(page 7-02)
Finally, a mistake that's not my fault.......
The rudder spar seemed to be coming along nicely. I did all the match drilling, deburring, and primed the mating surfaces. When it came time to rivet the spar caps to the spar and ribs, each rivet that I squeezed resulted in a shop head that was at a pronounced angle to the surface of the spar web. Naturally, I blamed myself, figuring I'd somehow squeezed without having everything aligned. Each rivet I squeezed had to be drilled out (my 487th favorite thing), eventually resulting in an oversized hole. I finally did a few test rivets using the fancy new Tatco squeezer I had been using (which came with the RV-12 tool kit I bought from Isham) and compared these with test rivets using my 20-year-old squeezer (which looks like a toy compared to the Tatco). Surprise! The rivets from the old squeezer were perfect, while the rivets from the Tatco had the slanted shop head. Upon looking closely at the Tatco, I could clearly see that the surfaces of the jaws were not parallel. I'm hoping Isham will exchange it. I'll have to go up one rivet size for the holes that became hogged out due repeatedly having to be drilled out.
At this point, I could permanately bolt the upper rudder hinge to the vertical stab spar. Van's instruction manual calls for 20 to 25 inch-lbf torque for AN-3 bolts, which, to my calibrated elbow, seems like too little. The bolts go into nut plates which are riveted to spar caps on the other side (not visible) of the v-stab spar. After a bit or research and pondering, I measured the torque required to turn the bolt in the threaded portion of the nut plate, and found that it takes approximately 10 ft-lbf just to overcome the squeeze produced by the out-of-round shape before the bolt bottoms against the washers. I added the thread drag to the lower end of the spec, and tighten to 30 inch-lbf. I may increase it to 35.
The rudder spar seemed to be coming along nicely. I did all the match drilling, deburring, and primed the mating surfaces. When it came time to rivet the spar caps to the spar and ribs, each rivet that I squeezed resulted in a shop head that was at a pronounced angle to the surface of the spar web. Naturally, I blamed myself, figuring I'd somehow squeezed without having everything aligned. Each rivet I squeezed had to be drilled out (my 487th favorite thing), eventually resulting in an oversized hole. I finally did a few test rivets using the fancy new Tatco squeezer I had been using (which came with the RV-12 tool kit I bought from Isham) and compared these with test rivets using my 20-year-old squeezer (which looks like a toy compared to the Tatco). Surprise! The rivets from the old squeezer were perfect, while the rivets from the Tatco had the slanted shop head. Upon looking closely at the Tatco, I could clearly see that the surfaces of the jaws were not parallel. I'm hoping Isham will exchange it. I'll have to go up one rivet size for the holes that became hogged out due repeatedly having to be drilled out.
At this point, I could permanately bolt the upper rudder hinge to the vertical stab spar. Van's instruction manual calls for 20 to 25 inch-lbf torque for AN-3 bolts, which, to my calibrated elbow, seems like too little. The bolts go into nut plates which are riveted to spar caps on the other side (not visible) of the v-stab spar. After a bit or research and pondering, I measured the torque required to turn the bolt in the threaded portion of the nut plate, and found that it takes approximately 10 ft-lbf just to overcome the squeeze produced by the out-of-round shape before the bolt bottoms against the washers. I added the thread drag to the lower end of the spec, and tighten to 30 inch-lbf. I may increase it to 35.
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