The nose cone: it fits, but it doesn’t fit.

The nose cone is a reasonably nice plastic cone, sized, at least roughly, for high-power tubes. They’re probably just about perfect for what appears to be the standard 2.56″ (65.0 mm) I.D. and 2.63″ (66.8 mm) O.D. tubes, with a 0.035″ (0.89 mm) wall thickness. I’m using Blue Tube (from Always Ready Rocketry), though. The I.D. of Blue Tube is standard, so things like nose cone shoulders, centering rings, and bulkheads will fit just fine. But, the wall thickness is nearly double a conventional high-power tube, at 0.062″ (1.57 mm). The shoulder of the nose cone fits just fine, but there’s a lip between the top of the tube and the nose cone: the edge of the nose cone sticks out.

The plastic nose cone is just a little bit too small.

It would be easy enough to sand down the nose cone (assuming the wall isn’t compromised!). Sanding down the body tube, ideally tapering it in some nearly-imperceptible way, is another thing, though.

I decided to get a new nose cone. Bill Saindon of Balsa Machining Service was very helpful in this regard. I measured things very carefully, and sent him the specs of what I wanted (this-and-such should diameter, that-and-such diameter of the nose cone body; he has some standard shapes, one of which seemed just right). I sized the new nose cone to be about 0.003″ over the tube diameter, knowing I would be sanding it smooth.

When it arrived, it fit perfectly. I’m now sanding, filling sanding, filling, sanding, and filling some more to get a nice, smooth finish.

Post Scriptum: Bill is no longer providing semi-custom balsa machining services. My order was in transit when I learned of this change, and I talked with Bill. I am very grateful that he made my nose cone: it was his last semi-custom job.