anti-zipper technology

[Elapid]

seems to me if you could limit the force on the shock cord, there wouldn't be any ZIPPERS.
there are some very simple and effective ways of doing this that i picked up from another hobby.

any interest?

they already make a commercial product that would be perfect for HPR as-is; smaller units, while not manufactured could be easily produced quite cheaply.

 

[KermieD]

This'll sound weird, but I've never, ever had a zipper. All my HPR birds are built with a baffle system instead of a MMT shock cord, and it's just never come up on a LPR bird.

 

[Elapid]

either.

if the ejection charge goes off early (a possible cause of zippering), or too late (more common), or you just load the wrong motor...you end up with ruined models!

I'm planning on experimenting to see if this system will really work by using short delays to eject the recovery system at high velocity. i don't see any possibility that it won't work.

Mmmm... so certain are you?
[/Yoda]

 

[Stones]

I agree with Kermie. Never had a zipper but, that doesn't mean it can't happen, obviously.
So, what's this idea? We always have interest for anything that makes for 100% recovery.

 

[Stymye]

I also have never had a zipper,I have been lucky so far I guess
but I'm always interested in new technology,
lets see it !

 

[wwattles]

I've only had one zipper, and it was a result of putting in too short of a delay. I experimented recently with my own "CHAD anti-zipper device" consisting of a large wrap of electrical tape around the shock cord where it would contact the end of the BT. I intentionally put in too short a delay, and it worked fine. Basically it changed the kevlar shock cord from a cutting thread into a bludgeoning ball.

I know someone out there (can't remember who right now) makes a ball wrapped in a kevlar sleeve with connection points on both ends that does the same thing.

WW

 

[solrules]

Originally posted by wwattles


I know someone out there (can't remember who right now) makes a ball wrapped in a kevlar sleeve with connection points on both ends that does the same thing.

WW

Giant Leap's Fireball is what you are talking about. Personally, I have not had a zipper either. My preferred way of zipper prevention is a small (1") wrap of fiberglass on the booster section, at the connection point of the tubes.

There is an article about an anti-zipper method on Infocentral

 

[Elapid]

commercially made load-limiters for aid climbing would keep the forces in check. they activate at 800 lb and limit the force to 1200 lb iirc.
for smaller rockets, a simple velcro tee would work fine, i think. poossibly velcro dots.

here's a link
Screamers...that about sums it up!

https://www.yatesgear.com/rescue/load/

 

[rocketkid88]

but its bound to happen sooner or later. i just recently experienced my first 'estes dents' as welll... thats another problem tho.
in on of the rockets im working on i recently put a hole in a small spongy ruber ball and slipped it over the kevlar, then just a wrap of tape above and below the ball to make sure taht it didn't adjust positions. with the ball positioned so when the cord is extended it is right at the mouth of the tube i dont *think* i should have a problem with zippering

i like the idea on that page, i've thought of using a slippery half-hitch or something before on my lpr just to ease the force of ejection, but have thought it to risky.

 

[wyldbill]

Originally posted by Elapid
here's a link
Screamers...that about sums it up!

I took a 20 ft. lead fall onto a screamer several years ago. It was an older model and had several (~12?) horizontal tacks instead of the linear ones. Tore all the tacks out. One of the most terrifying sounds I've ever heard.

 

[Reeferjon]

Just had my first zipper.. D12-3.. the tube had been reinforced with CA, I used Kevlar... I think I will try a little heat shrink tube on the Kevlar at the length where it exits the body.
In the mean time.. whats the best way to repair.

 

[swimmer]

Rj,

I've had a "couple" zippers. One way to fix them is to cut the bodytube off below the zipper. Or, cut off, add a coupling and a new section of bodytube to bring back the rocket back to original length.

If the zippered piece is still attached work it back to its original position. I usually pull on it till it straightens out. Cya it back into the bodytube. You'll probably have to fill the outside of the bodytube to get it smooth. Sand on the inside a little to smooth. Use some thin epoxy and apply a thin coat over the inside to strengthen the zippered area. When dry, sand smooth. I fixed a zipper in a 3" rocket like this and it is hard to see where the repair was made.

 

[Reeferjon]

Thanks Swimmer... will give the repair a go.. if it looks bad will cut the tube back.

 

[jraice]

I would say the best way to prevent the zipper would be reinforcment of the tube edge. This way you prevent zippers and protect the edge of those costley tubes from dents or cracks.

 

[rmpitzer]

Originally posted by jraice
I would say the best way to prevent the zipper would be reinforcment of the tube edge. This way you prevent zippers and protect the edge of those costley tubes from dents or cracks.

A wrap of 2" Kevlar tape on the leading edge does an amazing job.

I never experienced a zipper either....until I made my first 7.6" (glassed) rocket. Haven't had a zipper since using the Kevlar tape edge on tube.

 

[jraice]

More info? Sounds interesting, I need something to prevent zippers and dents on the edge of a 7.5" tube

 

[Stormbringer]

I just use foam board cut into disks and epoxy the centers to the line.

 

[rmpitzer]

See my reply in the high power thread.

Kevlar tape is kevlar that comes in strips (it's not sticky, like tape you are thinking). You can either cut a recess in the tube and lay the kevlar in the recess, then glass over it to make it smooth. Or...if you don't care how it looks, just wrap it around the tube.