The most stupid question

What failure causes a zipper?

geodehunter said:

What failure causes a zipper?

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Not necessarily a failure -- it can be a delay that's too short or too long. How a recovery system is packed can play into it, as well.

-Kevin

The shock cord getting yanked by the recovery device in such a way that it cuts the airframe tube. This occurs almost exclusively with thin shock cords, like Kevlar and braided nylon. (At least, to the extent of my knowledge.)
And no, its not a stupid question at all. Everyone has to learn some time.
EDIT: Must learn to type faster!

Rocketbuilder said:

The shock cord getting yanked by the recovery device in such a way that it cuts the airframe tube. This occurs almost exclusively with thin shock cords, like Kevlar and braided nylon. (At least, to the extent of my knowledge.)
And no, its not a stupid question at all. Everyone has to learn some time.
EDIT: Must learn to type faster!

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Believe me, it can happen with thick tubular nylon, too ... ahem ... or so I've heard.

Mis-timed ejection events for a multitude of reasons and the primary cause.

--Lance.

geodehunter said:

What failure causes a zipper?

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First- the ONLY stupid question is the one that isn't asked. I trained all three sons to 'ask the next question' so any doubts are removed from their minds and I know they understand the basic idea behind the answer and concept.
A zipper occurs from a few events- most often early or late deployment when the rocket is moving at speed. That's one of the reasons you want to sim your flight to get the optimal delay when the rocket is moving the slowest (apogee) any later and it starts to gain speed (terminal velocity is unfriendly to parachutes, too!) Under boost, it can wreak havoc with everything including the loss of the airframe completely if it shreds your recovery system from the rocket. An easy way to help prevent this is just a piece of duct tape wrapped around your recovery line to make a flat pad that dissipates the energy from the line ove a larger area making your tube less susceptible to the 'zipper effect'. There are tons of other ways I'm sure the guys will chime in with, but start with you r delays times first. Straight smoke and good chutes!

yeah- I need to learn to type faster too-spelling helps! dang!

You mean like this? Should have took that two seconds out...

chadrog said:

You mean like this?

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Ouch...

chadrog said:

You mean like this?View attachment 86560 Should have took that two seconds out...

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Yip, That's what I am talking about. That has to make a guy sick when it happens.

geodehunter said:

Yip, That's what I am talking about. That has to make a guy sick when it happens.

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Sucks it does, but it's not a real big job to fix. I'm actually going to use it to make my Goblin a bit scarier - the fix will be adorned with scarring and stitches.

the only ziper i have suffered so far was a result of a dual deployment issue which caused the rocket to be comming in ballistic when the motor ejection backup saved the day.

geodehunter said:

What failure causes a zipper?

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[video=youtube;DteHxi2U5KM]https://www.youtube.com/watch?v=DteHxi2U5KM[/video]

JAL3 said:

[video=youtube;DteHxi2U5KM]https://www.youtube.com/watch?v=DteHxi2U5KM[/video]

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Love that show

I love the show too!!

It's a Montreal Production. There is jsut music on the segments, so that it can be english or French, or any other language!

Incedently, the 'structure' you see in the background of the intro is the Turcott Interchange. it's basically the interchange of 3 major hiways here in Montreal; the 20, the 15, and the 720. It's the main artery into the city from the west, the main artery off / to the Champlain Bridge, and is also the main north south link of the city. It's due to be demolished & rebuilt over the next 5-7 years. it's a major traffic headache, with it being closed / paritally closed for years while they carry out 'preventative maintenance'..

Can we say 'Neglet'?!

It's a failure of the airframes shear force to exceed the shock cords shear force. Please excuse the Smart A$$ response.