Fire retardent

Anyone ever tried spraying shock cords with fire retardant?

Yes. I buy the tubular kevlar kind. I spray that shock cord right into my rockets.

I dont treat my nylon shockcords with anything, but i do put a strip of ductape on the 6-8" close to ejection charges

Eric said:

Yes. I buy the tubular kevlar kind. I spray that shock cord right into my rockets.

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You know what he meant..

While I have never treated the shock cords, I have used a mixture of boric acid and borax dissolved in water to treat cotton canvas for use as chute protectors.

+1 on tubular nylon...I wrap 12"+ from the ejection charge with masking tape. Don't forget the portion that passes through the eye bolt. I have also used larger tubular kevlar around the nylon, but end up masking taping both ends anyway.

Jeff Curtis said:

Anyone ever tried spraying shock cords with fire retardant?

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Combustion isn’t the problem.

Even with fire retardant, the ejection charge still melts Nylon at 515 °F.

I suppose you could use flame retardant over cotton or linen, but then your shock cord would be significantly weaker than Nylon.

I seem to recall Wool is naturally fire retardant... and even more inappropriate for a shock cord.

Though I remember an article about chains of slip knots allowing any cord to be far tougher than the cord alone... as long as the knot doesn’t pull out.

That might make for an interesting science project. Sadly, my son is too young for daddy to help out with a science fair.

I wonder if Starlite could be modified to be infused into fabric.

The chain of slip knots is to act as a shock absorber with very low rebound. It allows dissipating the impulse over a longer period of time, therefore the force is lower.

Gerald

I got a bottle of the spray stuff, soaked one nylon cord with it. Won't be able to try it till April though

Jeff Curtis said:

Anyone ever tried spraying shock cords with fire retardant?

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Jeff I realize this is an old post here's a link on I how treat my shock cords.
https://www.rocketryforum.com/threads/fire-resistant-estes-elastic-shock-cords.156743/

Applying a fire retardant is applying a chemical concoction to a solid in the hopes of improving fire resistance. But, people here are looking at applying fire retardants to things that might not have been the originally intended material.

Shock cords are structural items. If you are going to apply a chemical to them, then you need to ascertain what this does to the structural properties. As a for-instance, apply oil to nylon. Wait a few years. Pull it apart with your bare hands.

Gerald

Jeff Curtis said:

Anyone ever tried spraying shock cords with fire retardant?

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Yes.

Unfortunately, no longer available.

G_T said:

Applying a fire retardant is applying a chemical concoction to a solid in the hopes of improving fire resistance. But, people here are looking at applying fire retardants to things that might not have been the originally intended material.

Shock cords are structural items. If you are going to apply a chemical to them, then you need to ascertain what this does to the structural properties. As a for-instance, apply oil to nylon. Wait a few years. Pull it apart with your bare hands.

Gerald

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check out this shock cord that's been in use for years with no problems.

complex solutions to a simple problem...begging for a failure.....

just use kevlar.

cbrarick said:

complex solutions to a simple problem...begging for a failure.....

just use kevlar.

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+1, and the retardant solution only protects them from actually burning, not from the heat itself which is what damages nylon and elastic the most.

rharshberger said:

+1, and the retardant solution only protects them from actually burning, not from the heat itself which is what damages nylon and elastic the most.

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This is what I was wondering. Actual burning does not seem to be the problem, but I've certainly had elastic shock cords get charred and significantly damaged when the chute gets jammed. Untreated elastic seems to do just fine when the ejection works correctly. I *do* use Kevlar from motor mount to just before the end of the BT, so all my elastic is always on the safe side of the wadding.