All of your advice worked perfectly, as far as I could tell, when I used it in RS7. However, I just downloaded the trial of RS9, and when ever I try to put tube fins on the rocket, it cuts the altitude almost exactly in half, from 1000' to 500'. At first I thought that this might be a problem of turbulence through a skinny hole, but even when I increased the ring fin to a 6" tube around my BT70 body tube (I intend to use about a 4" ring fin in the final run) it had exactly the same effect. Next I thought it could be a case of serious over stability (it was around 7 calibers) but with super large fins, with aproximately the same over stability, the flight still went its normal height of 1000 feet.
A little more spicifics on the rocket, in case it helps you at all, it is flying on an E30, with about 100g of nose weight in payload. I attached the file, for any further information. Flight 1 is with normal fins, and flight 2 is with the attached tube fins.
Thanks
edit:
Ok, so I did a little more investigation, and it turns out that the rocket with the ring fin has a calculated Cd of ~1.6, while the one with similarly sized regular fins has a Cd of only about 0.3 Do you guys have any idea what is causing this, and/or how I can avoid it?
edit 2:
Another interesting tidbit, is that with tube fins of the same BT70, it ends up having a Cd of .6
Is there any way of having nonplanar fins without the Cd skyrocketing? (no pun intended) If not, that is really unfortunate, because tube and ring fins are so much better at dealing with cross wind.
View attachment TARC Tube Fin.rkt