Rocksim question

[AP aroma]

Hello forum,

I have a couple of scratch built rockets that I built before I had Rocksim. Is there a way to get an approximate altitude on the flight with a given motor without going through all the design components? It's too late now to weigh the body tube, fins, motor tube, etc.

Thanks,

Jim

 

[Ronz Rocketz]

In OR, I weigh the whole rocket and override the CG. I find that’s more accurate than weighing each piece because weighing separately doesn’t factor in glue and paint. Im not sure how you’d do it in RS.

 

[Bill S]

I use RS, and what I do is weigh as many parts as possible, using the mass override for each part, also add CG if possible. This gives you a weight for all the parts, which obviously doesn't include glue, paint, etc.

Just for my own info, I weigh the rocket when assembled, but not primered/puttied or painted. Measure CG. Then add a mass object to the body tube, calling it "glue and paint weight". Move the mass object up and down the tube until you find a spot where it closely matches actual measured CG. Write down the weight.

Prime/putty/paint the rocket, and note the new weight and CG. Add the difference between the current weight and the last weight to that mass object until the new CG is a close match. Write down the final CG and weight. Check the stability number; you want it over 1. If not, you might have to add some nose weight, since the rocket is "done" you probably won't want to modify it at this late stage.

I don't bother trying to get the CG exactly matching; its too much trouble in some cases. As long as you are pretty close, good enough.

 

[user 30299]

Hello forum,

I have a couple of scratch built rockets that I built before I had Rocksim. Is there a way to get an approximate altitude on the flight with a given motor without going through all the design components? It's too late now to weigh the body tube, fins, motor tube, etc.

Thanks,

Jim

If you have the basic rocket already in RockSim, then just use the Mass and CG override option for the overall rocket. Weigh your rocket - without the motor, find its CG by suspending it on a string - or setting it on sharp edge.

If you have not created the file yet, then just go out to the ThrustCurve app and use that. Fill in the basic info on the rocket and it will give you motor selections and altitudes.

 

[AP aroma]

Thanks folks, your input and time is appreciated.