Wing Skin Stiffeners

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Last Update:

May 12, 2011

 

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Here’s the stiffener blank with the wing rib form block. I decided to try the method outlined in the BearTracks newsletter to form the bend with heat from a torch.

To establish the correct bend you screw the stiffener to the wing rib form. Here the stiffener is captured under a large washer screwed to the form. I left the washer just loose enough to let the stiffener expand as it heated up. I drilled a hole in the fore end of the stiffener to attach it to the form.

You can see that it has quite a ways to bend to mimic the airfoil shape.

Here’s the fore end screwed to the form blocks. I used a finish washer to distribute the load around the hole. You can also put a little fiberglass insulation material under the stiffener at the two ends to help keep your form block from burning.

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The stiffener is pulled down to the form and ready to be heated with the small torch on the table.

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Heat the stiffener evenly by moving the flame slowly up and down the length. Put the torch closer than shown here. Use the blue cone to direct the heat. I was supprized at how much heat was needed to make the stiffener take the required bend.

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First two stiffeners done! This method works very well. Just keep checking the bend by unscrewing the fore end a little to see if it is still under tension.

Shawn Burns posted a tool and method for making joggles. The tool is simply a piece of steel the appropriate thickness with a slot cut into an edge. Round and polish the cut edges to keep from scratching/cutting the aluminum you are going to joggle.

Above the tool is the stiffener before joggling.

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One side joggled and one to go. Place the tool on the flange and squeeze the tool and flange in a vice to form the joggle. Be sure you place the tool ‘under’ the part of the flange to be ‘raised’

Worked great. Thanks Shawn.

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