Nose Skin Brake

How To Bend a Longish (12 foot) Wing Nose Skin On The Cheap - David Barth

I pondered a long time on the issue of how to bend the wing nose skin for my Zenith Zodiac 601 XL project. This is a bend in the entire length of a 12 foot sheet of .025 6061 T6 with a bend radius of about an inch. In the plans it says to use a long section of pipe of an appropriate diameter and a press brake. 12 foot press brakes that can handle a bend like this are not too easy to find. I figured there had to be an easier way using materials I had around the house. I had heard a lot of suggestions but nothing that would really work well for such a long bend without an investment in time, tooling and money.

Here is the truly simple solution to the nose skin bending problem. If you are building an airplane you probably already have what it take around your home or shop. The two things I had to press the skin with that had sufficient length and stiffness were my floor and my work table. I just had to determine how to best use them to do the job. After trimming the 12 X 4 sheet to 900 mm width, I used ratchet straps (I only have 4 of those so I supported the edges of the material with wood slats) to start the folding process while the sheet was lying on the table. Once the process was started I switched to thin plastic packing straps. I thought with the pressure on the skin (not now but during the actual bending) the ratchet straps might be thick enough to mark the .025. I used 12 of them so the spaces in between were small and the stresses on the edges of the skin were small. Still, I used wood slats along the length on both edges to support the skin and spread out the forces from the straps. (1/4" X 3" X 8' wood straps I had around)

These packing straps have wire clips that allow you to tighten them. I tightened them incrementally from one end to the other and back again several times until the edges of the skin were about an inch apart. You could bring them right together and hold them with duct tape I suppose. I may do that for the next one. Then I laid a piece of scrap carpet (short pile - I don't think shag would do a very nice job) on the concrete floor along the side of the work table and laid the skin down on it. We then tipped the table over on its side. the next step was to lay it down on the floor and the skin so that the nose was just back of the edge beam of the table. See the illustration. Then press down on the edge of the table (my 12 foot table is very stiff and makes an excellent brake) and check the radius against a nose rib. Do it again until you are satisfied. It was a very uniform bend. If your table isn't that stiff use two or three helpers to push to a uniform height. You can control the radius somewhat by putting a stop under the table edge so it can only be pressed so far down. I would suggest a test piece if you don't want to experiment with a 3 X 12 foot piece of expensive sheet.

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