Unprotected nylon tubular shock cord

[Steven88]

Good evening. I have launched my 5.5” diameter Loc Big Nuke one or two times without having protectors around my nylon shock cords. I am wondering if the ejection charge gasses pose a threat to them becoming brittle and breaking beings they were unprotected? I am wondering if I should purchase some new ones, especially since this rocket has been extended and weighs a few pounds more than the stock built. It would be cheap insurance if it would keep things together in the future.

Thanks in advance,

 

[heada]

I've used unprotected tubular nylon more than 12 times in a single rocket without a noticeable difference between flights. They'll get flash burns but the integrity isn't compromised.

There are kevlar sleeves you can put over the nylon but in my experience they're not required. If you swap for tubular kevlar, you'll need a much longer line compared to nylon.

 

[tjsnakez]

I have an old 5.5" nike smoke with tubular nylon that has more flights than I can count (over a dozen for sure). You can kinda tell when it needs to be replaced because it will become extremely crunchy and not just a little crispy haha technical terms here. You should be good for the foreseeable future.

 

[David Schwantz]

All above may be fine, but I have snapped a nylon cord before. It did show signs of heat fatigue.

 

[kalsow]

Duct tape wrapped around the bottom few feet of the shock cord works wonders .... and it's easy to replace when it show signs of scorching.

 

[David Schwantz]

hi Bill, what color is best

 

[Handeman]

I agree with @kalsow about tape. I find electrical tape comes off easier than duct tape and it's pretty cheap when you buy a 6 pack sleeve at Harbor Freight.

I have a PML Callisto that uses a 1" Nylon strap for the motor mount to piston connection. I have no idea how many flights I have, but I've been flying it since 2003. It's flown almost every launch I've been to and usually multiple times, so somewhere around 125 - 150 flights would be my guess. That strap is stiff and singed on the outside, but still going strong.

 

[cls]

Tubular nylon is so cheap, just replace it. Keep 50' of it around in your building supplies.

 

[cwbullet]

I agree with @kalsow about tape. I find electrical tape comes off easier than duct tape and it's pretty cheap when you buy a 6 pack sleeve at Harbor Freight.

I have a PML Callisto that uses a 1" Nylon strap for the motor mount to piston connection. I have no idea how many flights I have, but I've been flying it since 2003. It's flown almost every launch I've been to and usually multiple times, so somewhere around 125 - 150 flights would be my guess. That strap is stiff and singed on the outside, but still going strong.

You can also shrink-tube your knots and areas of concern.

 

[mtnmanak]

I have used nylon for years (usually with nomex protectors) and have not found any issues with material's longevity, as long as you take steps to protect it. It does wear out, but, as has been noted, it is very cheap compared to Kevlar, so it is still economical to replace it.

The main reason I have spent the past couple years slowly investing in a full set of Kevlar cords is space saving. Kevlar is simply far more compact and much lighter at similar strengths compared to nylon, which makes a big difference in smaller diameters. In many of my 3" and 4" diameter rockets, shoving the nylon and all the laundry into the payload bay was getting to be a challenge that Kevlar greatly reduced.

If you use nylon, take reasonable steps to protect it (tape or nomex protectors) and it will last you for years. If you want some space/weight savings, invest in Kevlar.

 

[MidOH]

Can you reach the attachment point on that rocket? On the Goblin I used a quick link, and can remove the cord to inspect it. I doubt tubular nylon will fail without plenty of wear warning.

 

[Onebadhawk]

I always recommend using simple masking tape on the nylon where it will be exposed to the bp charge..
It's easy to do, you always have it on hand at the launch, and when it's showing it needs a bit more you just add it..
I do make nylon harnesses, but use Kevlar myself.
The nylon will degrade to the point of making you uneasy about it before a flight..
Kevlar packs so much smaller, I just think Kevlar's more betterer all round..

Teddy

 

[MidOH]

I've used aluminum tape for that. It's at any ace hardware store for sealing ducts.

Makes for really cool looking metal thrust rings as well.

 

[kalsow]

hi Bill, what color is best

Hi Dave!

Well, unicorn, of course.
https://www.amazon.com/Duck-241704-...0260427&sprefix=duck+tape,aps,236&sr=8-9&th=1

 

[Rocketclar]

I, too, have used lots of tubular nylon. I have several PML pistons and the nylon webbing has stood up well for many flights. After every launch, I soak all of my recovery lines (nylon or Kevlar), blankets, shock cord protectors, etc in a bucket of water to get the acidic bp residue off. BTW...I buy my nylon at REI by the foot.

 

[Wayco]

I have several rockets that still have tubular nylon, one is my L3 rocket, a Darkstar Extreme. It has Nomex sleeve on the shock cords.
I failed my L2 flight with a broken tubular nylon shock cord. It had a couple of crispy spots that my inexperience assumed would be good.
Most of my rockets have kevlar shock cords, which I make up myself, with a few from OneBadHawk, because Teddy is my friend, and he makes good stuff.
I also wrap all my shock cords near the avbay with green masking tape, even kevlar. Black powder residue is nasty stuff.

 

[Pem Tech]

Tubular nylon is so cheap, just replace it. Keep 50' of it around in your building supplies.

The last time we restocked it was scarce as hens teeth. Ended up spending way too much for it.
Ohhhhh, for the days when spools of 9/16" TN flowed like water.