Replacing shock cord, what’s the best approach?

[ShakyShane99]

Hello about a month ago I launched a Estes Alpha in the back yard, I was pushing the envelope hehe, decided to lunch it with a c6-5 and the wind grabbed the parachute and it went into the woods. Lucky for me I found it on the ground today. But it was broke by the shock cord. I have a spare shock cord and nose cone from a failed attempt to build this rocket long ago. My main question is what would be the best way to do it? Should I rip out the old one? Or just mount the new one around the old one. Thanks. Apologize if this sounds dumb.

 

[Williamhimka]

Could you possibly post some pics of the current situation?

 

[ShakyShane99]

Could you possibly post some pics of the current situation?

It was literally just snapped. I went ahead and installed the new shock cord exactly the way it was installed the first time. Might be a tad bit of weight added but i doubt it’s enough to matter. Super surprised to find it in perfect condition besides the shock cord and parachute being missing.

 

[Williamhimka]

It was literally just snapped. I went ahead and installed the new shock cord exactly the way it was installed the first time. Might be a tad bit of weight added but i doubt it’s enough to matter. Super surprised to find it in perfect condition besides the shock cord and parachute being missing.

Forgive me if I’m missing something, but I’m assuming your problem is solved now? Saw that you said you went ahead and reattached the new one.

 

[ShakyShane99]

Forgive me if I’m missing something, but I’m assuming your problem is solved now? Saw that you said you went ahead and reattached the new one.

Correct

 

[PDawg]

Nice! Send it up again, maybe use a C6-7.

 

[MarsLander]

Drill a hole through both motor mounts from the rear. Get a plastic Q-tip. Glue it into the holes to provide a channel from the motor mount to the parachute space.

On one end of a kevlar thread tie it around a spare motor tube. Take it off. Thread the kevlar string through the glued in q-tip. Wrap the loop you tied over the rear end of the motor tube. Poof...replaceable shock cord.

Basically doing this after the fact...

https://www.apogeerockets.com/education/downloads/Newsletter338.pdf

 

[Back_at_it]

Going forward, I'd stop using the rubber shock cord. Replace it with a piece of Kevlar attached to the motor mount or upper centering ring in larger models.

The Estes tri-fold mount works great and is very strong if done correctly but I don't care for it in smaller rockets as it tends to take up too much space and could hinder the recovery system.

The next time you need to replace one of these try this. Stick your knife blade under what is left of the tri-fold mount inside the tube. Drip a couple of drops of hot water on the knife blade and wait about a minute. The mount will come loose. You can then sand away any left over glue.

 

[bjphoenix]

I've used a small sanding drum in a Dremel to take out most of the glue and paper from the old tri-fold mounts. Everything I've built lately I've used kevlar cord and I've modified a few older rockets to use kevlar. I experimented with the tri-fold mount and ended up with something similar using a piece of heavy cloth instead of the paper. (I have a separate thread on this.) The mount does become a blob in the front of the tube but it is also very strong and away from the hottest ejection gases.

I've also retrofit a few by drilling through the centering rings from the back. I just drilled small holes, taped kevlar to the end of a small piece of wire and fed it through both holes that way. I didn't use the small plastic tube trick.

When I build LPR now I put a short leader of kevlar on the rocket, enough to stick out the front of the tube 6" or so with a loop in it. I have a separate 8' or 10' kevlar cord that I move from rocket to rocket with heavy snap swivels on each end. And for the most part I just use 2 parachutes for most of my launches.

 

[suborbital]

Hello about a month ago I launched a Estes Alpha in the back yard, I was pushing the envelope hehe, decided to lunch it with a c6-5 and the wind grabbed the parachute and it went into the woods. Lucky for me I found it on the ground today. But it was broke by the shock cord. I have a spare shock cord and nose cone from a failed attempt to build this rocket long ago. My main question is what would be the best way to do it? Should I rip out the old one? Or just mount the new one around the old one. Thanks. Apologize if this sounds dumb.

I see your problem, you lunched the C6-5 without condiments....

 

[bjphoenix]

Here is a photo of one method for retrofitting. This was actually a new build but I forgot to install the shock cord before I put in the fin can so I had to retrofit just like it was an old rocket. I drilled a hole through both centering rings with a long drill bit, I pushed a long wire through the holes, stuck the shock cord to the end of the wire with a small dab of glue, then pulled the cord back through the holes. I hook a loop in the cord around the motor tube and hold it with a dab of glue. If necessary the old cord could be pulled out and a new one put back in there. This works with normal rockets with relatively short motor mounts, not so well with 3 or more centering rings, baffles, etc. The long wire I used is one of those little flags that utilities use to mark underground lines in your yard. I had to buy a batch of them recently to mark the heads of my lawn sprinkler system.

 

[86mustang408w]

I would just cut paper and make a new mount like you did, there are better alternatives to those Estes cords like said. You can put a spill hole in the chute too, you could probably get away with a streamer so it won't wonder off.

 

[K'Tesh]

The rubber shock cord worked as advertised. It failed before the rest of the rocket failed, thus you are able to repair the damage and the rocket lives to fly again. Kevlar, and the thread would have been about replacing the lost rocket, or trying to salvage a rocket from just a set of fins.