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-   -   Kevlar Cord (http://www.oldrocketforum.com/showthread.php?t=18225)

chrism 12-17-2019 09:28 AM

Kevlar Cord
 
Hey guys would this Kevlar cord from Emma kites work as shock cord mounts?

https://www.amazon.com/emma-kites-1...s/dp/B01CXPGN1E

jetlag 12-17-2019 10:29 AM

Absolutely! I use it in every build. I tie a loop at just shy of the front end of the BT, then attach the elastic shock cord to the Kevlar loop using a loop I made in the elastic. Having them attach that way helps to minimize any zippering and is easier on the body tube end. The Kevlar will slice through the BT otherwise.

Hope this helps!

I do love their pricing for this Kevlar cord and the various sizes available. Just don't be in a big hurry, as my orders came across the ocean!

Allen

astronwolf 12-17-2019 11:38 AM

The Emma Kites braided kevlar cord is good. I like the 500-lb. cord for model rockets. It's narrower and more pliable than 1/8" elastic, so it packs into the airframe easily.

jeffyjeep 12-17-2019 04:14 PM

It's what I use also. 100 lb. for 18mm engines, 500 lb for 24mm and larger engines. I anchor it to the engine mount assembly.

ghrocketman 12-17-2019 07:06 PM

I just go with 500lb for everything.

LeeR 12-18-2019 12:24 AM

I have 100 lb. for little rockets, the bigger rockets get heavier cord. I believe itís 350 lb.

jeffyjeep 12-18-2019 09:50 AM

Another thing to consider is to try to get Kevlar that's NOT waxed. The unwaxed keeps knots much better. I've used both and I won't use waxed Kevlar again.

astronwolf 12-18-2019 10:43 AM

The Emma Kites cord on Amazon is not waxed.

tbzep 12-18-2019 10:57 AM

Quote:
Originally Posted by jeffyjeep
Another thing to consider is to try to get Kevlar that's NOT waxed. The unwaxed keeps knots much better. I've used both and I won't use waxed Kevlar again.

Surely there's a navy knot that can handle waxed kevlar. :p

jeffyjeep 12-18-2019 03:02 PM

I use a bowline and/or a lark's head knot for almost everything rocket related and the waxed Kevlar can destabilize either one because the wax acts a lubricant.

tbzep 12-18-2019 03:26 PM

Quote:
Originally Posted by jeffyjeep
I use a bowline and/or a lark's head knot for almost everything rocket related and the waxed Kevlar can destabilize either one because the wax acts a lubricant.

We've been told in the fire service that the bowline, while excellent for natural fiber rope, isn't so hot for synthetic. We are supposed to use a figure eight now. I still use bowline when I am tying it around something, but the figure eight on a bite is super easy for making loops. I'll have to get some kevlar out and fool with it.

I had to look up lark's head. I use it for some stuff but I don't remember learning it, much less naming it.

ghrocketman 12-19-2019 04:49 PM

I use unwaxed kevlar exclusively.
I soak the knot with epoxy and have never had one let loose.

bernomatic 12-23-2019 02:49 AM

I've been using the World Fairs Knot now for about 5 years and have not had any issues.

jeffyjeep 12-23-2019 08:30 AM

Quote:
Originally Posted by bernomatic
I've been using the World Fairs Knot now for about 5 years and have not had any issues.


I like it! Itís almost a hybrid of the bowline and the larkís head. Iím going to try that on my next coneó which is a Russian BUK missile.

PaulK 12-23-2019 06:26 PM

Quote:
Originally Posted by bernomatic
I've been using the World Fairs Knot now for about 5 years and have not had any issues.
I've never seen that one, I'll have to give it a try too!

electromag.11 04-11-2022 10:10 PM

So use both elastic AND kevlar?
 
Quote:
Originally Posted by astronwolf
The Emma Kites braided kevlar cord is good. I like the 500-lb. cord for model rockets. It's narrower and more pliable than 1/8" elastic, so it packs into the airframe easily.


I'm considering buying some Kevlar cord - but I should use elastic too?

Is there any way you could post a pic to show this?

jeffyjeep 04-12-2022 08:55 AM

Quote:
Originally Posted by electromag.11
I'm considering buying some Kevlar cord - but I should use elastic too?

Is there any way you could post a pic to show this?


I guess it depends on who you ask. If your Kevlar cord is very long than you might not need elastic also. Personally, I only use the Kevlar as a leader and tie the elastic to it just inside the open end of the body tube so the Kevlar doesnít slice through the body tube at ejection.

ghrocketman 04-12-2022 10:15 AM

Use both just as jeffyjeep above describes for up through "G" power.
Anything HPR just use Kevlar, in a LONG length.

tbzep 04-12-2022 10:19 AM

Regardless of your choice, go long. The "Estes dent" can happen with straight kevlar and with shock cord, but the longer it is, the better chance for drag to dissipate some of that energy so it won't rebound hard.

electromag.11 05-29-2022 09:33 PM

Good tip!
 
Quote:
Originally Posted by jeffyjeep
I guess it depends on who you ask. If your Kevlar cord is very long than you might not need elastic also. Personally, I only use the Kevlar as a leader and tie the elastic to it just inside the open end of the body tube so the Kevlar doesnít slice through the body tube at ejection.


Thanks for the information!

barone 05-30-2022 07:46 PM

Quote:
Originally Posted by tbzep
Regardless of your choice, go long. The "Estes dent" can happen with straight kevlar and with shock cord, but the longer it is, the better chance for drag to dissipate some of that energy so it won't rebound hard.

In the day, long was considered three times the length of your model....

electromag.11 05-31-2022 03:36 PM

Three times the length of your model.
 
Quote:
Originally Posted by barone
In the day, long was considered three times the length of your model....


I've seen that multiple times, so I'll use that going forward. Thanks!


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