Underpants Elastic Bands and other mistakes

 The Thrifty Rocketeer blog continues....

Normally, this blog tries to give you some helpful, positive tips. 
But today, we will look at a couple of things NOT to try.

Just tonight, I was chatting with some rocketry friends by Zoom, and one of the more senior guys holds up a couple of pieces destined for his high power rocket. He's asking for help and advice on how to proceed.

He's got a medium sized carabiner in his right hand, and in his left is a strip of what he is calling an elastic band. (It looks more like the headband that Spock wears in Star Trek IV: The Voyage Home, but no matter.)

It's a long length or skein of two inch wide elastic band that looks like it might either go in a truss, a bra, or some form of back brace.

And he's asking, "How do I attach this to that?"

The discussion starts and rules out sewing (cause the stitches won't stretch), rivets (cause they'll pop whenever it stretches), grommets (for the same reason) and glue, (as it  won't "give" without cracking).

One rocketeer said, "Dump it, just get a nylon rope or similar woven tube, and tie it on", just as you would in mountain climbing.

We all  pretty much agreed that the two inch width of the elastic band won't allow for a tight knot to be tied around the carabiner, so we settle on the nylon tube/rope idea.

Now this started me thinking about the time that I considered making my own shock cord out of elastic.  I was doing a scratch build for a recycling display on how you could turn ordinary trash into a very simple rocket and nosecone with plastic Wal-Mart bag parachute.  For a shock cord, I had settled upon an old pair of men's tighty-whitey briefs.

I convinced my wife to lend me her pinking sheers, and I used a seam ripper to free the elastic band from the pair of shorts.  Very quickly, I tired of the seam ripper, and went for a straight sharp pair of fabric sheers, and just cut as close to the waist band as I could. 

Now that I had the loop of elastic free, I don't recall if I cut across the seem or ripped it free, but I wound up with a single length of one inch wide elastic that still had a lot of stretch in it.

Deciding that the band was too wide, I took the fabric sheers and cut down the middle of the band leaving an equal width of elastic band on either side of the cut.  What I hadn't counted upon was the fraying, which started immediately.  The two elastic strips, while about 42 inches long, curled and buckled, refusing to lay flat.

This was symptomatic of how the elastic band would behave no matter how I cut it , stretched it, or steam pressed it.  I learned that you CAN'T cut an elastic band lengthwise had have it work.  (Now, for the purposes of my poster board display of the parts of a rocket, it worked well enough, but for actually use in a rocket, my idea would not have worked.)  

What WOULD work is the purchase of about 3 feet of narrow 1/8-1/4 inch elastic from Joann Fabrics or similar shop.  Except for the run on this material to make masks during the pandemic, this would work for smaller, low-power rockets if you needed to replace a shock cord.

**Note, I have already discussed the use of garbage bag rubber bands to be pressed into service in an earlier blog entry, and I still stand by that idea, expensive though it may be.

This has been the Thrifty Rocketeer, asking what is your favorite shock cord material?