Probably being redundant, here, but use RockSim or OR to get the CP. Then get the rocket flight-ready and get the actual CG by balancing it.
THANK YOU, JOHN! You rock!!! Been preaching that for years...virtual world simulation will only get you half way there!
If it is less than one caliber, then it should be considered unstable.
I've always understood it as between 0 and 1 calibers you have marginal stability. IE, the rocket has some level of stability, but a small safety margin. Rocket may wander but is not likely to do loopty-loops. Many rockets and rocketeers are marginally stable and fall in this range, believe it or not!:wink:
CG on top of CP would be neutral stability; the rocket will fly unpredictably.
CG aft of CP: Rocket is unstable: will perform loops, land shark, hunt down the innocent, and so on.
Disclaimer: I'm not advising less than 1 caliber of stability; just noting that having less than 1 caliber of stability does not always mean rockets exhibiting unstable flight characteristics.
P.S. Loc IV is a pretty stable design with those decent sized and spanning aft swept fins. I've flown a pile of flights on IV's and Heavy Duty Beauty's with motors ranging from C11's (okay, as outboards), to I200's. No noseweight, no problem... but we all build different so take John's advice to mark the CP on the rocket and check ACTUAL CG of the loaded rocket!
Cheers!