OpenRocket "Too Many Parallel Fins"

[El Phantasmo]

I've modeled my nearly completed MIM-23B Hawk in OpenRocket with as much the external components as possible. I added the 2 "wire guides," by tricking OpenRocket into thinking they are very short and wide fins. Now the simulations give a "too many parallel fins" error. I looked up the error in the source code. I kind of understand what's going on, but I don't know how important the error is. Can I safely ignore the warning? The change in the simulation results are barely noticeable.

Attached is the OprnRocket file: mim-23b hawk.ork

[AlfaBrewer]

I get this when simulating tube fins on OR. My rough estimate of height based on my finely calibrated eyeball (HA!) found the sim to be accurate enough.

I was working on an upscaled Mudwasp with 6 tube fins and 6 regular fins. I did use the freebie trial of Rocsim to compare OR against and got fairly similar results.

[El Phantasmo]

I removed one set of "wire guides"/fins, and I simply extended the ones on the transition to cover the length of the rocket body. This removed the "too many parallel fins" message, as there are no longer 2 parallel fins comprising the "wire guide."

[Sampo]

Hi,

The number of parallel fins affect a coefficient on how much fin-fin interference reduces the lift the fins produce. As the Barrowman methods don't allow completely arbitrary fin shapes and positions like OR does, it approximates by counting the number of fins along the same body tube section, and assumes the interference to be similar to the interference of same-sized fins. Thus if you have extremely small fins in parallel with larger ones, it may slightly decrease the computed stability. Once you go over the warning threshold of eight fins, they shouldn't have any further effect though.

Cheers,
Sampo N.