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My desire to have a center section in which to store my ballistic chute will make the cabanes slope out similar to the cabanes on the ArcoSport and Hatz biplanes. | |
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First an explanation: My cabanes are of 6061 tubing, pre-bent diameter is 1.3/8" 0.049 wall. I wanted them streamlined so build a jig to smash the tubing, this a cross view, the jig is 3" steel Channel. I put masking tape on the surface that the Aluminum would contact so the rough surface of the steel wouldn't mar the Aluminum. See I-Struts |
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I did some tests with short pieces of tubing until I found the shape that I liked. In those tests, I noticed that in the part of the tubing that had the sharpest bend, there were some stress cracks. I did some research and found that I could do a temporary anneal on 6061 by heating it to 900 F. (Full annealing should be done at 775 F for 2 to 3 hours followed by controlled cooling at 50 F per hour down to 500 F, then air cool.) The soot from acetylene burns away at @900F, so I but some soot on the tubing and then burned it of with a Propane weed burner. The pieces smashed after annealing didn't crack. |
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When I started, dimension "A" was 1 3/8" and dimension "B" was wide enough to get the tubing in the jig with the tubing flush with the top edge of the channel, I tightened the nuts on the top of the jig only until dimension "B" was 11/16" |
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In this photo you can see the jig with an unsmashed tube, some tubing with soot on it and the end profile of a smashed tube. | |
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$$$$. | |
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$$. | |
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$$$. | |
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