Little Lunar Express, Part 3 — Attaching the Motor / Recovery Assembly to the Boattail
Today I attached the motor mount tube to the boattail (the bottom section of the airframe). For this step, the motor / recovery assembly, boattail, middle section of the airframe, and centering ring are temporarily assembled together to properly center the motor / recovery assembly. To prevent problems during this step, it is important to first check that these pieces fit together properly and sand them down if they do not.
1) Checked fit of centering ring, airframe, boattail, and motor / recovery assembly and sanded until pieces fit snugly.
2) Scuffed outer end of motor mount tube and inside end of boattail to prepare for epoxy. Slid centering ring over recovery tube.
3) Applied thick, heavy bead of epoxy to the end of the motor tube and inserted the motor tube assembly into the boattail. Made sure that the piston strap was not in line with a fin slot in the boattail, then pressed the pieces together firmly.
4) Slid the centering ring down all the way to the shoulder of the boattail. Slid the airframe over the centering ring and boattail. (Note: if it doesn't slide easily, a few taps of the acrylic face of a machinists hammer can help). Placed entire assembly vertical to dry, motor mount side down.
5) Skipping ahead, since I had leftover epoxy, I pulled the free end of the piston strap through the slot in the piston bulkplate, fed it through the D ring, and back through the slot. Then I folded the short end of the strap flat against the underside of the bulkplate and epoxied it in place. I held it down with blue tape while it dried.