Jet Bike

[Rattlesnake Gal]

How soon before we see either one of these on the lake?
Aqua Jet Jet Bike
Universal Hovercraft - This one has wings!

[B R]

that Jet Bike looks an awful lot like the old model Wet Bikes with the movable ski out front. i used to own one in the mid 80's. they too had a front ski, but had a stationary jet. you turned it just like a motorcycle - leaning. none of these 90 degree turns. these things used to take quite awhile to learn to ride. it was always fun watching a new rider. it was hard enough just to get the thing to plain out, then you had to turn it.

they were faster than the old style jet skis and could actually pull a skier (which was darn good back in '85)

anyone else remember the wet bike.

[islandAl]

Yes, we had a wet bike back in the late 80's or so. My son had a ball on it, but old dad could not master it. Not stable like the almost "boats" of today (all the weight was on top and loved to tip over while tring to mount and get going). It looks like the new one could be more stable at the low speeds.

Those hovercraft items look like a nice addition for us island folks to be able to visit "year round" without waiting for the ice to form in winter or breakup in spring. Just where to keep it on the main land is the problem.

[Mee-n-Mac]

Originally Posted by Rattlesnake Gal

How soon before we see either one of these on the lake?
Aqua Jet Jet Bike
Universal Hovercraft - This one has wings!

The "Howerwing" looks interesting, a cross between a conventional hovercraft and a WIG. If you had enough land to get up to ground effect speed, it might just be the ticket to getting across the lake on a choppy day. Not much "luggage room" though.

WIG = wing in ground, a "plane" that really doesn't fly normally but relies on the added lift you get when flying low (ground effect).

[madrasahs]

Originally Posted by Rattlesnake Gal

How soon before we see either one of these on the lake?
Aqua Jet Jet Bike
Universal Hovercraft - This one has wings!

The Hovercraft Universal photo -- with the "three" airborne hovercrafts -- has been doctored. It's one hovercraft with three views of it, sandwiched onto one print.

The largest aircraft in the world -- the Russian Antonov 225 -- uses the same principal (as the Hovercraft Universal) to fly just 20 feet above the water. It has a 10,000 nautical mile range. http://webplaza.pt.lu/public/heisten...ov/antonov.htm

Two years ago, Swift Oceanics made an all-aluminum Jet-Ski capable of over 90 MPH "right out of the box". The example in the article was black, and appeared in Popular Science magazine. The Laser X-2000 had 175 four-cycle power, and weighed 290 pounds. I mean, why buy an ordinary Sea-Doo?

One of the earliest Jet-Ski designs was the "Skeeter". It was an outboard-powered widow-maker. To look at it, there was no question that it was the first PWC design.

I hope NOT to see any of these on Winnipesaukee. (Except the Antonov -- and that one, just once).

[KevinPlante]

Originally Posted by Mee-n-Mac

WIG = wing in ground, a "plane" that really doesn't fly normally but relies on the added lift you get when flying low (ground effect).

You do not get more lift by flying in ground effect. You do, however, have less drag because the wingtip vortices are disrupted by the ground being there.

Don't believe me? Think of it this way - How many g's are you pulling in ground effect? I would hope about one. g = L/W and we can assume weight will not change a noticable amount while going into and out of ground effect. Since you are not pulling more g's, the only variable left is lift, which cannot change by itself.

[Mee-n-Mac]

Originally Posted by KevinPlante

You do not get more lift by flying in ground effect. You do, however, have less drag because the wingtip vortices are disrupted by the ground being there.

Don't believe me? Think of it this way - How many g's are you pulling in ground effect? I would hope about one. g = L/W and we can assume weight will not change a noticable amount while going into and out of ground effect. Since you are not pulling more g's, the only variable left is lift, which cannot change by itself.

Not being an expert in aeronautics I may not have said it quite properly but let me check if my understanding (however worded) is basically proper. While you are correct about the less drag due to vortex disruption, I also believe there's less downdraft as a result of vortex disruption as well. This reduction gives the wing more ?lift? than it would have were the ground not there. Take away the ground (changing nothing else, airspeed, AOA, wingform, etc) and the "aircraft" (flying @ GE altitude) will fall. Imagine WIG'ing along on a mesa top and "flying" off the edge. Equivalently the "aircraft" would (for a given wing design) have to fly faster, or at a different/higher angle of attack, to maintain a steady altitude at a higher (say 1000 ft) altitude than it would at a ground effect altitude. Alternately the wing could be smaller, generating less total lift, if the "aircraft" were to be confined to GE altitudes, but thus loosing the ability to truely fly in the conventional sense. It was the stubby nature of the winglets on the "Howerwing" that reminded me of the Russian ekranoplans I've seen pictured and read about before. I recall reading an article on how the US military is looking into WIGs as a gap filling transport craft (btw C5's and naval ships). In this case the military was looking to get greater payload carrying capability via a WIG, vs a conventional airplane, by virtue of the added ? lift ? (for lack of a better word) afforded by ground effects. Anyway that's my understanding.

ps - Great link RG ! I've not thought about hovercraft in probably 20 years. I was amazed to see what relatively sophisticated craft even a semi-handyman could build for pretty small $$. Aaah if only I had the time. I'd build one with a daggerboard (and retractable rudder ?) so it would corner more like a boat. It'd be fun to pull up to Wolfeboro some Sat noon in July, past the waiting boats and up the launch ramp to "dock" in the auto parking lot.

pps - Now I'm wondering if you couldn't give up the amphibious nature of a hovercraft and use an outboard (or some kind of outdrive) to propel the hover, err boat, err hoverboat. I don't know about the relative efficiencies of air vs water props, might not be too different if I understand the lesson of MITs "Decavitator" correctly. Any person standing nearby would sure appreciate the screw design rather than the prop wash. Perhaps another hybrid design is the ticket ...