Sources for 1/8" wide elastic shock cord?

[Rktman]

Anyone know where I can buy 1/8" wide, flat elastic shock cords for LPR? Odd'l Rockets used to carry a flame resistant variety but don't anymore, and online searches haven't turned up anything.

 

[neil_w]

Amazon? https://smile.amazon.com/Dritz-Braided-Elastic-8-Inch-4-Yard/dp/B004KYZ5BQ/

Michael's and/or Joanne's might have it.

 

[jmasterj]

The local Walmart does too.

 

[Hobie1dog]

Hobby Lobby is where I buy mine in various widths.

 

[waltr]

ASP rocketry
https://www.asp-rocketry.com/ecommerce/Flat-Cloth-Covered-Elastic-for-Shock-Cords.cfm?cat_id=62

 

[cwbullet]

I would not recommend electric cords. They are better in underwear and not rockets. Use nylon or Kevlar.

 

[Rktman]

ASP rocketry
https://www.asp-rocketry.com/ecommerce/Flat-Cloth-Covered-Elastic-for-Shock-Cords.cfm?cat_id=62

YES! That's the stuff.

 

[Rktman]

I would not recommend electric cords. They are better in underwear and not rockets. Use nylon or Kevlar.

Sure hope you meant "elastic" and not electric.
Anyway, I use the elastic as a kind of "bungee cord" to absorb the shock of the ejection charge. I attach it between two points on the kevlar shock cord, leaving a length of loose kevlar between the elastic. Works really well to dampen the force of the ejection charge and drastically reduce snapped shock cords (I use it on my BG rear-eject system, which typically doesn't have as long a shock cord as the traditional front-eject motor pods).

 

[Rktman]

Thanks for all the feedback gents! Since Odd'l Rockets no longer makes their flame resistant elastic cords, I'm going to try making my own elastic cord "flame resistant" by soaking it in borax and boric acid. Seems to work well for homemade wadding after all.

 

[cwbullet]

Sure hope you meant "elastic" and not electric.
Anyway, I use the elastic as a kind of "bungee cord" to absorb the shock of the ejection charge. I attach it between two points on the kevlar shock cord, leaving a length of loose kevlar between the elastic. Works really well to dampen the force of the ejection charge and drastically reduce snapped shock cords (I use it on my BG rear-eject system, which typically doesn't have as long a shock cord as the traditional front-eject motor pods).

View attachment 562569

Ok. I have never found it needed but that is better than the Old LOC and Estes Midpower cords.

 

[BigMacDaddy]

These work great and seem quite flame resistant.
www.walmart.com/ip/Dritz-1-4-White-Braided-Elastic-Value-Pack-16-yd/306777509

I do agree that Kevlar is cheap enough to use for everything and takes up much less space.

 

[neil_w]

I would not recommend electric cords. They are better in underwear and not rockets. Use nylon or Kevlar.

Elastic works well in LPR and smaller MPR stuff. I don’t get the hate for it.

 

[ep29030]

I bought elastic for LPR kits in 1/8", 3/16" and 1/4" from Mandala on eBay. Could only get the 1/8" in black and white, but I got the rest in bright orange. Used to be able to get cotton elastic (flame resistant) but can't find it anymore.

https://www.amazon.com/Mandala-Crafts-Elastic-Braided-Crafting/dp/B089YXC7D4/

 

[ep29030]

Sure hope you meant "elastic" and not electric.
Anyway, I use the elastic as a kind of "bungee cord" to absorb the shock of the ejection charge. I attach it between two points on the kevlar shock cord, leaving a length of loose kevlar between the elastic. Works really well to dampen the force of the ejection charge and drastically reduce snapped shock cords (I use it on my BG rear-eject system, which typically doesn't have as long a shock cord as the traditional front-eject motor pods).

View attachment 562569

Another easy way to get some shock absorption on the fly is to bundle sections of kevlar strap (Z-folded) then wrap in a rubber band (or 2 or 3). The rubber band absorbs opening force as it is stretched and broken/flies off. Plus it helps to organize recovery train as you are packing the airframe. I use small, short rubber bands horse people use for horse manes.

 

[BEC]

Back in the day (say late 1960s), Estes used Sig Contest Rubber (for rubber powered airplanes). I have one model that's over 50 years old that still has a good rubber shock cord made from that lovely dark grey stuff.

Here is the current closest equivalent: https://www.faimodelsupply.com/product-category/tan-super-sport-rubber/

I won't live long enough to see if this stuff will last that long as shock cords. But I am now using their 1/8 and 1/4 inch stuff to replace shock cords (whether rubber or elastic) as needed, and in any new builds. I bought a 1/2 lb. box of 1/8 inch and it's probably a lifetime supply (seeing as I'm 67 now).

I can see that cotton-covered elastic could be a good choice as well.

 

[cwbullet]

Elastic works well in LPR and smaller MPR stuff. I don’t get the hate for it.

No hate. It may work well for you but for me, it just wears out to quickly, and I hate replacing it.

 

[Rktman]

Another easy way to get some shock absorption on the fly is to bundle sections of kevlar strap (Z-folded) then wrap in a rubber band (or 2 or 3). The rubber band absorbs opening force as it is stretched and broken/flies off. Plus it helps to organize recovery train as you are packing the airframe. I use small, short rubber bands horse people use for horse manes.

That's a really intriguing approach. I'm definitely going to try that technique on my latest build.

 

[augendoc]

Fabric covered shock cord is more heat resistant than bare material. If you can find cotton covered elastic, that adds a level of heat resistance over the usual nylon or polyester. This material is typically called swimsuit elastic. The only supplier of cotton clad swimsuit elastic I could find on Amazon was Dritz. I emailed them about their elastomer and they confirmed it was latex.

The stuff you want is cotton wrapped neoprene. The neoprene is more heat resistant than natural rubber and will hold up better for the long haul, unlike latex which gets brittle with age.

The only internet source of cotton swimsuit elastic where I have been able to verify the elastomer as neoprene is Sewsassy.com. Unfortunately, unless you want to buy wholesale, minimum order is 10 yards at about $0.53/yd and they add an extra $1.00 for orders totaling less than $15.00. Plus shipping, of course.

The absolute ideal would be cotton wrapped silicone rubber, which I am not sure anyone makes. The closest I have found is silicone rubber bungee material for collapsible tent poles, made by MSR. The wrapping is either nylon or polyester and the diameter is about 3.5 - 4 millimeters. Stretch-wise, this is about equivalent to 1/2” flat material. The silicone is heat resistant to 600 degrees F, is resistant to chlorine, oil, and solvents, and does not oxidize and break down with age.

Even with reliable materials, you should consider the elastic a replaceable item. Attach to a kevlar loop, inspect often, keep clean, and replace as needed.

If anyone knows of a reliable source of flat silicone rubber cotton-covered elastic in 1/8””, 3/16”, 1/4” or 3/8” sizes, please let me know.

 

[Rktman]

Fabric covered shock cord is more heat resistant than bare material. If you can find cotton covered elastic, that adds a level of heat resistance over the usual nylon or polyester. This material is typically called swimsuit elastic. The only supplier of cotton clad swimsuit elastic I could find on Amazon was Dritz. I emailed them about their elastomer and they confirmed it was latex.

The stuff you want is cotton wrapped neoprene. The neoprene is more heat resistant than natural rubber and will hold up better for the long haul, unlike latex which gets brittle with age.

The only internet source of cotton swimsuit elastic where I have been able to verify the elastomer as neoprene is Sewsassy.com. Unfortunately, unless you want to buy wholesale, minimum order is 10 yards at about $0.53/yd and they add an extra $1.00 for orders totaling less than $15.00. Plus shipping, of course.

The absolute ideal would be cotton wrapped silicone rubber, which I am not sure anyone makes. The closest I have found is silicone rubber bungee material for collapsible tent poles, made by MSR. The wrapping is either nylon or polyester and the diameter is about 3.5 - 4 millimeters. Stretch-wise, this is about equivalent to 1/2” flat material. The silicone is heat resistant to 600 degrees F, is resistant to chlorine, oil, and solvents, and does not oxidize and break down with age.

Even with reliable materials, you should consider the elastic a replaceable item. Attach to a kevlar loop, inspect often, keep clean, and replace as needed.

If anyone knows of a reliable source of flat silicone rubber cotton-covered elastic in 1/8””, 3/16”, 1/4” or 3/8” sizes, please let me know.

Thanks for all the research and info!

 

[SolarYellow]

Found cotton down to 1/4 inch.

https://goodsstores.com/products/natural-cotton-elastic-560-504-505?variant=30291713785927
Maker is old school USA and doesn't seem to have a web site. Google finds their phone number easily.

 

[SolarYellow]

More cotton down to 1/4 inch.

https://www.amazon.com/Dritz-Swimwear-Braided-Elastic-Natural/dp/B004KYZ700

 

[SolarYellow]

Jo-Ann Fabrics is having "doorbuster" online-only deals on small-package sizes of the 1/4 and 3/8 Dritz cotton swimwear elastic. It's latex, not neoprene, but it's cheap if you want to try some.

https://www.joann.com/cotton-swimwear-elastic-natural/11384351.html
https://www.joann.com/cotton-swimwear-elastic-natural/11384435.html

 

[Back_at_it]

This is what I use on my LPR rockets. Just be sure to have a Kevlar leader inside the rocket as a permeant attachment point.

Think of the elastic as disposable. Mine last about 8 to 10 flights then it's time to replace it but it's so cheap I don't care.

https://www.amazon.com/Coopay-Length-Elastic-Stretch-Sewing/dp/B07V9DWMP3/ref=sr_1_9?keywords=elastic%2B1%2F8&qid=1684526112&sr=8-9&th=1

 

[MidOH]

https://www.emmakites.com/collectio...vlar-line-utility-cord?variant=29193039806569
I ordered this in 550 and 2000#.

 

[Rocketjunkie]

I've bought it at Wal-mart https://www.walmart.com/ip/Dritz-1-8-Soft-Stretch-Elastic-4-yd/55283637?from=/search