Hovercraft B/C

[Jake R]

1. I saw someone post that centrifugal blower fans were the best, is this true, and what type is best? (for holding 2 kg) or should i use a computer cooling fan?

2. we were going to use a foam meat tray as a base, but we cannot find a singular meat tray with the right dimensions (14 x 18 inches then we would cut to size); all of the ones online come in boxes of 100 and cost 50 dollars, the ones at grocery stores are too small (we want it about 35 by 35 centimeters). where could i get one ?(besides the kit because we only need the base).
also any recommendations for propulsion fans or batteries would be helpful.

[shrewdPanther46]

centrifugal blowers are the best. Idk what type, look at static pressure. If you read through this forum really carefully, you will find answers to all of your questions in detail.

I do recommend, however, against a foam tray as it is often flimsy, and a lot of weight would be on it with a maxed out hover...

[jajefan]

The issue is that nothing in the problem indicates that Poiseuille Equation should be applied (viscosity, laminar flow, etc).

I think that is a fair criticism. The ES agreed he should have given more information to indicate the Poiseuille equation was needed. I think his assumption was that most pipes meet the requirements of using Poiseuille: they are reasonably long and not so wide as to generate turbulent flow.

I know this isn't the place to get clarifications, but are the tests allowed to test content not specifically listed in the rules manual? My concern arises from the fact that under rule 4. b. iv. Fluid Mechanics (Div C), Puiseuille's equation is not listed as a topic. It would be good to know for future competitions, as my team did not prepare adequately for topics outside of those listed for the invitational.

[jajefan]

For those wondering about a good material to build your Hover out of, I would highly recommend taking a look at Adam's Foam core Board found at Dollar Tree and other Dollar Stores. Each sheet is 20 x 30 in, and is around 5 mm thick, and only costs $1, making it both a sturdy, lightweight, and cheap material.

(In fact, some of you might know FliteTest https://www.youtube.com/channel/UC9zTuy ... Ez1216noAw, which is where our team got many of our building techniques, designs, and inspiration from. Hot glue and foamboard can work wonders (and can surprisingly hold 3 kg of weight without imploding!)).

For those wondering about batteries, 8.4V NiMH is undoubtedly what most hovers capable of 16 rolls are using. Our team has found that the stable (nominal voltage) during runs is somewhere from 9-9.2 volts after dropping from around 9.5 volts fully charged, and provides sufficient (and with our hover design, often too much) pressure in order to make a near frictionless skirt. You definitely need a custom battery charger if you are buying a NiMH, though, and I'd recommend https://hobbyking.com/en_us/turnigy-acc ... pable.html (don't buy unless you have soldering skills or a friend that can help!).

For those who are wondering about designs, https://www.youtube.com/watch?v=pdGs4x0sbLs is a good place to start. CAD up something similar for the "base plate" as I like to call it, and use foamboard or another light material as the "hull" instead of 3D printing like Peter did. With a sufficient surface area for your hull (we have a 32x26 cm base), you should be able to lift all pennies and everything without a problem and have a near frictionless bottom during runs.

Connectors of choice: XT-60

[SPP SciO]

2. we were going to use a foam meat tray as a base, but we cannot find a singular meat tray with the right dimensions (14 x 18 inches then we would cut to size); all of the ones online come in boxes of 100 and cost 50 dollars, the ones at grocery stores are too small (we want it about 35 by 35 centimeters). where could i get one ?(besides the kit because we only need the base).
also any recommendations for propulsion fans or batteries would be helpful.

I would recommend getting a nice chunk of that blue or green 1” foam. They’re sold in large sheets but a big box home improvement store may have big enough scraps around. Or just keep your eyes peeled for the distinct pastel-colored foam in the dumpsters you pass!

But that stuff is very easily workable, plenty stiff, and likely the best strength to weight ratio material that’s common and inexpensive. A vehicle that can manage 16 penny rolls will have some beefy fans and batteries; it’s plausible the whole thing will come in close to 5kg. But it’s certainly doable, if you max out the area for weight displacement.

[rc2000]

Would anyone mind recommending me some DC motors & props for lift. I've really been struggling with it. For thrust I plan on using a computer fan.

Also: Im using 2 of these https://www.amazon.com/1600mAh-Battery- ... +volt+nimh to power my hovercraft. Any tips on connecting them?

[kinghong1970]

search amazon for mini tamiya connector male

or cut the connector and solder

https://www.amazon.com/s/ref=nb_sb_noss ... ector+male

[RestingDoll]

The issue is that nothing in the problem indicates that Poiseuille Equation should be applied (viscosity, laminar flow, etc).

I think that is a fair criticism. The ES agreed he should have given more information to indicate the Poiseuille equation was needed. I think his assumption was that most pipes meet the requirements of using Poiseuille: they are reasonably long and not so wide as to generate turbulent flow.

I know this isn't the place to get clarifications, but are the tests allowed to test content not specifically listed in the rules manual? My concern arises from the fact that under rule 4. b. iv. Fluid Mechanics (Div C), Puiseuille's equation is not listed as a topic. It would be good to know for future competitions, as my team did not prepare adequately for topics outside of those listed for the invitational.

The listed topics are more of a guide rather than a strict set of what can and cannot be tested; even so, I would consider Poiseuille to be a subtopic in viscosity.

[reed303]

search amazon for mini tamiya connector male

or cut the connector and solder

https://www.amazon.com/s/ref=nb_sb_noss ... ector+male

For those who might be unfamiliar or unable to solder wires, "wire nut" connectors like these are useful
https://www.lowes.com/pd/Utilitech-25-P ... /999953854
Strip off about 3/8" of insulation , and twist the wires together with the connector. The gray or blue size should work for most hovercraft wiring. They also make re-wiring very easy.

[Jake R]

I know that you need a high static pressure for lift fans, but does cfm matter for list as well? for example, i found this one that i might use https://www.digikey.com/product-detail/ ... ND/5230580 is that a good choice for lift? (max load)