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Personally I'd say it's less likely for the rocket to catch an updraft than to have its flight disrupted by the wind, but I have very little experience to speak out of. BTW, where do you guys test the rockets? There's no safe place in NYC to do so, and I'm sure that's why the event doesn't run at Regionals.

Our regional competition is tomorrow morning and I was wondering what the steps for competing are. Are we expected to fill the water bottles ourselves within the time allotted? Do we also mount the rocket on their launcher? Pull the trigger? I assume they will take care of all the timing...

Also, is it safe to assume that "Sparkling water" bottles are the same as carbonated? I.e. they will qualify for the competition?

gmui wrote:Our regional competition is tomorrow morning and I was wondering what the steps for competing are. Are we expected to fill the water bottles ourselves within the time allotted? Do we also mount the rocket on their launcher? Pull the trigger? I assume they will take care of all the timing...

Also, is it safe to assume that "Sparkling water" bottles are the same as carbonated? I.e. they will qualify for the competition?

I think you're supposed to do everything (fill the bottle, mount the bottle, pull the trigger, etc.) yourselves except for pressuring the rockets and taking the required measurements. Varies competition by competition though, so your regionals might be a little different from my description.

gmui wrote: Also, is it safe to assume that "Sparkling water" bottles are the same as carbonated? I.e. they will qualify for the competition?

Yes, they should qualify.

If you want to make your bottle go REALLY high, and float down slowly, you SHOULD use a backslider. My competition was in February, and I got 4th. I honestly regret NOT using a backslider because that was what I was gonna do but in the end, decided not to. The people who one first place used a backslider and got around 15-20 sec. (estimating)

I need help incalculating the center of pressure. I've looked on-line. It doesn't translate well to a cone shaped nose cone. Any advice?

ls20817 wrote:I need help incalculating the center of pressure. I've looked on-line. It doesn't translate well to a cone shaped nose cone. Any advice?

Would something crude like holding it in front of a large fan and seeing where it balances work?

EDIT: Read that as Center of gravity, not pressure. My bad.

I am trying to help my kids prepare for bottle rocket in a few weeks - we have built and tested many rockets but our best time is right around 10 seconds.

We have used plastic flourecent light tubes for the nosecone . . approximately 3 feet . . 450 ml of water, 3 fins, 1 L bottle and the weight of the rocket ends up right around 120-130 grams. Our rockets tend to go fairly high, then fall backwards (straight down, the reverse of how they went up) for about half the height, then level out and backslide the rest of the way.

Are the teams that are getting 15+ seconds using paper nosecones? My kids are getting frustrated and I want to be able to help them but I am running out of ideas.

ls20817 wrote:I need help incalculating the center of pressure. I've looked on-line. It doesn't translate well to a cone shaped nose cone. Any advice?

This website is awesome, given that you have a conventional design http://physics.gallaudet.edu/tools/rocketcop.html