I really like "bungee cord"..............

............That is for lighter mid -high powered rockets. Had my 14 year old NC Big Brute come in ballistic for about 1500ft yesterday, and at about 400-500ft the ejection charge finally fired. The rocket recovered perfectly, no damage to anything.

I have used small diameter bungee (bought at EMS) in some rockets. Pros: It's much more durable and heat tolerant than flat elastic. Con: Boy oh boy, does it ever store energy when it is stretched. :y:

I use the flat, 3/4 inch on the Big Brute (15 ft. long) and use a Nomex sleeve on the bottom 12 inches. I use dog barf with all my elastic shock cord rockets, rather than a chute protector. Depending on the rockets size and weight I use between 1/4 - 3/4 in. and make the length as long as possible for a comfy fit.

I've decided that elastic should be heavier than typically used. I've seen stressed-out elastic, especially around knots, and in flight it appears to reach its full length best I can see. I had troubles keeping a heavily weighted nose cone attached to a rear-ejection rocket, as though the deceleration still had a very high peak despite the elastic. OTOH I have had some pretty amazing recoveries that I don't think would have gone well without elastic, even using rather lightweight stuff. Anyway I think 3/4" sewing elastic could be preferable on rockets as little as 1 pound, rather than the 3/8"-1/2" typically used (wider is also usually thicker). HPR can still benefit from elastic, but yeah you're talking bungee cords, multiple thick bundles possibly. Since this makes it huge if also very long, use Kevlar for length. Sewing elastic has poor elastic properties anyway, it's equivalent to a short length of perfect spring plus a longer part of nonelastic. On the plus side, its breaking point is far beyond its elastic force limit.

Or if you use coaxial Kevlar or nylon braid, you can always use an 80% length of elastic cord inside the coaxial braid to absorb the opening shock without much rebound. Best of both worlds.

Bob