potential cord protector

[watermelonman]

I have some painters cloth that is hefty and at least somewhat flame resistant. I also have some shock cords that need protecting. Anyone think it would work fine, or be a particularly bad idea?

[video=vimeo;114083126]https://vimeo.com/114083126[/video]

My first thought is that the amount of heat tested in that video would have absolutely annihilated an Estes shock cord. Then I thought, even if a cord or parachute melts, maybe that is a better failure condition than embers staying within cloth and potentially setting the whole rocket aflame while descending to ground level. Also a shock cord would be more likely to get hit with embers and debris that quickly bounced off, while the cloth could hold them in and thus stay in contact longer, resulting in more fire potential.

Other thoughts?

 

[blackjack2564]

It would work fine if you soaked it in a solution of Borax [ or Boraxo Soap powder] and water for several hours, then dry.

I just use a section of the next larger TN [9/16 tn fish through 3 ft of 1in TN for protection] or wrap the cord with regular masking tape.

 

[ksaves2]

Mix 6 parts/lbs borax, 5 parts/lbs boric acid, 100 parts/12 gallons (45.4 L) water in a large container. Do the math for smaller amounts. I soak pieces of cardboard to make disposable/ejectable partitions and you can even wrap some around the shockcord closest to the ejection charge flash in lieu of a cord protector.
You can roll the cardboard pieces while wet as they get stiff and crack if you use it for a shockcord protector rather than attempting to rolling after they dry. Flat pieces make for good cutable partitions.

The good 'ol wrap the shockcord with duct tape is pretty decent too. I've hit the treated cardboard with a blowtorch and it simply carbonizes. Good protection for a flash situation. Kurt

 

[luke strawwalker]

First thing I'd recommend from experience-- DUMP the stupid Estes "rubber band" shock cords. The rubber tends to dry rot in a VERY short period of time. I've had a few Estes rockets pop the cord when the parachute opened, one on its SECOND flight! Core sampling from apogee and streamlining in does bad things to your rocket, trust me.

I would HIGHLY recommend replacing the rubber band crap Estes puts in their kits with regular sewing elastic from WalMart. I typically use 1/4 inch elastic, though for smaller, lighter rockets, there's round or 1/8 inch flat elastic as well, which will take up a lot less room inside a small rocket. I also recommend at least DOUBLING the length from what Estes puts in their kits. At least three times the rocket body length is a good starting point. You can't really have too long of a shock cord (so long as it will fit inside the body tube with the parachute and wadding/chute protector/whatever you use to prevent them being burned at ejection, but you can DEFINITELY have too short of a shock cord! Estes cords are typically at the very edge of too short, to WAAAAY too short!

As for "protection", unless the rocket is particularly short (putting the cord particularly close to the upper end of the motor) I've found that there really isn't much need for "protecting" it, so long as you're using a good amount of wadding, dog barf, or whatever to protect the chute and recovery gear from ejection.

Good luck! OL JR