Hovercraft B/C

geniusjohn5
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Re: Hovercraft B/C

Postby geniusjohn5 » December 2nd, 2017, 6:31 pm

Unome wrote:
geniusjohn5 wrote:Someone told me that holes poked in the skirt of a Hovercraft make it more effective? Can someone explain how so?

Without holes in the skirt (or some sort of opening), there's no hovering. The hovering is caused by air rapidly rushing out of the hole/holes (anywhere from one fairly small hole to dozens/hundreds of miniscule ones) and escaping horizontally, pushing the bottom of the skirt up.



Sorry I'm very new to Hovercraft? Can you elaborate on that concept more? Thanks!
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Re: Hovercraft B/C

Postby reed303 » December 2nd, 2017, 6:51 pm

geniusjohn5 wrote:
Unome wrote:
geniusjohn5 wrote:Someone told me that holes poked in the skirt of a Hovercraft make it more effective? Can someone explain how so?

Without holes in the skirt (or some sort of opening), there's no hovering. The hovering is caused by air rapidly rushing out of the hole/holes (anywhere from one fairly small hole to dozens/hundreds of miniscule ones) and escaping horizontally, pushing the bottom of the skirt up.



Sorry I'm very new to Hovercraft? Can you elaborate on that concept more? Thanks!


Some reading here may help: https://scioly.org/wiki/index.php/Hovercraft#Skirt
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Re: Hovercraft B/C

Postby mattruff » December 4th, 2017, 11:51 am

Are we able to use elastic band motors in our hovercraft?

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Re: Hovercraft B/C

Postby SPP SciO » December 4th, 2017, 3:39 pm

dmis wrote:
farmerjoe279 wrote:
shrewdPanther46 wrote:
I was able to lift more than 2kg with a wimpy skirt like that. I Have to agree with the others in that the issue is most probably your fan, although it could be your power source


My fan can cut of a finger. A FINGER! Also I think i have a good battery. Probably because my motor ways like 2 pounds :P


Spinning fast and having a sharp edge does not necessarily make a blade best for the hovercaft. Thought realistically, I would expect you are right about the problem,


Our team is having some trouble solving the weight problem. The more powerful the motor, more powerful battery, all add extra weight. Last year, it wasn't a problem, because of the 2kg limit, but the penny challenge is tough!

Here's what we're working with:

https://www.digikey.com/product-detail/ ... ND/4702514 for a propulsion fan,
https://www.digikey.com/product-detail/ ... ND/2560506 for the lift fan.

Both of them are running on 8.4v NiMH battery packs, which are much heavier than equivalent output lithium batteries. I am not sure if I would advise other teams to buy these fans, since they're expensive, and in our limited experience, they haven't been working out great. The first one is super dangerous too - shielding absolutely a must before even turning it on to test.
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Re: Hovercraft B/C

Postby Birdmusic » December 4th, 2017, 5:03 pm

mattruff wrote:Are we able to use elastic band motors in our hovercraft?

I doubt that would be very effective, since everyone else will probably be using electrical motors, however, it is allowed.
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Re: Hovercraft B/C

Postby timothyre » December 7th, 2017, 6:38 am

Just a very quick question that one of my students asked me. The rules for hovercraft state that "Commercial batters, including rechargeable, not exceeding 9.0 V as labeled, may be used to energize the motors on the vehicle." My student asked me if that was limited to 9.0 V batter PER motor, or 9.0 V to power both motors. I am pretty confident that it is 9.0 V TOTAL for the vehicle, but told him I would check to be 100% certain.

Thanks

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Re: Hovercraft B/C

Postby LittyWap » December 7th, 2017, 6:43 am

timothyre wrote:Just a very quick question that one of my students asked me. The rules for hovercraft state that "Commercial batters, including rechargeable, not exceeding 9.0 V as labeled, may be used to energize the motors on the vehicle." My student asked me if that was limited to 9.0 V batter PER motor, or 9.0 V to power both motors. I am pretty confident that it is 9.0 V TOTAL for the vehicle, but told him I would check to be 100% certain.

Thanks



The limitation is 9V per motor. At competitions last year, proctors made sure to check if batteries were run in series. It doesn't matter how many batteries per motor, the electromotive potential across the circuit has to be less or equal to 9.0V. There's no limit on amperage.
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Re: Hovercraft B/C

Postby geniusjohn5 » December 7th, 2017, 6:41 pm

For the written exam, do sig figs and uncertainties matter?
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The chemist replies, "I shall find a solution."

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Re: Hovercraft B/C

Postby Birdmusic » December 7th, 2017, 7:42 pm

geniusjohn5 wrote:For the written exam, do sig figs and uncertainties matter?


I believe the SOInc guidelines say that sig figs only matter for Division C, however, I guess its up to the test writers.
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2018 Results
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Crime Busters: 1/2
Disease Detectives: 1/5
Hovercraft (both builds failed, rip): 11/9

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Re: Hovercraft B/C

Postby gcrewmc3 » December 8th, 2017, 2:12 pm

Hello fellow Olympians,
I was wondering if you can have two 8.4 volt batteries on the hovercraft to power the motors? I know the rules say you can’t have more than 9 volts in a battery.

Thanks!

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Re: Hovercraft B/C

Postby retired1 » December 8th, 2017, 3:08 pm

Can you stand that amount of weight?

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Re: Hovercraft B/C

Postby Birdmusic » December 8th, 2017, 4:27 pm

gcrewmc3 wrote:Hello fellow Olympians,
I was wondering if you can have two 8.4 volt batteries on the hovercraft to power the motors? I know the rules say you can’t have more than 9 volts in a battery.

Thanks!


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2018 Results
Regionals/States
Crime Busters: 1/2
Disease Detectives: 1/5
Hovercraft (both builds failed, rip): 11/9

geniusjohn5
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Re: Hovercraft B/C

Postby geniusjohn5 » December 9th, 2017, 7:01 pm

Just a quick clarification: Is the hovercraft this year(2017-2018) generally going to be a lot bigger than it was last year(2016-2017)?
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The chemist replies, "I shall find a solution."

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Re: Hovercraft B/C

Postby Adi1008 » December 9th, 2017, 7:02 pm

geniusjohn5 wrote:Just a quick clarification: Is the hovercraft this year(2017-2018) generally going to be a lot bigger than it was last year(2016-2017)?

The increased the maximum dimensions to 40x40cm so it's reasonable to expect bigger devices than last year
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Re: Hovercraft B/C

Postby geniusjohn5 » December 10th, 2017, 6:54 am

This may sound like a really dumb question but I'm an extreme newbie to this event. Does the hovercraft float on the air-contained skirt or is there a little bit of plain open air beneath the skirt?
The physicist says, "In the universe, does matter really matter?"
The chemist replies, "I shall find a solution."


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