building a hovercraft?

Question

in my physics class we're building hovercrafts. They look like this: http://www.amasci.com/amateur/hovercft.html
my question is, is it advantageous to have a longer or shorter plastic "skirt"? and the whole in the center(like the doughnut hole), should it be bigger or smaller?

Answer 1

The higher the skirt, the more "flex" it have over rougher terrains. However, the more air will spill if the skirt rips. The lower the skirt, the less flex the skirt will have over rougher terrain, but you get more "ground effect" from the jet of air hitting the ground. Keep in mind that you may not have enough "air pressure" from one leaf blower to lift up a really high skirt due to all the places you can leak.

As for the hole in center, the idea is to regulate the amount of air that comes out so it goes out evenly to all sides.

Technically speaking this is NOT a hovercraft, as its principles is closer to air hockey (tech term is "air film bearing"), with small nozzles sending a thin film of air between the "skirt" and the ground. Using a plastic bag makes it flexible and keep the film of air between it and the ground.

You may also want to read this:
http://www.instructables.com/id/Simple-Rideable-Hovercraft/

Answer 2

That could be part of your experiment. Determine which is better...Longer or shorter skirt or bigger or smaller hole? You'll probably have to build at least 5 hovercrafts. 1 as the Control 1 with a longer skirt 1 with a shorter, 1 with a big hole, one with a small hole.