lcorinth
Well-Known Member
- Joined
- Aug 5, 2014
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A few times I've noticed that the CG seems a bit too far forward in OpenRocket than on the real thing. I figured this had to do with the fact that it doesn't take glue into account or something.
But lately I've noticed that the CG seems farther forward than it should be, even without glue weight.
And I've really noticed this when you open a RockSim file.
I like that you can open either .rkt or .ork files with OR - it means I can download some premade sims of some of the rockets I have.
But check these out. Here's a picture of the Quest Big Dog, the RockSim file of which I downloaded from Apogee:
Now here's a more extreme example. I don't know what RockSim file I started with, but I used an already-designed rocket, played around with it a bunch, and ended up with this:
That CG is nuts!
I checked the mass of the components, and they're not too far off from the real thing, so I don't know what's going on here. And the weird thing is, even if I zero out the mass on the stuff on the front, and add a ton of mass on the stuff on the back (i.e., lead fins), the CG is still way forward.
I know you can override the CG of the rocket as a whole. But when I've done that, I found that when I add motors, the CG doesn't change - it stays where you put it.
I'm wondering if anybody else has noticed this, and what to do about it. Also, in files originally designed in OR, does anybody think the CG is a bit too far forward, even accounting for glue and such?
[Edit] I should note that I worry that if the CG is off, the CP may also be off, when importing RockSim files into OR - can anybody address this concern?
But lately I've noticed that the CG seems farther forward than it should be, even without glue weight.
And I've really noticed this when you open a RockSim file.
I like that you can open either .rkt or .ork files with OR - it means I can download some premade sims of some of the rockets I have.
But check these out. Here's a picture of the Quest Big Dog, the RockSim file of which I downloaded from Apogee:
Now here's a more extreme example. I don't know what RockSim file I started with, but I used an already-designed rocket, played around with it a bunch, and ended up with this:
That CG is nuts!
I checked the mass of the components, and they're not too far off from the real thing, so I don't know what's going on here. And the weird thing is, even if I zero out the mass on the stuff on the front, and add a ton of mass on the stuff on the back (i.e., lead fins), the CG is still way forward.
I know you can override the CG of the rocket as a whole. But when I've done that, I found that when I add motors, the CG doesn't change - it stays where you put it.
I'm wondering if anybody else has noticed this, and what to do about it. Also, in files originally designed in OR, does anybody think the CG is a bit too far forward, even accounting for glue and such?
[Edit] I should note that I worry that if the CG is off, the CP may also be off, when importing RockSim files into OR - can anybody address this concern?
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