I'm not convinced that's cause and effect. I was actually going to recommend going a bit larger with the tube fins.
Not often I disagree with you, but I think weathercocking of more along the “Carboard CutOut” physics impact than Barrowman physics. My reasoning is that it is a reaction to airstream vector (in this case wind) hitting the model relatively directly transverse to the longitudinal (pointy) axis. Tube fins “stick out” less, so they offer less transverse surface area upon which the wind acts.
if I am correct, if you have two rockets which have identical stability and are otherwise identical in body and nose cone size, shape, and weight,
rocket A has three “normal” fins.
rocket B has 12 fins, which have shorter hemi-spans but are otherwise identical in length, thickness, etc.
the B fins will be a bit more than 1/3 the hemi-span of A (because less hemi-span is less efficient) so somewhere between 1/3 and 1/2.
my theory is A will weathercock more, because regardless of presence or absence of rotation around the long axis (as seen from onboard video cams, most low power rockets rotate at least a bit, sometimes a LOT), at any given moment Rocket A offers more surface area perpendicular to the wind.
regarding larger tube fins, my main reluctance is structural. The larger the tube fin, especially since mine have cut outs, the more susceptible to fin flutter and simple bending forces. The BT-5 fins are holding up well, the BT-50 not so much. I may get some coupler material from BMS, or just double the thickness of the tubes.
Maybe cut a long slit the length of an 18” BT-50, coat outside with white glue, and slide it inside an intact 18” BT-50 and let dry before cutting first into lengthwise segments, then applying to rocket, then cutting out the “waterwheel” clockwise segment.
I also suspect that longer hemispan fins, while initially certainly far more effective at “catching air” to start the rotation, may BECOME an inhibition to rotation beyond a certain speed. It’s kinda like the original RotaRoc helicopters with no swivels or axles. The fins sticking out on descent likely reduce or inhibit rotation somewhat. It is one of the things I liked about the Fliskits TiddlyWink as well as the Gyskelion, Dandylion, DareDevil, and SunDancer helicopters, the fins used on Ascent don’t cause air resistance to rotation. Unfortunately, as
@Rktman has pointed out, when located at the tips the mass effects angular momentum inertia, which is certainly bad for getting rotor spinning started (and come to think of it, for these models as well), and a generally a negative at flight termination as the rapid spinning inertia tends to break the fins/rotors.
@Dotini, your models have definitely proven me wrong, is was certain that without a ring for protection this fins would snap right off.
again thinking out loud, the largest diameter I am using should GENERATE more Magnus force (although I haven’t proven that in my models) but it will take a bit more time to get up to speed. However, while the “cool” factor of the Magnus force as YOUR models have shown is off the charts, the PRACTICAL value of it is still to me a mystery. But hey, if we wanted practical we would just have 3FNC, a chute, and call game! In any case, since it doesn’t slow the model, there isn’t as much urgency in ramping up the RPMs immediately post deployment as there is for a competition helicopter model.
i do wonder if maaaaaybeeee the Magnus force may turn the model into the wind, but I kind of doubt it.
