Shock Cord Material

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Andy Greene

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Sorry if this has been gone over a 1000x ,
Im at the point in a scratch build that I need to consider shock cord material- in the past I have used 4 mm 550 paracord , and never really had any problems even though it isn't flame proof.
I usually add a Nomex square and a little dog barf. Just wondering out loud if there is an "off the shelf " option I can pick up today, that may be a better way to go ? My only concern with the paracord is - over time - will I have an issue ? The rocket itself will never see more than a G80 and its not real heavy at all, its the potential repeated burns that I worry about. I kinda like to get the mount installed today :rolleyes:
 
Sorry if this has been gone over a 1000x ,
Im at the point in a scratch build that I need to consider shock cord material- in the past I have used 4 mm 550 paracord , and never really had any problems even though it isn't flame proof.
I usually add a Nomex square and a little dog barf. Just wondering out loud if there is an "off the shelf " option I can pick up today, that may be a better way to go ? My only concern with the paracord is - over time - will I have an issue ? The rocket itself will never see more than a G80 and its not real heavy at all, its the potential repeated burns that I worry about. I kinda like to get the mount installed today :rolleyes:

Consider a spool of braided Kevlar string from Amazon. Or a couple spools of different diameters and load bearing ratings.
It's heat and [FONT=&amp]abrasion [/FONT]resistant, and insanely [FONT=&amp]durable.
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The only downside (upside?) is that it's kinda hard to cut to size.

https://www.amazon.com/gp/product/B01850OST0/?tag=skimlinks_replacement-20
 
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I just picked up some of that stuff in the 380lb strength. It's a little thinner than I expected but should be great for LPR....unfortunately, I'm planning on running it in an estes mid power bird so......we'll see how it goes. I assume as long as I use a long enough length of it, by the time it pulls tight, the force will be plenty low.
 
I've had a few kits with only 9/16 tubular nylon. No issues. I use para-cord in a lot of my birds. I do, however, have a roll of 1/8" Kevlar cord, what I put in the lower (inside the BT) portion of the shock cord. the other / upper 2/3rds of the length is para-cord. cost & stretch is the reason why.
 
As far as the off the shelf and pick it up today, well I'm a bit late anyway, but it depends on what kind of shops you have available in your area.

Have you ever heard of mule tape? It's flat braided kevlar, nylon, polyester, maybe even fiberglass. Electricians use it to pull wire through conduit, measure conduit and various other things. If you have a good industrial supply store around you may can grab some locally. Grainger, Home Depot, maybe Fastenal. Maybe find an electrician shop, they may have scrap they'll spare. No anyone who works in a paper mill? Usually can find it there.
Local kite store may have kevlar.
Some tree/landscaping places have different kind of straps for lifting, anchoring, etc.
Upholstery shop may have heavy duty stuff.
Somewhere that sales bowfishing/spearfishing supplies may have kevlar line.
 
It depends on how big your rocket is. For anything I've built up to MPR, I use .25 inch elastic that I bought in an entire spool at Hobby Lobby some years ago.. When I get nervous that it might not be strong enough, I also use a longer length of Kevlar so that it only "works" once the elastic has fully (or almost) fully stretched.
 
Check out One Bad Hawk Recoveries webite, Teddy carries 1/8" tubular/woven kevlar and smaller diameter. I have some 1/8" kevlar I use many of my MPR and smaller HPR builds it works great.
 
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