Hovercraft B/C

dmis · Post by **dmis** » February 7th, 2018, 3:05 pm

dmis wrote: 22. The mass flow rate through a cylindrical pipe of cross sectional area A =0.500 m2 is 1500. kg/sec. What is the pressure drop over a distance of 10.0 m?

@nicholasmaurer, did the es ever provide you an answer to this problem?

Post by **sciduck** » February 7th, 2018, 3:20 pm

geniusjohn5 wrote:Also could using a hovercraft that is much smaller than the track width(like a hovercraft from last year) work for this year? Since it would just be hugging the rails of the track.

Yes, but honestly a larger hovercraft would be better because it's easier to hold more weight.

Post by **antoine_ego** » February 7th, 2018, 5:36 pm

geniusjohn5 wrote:If I connected two 9v batteries in parallel, would that have any effect on the speed of the fan/motor? I'm trying to get my hovercraft to move forward but it is unable to

Honestly, I'd just invest in a nice and powerful 8.4 NiMH pack. These can be overcharged up to 10.2V, which is legal since the 9.0V limit is dependent upon the label. If you can't get your craft to move forward, the battery is most likely not at fault. You probably need to redesign your skirt to reduce friction, or get a more powerful back fan. A better back fan is honestly the best solution.

farmerjoe279 · Post by **farmerjoe279** » February 8th, 2018, 7:52 am

antoine_ego wrote:
geniusjohn5 wrote:If I connected two 9v batteries in parallel, would that have any effect on the speed of the fan/motor? I'm trying to get my hovercraft to move forward but it is unable to
Honestly, I'd just invest in a nice and powerful 8.4 NiMH pack. These can be overcharged up to 10.2V, which is legal since the 9.0V limit is dependent upon the label. If you can't get your craft to move forward, the battery is most likely not at fault. You probably need to redesign your skirt to reduce friction, or get a more powerful back fan. A better back fan is honestly the best solution.

Any ideas on the back fan?

Post by **antoine_ego** » February 8th, 2018, 8:05 am

farmerjoe279 wrote:
antoine_ego wrote:
geniusjohn5 wrote:If I connected two 9v batteries in parallel, would that have any effect on the speed of the fan/motor? I'm trying to get my hovercraft to move forward but it is unable to
Honestly, I'd just invest in a nice and powerful 8.4 NiMH pack. These can be overcharged up to 10.2V, which is legal since the 9.0V limit is dependent upon the label. If you can't get your craft to move forward, the battery is most likely not at fault. You probably need to redesign your skirt to reduce friction, or get a more powerful back fan. A better back fan is honestly the best solution.
Any ideas on the back fan?

Some people say that high static pressure is less important in a back fan than high CFM. Personally, every time I've used a high CFM fan it's performed worse than my high static pressure fans. However, the most powerful ones are definitely motors with props attached to them; I've seen them propel crafts at 1m/s at top speed.

IvanGe · Post by **IvanGe** » February 8th, 2018, 6:09 pm

farmerjoe279 wrote:
antoine_ego wrote:
geniusjohn5 wrote:
If I connected two 9v batteries in parallel, would that have any effect on the speed of the fan/motor? I'm trying to get my hovercraft to move forward but it is unable to

Honestly, I'd just invest in a nice and powerful 8.4 NiMH pack. These can be overcharged up to 10.2V, which is legal since the 9.0V limit is dependent upon the label. If you can't get your craft to move forward, the battery is most likely not at fault. You probably need to redesign your skirt to reduce friction, or get a more powerful back fan. A better back fan is honestly the best solution.

Any ideas on the back fan?

use something that is very powerful, like a RC Motor for a toy truck or perhaps a computer cooling fan. What I like to do is make the propeller as big as it can be so there is the greatest propulsion. My propeller currently is like 30cm in diameter

geniusjohn5 · Post by **geniusjohn5** » February 9th, 2018, 9:18 am

The rules state that the craft must be impounded in a 40x40x40 cm box? Can the dimensions of the box be any less or does it have to be exactly 40 cm?

geniusjohn5 · Post by **geniusjohn5** » February 9th, 2018, 9:18 am

How do you convert rpm to cfm? If you can't convert directly between the two, can you estimate the cfm based on the rpm and vice versa? Thanks.

shrewdPanther46 · Post by **shrewdPanther46** » February 9th, 2018, 9:37 am

geniusjohn5 wrote:How do you convert rpm to cfm? If you can't convert directly between the two, can you estimate the cfm based on the rpm and vice versa? Thanks.

Rpm*volume of air capable of moving

So you would need a couple factors like surface area, etc.

This is all done ignoring volumetric efficiency (so assuming perfect efficiency, it just depends on how much fluid it can displace)

shrewdPanther46 · Post by **shrewdPanther46** » February 9th, 2018, 9:38 am

geniusjohn5 wrote:The rules state that the craft must be impounded in a 40x40x40 cm box? Can the dimensions of the box be any less or does it have to be exactly 40 cm?

Srry for responding in separate thing, but it can be smaller. Just has to be able to fit in box.

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