Saturday, May 6, 2017

North Coast Rocketry SA-14 Archer - Building Up the Tube

The centering rings of the SA-14 Archer fit a little too loosely on the motor tube. The instructions suggested that if that's the case in your kit, you can make the outer diameter of the tube a little larger by wrapping masking tape around it.

The thing is, the centering rings and the fins will be glued to the motor tube, and I have rather cheap, low tack masking tape. I worried that if I did the tape method, it might mean my fins were attached by a rather weak bond.


I'd read this post on on how to make your own Kraft paper tubes. As you probably know, Kraft paper is the material most model rocket body tubes and many mid and high power motor tubes are made of, and it's possible to roll your own. Rocket body and motor tubes are just strips of paper, built up layer by layer and glued in place. Enough layers make the tubes strong enough for a high thrust rocket motor.

I decided to try this technique to add a layer or two of paper to the motor tube, making the walls just a bit thicker. With wood glue, the paper would bond to the tube very strongly, and the new paper surface would simply be part of the tube.

Here's how it went:

And here's the finished motor tube.

You can see how solid it is, and even though there are slight surface imperfections, it's quite smooth. If I'd gone too far with the wall thickness, I could now sand the tube down to get just the right fit.

This turned out really great, and I'm glad I thought to try this. Trying it did make me nervous, but it was really much easier than I thought it would be. On more than one occasion, I've wanted to build up a tube or make it a little stronger. Now I have one more technique I can use should the need arise.

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