11th March 2012, 07:04 PM
Estes - Space Eagle - Shock cord issue...
My son and I are in process of completing his first rocket and I notice an issue with the shock cord. This really caused me to rethink how we complete the recovery system for our rockets. See attached photo: Notice the bubbles in the cord.
Most all my builds in the past I add the engine mount and shock cords after painting. I have also had the occasional failure due to chutes sticking to paper in small tubed kits.
Coming back into the hobby and TRF I have been reading threads about kevlar cords etc.... I also just completed a Quest Navaho using this system for the first time. Though the mount is a little different - 2 centering rings. What I have not found are details on how to use them on a regular Estes engine mount. Do I need two centering rings vs. the one that many of the mounts come with?
The engine mount is already in on this kit, but this would be helpful for future builds.
Last edited by Real Deal; 11th March 2012 at 07:08 PM.
11th March 2012, 11:24 PM
Hmmm... Never seen a shock cord that looked like that before, though I'm fairly new to rocketry. I would say it is a factory defect. (Maybe you should contact Estes to see if they will send you a replacement kit? )
Also, did you mean to say that many of the engine mounts only come with one centering ring?
As far as attaching the shock cord to the stock Estes centering rings, I think it would work fine, though I could be wrong. One thing I have seen many people do is attach a fairly short piece of elastic at the end of the Kevlar shock cord, and attach the nose cone to the elastic, to dampen the shock of the deployment. Of course, the elastic will not be nearly as strong as the Kevlar, but if it is not a huge rocket I don't think you should have any problems with it breaking.
I know [POW]Eagle159 uses the Estes method to attach the shock cords to all of his rockets, even the larger ones.
12th March 2012, 12:07 AM
I may have my part names incorrect... But here is an example of what I call an engine mount with one centering ring. Only one green on blue vs. two smaller ones on blue.
12th March 2012, 01:17 AM
I think estes often uses that style centering ring on rockets where the body tube is only 1 or 2 sizes larger than the motor mount tube. plenty of vendors sell centering rings that size outer diameter but nowhere near as long so you use two. 2 definitely makes it easier to mount a kevlar shock cord. If you havent added the motor mount to the rocket yet you could get a pack of the short style centering ring and add it to the end of the mount. Once you get to larger body tubes then the centering rings become heavy card stock so they are very thin lengthwise
12th March 2012, 01:28 AM
It looks like your engine mount is already glued together.
Originally Posted by Real Deal
Next time you could cut (or file) a notch on the inside of the long centering ring for the Kevlar to fit under. It's a little harder to do it on the long centering rings.
Or with the mount already glued together:
With a small screwdriver you might be able to lift the upper end of the engine hook and slip the Kevlar
Tie off the Kevlar around the hook and you would be good to go! Some of the Semroc kits are done this way.
12th March 2012, 01:28 AM
The Kevlar cord can be tied around the engine hook ala Semroc style. As for the shock cord, you can get elastic cord from the craft dept. at Wal-Mart and cut a piece to length.
12th March 2012, 01:47 AM
Originally Posted by hcmbanjo
Yes both the Space Eagle and the Payloader II have their engine mounts complete. Already committed before running into issue.
This is more post is more for future builds. I robbed another kits shock cord to complete today.
Thank you all for your help. Ordering up some Kevlar tonight. Also found this link too... http://www.nar.org/HowToBuildAModelR...vlarPage6.html
12th March 2012, 01:59 AM
if you really want to use kevlar - you could purchase some of the centering rings and using a dowel or brush attached to a handle put some glue way down the bt and slide the new block with kevlar attached down the front till it hits the glue location, and viola. also i have seen some folks do kevlar on the outside... but i can't find any pics...
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