RockSim Mass and Cg overides question

[dbrent]

I'm assuming the mass and Cg overides are without motor and RMS hardware but including any motor mount adapters (e.g. 54-38mm) required... Is that correct?

Thanks,
Don

 

[gpoehlein]

That is my understanding. That way, you can install any motor and it will still be correct. But it needs BOTH mass and CG data if you do the override. In a pinch, if you only have one or the other, let it calculate the mass and CG, then write down the number you are missing and plug that it - better than nothing.

 

[bobkrech]

Why guess? Draw a simple rocket and lock the mass and cp and then install 2 motors with a greatly different mass and impulse. Look at the CG and mass in the output file.

Bob

 

[hardinlw]

I weigh the rocket without engines and add a mass item equal to the difference between the actual weight and what Rocksim predicts. Position it to get the CG right and it will now work with any engine. If you need an adapter, create it as a mass item and put it in the correct position.

 

[dbrent]

I can measure the actual Cg and Mass very easily, I just wanted to know what RockSim expects to be included in those overides.

 

[rstaff3]

As mentioned earlier, the mass in the model should include everything except the actual motor, the mass of which Rocksim will account for when you load the engine(s) into the model. Remember the 'chute, cordage, protectors, etc.

I almost never try to get all the masses right anymore and often don't even add centering rings. In the last step, I measure CG and mass and then iterate to find the required nose weight, if required.