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Terrences Web Site
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Date: 7-23-2010
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Number of Hours: 5.00
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Manual Reference:
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Brief Description: Remove rivets from left spar cap
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1. I drilled and removed the 3/16" rivets as described in the 3/20/10 log entry. That procedure worked w/o any problem except for 5 "stubborn" rivets. Typical stubborn rivets are shown in Figs. 1 & 2. While the spar caps separated on a couple of the stubborn rivets, that did not occur with all as shown in Fig. 2. The rivets would move part way out and then freeze, and the rivet gun could not move them further. I suggest three reason for the problem.
- The compressor was set at ~55 psi rather than the max pressure. That happened because there is a lock nut on the pressure regulator adjustment that I had not noticed, so when I turned the regulator control know to increase the pressure to maximum, it would not turn. Unfortunately, I did not look at the pressure gage and check the pressure. I didn't notice the lock nut until I tried to reduce the pressure for the 5/32" rivets.
- I may have drilled the holes into the manufactured heads a bit too deep. That could have allowed (as shown in Fig 1) the 3/16" punch to extrude the rivet material to the outside of the hole. That was ocurred with all of the stubborn rivets.
- The measured diameter of the rivet gun punch was 0.171", somewhat less then the 3/16" (0.1875") diameter of the rivets.
2. After gettin all the top rivets out, I then used a #11 drill to clean out the holes and drill the 5/32" holes to the larger size. Unfortunately, I drilled the last hole. The problem is that this hole is supposed to get an AN3 bolt rather than a rivet, and a #11 hole is too large diameter for an AN3 bolt. I think a logical work-around would be to drill and ream a close tolerance 3/16" hole half way between the last two holes in the extrusion, and use that for the bolt. Then I would fill the #11 hole on the end with a 3/16" rivet. I'll bounce this off the Zenair tech support guys.
On balance, I believe that all items above may have contributed to the problem.
--continued
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Stubborn rivet_1
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Stubborn rivet_2
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Spar with top spar cap angle removed
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