioned that we are changing how the main spars are built for the Model 5 and Model B. Instead of all the separate pieces of spar cap strips built up with either one or two layers of .125 x 1.250 - we are doing something new that has been in the works/discussion since the last time Bob was at Oshkosh a few years ago. It took a while to find an economic way to get these done. But the parts are now in production. The first batch will go to the factory in the next week or two to be used on the first production run of Model 5 kits.

    At first, our intention was to just make the cap strips themselves of one pice of .250 x 1.250 bar stock - milling it down to .125 where needed. Basically copy what has always been done but with a one piece cap strip. Bob starting thinking how these parts could be made all in one piece as well as changes to make it lighter and stronger. So he redesigned it so take advantage of making it all in one piece. As you see in the pictures it will arrive at the factory with all the holes drilled but a little undersize. The factory will de burr the edges and holes and then a main spar should go together in less that one day. Final drill, de burr, primer, and the next day rivet the spar together.

    We will likely make these available to scratch builders also but in a few months when we are caught up with enough of them made for the factory's needs. This will not be lowest cost way to build a spar but they will save considerable build time. spar cap strip2.jpgSpar cap strip1.jpgspar cap strip3.jpg Mark

  • #2
    Those look great Mark, do you have a number for the weight savings?


    • #3
      That is art work. If my spars weren’t done in would order a set.
      Scott Ahrens
      Bearhawk Patrol Plans Built


      • #4
        We do not have a weight savings number. Perhaps we should weigh an original spar and a new one to see. If we can still do that as going forward we hope to make all the Model B & Model 5 spars using this one piece part. Mark


        • #5
          Will these be available for the Patrol spars (basically identical to the Model B, right???) as well? If so, put me down for a set as soon as they're available!
          Patrol plans #398


          • Mark Goldberg
            Mark Goldberg commented
            Editing a comment
            We will be doing these for the Patrol. But they are not identical. The Patrol cap strips are 1" wide and the Model B & Model 5 have cap strips 1.25" wide. We have discussed it with the machinist and it should not require too much re-programming to get the parts for a Patrol spar. It will happen sooner or later. Mark

          • Russellmn
            Russellmn commented
            Editing a comment
            Not trying to be difficult, but aren't the spar webs the same? So the Patrol COULD use the larger capstrips? Just aren't needed and is added weight?

        • #6
          whats also great about this for the scratch builders is the spar is a template to drill your holes in your spar web....a huge time saver and ensures no mistakes.....
          Last edited by way_up_north; 07-30-2020, 10:42 PM.


          • #7
            I think this is what geraldmorrissey has been preaching all along.
            Scratch building Patrol #275
            Hood River, OR