Nomex Sleeving

Hello,

I'm just curious to know if anyone uses nomex sleeving around their shock chords as an extra layer of protection from the high-temp ejection gasses.

Was thinking about using it for the first 12" or so closest to the motor tube.

What are your thoughts?

Here is a link to the nomex for your inspection.

https://www.cableorganizer.com/nome...P03mNdS3ZDkdTss4XSaipLI7K_k2WjShoCTpUQAvD_BwE

Thanks,

Keith

I've used Nomex sleeves for years that my wife sewed out of Nomex fabric from used US Forest Service pants. Before she sewed them, I bought Nomex shock cord sleeves from rocketry companies. I think Top Flight probably makes some that slide right onto tubular nylon shock cords.


Steve Shannon

As Steve suggests-most use nomex sleeves from rocketry companies. The typical price for a 1 inch wide 30 to 36 inch long nomex shock cord protector is $10 to $14. Also, as CJ recommends (https://www.rocketryforum.com/showt...R-3-OR-ANY-GLASS-KIT-BUILD-quot-STARTS/page10 ; frame # 271) wrap the shock cord loop with 2 layers of tape for a 10 to 12 inch length. I've found that for "aggressive" BP charges, the addition of tape helps to prevent damage to the cord even when a nomex cord protector is used.

Fred, L2
ICBM member, Camden,SC
KG4YGP

I got a length of sewn nomex sleeving with my Talon 2. sadly, it didn't' fit the tube, so I left it out. I have used a length of silicone impregnated fiber sleeving (used to protect wires in hot environments & sharp edges - "liberated" from work!). And recently I typically add a layer or two of shrink tubing, to help secure the knot.

But really, of all the rockets I've flown, I've never really seen a need for that extra level of protection,. if anything, add a lower length of Kevlar.

I had a MP rocket that had well over 50 flights. the 9/16" tubular nylon shock cord was nicely scorched but never burnt thru. The Estes shock cords tend to burn thru after a few launches though.. Now, I add a length of Kevlar to the lower / internal section of those builds.

I used to be an offshore kayak fisherman. Sharks were always fun to catch. From those days I have about 100 yards 3000# rated braided wire I used to make shark leaders out of. Now I use that wire for my motor ejection rockets for the "in the booster tube" section of the recovery system. For the connections I use double crimps and then coat the crimps in epoxy. The wire leader goes from the eye bolt in the fore centering ring to about 2 inches shy of the end of the booster tube. Then I attach the recovery harness. No need to protect the wire leader from an ejection charge.... at least not yet.
And if I ever get a zipper, it'll be a really clean zipper. :wink:

The wire protecting sleeve the original poster linked to is not a fine enough weave for our purposes in rocketry..
When it expands you can see right through it...
To get a piece that doesn't need to expand is cost prohibitive and it's still a loose weave to allow for expansion...
Wildman makes Nomex harness protectors that are a very dense Nomex material..
Perfect for rockets ..
And they aren't expensive at all..
Why bother with something else ??
Don't you like your local vendor at your launches ??
If you'd like him to keep coming,,
you have to show him he is needed...
I hope no one minds my saying so,,
but sometimes I see people cutting out their local vendor to save less than they have to spend on shipping.......

Teddy

I always use the regular Nomex sleeves purchased from rocketry companies, typically on the first foot or two of the harness. I usually slide it over the quicklink or eyebolt which helps keep that a bit cleaner too.

If you have it long enough it can protect the harness from the edge of the airframe. I have heard of high flights where windmilling has effectively cut through the harness. The Nomex protector puts an extra layer of protection in place. I also sometime run the harness loop long and knot it outside the bay. That gives twice the amount of harness that would need to be worn through. The bowline is more accessible too.

I have two big rockets with the Nomex sleeve at both ends of the avbay. For larger projects where you want the stretch factor of tubular nylon, this is a good fix. So many of my projects have limited space and are optimized for weight, and the only answer for that is Kevlar. As long as you have bulletproof anchor points, you don't need the stretch that tubular nylon gives you. Since my first attempt at L2 failed due to a crispy spot on the TN shock cord, I tend to use kevlar, and wrap some 3M green tape on it at the avbay end.
This stuff is amazing:
https://www.acehardware.com/product/index.jsp?productId=19709256

Or....for something completely different and very effective....thick-wall heat shrink.
Doesn't fold up nice, but shrugs off BP charges....

What about wrapping the cord with a layer of teflon pipe tape? Secure each end with heat shrink tubing (or tape). The stuff for gas is thicker.