Estes Strikefighter, Kit #2015, Build, Part 4, Engine Mount

The 20/55 rings were loose on the BT-20.

TIP: The inside diameter of the ring can be made smaller and a tighter fit by applying a thin ring of glue on the inside edge. Let dry before sliding back on the BT-20.

Use a rotary punch to make slight relief notches for the engine hook and Kevlar line.

On top is the upper ring,

The bottom pic is the lower ring.

The Kevlar line is tied tightly around the BT-20 tube using a square knot. 

Note it goes under the top of the engine hook.

After tying the knot, rotate it around the tube opposite the engine hook.