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Form blocks for the wing spars?????

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  • Form blocks for the wing spars?????

    Well while driving home from work my mind was on building, as usual. I came up with and idea that im just not sure about and wanted to ask people with more experience. Since 8’ metal breaks are hard to come by and way to expensive to buy, I started wondering if a person could make some form blocks out of MDF, radius the edges, and coat them with PC wood petrifier to make the spars. Now im not suggesting clamping the metal between the two blocks and hammering the edges over because I wouldn’t want to cause any undue stress to the spars but what I would do is to make a way to press the form block and metal in between two other boards that were spaced correctly to bend the flanges over the form block. Any thoughts?

  • #2
    Builders have created home-made brakes with varying degrees of success. You need a lot of rigidity to keep the bend straight. A steel brake that big will usually weigh over 1000 pounds.

    In the context of how much r&d you'll have to do, and how much aluminum you will go through in testing, it may well be worth a day's drive to borrow time a brake.
    Last edited by jaredyates; 07-05-2019, 11:03 AM.

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    • #3
      At one time I owned an 8 foot leaf brake that I did aluminum race car chassis on. It worked well. When it came to doing my spars, I found a shop in Indianapolis that had a big press brake. That was way more accurate than my leaf brake and the radius is exact. Also, the spars are the only job that requires that big a brake. I still have a 4 foot finger brakes and a 4 foot press brake.

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      • #4
        I made a brake using steel angles. Roughly followed a design from the Zenith forums. Used it on my .032 LSA spar webs with good results. Look in my thread John's LSA build for a few pictures.

        Google "Dave Clay bending brake" and you'll be able to see several variations. It was even featured in Sport Aviation several years ago.

        Good luck.

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        • #5
          Sounds like a press break is the way to go. Thanks for the replies fellas!

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          • #6
            Originally posted by Cameron Ramsey View Post
            Well while driving home from work my mind was on building, as usual. I came up with and idea that im just not sure about and wanted to ask people with more experience. Since 8’ metal breaks are hard to come by and way to expensive to buy, I started wondering if a person could make some form blocks out of MDF, radius the edges, and coat them with PC wood petrifier to make the spars. Now im not suggesting clamping the metal between the two blocks and hammering the edges over because I wouldn’t want to cause any undue stress to the spars but what I would do is to make a way to press the form block and metal in between two other boards that were spaced correctly to bend the flanges over the form block. Any thoughts?
            I have access to a brake so I'm not doing what follows .....but the thought has crossed my mind...

            i call it slam forming.....spar material sandwiched between 1 inch plywood with flange area sticking out.....the lip/flange of the spar is resting on another piece of plywood same lenthgh.....you drive up on the the wood with your car...forcing the whole edge down and formed in one fast slam form....

            was as thinking of using a hot parking lot to put temp nails to hold the wood edges close....the drive the family car onto the spar sandwich.....

            patent pending...lol...
            Last edited by way_up_north; 07-12-2019, 06:44 AM.

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            • #7
              Well that was kinda the idea I had. I want the spars to be perfect.....cause.....they’re kind of important and I want this plane to last a long time. I just thought that a form block would make each spar the same instead of taking a chance of not lining one up on a break perfectly. Thanks for the information though.

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