this weekSomething in the Air

December 15, 2004

Hoverboards

The next generation of skateboards?

I remember the exact moment I lost my faith in advertising. I was about eleven years old, and an avid reader of Boys’ Life Magazine. Well, I was an avid reader of the ads at the back, anyway. Every month I salivated over the wondrous gadgets that could be mine for just US$4.95, plus postage and handling, allow 8 to 12 weeks for delivery, some assembly required. There was the crystal radio kit, the Sea Monkeys, the spy camera, the switchblade comb, the mobile crime detection lab, the “remote control” helicopter…I believed every one of the ads when they promised the most amazing products that would make me the envy of all my classmates in exchange for a few weeks’ allowance. But one ad in particular tantalized me month after month for a couple of years. I was so excited about it that I finally saved my money and sent away for it—my first mail-order experience. For $5, the ad promised “easy-to-build” plans for my own personal hovercraft. “Capable of lifting 200 pounds,” the ad said. “Powered by a vacuum-cleaner motor.” I wasn’t sure where I’d get one of those, but that was a minor problem. All I needed was the knowledge of how to construct it, and soon I’d be gliding to school on a cushion of air.

For weeks, I checked the mailbox eagerly every day, and when the plans finally arrived, I was ecstatic. I tore open the package and began reading it at once. It took me about five minutes to get the gist of the plans and another five for the impact of what I had just read to sink in. That was when I started to cry. What crushed my dream were two important points that the ad hadn’t bothered to mention. First, although the completed hovercraft would indeed lift you an inch or so off the ground, it provided no means to propel itself. If you wanted to move forward or steer, you had to push yourself along with a stick. And as if that weren’t bad enough, that vacuum-cleaner motor had to be plugged in—you could only travel as far away as an extension cord would reach. I was devastated and infuriated—what was the point of that? With my mother’s help, I wrote a letter of complaint, sent the plans back, and got a refund for my $5. But I never regained my trust in advertising.

Truth or Friction?
Despite this traumatic experience, the idea of a personal hovercraft continued to intrigue me for many years. Ordinary hovercraft, of course, float on a cushion of air confined by a flexible rubber skirt, and use a powerful (and very noisy) fan to keep it inflated. This is not new or complicated technology, but it’s also not as useful as it may appear at first glance. Hovercraft are great for moving quickly over broad, flat surfaces like water, ice, or a well-manicured lawn, but useless (not to mention dangerous) on city streets. Without the friction provided by tires against a road, hovercraft can’t steer precisely, slow down or stop quickly, or regulate their speed going downhill.

But nowadays, the ads for personal hovercraft are more sophisticated. “What you really want,” they tell me, “is a hoverboard—a floating skateboard,” like the ones seen in Back to the Future II. Marty McFly’s fictional hoverboard, like Luke Skywalker’s landspeeder in Star Wars, floats well above the ground with no visible means of support—but otherwise works pretty much like an ordinary wheeled skateboard. And now a number of Web sites are peddling plans to build your very own hoverboard—or even complete, ready-to-ride models. Is this another case of wishful thinking?

Stand and Hover
The products being described as “hoverboards” fall into two broad categories, which I’ll refer to as “silly” and “crazy.” The silly category contains devices that are functional but much more trouble than they’re worth. For example, a British company called Airboard Europe is selling the Airboard, a personal hovercraft that you stand on to ride. It’s quite a bit larger than a skateboard, at 5 feet, 3 inches (1.6m) in diameter, and weighs 187 lb. (85kg). Unlike regular hovercraft, it uses a drive wheel for acceleration and steering and “friction devices” for braking. Although Domino’s Pizza did a brief test to see if it might be usable for delivery, it’s not designed to be used on streets or sidewalks, and the price—£9995 (about US$19,000)—makes it a bit of a splurge for your average high school student. Another mini hovercraft design, the Hoverboard by Future Horizons, Inc., is rectangular and about half the size and weight of the Airboard; it’s also a steal at a mere $9,000. These companies get an A for effort: sure enough, you can stand on their hoverboards and ride them more or less like skateboards. Unfortunately, the designs are also silly, because they’re huge, heavy, noisy, and expensive—and thus completely bereft of all the advantages of an ordinary wooden skateboard.

The crazy category, on the other hand, is where things really get interesting. Numerous Web sites and mail-order catalogs are selling a 28-page booklet called “Hoverboard Design Notes” (at prices ranging from $10 to $35). The originator of this document is HoverTech, a small company working on developing alternative means of transportation. Their basic idea is a new twist on the cushion of air that all hovercraft use: they propose to ionize a column of air, and then surround it with a cylindrical magnetic field, which would prevent the air from escaping around the sides in a manner analogous to the conventional rubber skirt. The advantages of this approach would be nearly silent operation and higher ground clearance—producing that sci-fi-like “floating” effect. The science behind such a design appears to be sound, at least in theory. But apart from some very difficult mathematical and engineering problems that would have to be solved, there’s a little matter of power: I have serious doubts that a few rechargeable batteries are going to provide the sort of juice that would be needed, and I think I may have mentioned my feelings about extension cords on hovercraft.

I call this approach “crazy” because it’s odd, complex, and ambitious. It may also be impractical, absurdly expensive, and technologically problematic—in fact, it may simply not work. But almost every good idea was crazy once, and this one just may succeed—eventually. Still, I haven’t forgotten the lesson I learned all those years ago: if it sounds too good to be true, it probably is. And besides, I’m saving my money to buy some Sea Monkeys. —Joe Kissell

More Information about Hoverboards…

If you’d like a $9,000 ready-to-ride Hoverboard (or plans to build your own), visit Future Horizons. They also sell the Hoverboard Design Notes (for $35) and—get this—the very same hovercraft plans I purchased for $5 when I was a kid, only now they cost $15. Save your money, kids!

It appears I was not the only person to have been underwhelmed by these hovercraft plans. Larry Gallagher, in his article Joy Ride (Outside Magazine, April 2003) recounts his experience with the very same plans, though he actually managed to build the thing and make full use of a 50-foot extension cord’s range! Interestingly enough, his article also talks about various kinds of hoverboards, as well as rocket belts (see Personal Flying Machines).

To get the Hoverboard Design Notes (now called Hovercraft Primer) from the source (and much less expensively, at $15), visit this page; also see Hovertech’s Hoverboard FAQ. Risto-Antti Paju of Queens’ College wrote an interesting paper analyzing the magnetic field design and two alternate proposals. It’s called Levitation by Electromagnetic Ion Confinement. (Note that the equations may not appear correctly in your browser.)

For information on the Airboard, visit Airboard Europe; an article about the Domino’s test is at icLiverpool.

The Gadget Show featured an episode on building your own hoverboard using a leaf blower engine.

cover art

Back to the Future II was not an outstanding film, but the hoverboards were pretty cool. You can also get the entire trilogy on DVD.