kevlar vs rubber

[estes$$$]

does kevlar work better for a shock cord then rubber beacuse I keep snapping the rubber ones when the ejection blast goes off

how much more of a cost is it then rubber

where do i find it i heard it comes in sheets

[jadebox]

does kevlar work better for a shock cord then rubber beacuse I keep snapping the rubber ones when the ejection blast goes off

how much more of a cost is it then rubber

where do i find it i heard it comes in sheets

If they keep breaking, it's likely that your shock cord is too short. The ones included in Estes's kits often are too short.

Ideally, you want the shock cord to be long enough that it doesn't need to stretch. The parts of the rocket should slow down enough before reaching the end of the shock cord.

But that's not always practical in a small model rocket.

So, a good compromise is to use a length of Kevlar thread attached to the motor mount or shock cord mount and a length of elastic or rubber tied between the Kevlar and the nosecone/parachute.

Kevlar thread looks much like string that you might use for kite flying, but has a stiffer feel to it and is usually yellow. You can find it in various places including online rocketry vendors, places that sell tennis or fishing supplies, places that sell sewing supplies, and places that sell industrial supplies. The last place I got some from was McMaster-Carr (http://www.mcmaster.com/).

-- Roger

[Ltvscout]

does kevlar work better for a shock cord then rubber beacuse I keep snapping the rubber ones when the ejection blast goes off

how much more of a cost is it then rubber

where do i find it i heard it comes in sheets
Semroc also sells Kevlar which many people prefer over the elastic or rubber shock cords. You can find it here:

http://www.semroc.com/Store/Scripts/ProdList.asp?idCategory=69

[JRThro]

Or you always have the option of replacing the stock rubber band shock cord with a longer piece of sewing elastic. You can find that at Wal-Mart or craft stores like Jo Ann Fabric or Hobby Lobby, etc.

I generally use elastic that's the same width as the rubber band that came in the kit, either 1/8" or 1/4". The length I use is at least twice the length of the rocket, if not 3 times.

You can use the Estes paper tri-fold method with elastic shock cords, or you can attach the elastic to a length of Kevlar installed as someone else has described.