amused by rocksim

I wanted a rocksim file for the Estes hi-flier, so I went to rocket reviews/ rocksim library...started reading the 'report' was amused by the stability report whereby it said that the hi-flier was overstable. right. loaded it into OR stuck a C6-7 in it, max alt, 100' stability margin -.4 cal.
changed the motor over hang to the Estes standard 0.25" (from 0.5") and added the 6.7g of the provided clay to the nose...tada 1500'. do people not bother to check the instructions before submitting their design files? I will grant that the clay is a recent addition to the kit, but a half inch overhang for the motor?
oh, BTW, dried white glue has a density of approx. .75g/cm^3 if you want to include fin filets in OR.
Rex

I stopped trusting most sim files uploaded to rocket reviews a long time ago. Most folks are very sloppy on their sims. Whenever possible, I try to find the parts list and instructions to make my own.

Jerome

I'm one of those "sloppy" people. IMO, there's no point in building a super-detailed model of the rocket in the simulator. I just make the exterior accurate to get a good center of pressure.

It's easier and more accurate to override the measured mass and center of gravity once the rocket is complete than to try to get all the parts and adhesive bonds perfect.

JohnCoker said:

I'm one of those "sloppy" people. IMO, there's no point in building a super-detailed model of the rocket in the simulator. I just make the exterior accurate to get a good center of pressure.

It's easier and more accurate to override the measured mass and center of gravity once the rocket is complete than to try to get all the parts and adhesive bonds perfect.

Click to expand...

That is my approach as well... Get most of the main parts and the external stuff (fins, NC, tubes) and use a mass object to get the total weight and CG correct

the end of the motor sticks out into the airflow, ergo the position of the motor does affect CP (or at least it should).
Rex

I like to be accurate in my sim detail so I have a digital blueprint of my construction. This allows me to share or reproduce my build later.

Jerome

Obviously this is not a Rocksim problem. This is a user issue, and can be done in any simulation program. It is basically a matter of garbage in, garbage out.

I take great effort to make my sims accurate as I find it get very accurate sims then. You mileage may vary.

Rex R said:

the end of the motor sticks out into the airflow, ergo the position of the motor does affect CP (or at least it should).
Rex

Click to expand...

I don't think Rocksim is smart enough to do this. I just tried it to the extreme. The sticking out length affects the CG only, not the CP.

JohnCoker said:

I'm one of those "sloppy" people. IMO, there's no point in building a super-detailed model of the rocket in the simulator. I just make the exterior accurate to get a good center of pressure.

It's easier and more accurate to override the measured mass and center of gravity once the rocket is complete than to try to get all the parts and adhesive bonds perfect.

Click to expand...

Right. The hard part of getting a design file built for RS and OR is measuring and creating all the exterior dimensions. If somebody is willing to do this and posts the file, then that is a huge step, to which I say thank you. I'll take it from there. I don't care about the mass or any stuff "inside" the rocket, since my build will be totally different.