Building the (scratch) Au-198 (part 3)

Hey, look at what I found! Sheesh.

IMG_8246 OK, time to contemplate the shock cord. This being internally indistinguishable from a minimum diameter model, a replaceable Kevlar leader would be:

  1. Highly desirable, because there’s no way to keep the Kevlar far from the ejection blast, and
  2. Damn near impossible.

If the centering rings were wider and closer together, I could sneak the leader out of the BT-50 through a small hole and run it through a guide straw between the two rings, but they’re not wider and they’re not closer together — and the motor retainer throws another kink into that scenario too.

So I decided to take a different approach:IMG_8240 Stainless steel, more heat resistant than Kevlar. I had to set foot in Wal-Mart to get this, but I’ll be okay.

As for thrust rings, I actually ended up putting two in, sort of. One doesn’t act as a thrust ring. It’s a shock cord anchor, a little ahead of the motor. I cut a notch in the outer layers to accommodate the coast lock snap on one end of the leader.
IMG_8243Then I glued it in. The leader’s not removable but with any luck it won’t need to be. The snap’s rounded end sticks out below the ring, which is one reason this “thrust ring” isn’t being used as a thrust ring. The other is that it’s mounted too far forward, to get the leader’s end close to the front of the airframe. I tied the elastic to that and and to a screw eye I put in a block glued into the payload section.IMG_8249

And then I put in a true thrust ring, a compromise: It’s there, but it’s at E motor depth.

I glued the BT-55 section onto the rear end, and then glued in the fins.IMG_8252

So, anyone want to buy a couple pieces of aluminum angle?

(Kidding. I’m saving them all so I have a fifty-fifty chance of finding one when I need it.)


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