I want to use a kevlar shock cord on an already built rocket. It is for my Super Flea clone. The original cord was sewing elastic and it got torched on the first flight... Any recommendations on how to attach it?
Thanks!
For those who don't know, here are the plans/
https://www.spacemodeling.org/jimz/est0815.htm The Super Flea is the smaller rocket.
Been doing this kind of retro fit for years now.
I've found the best way without using the dreaded "Tea Bag" bulge is to use a spare centering ring , piece of Body tube Coupler, or if the model is minimum motor size a 1/4" section of spend motor casing as the Shock-Cord Anchor base for your Kevlar or Stainless Leader shock-cord mount.
DO keep in mind Kevlar is NOT flame proof. it is only HEAT resistant. it does NOT burn but degrades a bit every time it is exposed to temperatures at and above 468°c (900°f). our BP motor ignition temp is 487°C (909°F). I've now switched to Stainless Steel 30lb braided fishing leaders or several size Stainless Steel 7x19 strand aviation cable (wire rope) as my internal shock-cord anchors moving the Kevlar Up away for the initial heat and afterburn flame 12 to 18". With this Stainless/Kevlar/elastic shock-cord set-up I haven't lost a shock-cord in more then 8years with some of the smaller models having as many and 30 flights so far.
Anyway below are a couple pictorial methods for setting up either Kevlar/elastic or Stainless/Kevlar/Elastic retro-fit shock-cords.
To install either type:
* First clean out any soot build-up inside the model body with a piece of 120grit sandpaper wrapped and taped around a dowel long enough to reach the forward end of your motor mount from the forward end.
*Attach a stretched out cotton ball to the end of a 3/16 or so wooden dowel long enough to reach the same area with a few inches extra to hold on to.
*Make up the complete retro shock-cord of your choice, ready for inserting into the model.
*Mix-up some 5 or 30 minute epoxy or yellow carpenters glue and coat in lower forward end of the body tube just above the motor mount with glue or epoxy.
*Quickly insert the shock-cord retro mount centering ring and push it all the way down into the glue with a large diameter dowel big enough to set the ring squarely in the glue.
*Check the opening of your motor mount, remove any glue or epoxy that may of entered the forward end with a long Q-Tip then set the model Up Side Down and allow the epoxy or glue to cure.
*Retro-fit complete.
