I set the drill press up last night and rehearsed the procedure for drilling the holes in the booster tube for the PEM nuts to back the rail buttons. It was perfect. BUT, I was a bit tired and was having a hard time focusing my eyes at close distance (spotting the centers).
So I took a break for about 6 hours... BUT, I didn't sleep. Yeah, it's an issue.
Anyway.... do not work on important/detailed/precision work unless you are fully rested. I made a goofy mistake, and the ONLY way to explain it is fatigue.
Here's the setup, the mistake, and the fix...
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LEFT: Booster tube clearly marked for forward rail button drill center. If you look close, you can see that I have already installed the "backer" tool.
RIGHT: Since the backer had to go so far into the tube, I chose to insert the shims from opposite ends. Beveled them with a knife. Used the handle of one of the sanding tools to hold the backer in place while I inserted each shim.
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LEFT: Pointed up at the 320 watt fluorescent light fixture to see if there is any "daylight" between the tube and the backer at or near the drill site.
RIGHT: Pointed to allow the light to highlight the pencil line drawn down the centerline between Fins 2 & 3 (aka: the "back" of the rocket). It all looks great.
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LEFT: So, I set up this drill operation using a countersink bit because it has that nice sharp point and is approximately the same length as short 1/4" bit.
RIGHT: The good news is that the shimmed backer tool (aka: 2" PVC coupler and some wooden shims) worked wonderfully. The hole cut square and sharp with no observable blowout/tear-out.
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LEFT: You can feel AND see when the bit STOPS cutting fiberglass and is fully in the PVC. What you can't see very well here, is that SOMEHOW after setting this drill op up and checking it and rechecking it some many times over 6 hours.... I managed to drill the hole with its center NOT on the rail button line I drew specifically for this operation. That's the bad news.... Oof!
RIGHT: Some more good news is that I already repaired it... well, almost already repaired it. I used WS 105 resin and 205 hardener. After a minute or two mixing, I added less than 1 drop of rocketpoxy red dye and 4 teaspoons of 206 silica as a filler to try to simulate the resin/fiber matrix. I used the Ziploc to cover it and hopefully approximate the shape better and avoid a flat spot.
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ABOVE: Here you can see that the holes are not on the same line. I waited until the leftover epoxy cured in the mixing cup, but the repair was not leathered yet... I guess the Ziploc layer on both sides of the repair retarded the curing. In any event, I cleaned up what I could before it hardened. I will need to block sand and add fairing/filling compound to bring it back completely flush with the tube. But it will work....
Hate that I made a bone-headed mistake, but at least "first blood" has been drawn and I can relax a little and try to enjoy the build.
Time for a nap...
Bottom Line though.... the tool works. Setup worked. Procedure worked.... repair worked/is working. All good except for not knowing how I managed to rotate the tube AFTER it was set, checked, and verified.