Kevlar is very heat-resistant, which makes it an excellent candidate for model rocket shock cord material. It won't be bothered by hot ejection gases. As an added bonus, it is long-lasting. It will easily out-live nylon or elastic shock cords.
This high-tech shock cord material is offered for sale in custom lengths, or in 10 ft packages.
Want to buy a different length? Order per foot, $0.25/ft. Enter the desired length, in feet, below.
Can't decide which kind to buy? These answers to popular questions may help.
How strong should my shock cord be?
It needs to be able to hold the weight of the rocket, even if the parachute deploys at high acceleration.
Example: a 2 pound rocket deploys the parachute early, while undergoing 10 G's. Multiply the weight of the rocket times the G forces.
In this example : 2 x 10 = 20 lbs of force. The shock cord must have a tensile strength of at least 20 lbs.
As this example clearly illustrates, the Kevlar shock cord materials for sale here should be strong enough for just about any low or mid power rocket.
How long should a Kevlar shock cord be?
As a rule of thumb, the shock cord should be 2-3 times as long as your rocket. This largely depends on which rocketry hobbyist you ask, there is no real consensus.
For a model rocket that is 2 foot long, a Kevlar shock cord could be from 4 to 6 ft long. Personally, I prefer to err on the side of caution and strongly recommend going with 3 times the body length. For the same 2 foot rocket, that would be 6 ft.
Using a shock cord that is too short can result in damage to the body tube (zipper) at the time of ejection. Worse yet, it can prevent successful parachute deployment.