Rockethunter, you're rolling the dice by having spans under 1 cal. From personal experience, thats really when OR has problems with CP shift. I've seen flights that were supposedly .5-.75 cal stable at max V, go unstable. Only real common factor was the fin span. I've heard of other's similar experiences too.
If you're confident in your sims, go for it. Just reporting my experience.
Chris, I'm curious to see how you're going to do your fin can on your CNC. Do you have a 4th axis?
I just barely did a fincan similar on a manual mill, and I would have killed to have a little automation in there.
Also, do you want me to turn the fin can blanks? All the machining is on me. I still kind of owe you for blowing up that tower a few Aeronauts ago.
Alex
Not to get too off topic, but I feel the OR vs. RASaero stability argument is relevant to the construction of this rocket/rockets like it, so i'll continue the discussion of that. Taking mine as an example, here are the OR and RASaero CG and CP graphs:
For RASaero II, the stability is constant in the subsonic region around 2.5 cal, and then slowly decreases by ~ 1 caliber at mach 3, though because of the motors CG shift at peak speed the overall stability is ~5 calibers!
For OR, stability is initially low (just over a caliber) as it takes off at low speed, increases dramatically by quite a few calibers up through the transonic region then dramatically decreases at high mach as the CP moves forward, back down to around 1 caliber.
Its pretty amazing to me how wildly different these predictions are. I personally prefer OR as it seems to take into account things like the lack of effectiveness of the fins at low speed (you can shorten the length of the launch rail, and see the initial stability drop, sometimes to near zero for an instant which is usually a good predictor of weathercocking), rather than simply using a constant subsonic CP like RAS seems to do.
RASaero II still seems like it over estimates stability - there's so little CP shift at high mach, and 5 calibers of stability at mach 3 with a rocket with 4 fins 70% the diameter of the rocket seems a a bit to good to be true. IDK YMMV.
My biggest takeaway is that it seems to be a very hard thing to predict, and that simulations are best supplemented with empirical data and testing. What would be great would be someplace where people could post their design files with stability predictions, and then post the results of the flight (unstable, weather cocking, arrow straight, coning, etc.). Alex, if people posted actual data for the flights you describe where they have run into stability problems, future flyers might be able to use that info to makeup for the faults in the software that may have lead to those failures in the first place.