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Homemade Engine-powered and Human-powered Hovercrafts

Skirt Designs

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Here we will give specific instructions on how to make a wall skirt, and we will briefly explore into other types of skirts

As far as Hovercrafts go, there are three types of skirts to be concerned with: Bag Skirts, Wall Skirts, and Finger Skirts. Type I hovercrafts generally use Bag Skirts, Type II (our type) use Wall Skirts, and Type III large-scale professional hovercrafts for racing or recreation usually use finger skirts. You can mix and match the type of skirt with the type of hovercraft you're making, but as for now we've only tested Type I with a bag skirt and Type II with a wall skirt. As so far we don't know how to construct a Finger Skirt (they're really complicated), but down at the bottom of the page is a brief explination of what one is and how they work.

* IF YOU ARE MAKING THE SAME AS OUR HOVERCRAFT (type 2), ONLY THE WALL SKIRT WORKS. A finger/segmented skirt or real bag skirt requires the frame to have a huge air chamber built in and a ton of stuff that costs a ton and takes a ton of time, and a bag skirt like the one on hovercraft 1 doesnt work too well.




BAG SKIRT (Not like the ones on a racing or recreation hovercraft, but for one on a cheap homemade one):


HOW THEY WORK:

A bag skirt is like an intertube with a piece of plywood on top, holes feeding into the middle, and an air supply. When it inflates its the same principle as simply sitting on a O-shaped ballon, since that's essentially what it is.

Air goes into the bag, inflating it so it is about two inches high. The air inflating it goes out the holes located towards the center, making the air also build up pressure in a chamber between the ground, the plywood, and the inflated ring of the bag skirt (plenum chamber). The pressure eventually buld up enough so that it and the bag skirt is lifting the plywood, and the air slides out underneath the bag, creating a nearly frictionless environment.


HOW TO CONSTRUCT A BAG SKIRT:

This depends on what you're using the bag skirt on. If you're constructing a Type I circular, you'll want the bag skirt the cover the whole bottom, mounted in the center with a disc. This makes the skirt sections around the center inflate in a donut shape, carrying the outsides of the craft.



You will want a thick sheet of plastic, nylon, or other air tight and durable material. (trash bags have been known to work, but we cannot confirm this.) This sheet has to be at least two feet bigger than your craft. lay your craft on top of it. then take the corners and sides of the sheet and fold them up onto the top of the craft. Make sure the skirt has enough slck to inflate, becuase if it has none it wont lift. Or it will explode. Then staple the skirt onto the plywood in lots of places, and duct tape it a lot to the top, making sure no air can get out. Then attach your coffee can lid. Cut six holes about 4 inches away from the edges of the lid, and a little more than one inch in diameter. The reason the holes in the skirt need to be closer to the center is so that the air doesnt immediately go out of the bag and away from the craft, but goes into the center where the bag contains it like walls, and it lifts the whole thing up a tiny bit for the air to slide out.


NOTE: We have not guarantee this skirt to work on a type two craft.

On a Type II hovercraft you want to go ahead and have the piece of cloth be mounted in a donut shape. This means you're going to need a long straight piece of material (make sure it's thick enough by holding the sides of it and seeing how far you can push it down. You want at least 5 or 6 inches of slack without having to mount the two sides too close together) and you're going to mount the outside edge of the cloth in a oval around the outside of your hovercraft, and the inside edge in a smaller oval further inward on the bottom of the hovercraft. We reccommend that you first staple the skirt in place, then when you know its in the right place, seal it tight with caulk. Make sure you leave enough slack so that it has space to inflate, but don't make a skirt thats TOO loose. Just like in the Type I hovercraft, you'll need to space small holes on the bottom of the skirt to let air escape.


NOTE: We DO NOT reccommend using a bag skirt on your 8-by-4 Type II hovercraft because we HAVE NOT tried it before! If you try, you're doing so at your own risk of failure.
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WALL SKIRT: (not generally used on high performance hovercrafts because disadvantages in repair capabilities and terrain handling capabilities.


HOW THEY WORK:

Wall skirts hang down from the edge of your hovercraft (hence the wall name). The skirt inflates and pushes outwards, so the hovercraft rides on a cushion of air. It's like an electric inflating matress, if the bottom was cut out of it, and a piece of plywood placed on top of it, the matress would still inflate, but when it was fully inflated some air would pick it up still a centimeter more so it could slide out from underneath. A good bag skirt is like a wall skirt that uses an inflated wall to contain the air.



HOW TO CONSTRUCT A WALL SKIRT:

Find some airtight (make sure it's airtight before hand!) material to use for your wall skirt. Next, get enough material to fit around the outer edge of your hovercraft, and remember to always get a little bit extra. If you're constructing an 8-by-4 hovercraft like we did, we recommend making your skirt around 13-17 inches tall, but make sure it stays the same height all around. If you notice that the material you're buying comes in heights more than twice the height you want your skirt, just go ahead and buy enough so you can cut it up and sew different pieces of the skirt together. This is what we did, since we bought a 9-by-5 foot piece of material, and cut it up into three skirt segments that were each 15 inches tall and 9 feet long. We then sewed these pieces together, and double stitched them just to be sure. So you have a long material that is about 15 inches wide. If you just put this on the hovercraft the skirt would just flap out, so you need something to hold it. A rope is then attatched to the bottom and pulled tight. Make sure to use a strong rope that is braided rather than wound, so that if one part breaks it doesn't all fall apart. (We used a thick nylon rope for Home Depot) We folded an inch of the skirt over the rope and sewed it to itself to make a pocket. some people fold the skirt over the rope then duct tape it. But make sure that you make it with the rope already in it, and knot it so it doesn't slip out.


The top edge of the material is mounted to the edge of your hovercraft, and the bottom end should have a rope strung through it (take the material, put the rope on it, fold it over the rope, and sew the material on itself to create a slot for the rope to be in) to keep it tight. This keeps the bottom of the skirt from flapping outwards, so it will inflate. Cut the skirt so that you have an inch overlapping and sew it by hand. tie the rope, pull it tight and burn the ends to prevent fraying.


If your hovercraft doesn't inflate, try pulling your rope tighter. Before you finally cut the rope and seal the knot, try to make sure you haven't pulled your rope too tight, not allowing enough slack. Any part of the rope (like the knot) that's going to drag across the ground should get covered in something to protect it, like duct tape.



FOR EXTRA PROTECTION: Cover the part of the skirt that drags on the ground (the section that the rope is strung through) in duct tape or some other strong material so the sewing doesn't come undone and the rope doesn't come out.


FINGER SKIRT:


HOW THEY WORK:

Finger skirts are used on professional hovercrafts. A finger skirt has tons of little segments that each individually inflate that conform to the ground so the hovercraft can go over all terrain. Professional finger skirts are generally made out of very strong rubber material. The fingers are actually a bunch of seperated "little skirts" that inflate independantly. To build a finger skirt, you need a large hull with a built in plenum chamber and that takes a lot of work.



A FINAL NOTE ABOUT SKIRTS:

When picking a material, make sure it can take a lot of wear and tear. Keep in mind this material is going to be dragging along the ground a lot, and needs to be able to maintain it's air tight manner.

floatingyay.jpg
Our Hovercraft

hovercraft1.jpg
A bag skirt floating

underside.jpg
The bag skirt with a disc mounted in the middle

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hovercraft from xinventions.com



































floating.jpg
A wall skirt doing its job

hovercraftbottom.jpg
The bottomside, with top edge of the skirt mounted and bottom edge of the skirt pulled tight.

hover_test_drive_4.jpg
Hovercraft from xinventions.com
























hc110.jpg
A professional finger skirt

Have a question? E-Mail Mr. Hovercraft at mrhovercraft@gmail.com ! If you haven't noticed, we're all "Mr. Hovercraft".