Shock Cord Mount

I'm building my first HP rocket, a LOC R2/Arrow. I've built two MPR's and they were both Aerotechs. I've reached the point where I'm supposed to mount the body tube to the fin can. I've read ahead in the directions and it has me taping a loop of cord to the BT and then epoxing over the tape and part of the cord to form a shock cord mount. I've never done this and I wonder how strong it is? As an alternative, I'm considering sinking an eye-screw into the CR and epoxying it. I've already epoxied the CR to the MMT and tail cone so I can't put a U-bolt or an eye-bolt in. I've searched the forums and read about passing the cord through both centering rings and out the back end of the rocket. I really don't want anything but the engine hanging out the back. Also, since this rocket has a tail cone, there isn't a bunch of room at the back end.

So, would you recommend epoxying a loop of cord to the BT or using an eye-screw in the CR or even something else? What are the pro's and con's of each? Any advice is greatly appreciated.

-Gregg

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Get some killer hd kevlar strap cut a slot in top centering right next to motor mount pass the strap through slot wrap around motor tube and tie in a knot epoxie the crap out of it. Or cut 2 slots on opposite sidesand have it loop out the top

I would avoid eye screws if possible and use eye-bolts, with a washer and nut on the top and bottom to spread the strain over as much area as possible.

I don't particularly like epoxying my cord to anything, as I want it to be replaceable.

Make an ejection baffle and bolt to that.


Richard

Options, options, options! The venerable low-tech method of epoxying a loop of something (originally nylon, now you would use kevlar) near the top of the tube is actually a lot better than it sounds. It's pretty durable and less prone to zippering than if the shock line is anchored further down the tube. I have a couple of 28 year old LOC kits that were done this way and are still flying, and have never zippered the cardboard tubes.

If you use a U-bolt or eyebolt in a centering ring or bulkhead it needs to be accessible from the top to attach a quick-link; otherwise whatever is attached to it has to be considered non-replaceable. Whether you can use a baffle as a mount point depends on whether you are using motor deployment or electronics. Epoxying a loop of kevlar strap or cord along the sides of the motor mount tube works just as well and may be needed if the centering rings are too small for bolts. If you do that be sure to make the loop long enough to fish out the back of the rocket thru the MMT so you can replace what's attached to the loop.