Wednesday, July 06, 2011

Real-time design

In a prior incarnation, that title would invoke thoughts of hardware, embedded software, interrupts, etc.  Now it just implies that I have a general thought of what I want to build and start cutting stuff up and piecing it together until I'm satisfied.  ('Satisfied' is sometimes too strong a word.)

I am now working on the fins for the Never Say Never coffee bin rocket.  I'll take a photo when it starts to take form.  I cut two fins from luan plywood.  These are filled and are being installed.  I also cut an 8" piece of 8.25" sonotube.  I'm going to cut this in half and mount them on the fins.  How is TBD:
  1. Concave, facing inward (like an oblong ring-fin, but not contiguous).
  2. Concave, facing outward.
  3. On opposing fin tips (so the rear view would look lis the letter 'S').
I'm contemplating notching the tube for a firmer fit.  I'm going to add some supports (dowels?) across the half-tube sections and possible tip-to-tip inside the tube halves.

Stability?  In one plane, option #1 should provide stability approaching that of an ~11" ring fin.  In the other plane, it will be more like an 8" ring.  RockSim9 says the 8" version is more stable than the 11".  GIGO?  I'm not going to swing this thing nor can I make a full scale cut out.  So, I'll start with a RockSim design (two actually), add margin, and possible add some fins perpendicular to the 'skinny plane'.  Real-time design!