Elastic Shock Cord

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Jacob Denton - 31 Dec 2003 00:02 GMT

I'm a BAR building mid-power. I remember from my younger days that the Estes
kit elastic shock chords got brittle after a few flights and were subject to
sending my descending rocket in two different directions. My LOC Aura kit
has an elastic shock chord. Should I replace it with a Kevlar shock chord
from the getgo? I wonder if it's more likely to zipper with Kevlar than with
elastic?

TIA - Jacob

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Doc - 31 Dec 2003 01:03 GMT

> I'm a BAR building mid-power. I remember from my younger days that the Estes
> kit elastic shock chords got brittle after a few flights and were subject to
> sending my descending rocket in two different directions. My LOC Aura kit
> has an elastic shock chord.

Elastic belongs in your underwear, not your rockets. ;-)

Should I replace it with a Kevlar shock chord

> from the getgo? I wonder if it's more likely to zipper with Kevlar than with
> elastic?

Tubular nylon is the way to go. Use at least 15 feet.

> TIA - Jacob

--
Drake "Doc" Damerau
www.rocketmaterials.org
NEPRA President
NAR Section 614
NAR 79986 L3
www.nepra.com
Remove "My Shorts" to reply

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Dale Martin - 31 Dec 2003 02:12 GMT

Jacob,

DO NOT USE ELASTIC!!!! I did on a pre-production LOC A4/V2 3.9" and no
offense to Barry but this was extremely lacking. 1st flight certified L1
second flight broke and nose cone bit the big one, came in Ballistic from
about 1500 ft scared the heck out of us when nearly hit our vehicles. It
had a lot of shot in nose and carried quite a load on impact. Now use only
tubular nylon I got on ROL auctions a whole lot of it real cheap. About
15-20 foot should do nicely. Best of luck welcome back and
keep 'em flying!

Dale

--
Dale Martin
NAR 80678 L2
N0JFM

> I'm a BAR building mid-power. I remember from my younger days that the Estes
> kit elastic shock chords got brittle after a few flights and were subject to
[quoted text clipped - 4 lines]
>
> TIA - Jacob

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RayDunakin - 31 Dec 2003 02:55 GMT

<< My LOC Aura kit has an elastic shock chord. Should I replace it with a
Kevlar shock chord from the getgo? >>

I use a combination of kevlar and elastic. About half of the cord is kevlar,
which is the part that is attached to the rocket. It's heat resistant so it
won't burn through. Then I add a length of good quality "underwear" type
elastic (at least 1/2" wide) to that.
On larger rockets (4" diameter) I use 1" wide elastic.

Most folks these days skip the elastic altogether and just use a very long
length of nylon or kevlar cord.

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Ismaeel Abdur-Rasheed - 31 Dec 2003 07:17 GMT

unless I'm using an anti-zipper design (see below) I generally use
Kevlar to just past the body tube, then nylon tube from there

you could use all nylon, but then I'd recommend a Kevlar (Giant Leap) or
Nomex (Rebel Rocketry) shock cord sheath at the base

some anti-zipper techniques on shown on InfoCentral
at http://www.info-central.org/construction_antizipper.shtml

also peruse the recovery information there
at http://www.info-central.org/index.cgi?recovery

Doug at Pratt Hobbies has a good selection of Kevlar in small sizes for MR

at http://www.pratthobbies.com/sl.html
actually:
http://www.pratthobbies.com (left frame) -> Kevlar cords

Ed at Giant Leap has both Kevlar and Nylon tubing

at http://www.giantleaprocketry.com/products_recovery.asp
actually:
http://www.giantleaprocketry.com/hpdefault.asp (top) -> recovery
(then scroll all the way down)

also see the Rebel rocketry site
at http://www.rebelrocketry.com (left frame) -> Recovery

enjoy!

- iz

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Model Forum / General / Rockets / December 2003

Elastic Shock Cord