Not really. A positive margin is still positive. Anything larger than 0 should be stable. The problem is that it’s an estimate and could be inaccurate. That’s why a margin greater than 1 is usually required.Yep, switched to the barrowman method just to test in RockSim. It puts it in line with Open Rocket. However if the Barrowman method is accurate, holy **** this rocket is inherently unstable. Loading a G engine into the file downloaded from Apogee puts the CG and CP just 1.5 inches away from each other (.43 margin). Loading a 3 grain H puts that at .23
They do both fly successfully in the sim, but that seems sketch, no?
At 0 margin the rocket will not restore its flight. With negative numbers the rocket will always try to turn 180 degrees. The greater the number the greater the force trying to turn the rocket, whether restoring it to fly directly into the airstream or turning it around.