Bottle Rocket B

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Re: Bottle Rocket B

Post by SPP SciO »

calgoddard wrote:The space shuttle bottle rocket is very cool looking.

Glider rockets are not a good choice for SciOly Bottle Rocket competitions.

Like Elastic Launched Gliders the wing incidence (angle) required for high speed ascent (without looping) is not optimum for a low speed glide.

The flight time of the space shuttle bottle rocket in the video is only about 20 seconds. Many 2L backslider rockets can beat that time by a considerable margin (5 - 7 seconds) if they don't carry an egg. Many teams at the SoCal state finals last year got over 25 seconds per flight in the Bottle Rocket event.

Plus, the space shuttle bottle rocket shown in the video has a Gardena fitting on the bottle. The constricts the water stream, lowering the force of the thrust but extending the duration of the thrust. A Gardena fitting is lot legal under the 2016 Bottle Rocket rules.

Expect lower times this year in Bottle Rocket than last year as the weight of the egg will lessen the height at apogee and speed the rate of descent.

The winner at 99%, if not all, SciOly Bottle Rocket competitions this year will utilize the standard back slider configuration.
Thanks for the analysis - it seems like it's worth playing around with, but I'd bet you're right. It seems somewhat unfortunate though - out of all the build events, this seems to have the most restrictions on effective designs, yet the outcome is likely swayed by uncontrollable variables, like whatever the air is doing when it's your turn to launch.
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Re: Bottle Rocket B

Post by calgoddard »

SPP SciO -

It is definitely true that if two back slider bottle rockets at the same competition are both well designed and well constructed, the longest flight time of these two rockets will often be determined by ambient air conditions in the launch area at the time of launch. These ambient air conditions can vary significantly in just a few seconds.

In the hobby/sport of outdoor free flight model airplanes, at serious competitions, sophisticated electronic equipment is used to monitor local ambient air conditions on a real time basis, and to determine the precise optimum moment for launch. Use of such electronic equipment (and delaying your launch for 5 - 10 minutes while you monitor ambient air conditions) would likely not be tolerated by an Event Captain at a Science Olympiad Bottle Rocket competition.

All you can do is build the best bottle rocket you can, and prove that it performs well on a consistent basis with practice launches. Then you must hope for a little luck at the competition. Keep in mind that a well designed and constructed back slider bottle rocket launched in poor ambient air conditions can often beat a poorly designed and/or constructed back slider bottle rocket launched in good ambient air conditions.

The prohibitions in the 2016 Bottle Rocket rules against the rocket changing shape or deploying any type of recovery system leaves the back slider as the only viable design for winning the Bottle Rocket event this year.

By way of background, I estimate that I have personally observed over 300 bottle rocket launches.
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Re: Bottle Rocket B

Post by 12565853 »

I'm having trouble finding bottles with 2.2 cm necks instead of the reduced 2.1 size. Does anyone have a suggestion for finding the right size bottle?
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Re: Bottle Rocket B

Post by Boombloxer »

Do you guys know anything good to use as a nose thing? I've been using ping pong balls and they're working fine, but I'm wondering if there is anything better.

Thanks- Boombloxer
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Re: Bottle Rocket B

Post by Fanglin »

12565853 wrote:I'm having trouble finding bottles with 2.2 cm necks instead of the reduced 2.1 size. Does anyone have a suggestion for finding the right size bottle?
I don't know what launcher you are using, but I always use a Mtn Dew 2L bottle, because of it's reduced weight, and simple design. Actually a lot of soda companies make bottles like that, but Mtn Dew is most common. Here is an image Image
Problems are better pursued with General Electric GE90-115 engines.

2016 Nats:
Road Scholar:4th 8-)
Bottle Rockets: 9th
Meteorology: 11th
Gliders: 21st

(other events: Green Gen, Crime Busters, Helicopters, Hovercraft, Air trajectory)

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Re: Bottle Rocket B

Post by Fanglin »

oops, sorry about the size of the image...
Problems are better pursued with General Electric GE90-115 engines.

2016 Nats:
Road Scholar:4th 8-)
Bottle Rockets: 9th
Meteorology: 11th
Gliders: 21st

(other events: Green Gen, Crime Busters, Helicopters, Hovercraft, Air trajectory)

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Re: Bottle Rocket B

Post by geo101 »

Is it possible to have a bottle rocket on which the cone portion of the rocket comes off in flight, but remains attached to the rocket with a string?
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Re: Bottle Rocket B

Post by Fanglin »

No, the rocket mustn't change shape inflight.
Problems are better pursued with General Electric GE90-115 engines.

2016 Nats:
Road Scholar:4th 8-)
Bottle Rockets: 9th
Meteorology: 11th
Gliders: 21st

(other events: Green Gen, Crime Busters, Helicopters, Hovercraft, Air trajectory)

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Re: Bottle Rocket B

Post by Alexcazam »

JennFolsom wrote:First time for us to compete in Middle School Science Olympiad and meeting with our coach for the 1st time next week so lots of questions...

Competition parameters say no recovery system, but does that mean a parachute is excluded? I figure that a parachute is essential to this event and saw someone said you can, but hate to get DQed if not.

Anyone know?

On many of the example photos, more than just a single 2 liter bottle are used. Looks like a lot of long tube pieces, where do you buy those? Can I put anything additional on as long as not metal/sharp, etc.

Which type of 2 liter bottle brands do you like to use the most for this event?

Jenn

i use coke bottles
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Re: Bottle Rocket B

Post by asthedeer »

Alexcazam wrote:
JennFolsom wrote:First time for us to compete in Middle School Science Olympiad and meeting with our coach for the 1st time next week so lots of questions...

Competition parameters say no recovery system, but does that mean a parachute is excluded? I figure that a parachute is essential to this event and saw someone said you can, but hate to get DQed if not.

Anyone know?

On many of the example photos, more than just a single 2 liter bottle are used. Looks like a lot of long tube pieces, where do you buy those? Can I put anything additional on as long as not metal/sharp, etc.

Which type of 2 liter bottle brands do you like to use the most for this event?

Jenn

i use coke bottles
Technically, @Alexcazam, we *don't* use Coke bottles, because of the weird ridging/shaping of the bottles...we use bottles that are entirely round, which we've found to work better.

@JennFolsom-
No, parachutes are not allowed. However, bottle rockets seem to float fairly well even without parachutes.
Tube pieces...are usually flat thin pieces of plastic rolled up, either into a tube shape or in a cone shape. They balance out the weight of the bottle, help stabilize the rocket, and help it to float. We got our plastic at a printer's shop; it was the plastic for over head projectors.
I'm not sure what you mean by "anything additional"...but I don't think you would need anything in particular.
As I mentioned earlier, we tend to shy away from bottles shaped like this-
http://media3.picsearch.com/is?RdU5Ier4 ... height=255
but instead veer towards bottles shaped like this-
http://media3.picsearch.com/is?j-uulpvJ ... height=240
just because we found them to fly better.

Hope this helps!
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