Bottle Rocket B

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Re: Bottle Rocket B

Postby jgrischow1 » Wed Feb 29, 2012 3:14 pm

We can't seem to get above 10 seconds and I am wondering if anyone has any ideas. Yes, I have read this thread, last year's thread, the wiki, and Googled for hours.

We are using a 1 L bottle and about 425 mL of water.
Our nose cone is a long plastic tube, about 5 ft long and 1.5 in diameter.
Our fins are made from plastic folders and folded and taped for rigidity. They are trapezoidal, with bases of 3 in and 5 in and a height of 3 in.

We have two main problems that I see:

Height: The rocket doesn't seem to be going very high.
Delayed backslide: It falls the same way it came up (i.e. the opposite of a nosedive) for awhile before turning and backsliding.

My ideas:

Make the rocket lighter. Take away some tape, shorten the rocket?
Add weight to the tip so it goes up straighter and/or turns to backslide sooner (but we tried this a little and got some nosedives at the end of the backslide)?
Change the fin size/shape?
I don't think we have time to significantly alter the design of the nose cone to, say, paper. Our regional is Saturday.

Any ideas? Thanks.

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Re: Bottle Rocket B

Postby Balsa Man » Wed Feb 29, 2012 5:11 pm

Well, 10 seconds is not that bad....
Your list of things sounds about right.....
Your comment about not going very high makes me womder about launcher problems; is it homemade or commercial; is the nozzle right (not too tight, or loose/leaking); are you getting full pressure?
Why I wonder is that back a couple years ago, with C-Div (Egg-o-Naut- running 1 liter and parachute) we were getting close to 4 seconds of climb (so around 8 sec when parachute failed to deploy and it did a lawn dart. With any backsliding, that would get well over 10 sec.... You also can probably get a bit more with a bit more water; we were running 450-500ccs.
Good luck
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Fort Collins, CO

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Re: Bottle Rocket B

Postby jgrischow1 » Wed Feb 29, 2012 6:58 pm

Balsa Man wrote:Well, 10 seconds is not that bad....
Your list of things sounds about right.....
Your comment about not going very high makes me womder about launcher problems; is it homemade or commercial; is the nozzle right (not too tight, or loose/leaking); are you getting full pressure?
Why I wonder is that back a couple years ago, with C-Div (Egg-o-Naut- running 1 liter and parachute) we were getting close to 4 seconds of climb (so around 8 sec when parachute failed to deploy and it did a lawn dart. With any backsliding, that would get well over 10 sec.... You also can probably get a bit more with a bit more water; we were running 450-500ccs.
Good luck


Thanks Balsa. I think our launcher is OK. It is an Aquaport just bought this year. I don't see any leaking or tightness issues. The gauge reads 60. We will see.

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Re: Bottle Rocket B

Postby fishman100 » Wed Feb 29, 2012 7:59 pm

jgrischow1 wrote:We can't seem to get above 10 seconds and I am wondering if anyone has any ideas. Yes, I have read this thread, last year's thread, the wiki, and Googled for hours.

We are using a 1 L bottle and about 425 mL of water.
Our nose cone is a long plastic tube, about 5 ft long and 1.5 in diameter.
Our fins are made from plastic folders and folded and taped for rigidity. They are trapezoidal, with bases of 3 in and 5 in and a height of 3 in.

We have two main problems that I see:

Height: The rocket doesn't seem to be going very high.
Delayed backslide: It falls the same way it came up (i.e. the opposite of a nosedive) for awhile before turning and backsliding.

My ideas:

Make the rocket lighter. Take away some tape, shorten the rocket?
Add weight to the tip so it goes up straighter and/or turns to backslide sooner (but we tried this a little and got some nosedives at the end of the backslide)?
Change the fin size/shape?
I don't think we have time to significantly alter the design of the nose cone to, say, paper. Our regional is Saturday.

Any ideas? Thanks.

If your rocket is not going very high, you might be encountering stability issues. Do you see the rocket "wobbling" as it ascends? If so, then you need to make the rocket more stable.
Check to see where the CP/CG is; that might be affecting the flight of your rocket.

This applies for all rockets; make sure you minimize the amount of resistance on your rockets. A poorly taped nose cone that has air bubbles in it, etc. will decrease the time of your rocket!
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Re: Bottle Rocket B

Postby Balsa Man » Wed Feb 29, 2012 8:29 pm

Yup, for good stability, you want CP- center of areodynamic pressure- aft of the center of gravity. Bigger fins will move it aft; bit more drag, but if you need stability...
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Re: Bottle Rocket B

Postby fishman100 » Fri Mar 02, 2012 1:20 am

For those of you who have been to a competition, do you know the winning time?

Just curious given the different bottle size this year.
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Re: Bottle Rocket B

Postby jgrischow1 » Fri Mar 02, 2012 5:05 am

fishman100 wrote:For those of you who have been to a competition, do you know the winning time?

Just curious given the different bottle size this year.


If I'm reading it right, the winning combined time from Wright State was 41.29 seconds.

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Re: Bottle Rocket B

Postby jma » Sat Mar 03, 2012 9:13 pm

This is the launcher they used at our Regional tournament.

http://sciencekit.com/triple-bottle-roc ... IG0024114/

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Re: Bottle Rocket B

Postby jma » Sat Mar 03, 2012 9:31 pm

My coach was able to rent a launcher at a nearby school. :D But now I'm confused with the steps of building a rocket. After I find a good bottle and figure out the amount of water, do I make a nosecone and test the rocket with different types of fin ( # of fin, size, design, & material) or the other way around (use same fins & test with different nosecone)?
Thanks.

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Re: Bottle Rocket B

Postby chalker » Sat Mar 03, 2012 9:37 pm

jma wrote:My coach was able to rent a launcher at a nearby school. :D But now I'm confused with the steps of building a rocket. After I find a good bottle and figure out the amount of water, do I make a nosecone and test the rocket with different types of fin ( # of fin, size, design, & material) or the other way around (use same fins & test with different nosecone)?
Thanks.


Do both. Certain nosecones will work best with certain fins and vice versa.

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Re: Bottle Rocket B

Postby jgrischow1 » Sun Mar 04, 2012 1:20 am

fishman100 wrote:For those of you who have been to a competition, do you know the winning time?

Just curious given the different bottle size this year.


The winning combined time at the Cincinnati Regional was about 18.5 seconds, less than half that of the Wright State Invitational.

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Re: Bottle Rocket B

Postby fishman100 » Sun Mar 04, 2012 1:34 am

jgrischow1 wrote:The winning combined time at the Cincinnati Regional was about 18.5 seconds, less than half that of the Wright State Invitational.

jgrischow1 wrote:If I'm reading it right, the winning combined time from Wright State was 41.29 seconds.

Interesting; I'll build my own bottle rocket once I have the materials and once it stops raining and see what time I can get.
jma wrote:My coach was able to rent a launcher at a nearby school. :D But now I'm confused with the steps of building a rocket. After I find a good bottle and figure out the amount of water, do I make a nosecone and test the rocket with different types of fin ( # of fin, size, design, & material) or the other way around (use same fins & test with different nosecone)?
Thanks.

The way we did it last year was to find a good size for the nosecone (we used the same material for each cone so the only variable we needed to test was how long it should be), then experiment with fins, and then figuring out how much water was best for the rocket.
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Re: Bottle Rocket B

Postby skillfullparrot7 » Sun Mar 04, 2012 3:56 am

So yesterday at the OC Regionals in SoCal, it was very windy, and both of my rockets got very bad times(about 8 and 6 seconds) because the wind took them right back down after they were launched. Well, we got 4th in that event anyway, and we are going to state. Is there anything that could help reduce the effect of wind on the bottle rockets?
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Re: Bottle Rocket B

Postby fishman100 » Sun Mar 04, 2012 3:58 am

skillfullparrot7 wrote:So yesterday at the OC Regionals in SoCal, it was very windy, and both of my rockets got very bad times(about 8 and 6 seconds) because the wind took them right back down after they were launched. Well, we got 4th in that event anyway, and we are going to state. Is there anything that could help reduce the effect of wind on the bottle rockets?

Congrats; and if anyone invents a way to eliminate the effect of wind on the rocket I'd like to see it.
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Re: Bottle Rocket B

Postby MustangSciOly11 » Tue Mar 06, 2012 10:11 pm

We're worried about the wind also affecting our bottle rockets in a negative way, but I've also seen some rockets actually get a little help from the wind. The rockets seem to get carried by the wind upwards and use up more time in the air which may have happened at our regionals. Anyone else seen this happen?

Would you rather launch with no wind or with wind?


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