What does “Zipper-proof” design mean?

[Tomflysrc]

I know what a zipper is, in regards to rocket damage, but I’m wondering how this zipper proof design is achieved.

 

[Bat-mite]

Usually there is a foam stopper of some kind that prevents the harness from touching the tube wall. Like the GLR Fireball.

 

[Steve Shannon]

The “zipperless design” was a design first published in Sport Rocketry by Stu Barrett more than twenty years ago which has a bulkplated upper end to the fin can/motor mount part of the rocket and the shock cord attaches to an eyebolt or u-bolt. Because the shock cord is not inside the lower section no zipper can occur.
Here’s a much later article that discusses it but without crediting Stu:
https://www.apogeerockets.com/education/downloads/Newsletter290.pdf

 

[mpitfield]

As you will hear, there are many ways to get a zipperless (zipper proof) design, depending on the design of the rocket and materials used. For example the GLR fireball, as mentioned by John, is a commercial solution but I have seen at least a dozen variations, using tennis balls, foam, etc. One simple method I used on my Aerotech Arreaux, which is a MPR rocket, was simply to glue the coupler on the booster side instead of the payload tube, problem gone.

 

[Jozef]

Another option is to use a Jolly Logic cute release. A good investment if your budget permits with benefits beyond preventing airframe zippers.

 

[samb]

I agree with Steve that Stu Barrett pioneered zipperless design construction methods back in the day. Another place to read about his work is the old Info-Central site courtesy of the Wayback Machine.

https://web.archive.org/web/2005040...-central.org:80/construction_antizipper.shtml

 

[tim cubbedge]

Another option is to use a Jolly Logic cute release. A good investment if your budget permits with benefits beyond preventing airframe zippers.

That won't prevent a zipper if you have a very late delay charge. This is from a recent launch with a JLCR and a really late delay.

 

[Jozef]

That won't prevent a zipper if you have a very late delay charge. This is from a recent launch with a JLCR and a really late delay. View attachment 364773

Ouch! I have had two very late delays on CTI 4 grain H motors in a Mega Der Red Max, but no zipper. Most recently at Mini Midwest Power in May of this year. The launch video is at the tail end of the Youtube post. Used a 9/16 nylon harness with a Nomex sheath that is about 3/4 inch wide. Most likely spread the load. I recind my recommendation.

 

[Jozef]

My MDRM launch segment with the very late delay is as at 13:55 in the 2018 Mini Midwest Power video.

 

[ericm541]

I like zipperless designs, i've seen people incorporate a metal band around the end of the tube as well. If you want to do dual deploy with a zipperless you will probably need another coupler,bulkheads,etc, or just get a JLCR.

 

[MaxQ]

I agree with Steve that Stu Barrett pioneered zipperless design construction methods back in the day. Another place to read about his work is the old Info-Central site courtesy of the Wayback Machine.

https://web.archive.org/web/2005040...-central.org:80/construction_antizipper.shtml

Thanks samb for that Wayback Link.
IIRC...Info Central was on Darrell Mobley's old Rocketry Online Forum ...way back in the day, that was the source for all kinds of good "how to" info.
Stu Barrett also had a really clever way of using a single central threaded rod extending from the Alt Bay to attach to a single internal coupler nut inside the forward airframe (on a baffled bulkhead)- you basically screwed on the forward section of the airfame (the section with the main chute compartment), which eliminated all the little external screws around the outside.

 

[Nytrunner]

Thanks samb for that Wayback Link.
IIRC...Info Central was on Darrell Mobley's old Rocketry Online Forum ...way back in the day, that was the source for all kinds of good "how to" info.
Stu Barrett also had a really clever way of using a single central threaded rod extending from the Alt Bay to attach to a single internal coupler nut inside the forward airframe (on a baffled bulkhead)- you basically screwed on the forward section of the airfame (the section with the main chute compartment), which eliminated all the little external screws around the outside.

I think I get the gist of thay method. Buy it doesn't look like that bay's set for ejection deployment. Was that just a mockup of the linkage?

For the OP, here's a zipperless booster on a Pro Series II rocket I just built.

 

[MaxQ]

I think I get the gist of thay method. Buy it doesn't look like that bay's set for ejection deployment. Was that just a mockup of the linkage?

For the OP, here's a zipperless booster on a Pro Series II rocket I just built.

View attachment 364882

Old pictures...that Vulcanite had the ejection charges on wires simply routed through a hole on the bulkhead (hole is hidden behind the threaded rod in the picture).

 

[manixFan]

The only real zipperless design is Stu's. I've seen every other variation mentioned here end up with a zipper under the 'wrong' circumstances, including the Fireball, and as shown above, the JLRC.

The biggest problem with Stu's design is the loss of usable space in the booster section. You really can't use any of the space occupied by the coupler for anything. I suppose you could put an AV bay in there with a cord cutter but certainly not a standard dual deploy setup. But it does move the CG forward so there is that.

I use a wine cork or something similar around the shock cord where it meets the body tube on smaller rockets and a coupler with centering rings on both ends on larger rockets. (The coupler being several sizes smaller than the body tube.) Fortunately I've never had a zipper although I have had some dented body tubes.


Tony

 

[Sabrina]

Some people will get this - and for others... this will go right over your head.

This is a picture of me and my Dad at the RSO station at LDRS-33. The RSO took great interest in our rocket as soon as he noticed it "seperated" in the "middle" and was a "ZIPPERLESS" design. He asked us a lot of questions about it...

-How did we learn about the zipperless design?
-Did we build many rockets this way?
-Was it working out well for us?

 

[manixFan]

Anyone who knows Stu will recognize him immediately. Credited of course with the anti-zipper design.


Tony

 

[Hobie1dog]

The “zipperless design” was a design first published in Sport Rocketry by Stu Barrett more than twenty years ago which has a bulkplated upper end to the fin can/motor mount part of the rocket and the shock cord attaches to an eyebolt or u-bolt. Because the shock cord is not inside the lower section no zipper can occur.
Here’s a much later article that discusses it but without crediting Stu:
https://www.apogeerockets.com/education/downloads/Newsletter290.pdf

Thanks Steve

 

[mtnmanak]

I wouldn't call this approach "zipperless", but it may cause less zippers. I like to use kevlar attach points in all my boosters, including LPR and MPR. In small rockets, that is just a single piece of lightweight Kevlar attached to the motor mount. In larger diameters, it is usually a Kevlar loop attached to the motor mount. In big rockets, I have them constructed by Teddy at Onebadhawk with the appropriate hardware for the rocket.

The similarity for all of them is that I put a swivel as the end of the Kevlar and ensure the length of the Kevlar is sized so the middle of the swivel is even with the lip of the tube. Will this absolutely prevent a zipper? No. But, it makes it less likely. The larger, blunt body of the swivel has a tendency to bounce off the lip of the tube. Plus, you always know you have a built in swivel to reduce line twists.

Here is a small example from a Warp 7:



A medium example from an Estes Nike Smoke PSII:



And a larger example from a 7.5" LOC Bruiser EXP. In this case, I sized it so the quick link would hit the edge of the tube. I figured the broader surface area of the link would better shield against zippers:

 

[K'Tesh]

My zipperless work basically has a baffle built into the coupler, along with the the attachment point for the shock cord. The other end of the shock cord is routed inside the recovery bay and attached to either the bulkhead of the AV bay, or the nosecone. The chute is then tucked inside the recovery bay.

Something else to keep in mind is your separation point, and tension holding the rocket together... My BT-60 based upscale of the Estes Yellow Jacket separated at the black/yellow color divide. Problem was that this was behind what I'll call "the natural pick up/carrying point". The result was that several times I'd pick up the rocket, and the back end would fall off as I was walking with it (usually resulting in it falling onto the most fin damaging item around, even if it was the only potentially damaging item within a square mile). My poor Yellow Jacket had some pretty dinged up fins before I finally gave up on going zipperless for that rocket.

 

[samb]

Correction to the link I posted in #6: Stu Barrett's Info-Central article on his zipperless design.

https://web.archive.org/web/20120526063528/http://www.info-central.org/?article=132

 

[JohnCoker]

I'm glad the INFOcentral can still be found find through the way-back machine. There was a lot of good stuff there.