A semi wig

[creosote]

I found out that this builder was in town for a boat show, after the fact

Anyway here's a pic of a 'super light "semi-wing in ground effect" hull' from River Wild. http://www.jetboatracing.com/anatomy.htm

Any thoughts about semi wigs and how it might work? Such as when does it provide lift? Could it work as a canard for wing ships that have swept back wings?

[keysdisease]

Google Ekranoplan for some history. There are a couple of manufacturers making wig boats / planes for the recreational market. None have taken off (pun) yet but the technology, concept, history and engineering are proven.

Steve

[kach22i]

I think it need more wing, that is the lowest aspect ratio I've even seen.

Reference photos:
http://www.se-technology.com/wig/htm...code=0&craft=5



Studing WIG (Wing In Ground Effect)

[creosote]

I've seen many sites that talk about Ekranoplan, wingships and wing in ground effect. Those ideas are about gettting the boat off the water. That's why I don't understand the purpose of a "semi wing in ground effect". They race boats on whitewater like the Rouge River, noted for its jet boat tours.

I sent an email to the company that made the boat and asked what was the purpose of the wings. Do they act as an air cushion? The bottom of the boat is rather flat. Does it catch the spray and get some lift?

I'm going to browse through their forum and see what I can find.

[creosote]

Here are a few more pics that I could find...

So there is more than one of these kinds of boats.

[cthippo]

I think where they're going with this is a sort of hydroplane except that instead of the hull being lifted only by bouncing across the top of the water, it is also lifted somewhat by the wings. Just a guess though.

[keysdisease]

Originally Posted by creosote

The bottom of the boat is rather flat. Does it catch the spray and get some lift?

They may be using "lifting body" technology which would be what you are describing. This was developed from the SR71 and Space Shuttle neither of which have much of a wing and are "lifting bodies."

I would think the concept is to reduce wetted surface at the cost of as little aerodynamic drag as possible. By using "ground effect" the wings and aero drag can be much smaller than for true flight. This lends itself nicely because the trade off is by being a boat the structure has to be stronger (heavier) than a plane and wig tolerates weight very well.


Steve

[kach22i]

Much better photos, they do look like little wings now and not closed off sponsons.

I'm sure they are using a little bit of the main body for lift, at least above 35 mph. The body should at least be designed not to hurt the efforts of the stubby wings.

[anthony goodson]

How well does the jet work then ,if there is entrained air in the water beneath the hull.?

[creosote]

I've been watching videos, such as...

http://www.youtube.com/watch?v=WCB63...ist=QL&index=1

When the semi-wig boats are in the air it looks like that the wings provides enough lift so the boat lands more level than the non-winged boats. There are some videos where the boats go almost vertical. Semi-Wing boats looks like they get a turning moment to prevent a vertical landing when at speed.

[daiquiri]

Wanna see what it looks like seen from inside that shell? Check this out:
http://www.youtube.com/watch?v=fwO35...eature=channel
The action starts at 00:50. Insane.

[creosote]

This video is from one of the semi-wig boats.
http://www.youtube.com/user/racing16#p/u/12/T3XH2gJAzjU

Insane? Probably.
But is the ride more stable than the regular boat?

[keysdisease]

Originally Posted by creosote

Insane? Probably.
But is the ride more stable than the regular boat?

Define stable? At the speeds these boats are running and the water conditions a traditional hulled boat might be more apt to "catch air' and flip than a boat designed to "almost" fly.

The ride might and should be smoother because there should be less contact with the water.

Define Insane: Heck if you're here that question is already answered, we're all insane

[ancient kayaker]

Originally Posted by creosote

I've seen many sites that talk about Ekranoplan, wingships and wing in ground effect. Those ideas are about gettting the boat off the water. That's why I don't understand the purpose of a "semi wing in ground effect" ...

As an aircraft flies the force holding it up has an equal and opposite force on the air (I blame Newton) which is accelerated downwards as the aircraft passes. The energy to do that comes from the engine(s). Some of this air slides out to the side and creates a vortex off the wingtips which causes drag; the greater the vortex the greater the drag so modern aircraft use winglets at the ends of the wing to reduce drag by reducing vortex size.

A winged craft flying close to a flat surface is more efficient in 2 ways. The air is prevented from accelerating downwards by the surface, so it forms a backpressure that allows the craft to fly at a slower speed and still remain airborn. The wingtip vortexes are also restricted by the proximity of the surface, so they do not form to the same degree, and so do not create as much drag.

A wig has greater weight-carrying capacity and requires less power to fly than the same size aircraft, and is supposed to be more economical and smoother at the same speed than a powerboat.

(highly simplified ...)

[creosote]

Most explanations of wings state that a wing creates a high pressure zone under the wing and a lower pressure zone above the wing. This is done by the air moving at different speeds above and below the wing. The lift of the wing is the result of the high pressure air pushing the wing into the lower pressure air.

Drag is mostly a result of the length of the wing. But the drag of that wing is offset by the reduction of the tip vortex. This is the air that "cheats"; it doesn't push the wing into the lower pressure region, instead it goes around the wing at the tip.

For high aspect ratio wings, as in gliders and the U-2, getting the most lift is more important than drag.

For higher speed airplanes, drag is more important than a loss of lift, thus supersonic jets have low aspect wings.

There was a bold design near the end of WW2 that had special low aspect wings.
http://en.wikipedia.org/wiki/Vought_XF5U
The whole body was one round wing. To prevent the loss of lift from the tip of the wings, the plane had two propellers, one on each wingtip that rotated in such a way as to counter the flow of the tip loss vortex.

The proposed charcteristics of this design were fantastic compared to other propeller driven aircraft to the point where the prototype Vought V-173 could take off and land near vertically in a modest wind.

Thus there was a plane that brought the ground effect with it into the sky, sort of.

Anyway...

The design principal of the wing in ground effect craft is that the water surface prevents the formation of a large, lift stealing vortex. So if the tip vortex is reduced, the craft can have low aspect ratio wings.

The articles on the internet claim that wig effect happens when the wing is within a half a wing span of the ground and the effect is an 80% to 100% boost in lift. (Your results may vary)

This is why I thought that the little wings on the whitewater racers were for lateral stability. Normally the wings would provide equal lift on both sides of the boat. If the boat rolls to one side then the little wing would be close enough to the water surface for the ground effect to boost the lift on that side and roll the boat back to level.

But a trimaran can do that, why use a wing?
One, trimarans shouldn't race in rivers with rocks and sand bars. The little wings stay out of the water.

Two, as I watched videos of these semi-wig boats they "flew" flatter than other boats in the same race.

http://www.youtube.com/watch?v=_cAeQ...eature=related

This video is of a semi-wig boat crashing. It didn't pitchpole like a hydroplane speed boat. In hydroplane crash videos, if the bow lifts about 20 to 30 degrees the boat will flip.

There is of course a major difference in speed of these crashes, since the hydroplanes go about twice the speed of whitewater jet boats.

Here the same semi-wig boat from above goes 90 degrees vertical and recovers.
http://www.youtube.com/watch?v=jxaaK...eature=channel

If the semi-wig has the second effect of providing a righting moment to correct the pitchpole effect for high speed craft, why not use it on offshore race boats and hyrdoplanes?