shock cord material

so instead of using Kevlar and pay ridiculous prices and pre-made harnesses I opted out and started using fishing line. It's a lot cheaper, less weight and comes in a variety of tested strengths. It's easy to pack and doesn't tangle providing you know how to pack it. And to think how much money I wasted on Kevlar shock cords. What a joke.

I don't think I have ever wasted a dollar on rockets. Since it's a hobby that I love, I dont mind spending money on good items. I can see some of the braided fishing lines working okay, but only up to a certain point/weight.

And how does it handle the heat of an ejection charge.

And have you really "wasted" that much money on kevlar?

Eric makes a good point. I'm not sure how fishing line will handle the heat of an ejection charge.

You can get 200' of 100# kevlar on Amazon for $10.99: https://smile.amazon.com/dp/B01A9SU...mp-feature-scomp-wm-5&ref=aa_scomp&th=1&psc=1

That'd last a loooong time on my build bench.

I wouldn't trust any monofilament fishing line, as it's definitely NOT heat resistant. Some braided fishing lines are made of (or include) Kevlar, but it's a little challenging to figure out which brands do and which don't. I'd definitely be doing some testing with a high-temp heat source (aka. cigarette lighter) to see how they held up before trusting them for recovery duty.

Eric said:

I don't think I have ever wasted a dollar on rockets. Since it's a hobby that I love, I dont mind spending money on good items. I can see some of the braided fishing lines working okay, but only up to a certain point/weight.

And how does it handle the heat of an ejection charge.

And have you really "wasted" that much money on kevlar?

Click to expand...

Yes I wasted plenty of money on Kevlar if you must know and it holds up well with heat. Its a great alternative

beantownJPL said:

You can get 200' of 100# kevlar on Amazon for $10.99: https://smile.amazon.com/dp/B01A9SU...mp-feature-scomp-wm-5&ref=aa_scomp&th=1&psc=1

That'd last a loooong time on my build bench.

I wouldn't trust any monofilament fishing line, as it's definitely NOT heat resistant. Some braided fishing lines are made of (or include) Kevlar, but it's a little challenging to figure out which brands do and which don't. I'd definitely be doing some testing with a high-temp heat source (aka. cigarette lighter) to see how they held up before trusting them for recovery duty.

Click to expand...

I did some testing and I used a a lighter. Seems to be fine and no issues.

Sure as long as you only fly small, light, paper rockets on A, B, or C black powder motors. ANYTHING past that deserves better material.

AfterBurners said:

I did some testing and I used a a lighter. Seems to be fine and no issues.

Click to expand...

What type of fishing line are you using?

I was using dog barf and just your cheapo wadding and it works great, I just good down to Big 5 and pick the stuff up. You can also use those snap swivels which work great. Keep in mine I would use this on real heavy rockets, but I fly a couple AT kits on it. The 1.9 and 2.6" had no issues with a 29. Just trying to show you guys how to save a few bucks so you can use the money you save to buy other things like paint or finishing materials.

beantownJPL said:

What type of fishing line are you using?

Click to expand...

100lb test smaller rockets you could go with something less, say and A B or C

beantownJPL said:

You can get 200' of 100# kevlar on Amazon for $10.99: https://smile.amazon.com/dp/B01A9SU...mp-feature-scomp-wm-5&ref=aa_scomp&th=1&psc=1

That'd last a loooong time on my build bench.

I wouldn't trust any monofilament fishing line, as it's definitely NOT heat resistant. Some braided fishing lines are made of (or include) Kevlar, but it's a little challenging to figure out which brands do and which don't. I'd definitely be doing some testing with a high-temp heat source (aka. cigarette lighter) to see how they held up before trusting them for recovery duty.

Click to expand...

Yea- and that is WAY cheaper than high quality fishing line, like FIRELINE, and is MUCH stronger.

AfterBurners said:

100lb test

Click to expand...

Monofilament or braided?

Cory said:

Sure as long as you only fly small, light, paper rockets on A, B, or C black powder motors. ANYTHING past that deserves better material.

Click to expand...

I agree I'm NOT using this on a slug like a 4" and above. Something like that I would use maybe a 1/2" elastic or nylon cord 3" maybe a 1/4" elastic. Saves on weight ...saves on money. Why spend 25-45 bucks on a recovery harness. It's just a cord.

beantownJPL said:

Monofilament or braided?

Click to expand...

I used braided line

If you guys have concerns you can always fashion a nylon sleeve for the line. I know reading some articles here on recovery some of you have some sewing skills that would come in handy. The sleeve would be very small diameter and would get the job done. I never used a sleeve and haven't had issues. I just make sure I use plenty of dog barf or recovery wadding. Cheap and easy.

AfterBurners said:

I used braided line

Click to expand...

That makes sense, it probably is or has Kevlar or similar fiber. It would make sense since one of the selling points of braided line is abrasion/cut resistance ... one of Kevlar's main selling points. What brand are you using?

Also remaining thin and limp in higher test ratings ... another great property of Kevlar.

I just dont understand why now. If you have wasted so much money on kevlar. Then you have a huge supply of higher quality cord. Why go back to stuff ment for water and underwear. More power to you. Just dont see an ounce of logic to it.

Eric said:

I just dont understand why now. If you have wasted so much money on kevlar. Then you have a huge supply of higher quality cord. Why go back to stuff ment for water and underwear. More power to you. Just dont see an ounce of logic to it.

Click to expand...

Well, sounds like he's getting his braided fishing line cheaper than his source of Kevlar cord. He's tested it with a lighter ... didn't melt or burn. There's a really good chance it is Kevlar as a lot of braided fishing line is made of Kevlar. They don't care about its heat resistance, but the other properties of Kevlar are very good for fishing, especially when you're using higher test weight line.

Ok ... I've done a little research. Kevlar and Dyneema are two fibers commonly used in braided fishing line. Dyneema is actually the stronger of the two (15x stronger than steel vs. "only" 7x for Kevlar). They're both great in terms of strength and abrasion/cut resistance. Dyneema seems to be a bit more "slick", and will wear your fishing rod's line guides less, and will be a bit easier for knot-tying. However, only Kevlar has any appreciable heat resistance.

Kevlar "degrades" at 850F - it doesn't burn or melt. Dyneema on the other hand will melt at just 277F ... not a desirable quality where contact with ejection gasses is concerned.

So, it seems "fine" to use some brands or braided fishing line for shock cords, but you'd better test it first if you're not 100% sure what the line you're buying is made of. Break out your cigarette lighter ... if it melts, don't use it.

beantownJPL said:

Ok ... I've done a little research. Kevlar and Dyneema are two fibers commonly used in braided fishing line. Dyneema is actually the stronger of the two (15x stronger than steel vs. "only" 7x for Kevlar). They're both great in terms of strength and abrasion/cut resistance. Dyneema seems to be a bit more "slick", and will wear your fishing rod's line guides less, and will be a bit easier for knot-tying. However, only Kevlar has any appreciable heat resistance.

Kevlar "degrades" at 850F - it doesn't burn or melt. Dyneema on the other hand will melt at just 277F ... not a desirable quality where contact with ejection gasses is concerned.

So, it seems "fine" to use some brands or braided fishing line for shock cords, but you'd better test it first if you're not 100% sure what the line you're buying is made of. Break out your cigarette lighter ... if it melts, don't use it.

Click to expand...

And...I'm not using it in HPR etc. LPR - MPR Its an alternative in some scenarios.

just the standard

beantownJPL said:

What type of fishing line are you using?

Click to expand...

Just the standard braided line that Big 5 sells. I wasn't paying attention to the name. 100lb test

Just saying in stead of chutes you can make your own out of old t-shirts and some quality string. You want to use the thinner material type t-shirts. They also work great.

Another point.... For the "harness" on the Saturn V (so the top part comes down on an angle instead of command module down), I tried looking into fishing line. It was a monofilament and rated for 50#. I decided to do a comparison test against the chute cord Estes directs you to use. The fishing line broke with less than a 15# load, not the 50# it was rated for. I ended up returning it to the store....

And it also cuts like a knife being smaller in diameter...You can cut the legs off of plastic lawn chairs with regular 'ol dental floss..

So, I bought the spool of 100# Kevlar for $10.99 (Amazon Prime next-day delivery ... at least in my area) that I mentioned in one of my earlier posts on this thread. The brand is "Emma Kites" ... I assume their primary market is high-performance kite flyers.

I had previously been buying my Kevlar from Apogee who sells it "loose" for $0.34/foot - it'd cost $68 (plus shipping) to get 200' of kevlar from them.

I flame tested it, and it performs every bit as well as the stuff Apogee sells, and is just as difficult to cut with a pair of scissors. Both appear to be high-quality braided Kevlar line. The "Emma Kites" cord seems just a bit stiffer, which I've actually found to be very useful for manipulating through tricky spaces and for knot-tying.

I do try and support the smaller retailers like Apogee ... I buy a LOT of stuff from them. It's the small, passionate retailers that keep the hobby alive, but it seems silly to pay their nearly 7X markup for a functionally identical product.

That $70 savings will definitely translate into motors, kits and/or build materials out of Apogee's warehouse down the line.

Shock cord material differs depending on the type of rocket being built. For LPR and MPR rocketry i would still use the elastic rubber shock cord, the reason why i prefer the rubber shock cords over Kevlar, is they are easier to get for cheaper prices, also anyone can make/buy rubber bands and cut them. Another benefit to using rubber, is it always provided with rocket kits, now for larger build maybe the use of Kevlar may be more appropriate to use (higher temps). But overall the longevity and durability of rubber is almost the same as Kevlar but, it may not stand up to higher temps of ejection charges.

PS for LPR and MPR rocketry the likely hood of you replacing the shock cord in a month is slim, most likely before you ever have to replace the shock cord, you would of lost the rocket...

Yup, that's a tough one to justify. Probably geared more toward smaller scaled orders where it's not so noticeable..Cut charges do also apply (go to your local home store and discover a 1/2 sheet of plywood costs as much or more than a whole sheet) , as you've noticed it is not an easy thing to cut. Unlike poly material you can't simply heat seal the ends. I prefer to cut it with a razor or scalpel and a drop of ca holds the ends.

beantownJPL said:

So, I bought the spool of 100# Kevlar for $10.99 (Amazon Prime next-day delivery ... at least in my area) that I mentioned in one of my earlier posts on this thread. The brand is "Emma Kites" ... I assume their primary market is high-performance kite flyers.

I had previously been buying my Kevlar from Apogee who sells it "loose" for $0.34/foot - it'd cost $68 (plus shipping) to get 200' of kevlar from them.

I flame tested it, and it performs every bit as well as the stuff Apogee sells, and is just as difficult to cut with a pair of scissors. Both appear to be high-quality braided Kevlar line. The "Emma Kites" cord seems just a bit stiffer, which I've actually found to be very useful for manipulating through tricky spaces and for knot-tying.

I do try and support the smaller retailers like Apogee ... I buy a LOT of stuff from them. It's the small, passionate retailers that keep the hobby alive, but it seems silly to pay their nearly 7X markup for a functionally identical product.

That $70 savings will definitely translate into motors, kits and/or build materials out of Apogee's warehouse down the line.

Click to expand...

That's nice.
Emma kites is nice.
Do they drive their product to launches so it's available for you there ?
I sell an almost identical material.
Mine is 1/8" Tubular Kevlar.
I think it's 1500 lb rated, but I'd have to look it up..
You know there is no doubt it's top quality material if I deal with it at all.
That's a personal philosophy of mine "nothing but the best".
Cheap material or a less expensive manufacturing process or technique will come back and bite you one way or another.
Me posting here is a rare to never thing..
But I couldn't resist this because it's such a perfect example
that I keep my prices down as much as I can.
My product is not what you'll get elsewhere, and it's manufacturing cost isn't what a lesser product is..
I could cut corners and be lower in price.
I choose not too..
My manufactured harnesses are the best harnesses HP has ever seen in its history. Period.
This is not an inexpensive process, and is not said in a braggadocious manor.
It is a matter of fact that has been achieved over years of manufacturing thousands of harnesses with a passion for what they're used for..
My rant is over.
Here's the link to my equivalent product that's less expensive than Emma kites and Amazon and always has been.
( and you don't have to be a $100 / year Onebadhawk prime member or else I'll sit on your order for a week before I ship,
I generally ship the same or next day. But there can be extenuating circumstances that get in the way of that of course ).
https://onebadhawk.com/light-kevlar.html

Teddy

Wallace said:

Yup, that's a tough one to justify. Probably geared more toward smaller scaled orders where it's not so noticeable..Cut charges do also apply, as you've noticed it is not an easy thing to cut. Unlike poly material you can't simply heat seal the ends. I prefer to cut it with a razor or scalpel and a drop of ca holds the ends.

Click to expand...

Yeah, until now I would usually buy like 20' at a time when I'd be ordering other things. Defray the shipping cost and never sweatted the $7 or so for the shock cord. I'm sure lots of folks just buy the length they need when they order a kit or something ... certainly a convenience for people who only build a few models here and there.

Cutting with a blade is definitely the way to go. I also use a drop of thick CA to the ends to prevent fraying, and ALSO on my knots so that they'll never back out. I use thick CA because I find the thin wicks too far into the cord, making it very stiff. It can also damage elastic, so the thick CA gives a little more control when locking knots with it.

Matt_The_RocketMan said:

Shock cord material differs depending on the type of rocket being built. For LPR and MPR rocketry i would still use the elastic rubber shock cord, the reason why i prefer the rubber shock cords over Kevlar, is they are easier to get for cheaper prices, also anyone can make/buy rubber bands and cut them. Another benefit to using rubber, is it always provided with rocket kits, now for larger build maybe the use of Kevlar may be more appropriate to use (higher temps). But overall the longevity and durability of rubber is almost the same as Kevlar but, it may not stand up to higher temps of ejection charges.

PS for LPR and MPR rocketry the likely hood of you replacing the shock cord in a month is slim, most likely before you ever have to replace the shock cord, you would of lost the rocket...

Click to expand...

I only do L/MPR myself. I always toss the flat rubber shock cord that comes with most Estes kits. It doesn't stand up to ejection charge temperatures well, and it degrades over time. I've just had rubber band shock cords fail too many times. I've also had the three-fold shock cord mount fail on me a few times as well, so I don't use that anymore either except on minimum diameter rockets like the Hi Flyer.

On models where large shock loads aren't expected (light weight models, rear-ejection, streamer recovery, etc...), I usually just use a length of Kevlar, preferably anchored in the motor mount when possible, and tie on the nose cone and recovery device and I'm done. Its strong, light, long-lasting and doesn't get scorched by ejection gasses.

For models where some shock absorption is desired (Kevlar doesn't stretch much at all..), I usually create a Kevlar leader that I anchor either in the motor mount or ejection baffle, and bring that up just short of the top of the body tube. This helps prevent zippered tubes.

I'll also use some Kevlar to tie a harness onto the nose cone. Then I add as many feet of 1/8" round bungee cord ($19.99 for 100' at Amazon) as I need between them, and create a bight in the shock cord a few inches down from the nose cone to attach the 'chute to. This makes it easy to share chutes among several models, and avoids putting stresses on the end knot or nose cone harness.

I then use another length of Kevlar to lash down the tag ends of the bungee; this prevents it from a) being annoying while packing the chute, b) hanging up on anything or fouling the chute, c) allowing the knot to loosen over time, and d) the outer wrap from fraying.



Since switching to these techniques, I've never had a recovery failure attributable to either shock cord or anchor failure.

Onebadhawk said:

That's nice.
Emma kites is nice.
Do they drive their product to launches so it's available for you there ?
I sell an almost identical material.
Mine is 1/8" Tubular Kevlar.
I think it's 1500 lb rated, but I'd have to look it up..
You know there is no doubt it's top quality material if I deal with it at all.
That's a personal philosophy of mine "nothing but the best".
Cheap material or a less expensive manufacturing process or technique will come back and bite you one way or another.
Me posting here is a rare to never thing..
But I couldn't resist this because it's such a perfect example
that I keep my prices down as much as I can.
My product is not what you'll get elsewhere, and it's manufacturing cost isn't what a lesser product is..
I could cut corners and be lower in price.
I choose not too..
My manufactured harnesses are the best harnesses HP has ever seen in its history. Period.
This is not an inexpensive process, and is not said in a braggadocious manor.
It is a matter of fact that has been achieved over years of manufacturing thousands of harnesses with a passion for what they're used for..
My rant is over.
Here's the link to my equivalent product that's less expensive than Emma kites and Amazon and always has been.
( and you don't have to be a $100 / year Onebadhawk prime member or else I'll sit on your order for a week before I ship,
I generally ship the same or next day. But there can be extenuating circumstances that get in the way of that of course ).
https://onebadhawk.com/light-kevlar.html

Teddy

Click to expand...

Bookmarked! I'll keep you in mind for future purchases, especially as I start getting into bigger models. To date I've only built and flown up to BT-60 (except for my Saturn V) and E impulse engines. However, did recently acquire an "almost complete" rocket built from 2.5" heavy wall tubing, plywood fins and 29mm mount from my club's "garage sale" a little while back. Leaving that one for a winter project and fly it next spring.

I wish I had ANY vendor who would bring product to our launches. Unfortunately in MA, the hobby shops that deal with much in the way of rocketry are fairly few and far between and it's pretty rare to have one turn up at a launch. It's just not as popular of a hobby here as it is in parts of the country with more open space available. It's a shame really, but that leaves me MOSTLY fulfilling my needs online.

You definitely have a right to rant. As a participant in multiple niche hobbies, I fully recognize the need to keep small vendors such as yourself in business (my dad's actually a small vendor in yet another niche hobby...) and don't generally mind paying reasonable markup over what big retailers like Amazon can offer due to their volume. I never buy kits, motors or "specialty" items from Amazon - always either from someone like acsupply (Estes kits/motors), Apogee (Aerotech stuff, many build supplies, their kits, or other ones they retail), or directly from whatever bespoke kitter is offering the model (fliskits would be an example ... incidentally Jim Flis is a member of the same club as me).

I hear ya about the "Prime membership", but we share it for the whole family and definitely get the value out of it. It's more than just fast/free shipping though, as there are multiple benefits such as streaming movies and music, etc...