John, I personally NEVER use swivels - but that is a personal choice. For shock cord on a rocket like that, the 1/2" tubular would work great - It is 7,200# test.

Shameless plug- you can get that for $1.25/foot with free shipping on orders of 30' or more from www.3dogsrocketry.com 😀

Thanks. How about rail buttons? Railbuttons.com is belly up.

Talk to me baby - I have stainless steel railbuttons for both 1515 and 1010 rail with stainless steel screws. $10 a pair for 1010 and $20 a pair for 1515. Got you covered.

make sure it is kevlar shock cords.

I used (used nylon) on one rocket and it seperated
at apogee.

Thanks Mike, I am going with Kevlar from 3 dogs and Warren I am interested in your railbuttons. Still in planning stages but I will take a pair of 1010's and a pair of 1515's. Thanks.

just be sure to get a well rated one. I use the Rosco ones from Fruity Chutes.

In my experience, they keep the main from wrapping up with the NC.

I've also not used swivels. Sort of a matter of taste.

Swivels that work and are capable of handling rockets over 3-5# are essentially unavailable in the hobby. The only source I know of is the sailing industry and they are extremely expensive as well as quite heavy. Given that several thousand pounds of force may be exerted during deployment in a rocket that weighs over 30#, you'd probably experience what I did - watching parts of your rocket come in ballistic while others go floating away towards the horizon.

For smaller rockets, there are some saltwater fishing swivels that rate up to 500# or so. I personally wouldn't use them for anything over a couple pounds.