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| Note pink dots on hinge brackets-- that's the laser! |
After a short time reviewing the instruction manual, I decided to drill out the AN3 hinge bolt holes on the elevator hinge brackets to full size. I used 3/16" pop rivets with the mandrels pulled out as a spacer for the center of the holes, so that I could run a taught string through them to make sure they are all aligned along the hinge line. I redrew all of the centerlines and remeasured the positions of the hinge brackets, then set them all in place to check alignment. For giggles, I tried a laser pointer first. With minor tweaking, the laser went right through to the other end of the spar!
Ben suggested using the machinist's protractor to jig the brackets in place while drilling. We set it up for about 91 degrees. It didn't take much of an angle, but worked out perfectly. I was able to clamp the protractor to the spar flange, and rest the brackets against it at just the right angle to be perpendicular to the spar spanwise centerline.
Once one side of each pair was drilled & clecoed to the spar, I bolted the hinge bearings in place along with one thin large-area washer between the brackets. This made it easy to drill the other half of the hinge bracket pair to the spar. Then I drilled the #40 holes out to #30, and then #12 for the center bracket.
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| Machinist's protractor clamped in place to set angle of bracket |
Deburring was standard, but chasing the chips out that had lodged between the spar doublers and flange was a challenge. I did such a good job filing the edge of the doublers and getting a tight fit, the chip-chaser I bought from Avery was too thick! Had to use the Exacto knife to get the chips out carefully, without scratching the spar flange.
Finally, the last step of the day was to clean & prime all of the brackets and shoot one clean-up coat of primer on the rear face of the spar to cover up all the new dings.
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| Using the hinge bearing to space the hinge brackets |
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