Bearhawk Aircraft Bearhawk Tailwheels LLC Eric Newton's Builder Manuals Bearhawk Plans Bearhawk Store

Announcement

Collapse
No announcement yet.

Forming Lexan

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Forming Lexan

    I need to make landing light lenses. They are installed in the leading edge, not the tip so not a complex curve. Wondering if I could just use a heat gun and the leading edge skin as a form instead of making a separate form.

  • #2
    The only thing I'd be worried about with a heat gun is localized heating causing uneven shrinking and goofing with your optics. Just speculating on my part, I think perhaps an oven would provide more even heat, and "melt" the glass over a form more evenly? I'm not so sure my wife would be too keen on my trying this in hers, though

    Certainly can't hurt to try with a heat gun, though.
    Christopher Owens
    Bearhawk 4-Place Scratch Built, Plans 991
    Bearhawk Patrol Scratch Built, Plans P313
    Germantown, Wisconsin, USA

    Comment


    • #3
      Often there is moisture in the lexan and when you heat it with the heat gun that will bubble up. I understand the bubbling can be avoided if you dry it for a few days first. Perhaps above wood stove would be a wonderful place to do this?

      Comment


      • #4
        I think the wood stove idea is a good one. We experimented a bit with heat gun forming some scratch resistant coated lexan and it didn't work very good but I think you could do it with the stuff you'd use for a landing light lens.
        Scratch Built 4-place Bearhawk. Continental IO-360, 88" C203 McCauley prop.

        Comment


        • #5
          I have made very nice landing light covers using hardware store plexiglass type plastic. Make a leading edge shaped form using MDF and very thin plywood. Cut the clear plastic oversized since it will shrink when heated. Attaché it to the form with two sheet metal screws on either side of the leading edge to keep it in place as you go through the following. Place form/plastic in an oven and slowly heat until the plastic begins to sag over the form. Briefly remove and use a terry cloth towel to gently encourage the plastic to take the shape of the form. Continue heating/smoothing cycle until plastic has the desired shape. Let the plastic cool before removing from form. Cut to final size using a Drexel cutting disc.

          Ray Strickland
          Plans-built 4-place

          Comment


          • Bcone1381
            Bcone1381 commented
            Editing a comment
            I am unfamiliar with a drexel cutting disc. Was that a typo? Drexel or Dremel?

        • #6
          Rod,
          I did the same thing with 1/8 plexiglas, I made a couple of nose ribs out of 3/4 plywood and fastened them to a 8 x 12 piece of plywood with some alum to form the shape of the leading edge. Put the whole thing in the oven with the plexi balanced on the leading edge and heated it up. Works like magic. I cut the ply nose ribs in about an eighth so the finished lens matched the wing.

          Comment


          • #7
            I made my lense much the way the others above did except I put two layers of T shirt between my form and the lexan to protect it from form damage. I soaked the lexan with the T shirt and form in the oven for an hour below the forming temperature to drive out moisture before bringing everything up to forming temperature and finishing the lenses.

            Comment


            • #8
              These are some Great tips! Nice use for those nose rib for blocks and scrap pieces of aluminum for the pattern. What is the forming temp for Lexan and for Plexi?
              Brooks Cone
              Southeast Michigan
              Patrol #303, Kit build

              Comment


              • #9
                325 F for plexiglas, not sure about lexan. Good reference http://www.plexiglas.com/export/site...ing-manual.pdf

                Comment


                • #10
                  350F-360F for Lexan (Polycarbonate), and sometime higher? https://www.tapplastics.com/uploads/...tion_Guide.pdf Page 8
                  Dave B.
                  Plane Grips Co.
                  www.planegrips.com

                  Comment


                  • #11
                    Lexan is great stuff, even bullet-proof when sufficiently thick, but can be turned to crap with a simple splash of gasoline. If there is a chance of splashing fuel on it I would consider a very thin cover-layer of acrylic
                    Last edited by bergy; 01-17-2018, 03:21 PM.

                    Comment


                    • #12
                      Sorry...my half-heimers struck again...I meant Dremel. Be sure to use the fiber-reinforced cutting discs.

                      Comment


                      • #13
                        Thanks for the advice guys. I made the form like suggested and covered it with flannel. I made it a little small as the lexan was going on the inside of the nose skin. The lexan started drooping around 320 deg and formed easily at 350. Made 4 lenses so I would have a couple spares.

                        Comment

                        Working...
                        X