MX-774 Kitbash Post 10 Tying Shock Cord

Many already know this technique, but for some who may not know it:

Since Kevlar was used in rocket building, zippers have occurred. If the rocket is traveling too fast at ejection (too short or too long a delay) the Kevlar cord can can cut through the body tube. Kraft tubing is no match for the 5X stronger than steel Kevlar.

One solution is to tie the elastic shock cord to the Kevlar BELOW the top of the body tube.

Picture 1: Feed the Kevlar out the top of the tube opposite the engine mount. Just below the lip of the tube, mark the Kevlar dark enough so you can find the mark later.

Picture 2: Feed the marked Kevlar back through to the rear of the rocket body, all the way through the engine mount. Tie a tight loop knot with the mark at the center of the loop. You can see the mark in the center loop bottom.

Picture 3: Tie the Elastic Shock Cord to this loop knot in the Kevlar. Be sure both knots are tight and apply a small drop of glue to the knots to set them. Feed Both tied cords back through the mount and out the top of the body tube. Remember the post about the long tweezers?

Picture 4: Here's the "Zipper Proof" shock cord out the front of the body tube. Both the Kevlar and elastic shock cord knots are below the top of the main body tube.