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Terrences Web Site
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Date: 3-26-2008
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Number of Hours: 2.00
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Manual Reference: 6W8A 11
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Brief Description: Adjust positon of bottom rear skin
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1. I reconsidered Caleb's suggestion to move the bottom rear skin rearward so that it would meet the edge distance specs on the main and rear spars:
- I found that if I moved the skin so that it just met the edge distance limit (5-mm) on the rear spar out near rib 8, then the holes on the front spar would be just out of the bend on the main spar.
- However, this leaves no room for error. If any hole "migrated" backward on the rear spar or forward on the main spar, then it wold no longer meet the spec.
- If there were an easy way drill round holes tangent to the rear edge of the rear spar pilot holes and tangent to the front edge of the main spar pilot holes, then the problem would be largely avoided. However, I do not have a way to do that on a structure like the wing.
- My experience is that a few holes do tend to end up a ways from the pilot holes.
- Caleb's suggestion would put the outboard end of the skin ~4-mm beyond the flange of the rear spar. I thought that overhang would have to be filed off for a clean build.
2. Fellow builder Laurens suggested drilling new holes for the rear spar between the drenched pilot holes.
3. I decided to adapt Laurens' idea to the front spar, i.e., line up the skin with the flange on the rear spar, and then drill new holes centered between the original pilot holes. I checked this out with Caleb. He thought that was a workable solution. However, he said that when the skin is overhanging like this, that usually means that there is twist in the wing. I told him that the wing appeared to meet all the twist criteria in the PAM, i.e., both spars level and 9° angle on the front spar.
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Blind edge rivet measure tool
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New main spar rivet line
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New main spar rivet line.
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