Rocksim mass manual override - CG

I've been having a few of these brain misses lately - it's either Alzheimers or perhaps those epoxy fumes.

Anywho, I'm pretty sure I understand this, but for some reason can't be certain. So I'll ask here to check myself.

When I do a manual override on the mass of a given component (in RockSim), and I also manually adjust the CG location, that location is figured from the front/tip of the part in question, NOT from the front of the rocket - YES?

Example: Let's say I've got an 8" coupler tube that weighs 72g., in a rocket that is 48" long overall, and it is located 28" from the tip. In "mass override" I plug in 4" for the CG. This means that RockSim assumes that those 72grams are centered 32" from the tip of the NC, or 16" from the aft end of the rocket. Is this correct? Do I have this right?

thanks, s6

In case no gives you a definitive answer, I would do the following:

Make a simple airframe (no nose cone, fins, etc.) and place 2 mass objects at either end, and see where the CG goes.

Greg

S6,

Your assumption is correct. It is my understanding that the individual CG override value is defined within the context of the individual component.

RockSim will automatically calculate the rocket's overall CG by considering all the individual components' location, weight and CG values and consolidate that into an overall weight and CG for the rocket. This makes it more user-friendly in case that you end up moving some of the components within the rocket's design because you will not have to re-calculate the override CG values for all the components where you entered an override value.

In other words, you did the right thing by plugging in 4" for the CG override value.

Here is a screenshot from within RockSim 9 using the "What's this?" button for the CG override field:



Cor Ruiten

I override CG for all individual parts to value 0 in Rocksim rather then inputting seperate CG values for every part. Once the rocket is completely built and assembled I'll balance the rocket to find actual CG and input that value into Rocksims overall Mass Override. The CP mark on the rocket is of main importance to me in the field. Once motor, chutes, electronics and everything else are installed, I'll balance the rocket to find CG and measure the difference compared to the premarked CP to verify sufficient stability. Works like a champ and is dead on accurate for me.