Hovercraft B/C

[Ash123]

Hey! I need some help figuring some stuff out about the fans for my hovercraft.
1) Are we allowed to use centrifugal fans
2) How can I calculate if the fan I picked out has the ability to lift a certain amount of weight? (Trial and error isn't really an option for me because my school doesn't reimburse)
3)What is the relationship between fan diameter, pitch, and lift generated?
4) what types of batteries would be best to use?
5) How can I figure out what types of wires I need so they won't burn out?
6) Could a computer cooling fan work for a thrust fan?
7) Does anyone know if there are any good thrust/lift fan combos out there?

Thanks a bunch! Good luck to everyone!

[copper.hat]

Can someone please confirm that overcharging is **not** allowed?

Rule 3f. has the ambiguous words 'as calculated by their labels" which I suspect has some folks thinking that it is permissible.

The Science Olympiad Battery Policy states "monitor recharging of batteries to ensure they are not being overcharged"
which suggests that the intent is to **not** allow overcharging.

This is just my opinion, but as an EE, i would suggest that the risk from overcharging NiMH is in the same ballpark as the risks of allowing Li-based batteries.

[arv101]

How close are you guys getting to 15 seconds and how many penny rolls are you using at that time?

[Ash123]

How close are you guys getting to 15 seconds and how many penny rolls are you using at that time?

Is fifteen seconds considered a fast time? I have no frame of reference since this is my first yet on hovercraft. However, speed is worth significantly less points than max weight capacity, so you might want to consider losing some of your speed points so you can carry more coins.

[arv101]

How close are you guys getting to 15 seconds and how many penny rolls are you using at that time?

Is fifteen seconds considered a fast time? I have no frame of reference since this is my first yet on hovercraft. However, speed is worth significantly less points than max weight capacity, so you might want to consider losing some of your speed points so you can carry more coins.

True, thanks.

[Adi1008]

How close are you guys getting to 15 seconds and how many penny rolls are you using at that time?

Is fifteen seconds considered a fast time? I have no frame of reference since this is my first yet on hovercraft. However, speed is worth significantly less points than max weight capacity, so you might want to consider losing some of your speed points so you can carry more coins.

If I understand correctly, going faster doesn't help; being closer to 15 seconds does

[shrewdPanther46]

yep

[dmis]

Can someone please confirm that overcharging is **not** allowed?

Rule 3f. has the ambiguous words 'as calculated by their labels" which I suspect has some folks thinking that it is permissible.

The Science Olympiad Battery Policy states "monitor recharging of batteries to ensure they are not being overcharged"
which suggests that the intent is to **not** allow overcharging.

This is just my opinion, but as an EE, i would suggest that the risk from overcharging NiMH is in the same ballpark as the risks of allowing Li-based batteries.

The battery policy is for safety, not for event rules. Since NiMH batteries don't have a set full charge voltage, it would be hard to argue that one particular battery was overcharged. A nominal 8.4v NiMH may charge to 10v before being fully (safely) charged. Also, the es would have no way to know if a battery is overcharged, and I have never seen one test the battery with a voltmeter.

I agree though that it would not be wise.

[shrewdPanther46]

Can someone please confirm that overcharging is **not** allowed?

Rule 3f. has the ambiguous words 'as calculated by their labels" which I suspect has some folks thinking that it is permissible.

The Science Olympiad Battery Policy states "monitor recharging of batteries to ensure they are not being overcharged"
which suggests that the intent is to **not** allow overcharging.

This is just my opinion, but as an EE, i would suggest that the risk from overcharging NiMH is in the same ballpark as the risks of allowing Li-based batteries.

The battery policy is for safety, not for event rules. Since NiMH batteries don't have a set full charge voltage, it would be hard to argue that one particular battery was overcharged. A nominal 8.4v NiMH may charge to 10v before being fully (safely) charged. Also, the es would have no way to know if a battery is overcharged, and I have never seen one test the battery with a voltmeter.

I agree though that it would not be wise.

NimH cells can be "overcharged". The term overcharged refers to when the battery is overcharged to a point where it is pressurized from the buildup of oxygen gas in the cell. At that point, cell capacity and life is lost. Thus, it makes sense for the rules to say "by the label," essentially saying that overcharging is practically inevitable in most cases, and would be the "correct" thing to do.

[ftf841]

How close are you guys getting to 15 seconds and how many penny rolls are you using at that time?

We got 7 seconds and 4 pennies at an invitational. Could've gotten a lot closer to 15, but the craft went a lot faster than we predicted.