Date:	6-6-2018
Number of Hours:	3.00
Brief Description:	Fix rear spar doubler orientation
I hate fixing avoidable mistakes. I marked the HS-906 doubler "up" direction wrong and now I get to pay for that error. There are 34 AN470 rivets I had to drill out to remove the doubler from the spar. My rivet removal tool paid for itself tonight. I drilled out all 34 heads and popped them off in five minutes. Getting the shanks out was a bit tougher. I used a #33 bit to drill down about 3/4 into the shanks. The smaller drill bit gave me a little margin away from the hole bearing surface. The rivet removal tool does a good job of centering the drill bit on the head, but it's not exact. I put a rivet caddy under the tail and started pounding. It took about an hour to remove all of the rivet shanks because I was being very careful to avoid damaging the spar and doubler. An examination of the holes showed very little markings from the removal process. I triple checked the orientation of the doubler and got it riveted back together without further drama. I also riveted the HS-912 hinge brackets to the spar. The last item was dealing with the unnecessary countersink on the doubler. I used a shorter rivet than called for in the instructions and double-flush riveted the two locations with the shop head resting in its intended location. In retrospect, I should've used an even shorter rivet. I couldn't get the tail flush with the surface, but at least it didn't clench. I thought about drilling it out, but the risk of screwing it up and having to buy new parts wasn't worth it. Structurally, it's sound.