We carry cord made from Kevlar
®, which is stronger than steel, but flexible and heat resistant. So, it can easily take the scorching heat of the rocket engine ejection charge. We recommend the shock cord in your rocket be a minimum of three times the length of the model. Longer is better, as that will help prevent zippering, which is a tearing of the tube by the cord cutting into the paper. A long cord allows the nose cone to slow down and prevent it from cutting the tube.
The Kevlar thread and cotton string are useful for parachute suspension lines. The cotton string is thick like carpet thread (Estes style string), and is great for when you're working with younger kids. Thin string can be harder for children to easily handle.
The Kevlar thread is great for competition style parachutes where weight is critical. It is the thinnest of all our materials, and is very strong.