Bottle Rocket B

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calliekernick
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Re: Bottle Rocket B

Post by calliekernick » April 10th, 2011, 2:28 pm

hey everyone, i have a rocket that has been getting consistent times of 21 seconds or so (up to 27 if it catches some wind while backsliding on the descent). we're looking to improve this time for nationals and hoping to hit 30 seconds. does anyone have any tips on how to increase time- maybe a way to make the rocket's descent slower? also, does anyone have any great designs that are getting 30-second times? thanks so much.

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Re: Bottle Rocket B

Post by Primate » April 10th, 2011, 2:43 pm

calliekernick wrote:hey everyone, i have a rocket that has been getting consistent times of 21 seconds or so (up to 27 if it catches some wind while backsliding on the descent). we're looking to improve this time for nationals and hoping to hit 30 seconds. does anyone have any tips on how to increase time- maybe a way to make the rocket's descent slower? also, does anyone have any great designs that are getting 30-second times? thanks so much.
You're starting to get to that point where you just can't make a backslider much better without a larger pressure chamber. Anything you can do to make it lighter is probably helpful, though you may already be at the optimum weight. You might also want to try using larger fins (more surface area to catch the wind) and adjusting their location/length of rocket accordingly.
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Re: Bottle Rocket B

Post by Cheesy Pie » April 10th, 2011, 3:33 pm

Check the Bottle Rocket Wiki and my Wiki.
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Re: Bottle Rocket B

Post by Littleboy » April 10th, 2011, 3:40 pm

Well if he has those flight times then he probably has the basics down so those won't do any good.

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Re: Bottle Rocket B

Post by Cheesy Pie » April 10th, 2011, 3:43 pm

You know how when you screw a nail into a space for it, and the more you turn it, the further it goes in? Try making your fins in a similar way. They wind around the rocket, so it spins as it goes up, gaining altitude and time.
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Re: Bottle Rocket B

Post by Primate » April 10th, 2011, 3:54 pm

calliekernick, what's your nose cone look like right now?
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Re: Bottle Rocket B

Post by Cheesy Pie » April 10th, 2011, 4:28 pm

Most importantly, follow the rules of the event. You want to be able to compete, right?
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Re: Bottle Rocket B

Post by thewinner » April 11th, 2011, 1:32 pm

Cheesy Pie wrote:You know how when you screw a nail into a space for it, and the more you turn it, the further it goes in? Try making your fins in a similar way. They wind around the rocket, so it spins as it goes up, gaining altitude and time.
That won't help unless you have helical rotors of some sort. Actually, if you waste some of the energy on making your rocket spin, the rocket will not fly as high. The only reason you would want your rocket to spin is if it wasn't stable (that's what rifling the barrel of a gun does) but your fins should fix that anyway.
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Re: Bottle Rocket B

Post by Cheesy Pie » April 11th, 2011, 5:53 pm

thewinner wrote:
Cheesy Pie wrote:You know how when you screw a nail into a space for it, and the more you turn it, the further it goes in? Try making your fins in a similar way. They wind around the rocket, so it spins as it goes up, gaining altitude and time.
That won't help unless you have helical rotors of some sort. Actually, if you waste some of the energy on making your rocket spin, the rocket will not fly as high. The only reason you would want your rocket to spin is if it wasn't stable (that's what rifling the barrel of a gun does) but your fins should fix that anyway.
Oh. Some other guy said that would work.
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Re: Bottle Rocket B

Post by Primate » April 11th, 2011, 6:56 pm

I've actually had better results with angled fins. Backsliding requires the rocket to be stable on the way up (that's why it's straight), and marginally unstable on the way down (that's why it's sideways). Normally, you accomplish this by delicately adjusting fin size, position, and mass distribution to change the center of pressure/lateral area/mass. But if you have the added stability of spinning, you can hit that instability point a little more easily and get a better backslide. At least in my experience.

Spinning probably also helps in the wind.
events 2012 gravity vehicle, robot arm, thermodynamics, tps

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