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drewbuildsstuff

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Hey Guys!

I'm fairly new to the rocket game, I have launched a couple store bought ones but never built one from scratch. I recently did a youtube video on one that I powered with co2 cartridges. I ran into a problem with it tumbling in the air after take off. Due to the power of the cartridge's weight is the biggest concern so I don't have a lot of room to add pieces or weights.

It was a lot of fun and I want to build another to see how high it will go if I can get it to go straight. Video is below if that helps give you an idea of what is happening. Any suggestions would be awesome!

 

prfesser

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Is there a particular reason for using CO2 cartridges? First, on TRF this would be considered "research rocketry", using other than certified motors, and that sort of stuff is relegated to the Research forum; access requires L2 certification from TRA/NAR/CAR.

Certified motors would provide considerably greater thrust as well as a means of activating a recovery system.

That was a darned good representation of a Saturn V, for a freehand effort!

Best -- Terry
 

kalsow

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I'd guess your rocket's center-of-pressure (CP) is ahead of its center-of-gravity (CG). For stable flight (without vectored thrust) you need the CG to be ahead of the CP. A foam rocket with four heavy CO2 cartridges in the rear and smallish Saturn V-like fins is almost certainly going to tumble.


If you really want to design rockets, use OpenRocket(free) or RockSim($$) before you light'er up.
 

Grog6

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This is a good start:
 

Scott_650

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It’s always fascinating watching someone come up with a more complicated and less successful method to do a fairly simple task 😆

The OP put a lot of work and planning into a less than optimal solution but I do have to give them credit for imagination and perseverance. Here’s my quick (cuz I have a mountain of leaves to get sucked up from the yard and not a lot of daylight to do it) take - if you insist on using CO2 cartridge power leave that out of any future discussion, as already mentioned that’s veering into EX motor territory so just keep that aspect to yourself, but regardless of the power source all aerodynamic/passively stabilized rockets work the same way - your version of the SV was massively tail-heavy with very thick section fins and you launched it from a very short rod, that’s a tailor made situation for exactly the flight performance you had. Something as simple as a swing test could’ve shown you that your design needed some changes for stable flight. It’s basic beginner rocketry that the CG must be ahead of the CP - rule of thumb for conventional planform rockets is ensure that at launch the CG is at least one body diameter (or caliber) ahead of the CP. Your design needs some substantial nose weight and a much longer launch rod - I did a quick search and found that a 16 gram cartridge weighs nearly 60 grams so times four is nigh on a pound. Plus I’d suggest at least a four foot 1/4” launch rod - preferably longer. Also, you evidently aren’t planning to include any kind of recovery system which, if you stick to launches on your own property isn’t an issue, but if you’re thinking of using your techniques elsewhere it could be - one thing you’ll see if you spend any substantial time with hobby rocketry folks is that safety is nearly an obsession - we’ve come way too close too many times over the years to loosing our hobby to let a safety lapse have an impact now. So please take every precaution to preclude injuries or property damage with whatever you do with any kind of rocket! Good luck with your path, it’s not one I’d ever choose but if it’s your focus I wish you well.
 

Grog6

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A culture of safety is the first step toward safe conduct; always think "What's the worst thing that could happen?"
When that involves other people, said action is a bad idea, and could end you up in jail, if you hurt someone.
 

Grog6

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One of my friends saw me write this; he mentioned that we rarely took that advice; and that was how we ended up telling Atlanta's finest "No, I haven't seen two guys with parachutes!" while stuffing said parachutes into the back seat of the subaru. :)
He was looking right at us, so IDK why we didn't get arrested. : )
People apparently get mad when you jump off their buildings, lol.
 
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