Estes V2 Build Part 13 Kevlar Lead

The instructions have you tie the rubber shock cord through a slit in the upper centering ring.
I'd rather use elastic instead of the rubber cord. The rubber would be too close to the ejection charge. I'll go with some doubled over 135 lb. Kevlar.

The centering ring will have to be reinforced. I wouldn't normally use Kevlar around a standard BT-50 engine tube but this is a thick walled tube.

Some scrap mat board would be used for reinforcement.
Circles were traced around a BT-50 and BT-60. Two quarter rounds will be used.

Here's how the reinforcement pieces will fit on the underside of the ring.
(This picture should actually be turned over so the Kevlar comes out the top.)

You normally wouldn't need reinforcement pieces but the slot is at the center of the ring. A single taut piece of Kevlar might tear through the ring.

This is actually one longer piece of Kevlar, looped around the tube.

Out the top the four strands of Kevlar are marked below the lip of the body tube.
The marks will be at the top of a tied loop.

This is the finished Kevlar leader from the underside of the centering ring.

1/4" elastic shock cord will be tied to the Kevlar loop.
With the Kevlar loop end right below the end of the tube, the shock cord can be easily replaced.
With the loops, this Kevlar should last longer than the rocket.