Calculating Air Flow and Pressure for a Hovercraft

In summary: The pressure is important because it's how much the fan is pushing against the skirt to create the lift. The higher the pressure, the more lift the fan will generate.
  • #36
You'll need to look at the fan curve for the fan to see what pressure it generates at that airflow.
 
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  • #37
the area inside the skirt will be approx. a 31 in diameter circle. i don't think that psi is correct. i was thinking of using at least one of http://www.homedepot.com/webapp/wcs/stores/servlet/ProductDisplay?storeId=10051&langId=-1&catalogId=10053&productId=100590976&N=10000003+90401+502756+4294965112&marketID=401&locStoreNum=8125...
 
  • #38
russ_watters said:
I didn't read all the posts, but in a hovercraft, the pressure needed is exactly equal to the weight of the hovercraft divided by the area of the skirt. It has to be. The catch, of course, is that if the fan isn't capable of generating that much pressure, it won't lift off.

Once the hovercraft lifts off, the height will be determined by what airflow the fan generates at that static pressure (the fan will ride its fan curve to that point as the hovercraft rises).

My guess would be that a bladed fan cannot produce enough pressure to lift a hovercraft. Bladed fans don't produce much pressure. A centrifugal fan/blower is what you would need.

If you want to measure flow/pressure, manometers and pitot-static tubes are pretty cheap or you can make them yourself.
Not to be a know it all but... That is not quite true about bladed fans. I have seen quite a few hovercraft with its lift provided by bladed fans. But I'm a new person about hovercraft myself however I've been able to pick up a few basic facts. The above mentioned is one.
 
  • #39
Not that deep.

Gentlemen (and of course, Ladies),
I agree with another "threader" in that curves for fans etc. is a little overkill. We after all are not designing a space shuttle but a hovercraft. The idea is to rise approx. 1 inch or so off the ground and pretty much remain there until you turn the machine off. The hovercraft, as far as I can figure, is in extreme "ground effects" and that's a good thing. Our requirements get more liberal, as far as weight per horsepower of the engine providing the lift, our physical dimensions also can vary more widely than if we wanted to travel to the moon, to provide an extreme example. Like " visitor from the Id" or something like that said, better to approximate and experiment around to get it flying and stable. I'm no expert but intuitively I feel that the powerful engines that are available today, I found a marvelous minibike engine on the trash pile( at least 3 hp), there is no worry ,really, about not having enough power to lift your craft off the ground 1 or 2 inches. Ditto, the fan and or certrifugal blower, the quality of "junk" out there, found in the salvage yard and even on the trash pile, is too good to worry about it"s self-destructing as you produce enough lift or push you craft along at a medium clip. Now racing is another matter which I'll steer clear of.
Basic info: the weaker the engine for lift the smaller the lift and the larger the bottom has to be in order to produce enough force to lift the weight of the craft and you. Those are the only limiting factors. Of course you see if the engine is very weak it might only lift the craft 1 mm which is tantamount to not lifting at all but actually it is lifting it. No good because you couldn't go anywhere unless you were on ice or extremely flat surface. Also we see that if the engine were too weak the bottom would have to be enormous to produce enough lift. So you really don't have to know too much more than that. Nevermind, the psi's, cfm's, densities, etc. that stuff will just prevent you from building your machine. The joke is once you calculate all that info and actually start to build the machine, 9 out of 10 times the calculations will be NA or just plain wrong. Not just for you but for everybody that's the case,( even engineers,or should I say especially).
Send us a picture of your craft when you finish.
 
  • #40
hey guys I am building a one engine hovercraft and i was wondering if 45lbs is too heavy for the deck?
 
<h2>1. How do I calculate the air flow needed for my hovercraft?</h2><p>To calculate the air flow needed for a hovercraft, you will need to know the weight of the hovercraft, the desired speed, and the air pressure you want to achieve. You can use the formula Q = m * v, where Q is the air flow in cubic feet per minute (CFM), m is the weight of the hovercraft in pounds, and v is the desired speed in feet per minute. You can also use online calculators or consult with a hovercraft expert for more accurate calculations.</p><h2>2. What is the ideal air pressure for a hovercraft?</h2><p>The ideal air pressure for a hovercraft depends on the weight and design of the hovercraft, as well as the surface it will be hovering over. Generally, a pressure of 1-2 pounds per square inch (psi) is recommended for a hovercraft to achieve lift and maintain stability. However, this may vary and it is important to consult with a hovercraft expert for specific recommendations.</p><h2>3. How does air flow affect the performance of a hovercraft?</h2><p>Air flow is crucial for a hovercraft to achieve lift and maintain stability. If the air flow is too low, the hovercraft may not be able to lift off the ground or may not be able to maintain a steady hover. On the other hand, if the air flow is too high, it can cause instability and make the hovercraft difficult to control. It is important to calculate and maintain the proper air flow for optimal performance.</p><h2>4. Can I use a fan or blower to generate air flow for my hovercraft?</h2><p>Yes, fans and blowers are commonly used to generate air flow for hovercrafts. However, it is important to choose a fan or blower that is powerful enough to provide the necessary air flow for your hovercraft. It is also important to consider the size, weight, and power consumption of the fan or blower to ensure it is suitable for your hovercraft.</p><h2>5. How can I measure the air flow and pressure of my hovercraft?</h2><p>There are several methods for measuring the air flow and pressure of a hovercraft. One common method is using a manometer, which measures the pressure difference between the air inside the hovercraft and the surrounding air. Another method is using an anemometer, which measures the speed and direction of the air flow. It is important to regularly monitor and adjust the air flow and pressure of your hovercraft for optimal performance.</p>

1. How do I calculate the air flow needed for my hovercraft?

To calculate the air flow needed for a hovercraft, you will need to know the weight of the hovercraft, the desired speed, and the air pressure you want to achieve. You can use the formula Q = m * v, where Q is the air flow in cubic feet per minute (CFM), m is the weight of the hovercraft in pounds, and v is the desired speed in feet per minute. You can also use online calculators or consult with a hovercraft expert for more accurate calculations.

2. What is the ideal air pressure for a hovercraft?

The ideal air pressure for a hovercraft depends on the weight and design of the hovercraft, as well as the surface it will be hovering over. Generally, a pressure of 1-2 pounds per square inch (psi) is recommended for a hovercraft to achieve lift and maintain stability. However, this may vary and it is important to consult with a hovercraft expert for specific recommendations.

3. How does air flow affect the performance of a hovercraft?

Air flow is crucial for a hovercraft to achieve lift and maintain stability. If the air flow is too low, the hovercraft may not be able to lift off the ground or may not be able to maintain a steady hover. On the other hand, if the air flow is too high, it can cause instability and make the hovercraft difficult to control. It is important to calculate and maintain the proper air flow for optimal performance.

4. Can I use a fan or blower to generate air flow for my hovercraft?

Yes, fans and blowers are commonly used to generate air flow for hovercrafts. However, it is important to choose a fan or blower that is powerful enough to provide the necessary air flow for your hovercraft. It is also important to consider the size, weight, and power consumption of the fan or blower to ensure it is suitable for your hovercraft.

5. How can I measure the air flow and pressure of my hovercraft?

There are several methods for measuring the air flow and pressure of a hovercraft. One common method is using a manometer, which measures the pressure difference between the air inside the hovercraft and the surrounding air. Another method is using an anemometer, which measures the speed and direction of the air flow. It is important to regularly monitor and adjust the air flow and pressure of your hovercraft for optimal performance.

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