So I had a weird idea recently but in doing some puttering around on the inter webs I am stymied by one thing...I want to build as much of a ~8" rocket out of concrete form tubes as possible including the nose cone. I know somewhere on the internet there are patterns to make N/C out of tubes but I can't seem to find them anywhere....anyone know where I can find them?
And the reason I am doing this project is well...not trying to save $$ or anything - guess I am a masochist lol.
-Dave
I built a few nosecones using the 'flower petal' method (not a real name, just what I called the methods shown above) early in my BARdom. I was using 2 1/2" tubes I was getting from the plotter paper leftovers at work. At this stage, I'll never do it again, but the results can be really good if you are in the mood to trade hours of your life for $. At 8", maybe its worth it and if you're a poor college kid, it might be, but I don't fly 8" rockets and I'm a poor middle-age guy now. . .
While I did it in CAD at the time, the same thing can be done with paper and math, as the ability to carefully cut the thick tubes vs. the error of doing things by hand are minimal, IMO.
One was a standard conical cone, so it was very easy. The other was an upscale of the 1906 Sizzler nosecone, which is either an ogive or 'tweaked' ogive, based on measurements.
To make the flat pattern, I measured the diameters at various locations along the nosecone - base and tip are obvious and I think I did 3 other points roughly equal distances up the cone. Once I had those diameters, convert to circumferences. Next, determine the number of 'petals' you want (I used 8, I think) and divide the base diameter into a bunch of centerlines for each petal. Now, draw lines (or points, but I like lines) at the right height and make the length the circumference of that height divided by 8, centered on the centerlines. Once done, connect the ends of the lines with a straight edge. Pretty close to correct.
The pain in the butt part is cutting that thick cardboard cleanly and then back chamfering the tube so it fits nicely. Then comes gluing it all together with epoxy and eventually filling and doing the real shaping of the cone. When done, it is heavy and strong as #^@$.
I think it is worth doing once, just to say you did it, but I think for an 8" custom nosecone, I'd do the foam/fiberglass method today. But, I'm glad I did it a couple of times and I would do it again if required.
In all fairness, I initially misread your question and know that you already know the above, but I typed it and maybe someone who didn't know the answer will get a little value from the post. Kind of a waste to just delete it because I answered the wrong question. . .doh!
Sandy.
