Hovercraft B/C

[Ashernoel]

First of all, it's not all about the motors, It's the skirt. I'm telling you right now, max lift is not taut, with a bunch of holes (like an airhockey table). I have won my region using a... much more... confidential design. Unless you are using a CD motor, you can lift 2 kg with the right skirt. At my peak lift, my vehicle hovers half an inch off the ground, and the fastest time was 1.17 seconds. Good luck to all of you, I shouldn't reveal more than that....

-p

2 meters in 1.17 seconds? Wow that would be crazy. Mine can do 2m in 3 seconds... but I need to get it to a consistent 20 which is the problem :/ And every skirt is different. Taught for you might only allow 1 mm of a cushion, but taught on another design with support posts may be half an inch. Either way, it comes down to accuracy in hitting that target time. Unless there is some way to increase kinetic friction to be greater than static friction, the hover will accelerate and many many variables will need to be accounted for. Welcome to the forums, though! Good luck at state!

[Tesel]

First of all, it's not all about the motors, It's the skirt. I'm telling you right now, max lift is not taut, with a bunch of holes (like an air hockey table). I have won my region using a... much more... confidential design. Unless you are using a CD motor, you can lift 2 kg with the right skirt. At my peak lift, my vehicle hovers half an inch off the ground, and the fastest time was 1.17 seconds. Good luck to all of you, I shouldn't reveal more than that....

-p

Frankly, some of that is quite exaggerated, and most of that has already been discussed.

Technically, if a skirt was constructed perfectly, it would be possible to hold 2 kg with a 350 Pa fan. Obviously this is not possible; instead, many students have been using the 1000 Pa blower fan which is almost ideal.

We've discussed alternate designs for a skirt - chances are, your "confidential design" is simply a wall skirt. If you read back in the thread, this is ideal as it reduces friction but much more difficult. Also, there is quite obviously no lift with a completely taut skirt... however half an inch seems to be a good balance of height. If friction can be decreased to a negligible level, there is some degree of "good enough". Rigorous testing of speed control is much more important than finding max lift.

[LittyWap]

Evidently, you are not as hospitable as asher. He recognized that I was new, and welcomed me with open arms. People like you are the crutch of these kinds of hobbies. Whenever someone expresses interest in these hobbies, you discourage them, brushing them off as someone who doesn't know better. Unfortunately for you, I know quite a bit about this event. Despite what you believed, I didn't have to read all the forum posts to be well versed in Hovercraft, and by the way, I already knew what a wall skirt was, or I wouldn't call it "confidential". If an eight time 1st place National team was impressed with my design, considering he (he being the student who built the craft) said: "I never thought of that before! I'll definitely test that out!", and later adopted the design, I think you can get off of your high horse.

-p

[Tesel]

Evidently, you are not as hospitable as asher. He recognized that I was new, and welcomed me with open arms. People like you are the crutch of these kinds of hobbies. Whenever someone expresses interest in these hobbies, you discourage them, brushing them off as someone who doesn't know better. Unfortunately for you, I know quite a bit about this event. Despite what you believed, I didn't have to read all the forum posts to be well versed in Hovercraft, and by the way, I already knew what a wall skirt was, or I wouldn't call it "confidential". If a eight time 1st place National team was impressed with my design, considering he (he being the student who built the craft) said: "I never thought of that before! I'll definitely test that out!", and later adopted the design, I think you can get off of your high horse.

-p

I'm sorry - that was a rushed post, and did not convey the intended message or tone.

I'm actually quite impressed with that fast design, and that you got a wall skirt working! Believe me, even though I can see you're new to the forums, I can tell that you are quite expert in the event. I am curious, though - how accurate is that type of skirt at low speeds? I feel like the friction on the bag would actually help to slow down a hovercraft with a bag skirt, so I'm assuming it's a little more difficult to do extremely low speeds with a friction-less wall skirt?

Again, I didn't mean to start any hostility, but I can see how my other message would be taken the wrong way. I wish you success with that design!

[Unome]

Evidently, you are not as hospitable as asher. He recognized that I was new, and welcomed me with open arms. People like you are the crutch of these kinds of hobbies. Whenever someone expresses interest in these hobbies, you discourage them, brushing them off as someone who doesn't know better. Unfortunately for you, I know quite a bit about this event. Despite what you believed, I didn't have to read all the forum posts to be well versed in Hovercraft, and by the way, I already knew what a wall skirt was, or I wouldn't call it "confidential". If a eight time 1st place National team was impressed with my design, considering he (he being the student who built the craft) said: "I never thought of that before! I'll definitely test that out!", and later adopted the design, I think you can get off of your high horse.

-p

I'm sorry - that was a rushed post, and did not convey the intended message or tone.

I'm actually quite impressed with that fast design, and that you got a wall skirt working! Believe me, even though I can see you're new to the forums, I can tell that you are quite expert in the event. I am curious, though - how accurate is that type of skirt at low speeds? I feel like the friction on the bag would actually help to slow down a hovercraft with a bag skirt, so I'm assuming it's a little more difficult to do extremely low speeds with a friction-less wall skirt?

Again, I didn't mean to start any hostility, but I can see how my other message would be taken the wrong way. I wish you success with that design!

Interesting; I would have thought the opposite. At low speeds, I would think that having more friction would mean that below some speed the craft would just stop moving forward, whereas with less friction you can control it more accurately.

[Tesel]

Evidently, you are not as hospitable as asher. He recognized that I was new, and welcomed me with open arms. People like you are the crutch of these kinds of hobbies. Whenever someone expresses interest in these hobbies, you discourage them, brushing them off as someone who doesn't know better. Unfortunately for you, I know quite a bit about this event. Despite what you believed, I didn't have to read all the forum posts to be well versed in Hovercraft, and by the way, I already knew what a wall skirt was, or I wouldn't call it "confidential". If a eight time 1st place National team was impressed with my design, considering he (he being the student who built the craft) said: "I never thought of that before! I'll definitely test that out!", and later adopted the design, I think you can get off of your high horse.

-p

I'm sorry - that was a rushed post, and did not convey the intended message or tone.

I'm actually quite impressed with that fast design, and that you got a wall skirt working! Believe me, even though I can see you're new to the forums, I can tell that you are quite expert in the event. I am curious, though - how accurate is that type of skirt at low speeds? I feel like the friction on the bag would actually help to slow down a hovercraft with a bag skirt, so I'm assuming it's a little more difficult to do extremely low speeds with a friction-less wall skirt?

Again, I didn't mean to start any hostility, but I can see how my other message would be taken the wrong way. I wish you success with that design!

Interesting; I would have thought the opposite. At low speeds, I would think that having more friction would mean that below some speed the craft would just stop moving forward, whereas with less friction you can control it more accurately.

I agree with you in some ways, and not in others.
Some teams have been problems just getting speeds that low at all, so friction is likely helpful in that case. A frictionless design would allow for more control, but only assuming speeds that low are even attainable.
Then again, I assume all teams that have a wall skirt working are easily able to control speed, so I'm interested to see what LittyWap thinks.

[LittyWap]

I greatly appreciate you apology, it's nice to know that your intentions were kind-hearted.

Admittedly, speed control is a big issue for us. Our discharge current is something like ~175 amperes, and when testing the craft with a resistor, the resistive material started to glow to orange hot (~1200 F). With such low friction, the craft is very easy to control, and we have been testing cover sheets that restrict the thrust fan. Those worked really well for Invitationals and Regionals, where there wasn't much competition, but I think I'm going to test weaker batteries, and reattempt resistors.

In short: The vehicle is very effortless to control, and friction never slows us down. The times usually vary +-0.2 seconds.

[petermai6655]

How do you control the speed of the hovercraft? Whenever I try to add a potentiometer, it smokes up because of the high current draw of the motor. Whenever I add a MOSFET to the circuit, to enable high current support, the motor's speed is significantly reduced. I tried many potentiometers and different types of batteries and still can't control the speed. Am I doing something wrong?

[windu34]

Evidently, you are not as hospitable as asher. He recognized that I was new, and welcomed me with open arms. People like you are the crutch of these kinds of hobbies. Whenever someone expresses interest in these hobbies, you discourage them, brushing them off as someone who doesn't know better. Unfortunately for you, I know quite a bit about this event. Despite what you believed, I didn't have to read all the forum posts to be well versed in Hovercraft, and by the way, I already knew what a wall skirt was, or I wouldn't call it "confidential". If a eight time 1st place National team was impressed with my design, considering he (he being the student who built the craft) said: "I never thought of that before! I'll definitely test that out!", and later adopted the design, I think you can get off of your high horse.

-p

I'm sorry - that was a rushed post, and did not convey the intended message or tone.

I'm actually quite impressed with that fast design, and that you got a wall skirt working! Believe me, even though I can see you're new to the forums, I can tell that you are quite expert in the event. I am curious, though - how accurate is that type of skirt at low speeds? I feel like the friction on the bag would actually help to slow down a hovercraft with a bag skirt, so I'm assuming it's a little more difficult to do extremely low speeds with a friction-less wall skirt?

Again, I didn't mean to start any hostility, but I can see how my other message would be taken the wrong way. I wish you success with that design!

Interesting; I would have thought the opposite. At low speeds, I would think that having more friction would mean that below some speed the craft would just stop moving forward, whereas with less friction you can control it more accurately.

I too am under Unome's impression, but then again I haven't had much success with low speeds.

[SPP SciO]

To chime in on friction - we had thought that making a skirt with extra friction would be able to cancel the effect of acceleration, letting the hovercraft travel at constant speed. The trouble was static friction. The idea would work, if competitors were able to give the hovercraft a little push to start, but rules 5L-N prohibit this possibility.