Parts of interest:
The four fins and correct dowel diameter for the BT-50 size upscale.
Four cardstock centering rings made in an earlier blogpost.
Four 1/4" diameter launch lugs.
The tube seams and balsa grain have already been filled.
The centering rings I cut seemed a little thin.
Four were initially cut, I decided to double them up.
To be sure they were perfectly aligned on top of each other, one was slid (dry, no glue yet) over the BT-5 motor mount tube.
A light coat of glue was spread evenly over the second ring.
I'm not gluing the rings to the tube yet, just joining the rings.
The two rings were closed using the (flipped) clothes pin clamps.
A second laminated ring was also made.
