New Source for Kevlar Thread and shock line

[Micromeister]

McMaster-Carr supply company www.mcmaster.com (phone 732 329-3200)
These fine folks have three kevlar thread and line sizes we can use.

For chute shroud lines:
#8800k41 thread size #69 (.014" dia) 28lb break strength 300yds @ 10.82/roll = .012/foot

For Shock Cords:
#8800k42 thread size #207 (.025"dia) 90lb break strength 100yds @ 10.02/roll = .033/foot

#8800k43 thread size #346 (.038"dia) 130lb break strength 66yds @ 9.92/roll = .05 foot

these spools packaged lines are twisted strand, and CA well, the 90lb is teh same dia as the 70lb braided Stren fishing line l've been using but about half the price.
Hope this helps

 

[astronboy]

Thanks!! I was almost out of Kevlar shroud line, and was just about to place an order at .10 a foot!! I just ordered a 300yd spool of the 28#, and a 100 yd spool of the 90# for shock chords.

 

[Cajunman06]

Thanks! I use this catalog almost daily and it never crossed my mind to check there.....I did just score some 370yds of 43lb (size 138) Kevlar thread off of Ebay. McMaster is slightly cheaper though. They've also got Kevlar fabric as well as other heat resistant fabrics that could be used for recovery protection.

Thanks for the tip!

 

[rocket trike]

Is this stuff twisted or braided. I am looking for the braid kevlar thread. Apogee carries it at $.10 a foot. Has any one use the twisted stuff for chutes

Tom

 

[astronboy]

It is twisted. I have been buying this thread from BMS for .10 a foot, and it works fine for chutes.

 

[powderburner]

I posted this info a while back in the 'scratch built' forum

Brownell makes a couple of archery bow string materials that you should check out. The first one is 'B-50' dacron, 0.018 diameter, 49 to 50 lb test. Available in black, white, green, red, yellow, blue, bronze, brown. A four ounce spool holds about 1100 feet and costs about $7 or $8. Try contacting FS Discount Archery in Tustin Calif at 800-824-8261 or online at fsdiscountarchery.com. Or try contacting 3 Rivers Archery in Ashley Indiana at 260-587-9501 or online at 3riversarchery.com. Or try Valley Traditional in Whitewater Colo at 970-243-8144 or online at valleytradarchery.com.

The cost of this stuff works out to less than .007 cents per foot (about HALF the cost of kevlar), it is waaaay stronger, and it is available in colors of your choice

 

[crashinj]

Powderburner how does that stuff take heat? Thats my main corcern on it, otherwise sounds good.

Crashin J

 

[jflis]

FlisKits offers a limited selection of Kevlar.

What we have up for retail is a set containing a 10 foot length of #35 and a 10 foot length of #8 for $1.05

If other lengths are desired, it would be no problem putting something together for 5-8 cents a foot

jim

 

[Micromeister]

No unfortunately Dacron doesn't stand up to much heat or flame, but hey; we're still using wadding right? My late father and I used to make our own Bow strings and alum. / or fibreglass arrows also powderburner, I think I still have a dozen alum field arrows, a half doz broad heads and my OLD full recurve 50lb Redwing hunter that hasn't been strung in at least 5 years. Ah yet another thing I miss since they closed the range. Anyway Decron and nylon string materials were one of the first items tried for shroud lines. They will work fine if you protect them well.

 

[powderburner]

Originally posted by crashinj
Powderburner how does that stuff take heat? Crashin J

It takes heat better than the sheet plastic the canopy is made from.

I don't know how to quantify the heat-resistance qualities of these materials. If you hold a burning match under it, will the Dacron burn through? Yes. So does Kevlar.

I have used this stuff for quite a while, along with cheap dime-store kite string. I don't have heavy loads on my 'chutes as I only do low power stuff, so I cannot answer for other applications.
I have also used Dacron as an internal shock cord anchor (tied to the motor mount, and using enough length to reach outside the body tube to tie on the shock cord) but give the string a quick coat of white glue before assembly.

I have never had the string burn through, either as an anchor or as a shroud line.

I don't know how else to answer your question, hope that helped?

----Dave Landgraf

 

[Micromeister]

Dave:
While I agree with you on the use of Dacron as Shroud lines for chutes. as long as they are well protected from the ejection gases. Actually its 36% elongation property is possibly a good thing for shroud lines. I must say you are living on borrowed time using Dacron as a shock cord mounts. Dacron has only a 340 degree maximum temp rating which is well under the burst heat of a BP ejection charge. Kevlar has a 600 degree working temp and 800-900 degree decomp. temperature. Kevlar is a much better choice for shock cord mounts.

 

[powderburner]

Actually, this bowstring Dacron only has a few percent stretch, an even then it is only under sustained load. This particular stuff is nowhere near 30+% or my bowstrings wouldn't work.

And the string characteristics may truly be way under the temperatures produced from BP ejection charges, I would defer to your data on that. However, I still question how much thermal energy is actually transferred into the anchor during the (very) short duration ejection flash, and whether that is enough to raise the temperature of the anchor line anywhere near melting. I just know that in my experience, these lines (coated with glue) work fine---they last longer than the rest of the rocket.

 

[Cajunman06]

This idea of coating the cord with glue is a new one to me. Seems like it would result in it being stiff. Guess I will have to experiment.

 

[Micromeister]

As an engineer I'd think you would have looked up the properties of the material by now.
If its a blend... what is it? If not then it is Decron like the Dupont Dacron developed back in the 1950's (ethylene glycol & terephthalic acid) which has an elongation to break strength of 36%. If it is Dacron' I've used the same stuff for Bow strings for a long time also. I have personally had shock cord mounts of dacron, nylon, polyproplene, elastic , and several other materials coated in white glue, carpenters yellow cement, epoxy and embedded in liquid nails fail at, or just above the motor mount/coating attachment points specifically "burned off".
What we are desputing here? Is the Likelihood for a failure of the shock cord mount, lose of the nose cone and chute and possible damage to the remaining body of the model worth worring about for less then a quarter (25cents). I don't mean to be argumentative but is seems to me Kelvar is by far the best choice for shock cord mounts anchored to the motor mounts in model rockets.

 

[airforce]

Micro, Thanks I've been reading these post and the first question in my mind was 'what about the heat???' Kevlar for me.

 

[powderburner]

If Kevlar makes you feel better, by all means use it. I haven't used it much simply because I didn't have any, else I probably would have tried it too. I was simply trying to suggest some less expensive alternatives, but two bits of Kevlar may be money well spent.

Most of my flying back in the 60s and 70s was low-power sport or contest (duration) stuff, and I was going for light weight where I could, in order to stuff in a bigger chute. Anyway, I flew lots of those old birds without problems with burned string.

I have also noticed a tendency for some modelers to 'overbuild' their birds a bit (or a bunch). At the first hint of a question of strength or durability, talk seems to go straight to fiberglassing, plywood fins, and the like. That is probably truly necessary for high-power stuff, but I have had very few failures with well-built rockets under D-E-F loadings. I have always been a big fan of simple, easy, and cheap.

 

[astronboy]

I cannot believe it .... UPS pulled up to my house at 12 noon, sharo, and dropped off my Kevlar order from McMaster-Carr . I ordered less than 24 hours ago!!

 

[n3tjm]

With Jim's kevlar that I ordered (SLK-3508-120) you get 10 ft 35 lb (Quest Type) cord, and 10' of real thin 8lb cord. I know what the 35lb stuff is used for, but I was wondering, what do I used the 8lb stuff for? Small rocket shock cords? Parachutes? Dental Floss?

 

[n3tjm]

I cannot believe it .... UPS pulled up to my house at 12 noon, sharo, and dropped off my Kevlar order from McMaster-Carr . I ordered less than 24 hours ago!!

McMaster-Carr is great! You click on it, its at your doorstop tomorrow! I just wish their url is easier to navigate.

 

[jflis]

Floss would be good... LOL

fool your friends, dip it in glue, then a pile of powdered pumice and watch them saw their teeth off, in the morning... LOL

I've found a million uses for that 8 lbs kevlar.

we (FlisKits) use it on our pop lugs, i've used it in attaching elastic shock cords to nose cones (push the elastic through the screw eye, fold and tie (like you would tie a fishing fly) the shock cord to itself. A knot in the elastic creates a weak point where the elastic can break. This would prevent that from happening.

Strengthening competition streamers, any small tieing jobs to secure items...

 

[n3tjm]

dip it in glue, then a pile of powdered pumice and watch them saw their teeth off, in the morning...

ROTFL!!!

Hmm, so thats what the thin Kevlar was for in my Cougar 660 some nice guy sent me. That pop lug is such a cool idea; I'll have to try it... good thing the Cougar comes with one

 

[Micromeister]

powderburner:
I'm with Ya 100% on the over building mod-Rocs, I have to keep reminding myself..We are holding the things together with Elmors glue and the like

N3tjm: that 8lb kevlar makes wonderful floss, ya can't wear it out Naw! makes good chute shrouds and attachment lines on Streamers.
Pop lugs are very neat, The thread attaches the wire fork and pin to the launch lug. Don't forget to put a little piece of masking tape near the top of the launch rod to stop the lug.

 

[rbeckey]

OK, so I am not the rocket scientist I though I was. I kinda figured out what a pop lug is, but how does it work and how is it assembled?

 

[Cajunman06]

You're right, McMaster's website is slow and not really friendly. But, when you think about it, when you have to keep a database of that much stuff, it's tough to incorporate ease into it. I prefer to use their "paper" catalog. Another example of their customer service. I emailed asking how to obtain a catalog and they replied that one would be sent out. Less that 48 hours later it was on my desk......FREE of charge. They know how to run a business.

 

[airforce]

Dental Floss, the waxed coated stuff but make it long enough to hang out the tube about 12 inches. See those teeth, now if you get something in your teeth while launching you can use the built in floss carried by your rocket. Wow, we could get the ADA to sponsor some rocket meets if we all use dental floss in our rockets. Maybe we should do one of those polls to check this out.
Any way, I think it sounds very holsome and helps us put on a good face
Ok, I'm finished.
:kill: Randy

ps.I bet it would work at least a couple times, I'm done

 

[n3tjm]

A pop lug can be attached to the rocket via some piano wire. One wire "hooks" into a hole in the boddy tube, while the other wire hooks around the back of two fins. The rocket is placed on the launchpad, and a few layers of tape are wrapped around the tip of the launch rail. The rocket takes off, and the tape stops the lug, but the rocket keeps going.

Jim, mind if I post a drawing from the Cougar's instructions showing this? Is there another post about this somewhere?

 

[powderburner]

Originally posted by rbeckey
pop lug ..... how does it work and how is it assembled?

I think these things had their heyday back just before piston launchers hit big

They are quite cool and really simple. Think of them as a removeable launch lug. You can still launch from a regular launcher with a plain launch rod, but the pop lug stays behind and the rocket flies without a LL, like it came out of a tower. You glue a pin to the front of the LL, with the pin point up, and another pin to the bottom of the LL, pin point also facing up (at least, that's the way I used to do them). I have seen some guys laminate on a short length of thin spruce to strengthen the pop lug, but I personally don't think it is necessary.
You find a suitable spot on your rocket (near the cg, between the fins, etc; the place where you would otherwise put on a permanently glued LL) and push the pins into the body tube. This is the tricky part: the pins should only go into the outer-most plies of the paper, and will cause a small (cosmetic) 'bump' where the pins go under the skin. You should wiggle them a little until they are ALMOST loose.
A heavy piece of tape at the top of the launch rod will stop the upward movement of the pop lug as the rocket goes by.
Tuning this system is the fun part: fit the pins too tightly and you cause your rocket to 'trip' over the end of the launch rod---if it slows down enough, it can take off in interesting new directions.
Fit the pins too loosely and your rocket may leave the pop lug at the base of the launch rod---see above comments about interesting new directions.
Fit the pins juuuuuust riiiiiight, and you will typically get a 10 to 15 % increase in altitude (if I remember the numbers correctly).

 

[jflis]

Originally posted by Micromister

Pop lugs are very neat, The thread attaches the wire fork and pin to the launch lug. Don't forget to put a little piece of masking tape near the top of the launch rod to stop the lug.

LOL I have to retell this...

I had just done a class at our convention (NEMROC) on competition and did a lot of discussion on pop lugs, towers, pistons and the like.

This one kid complained that pop lugs never gained him any altitude or time and most of the time actually HINDERED his flight points, as compaired to a tower, piston or even just using a regular launch lug.

This made no sense, so I suggested that we do some time trials at the next days launch...

sure enough, the pop lug was the worst of the lot, by a LONG shot...

that's when I realized that he didn't know about the tape on the top of the rod and his rocket would carry this VERY draggy pop lug for the entire trip...

LOL

yea, don't forget the masking tape on the launch rod... LOL

 

[powderburner]

You guys really disappoint me.


Here I give you a straight path to a cheap shot (no one has made any comments about the women in my life) and none of you has taken it!!!!!

 

[Micromeister]

rbeckey:
Heres a 1983 pop lug dwg and instruction sheet, Hope you can read it


Jim! I finially figured what LOL means and I did on that pop lug story...THAT WAS RICH Laugh my head off.