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Andrews Web Site
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Date: 8-16-2022
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Number of Hours: 4.00
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Manual Reference:
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Brief Description: Trying alternative skin forming method
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I was really struggling to get a good fit at the leading edge where the radius ot the skin fits down well against the rib. I remember that on my RV-4 the leading edge skin was simply bent in a 90 degree angle at the proper radius and pulled into place with clamps. I wanted to try that method with a smaller "scrap" piece of aluminum to see if the prebend was making the job harder than it needed to be. Image 1 shows bending the skin in the press brake. Image 2 shows fitting the skin. Since this wing is so thin (unlike my RV-4) it takes a lot of force to pull the skin down and would surely pucker rivets if simply riveted as RVs are done. Therefore I proved to myself that the prebend is needed. Another thing I noticed, is that the radius I put into the skin using the double thick form as shown in image 1 (and decribed long ago when I first built the tool) may be holding the nose radius to far back into the rib section even though it has more clearance than the lower form. The 90 degree test section I tried here would not fit fully down on the nose of the rib. Therefore, If I was to do another skin bend, I would use a generous brebend, and only one thickness of female form on the press brake. However, since I already had skins formed, I just continued to adjust the skin shape just aft of the radius by hand as shown in the previous entry. Spoiler alert, It turns out that when I end up drilling the skins to the ribs, they are not pulled down all the way on the inboard rib. There is perhaps an .080 gap. I will accommodate this in the sealant dams etc, but there is some concern as to whether this will affect the wing section. There is no flat spotting in the contour, and I struggle to think this is not within the noise level of the translation between the Riblett design and drawing accuracy. however, there is some possibility that this wing may fly uniquely to my airplane. At any rate, it is apparent that the prebend you put on these skins will have a lot to do with the contour of the wing section between the ribs (most o
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Bending up a little 90 degree test section
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Pulling the test part around the leading edge to examine fit and pull.
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