Wingboat Design

Russ,
The aspect ratio is the (in simple terms) span divided by the chord. Thus a long skinny foil (glider wing) has a higher aspect ratio than, say, the tailplane of a commercial airliner or a powerboat's rudder.

Steve

 

aerodynamic powerboat design

Foxxaero/John David - you should check out the AeroMarine Research site - they seem to have quite alot of information for combinations of aerodynamic and hydrodynamic lift/drag balances on powerboats. I think one of their engineers is the guy that has written some cool articles for Hot Boat magazine and F&PB magazine.

/Fastpowerboats

 

Foxxaero etal,
Fluid wants to flow from high pressure to low. Such is the case with the lower surface and upper surface respectively of lifting foils at the tips.Makes little nevermind when spans are large. In low aspect foils. this is a big piece of the action, generating vortices instead of lift. I can't see how ground effect changes any thing.There is a lot of confusion in the literature on how ground effect makes foils look like bigger aspect ratio than they really are.

Since there is not much advantage to WIG unless the TE is very close to the water, I let it "touch" and become the TE of the planning surface.(actually submerged a little) When touching, the dynamic pressure acts fully on the LS (a lift coef. of 1) This is affected by side leakage which is a function of Aspect ratio. I have side leakage factors derived from fluid dynamic bearing theory. I calculate the LS lift and the the conventional US lift seperately and then add them together. This is not nessessarily rigorous but seems to give good answers.

I am looking for photos of craft, Will post when I find.

Happy Wigging----- John David

 

Thanks All...

Thanks for your helping to clarify some of these aerodynamic principles and terms.

John, looking forward to your pics, You said ...

"Square law drag in air is mostly profile related and is minimized by reduction of frontal area and streamlining."

I am a WAY behind on the math and terms related to aerodynamic engineering, but I think I agree with your above statement...

About 'streamlining' - I did some research on streamlining many years ago. Have things changed since Buckminster Fullers studies in the 1930's? As I recall, one of the most important findings in Buckys studies was that , "it is more important how a shape exits air flow, than how it enters the air flow".... [although we all agree that reduction of frontal area and streamlining of that area is also important].

I think the Lippisch 'anhedral reversed delta ram-foil' shape best fits these requirements.???

What am I missing here?

Cheers

Russ

 

Hmmm. Looks familiar....

Lippisch X-112

 

Well, sort of. It would be better to say that it aspect ratio is the square of the span, divided by the area.

I know that's mathematically equivalent to span divided by chord. But the latter definition gets to the heart of the physics, while the former definition confuses the issue. It's not the fact that a high aspect ratio wing is skinny that makes it efficient. It's rather the fact that it has a large span.

 

Looks Similar ...

Hi Tom, yep you caught me. I first started researching Alexander Lippisch's studies in WIG in 1984. I first found reference to his WIG designs in Janes Encyclopedia of Hydrofoils and Hovercraft in 1984. Lippisch's gift to WIG technology was his 'anhedral reversed delta ram foil' (upon which many later designs were based). By 1979 the Lippisch / Fischer team had developed the X-114. In '84 I was originally doing research on blending hovercraft & hydrofoil design which led me to the Janes Encyclopedia, but when I came across the Lippisch / Fischer designs I immediately recognized the potential and genius of the anhedral reversed delta ram foil design, so decided to build my own model, which was finished and tow tested in 1986.

I'd be interested in hearing some analysis of the lifting step / air-ventilation modifications I did to the undersurface of the FX-1 (in 2002) --- (see pic in previous post --- I haven't tested the model since incorporating these modifications (the idea being to assist lift-off or 'breaking free' from the surface) ... any comments?

Here's another co-incidence. Since the late 1990's Hanno Fisher has been working on his 'HoverWIG' design. I found the cabin design originally proposed for the HoverWIG striking similar to the design of the FX-1 (although I am quite sure he never saw the FX-1 design which was completed in '86).

Here's the link to Hanno Fischers site ...

http://www.airfoil-development.de/index.html

 

Wing Boat Design

It seems to me, when we are talking about craft that use, wings in ground effect(wig) we should distinguish between vehicles that derive their propulsion from underwater propellors and vehicles that are propelled by air propellors or jet engines. I propose we call the former "wig boats" and the latter, "wig aircraft" The reason for making this disticntion is that wig boats can't move too much vertically ,else they lose propulsion as the prop leaves the water. The extent of allowable motion is only an inch or two above the planing height without any air lift. Of course wig aircraft can move any distance above the water surface but are restrained by the limits of ground effect. When flying without contact with the water how can it be a boat?

The Soviet Erakoplan is not a wig boat. As an airplane it must compete with other types of aircraft. It is a loser both technically and financialy. As boat "people" we should be using Wig not as a substitute for planning lift but to help reduce planning drag and make boats faster and more efficient.

Even though Wig aircraft are not viable for military or transportation uses, there may still be an application in recreational craft. But, should we be discussing aircraft on a boating forum?

 

WIG Classification

Hi John, The IMO is the international maritime organization which is the authority regarding classifications of marine craft. After many years of discussion regarding classification of WIG craft they finally settled on three classifications...

Type A WIG craft are those which can stabily lose contact with the water surface for momentary periods such as tunnel hulls and hydroplanes - these are classified as 'boats'.

Type B WIG craft are those which can stabily lift onto a ground-effect cushion, but cannot sustain 'free-flight' in an efficient manner - these are classified as 'boats'. An example would be the Flightship FS-8 ... (hovercraft are also included in this classification).

Type C WIG craft are those which utilize GE only temporarily on take-off or landing (sea-planes) ... or ... craft capable of operating most effeciently in GE but are also capable of rising off the GE cushion and entering 'free-flight'.

Would you argue that Ken Warbys jet powered WWSR 'Aussie Spirit' is not a 'boat' simply because it does not use water-propulsion as a means of thrust? Sorry, too late to bring up these protestations - already been decided by the IMO. Cheers

Still looking forward to your pics. Pic below is Ken Warbys' World Water Speed Record contender 'boat'. Also added pic of the FS-8

Russ

 

Thanks for info on IMO. Since their middle name is "marine" ,they are inclined to classify Wig aircraft as boats.Warbys boat is not a Wig anything.It is a type A craft, hence a boat.I am talking about Wig craft, that have no intentional contact with the water. If we understand the function, it doesn't much matter what we call it.Once,the lexographic committee (ASME) wanted to call the Wankel engine "a crankless engine" and some argued that that was incorrect;it really had a 'kinematic"crank.Say what?

 

Semantics get confusing

Hi John, I am struggling to understand the point you are trying to
make. Based upon your quote above [and if we were to accept your
distinction between "wig boats" and "wig aircraft"], then we would
have to agree that Warbys boat is a "wig aircraft" (because it does
not derive it's propulsion by an underwater propellor), yet in your
next post you agree that Warbys craft is a 'boat'?

Warbys craft, as well as all tunnel hulls and the newest 'unlimited
hydroplanes' depend upon surface-effect (wing-in-ground-effect) to operate
effeciently. The difference between the 'Aussie Spirit' and the 'Miss Budweiser'
lies mainly in the propulsion method - one using water-propulsion, the other
using air propulsion... but they are both 'boats'.

Also, I don't understand your statement that ... "Thanks for info on IMO.
Since their middle name is "marine", they are inclined to classify
Wig aircraft as boats".

The discussions within the international organization known as the IMO
regarding classification of 'WIG' went on for years, with many members
arguing vehemently against classification of WIG as 'boats'. Opponents
exhausted arguments such as your proposal (WIG boats vs WIG aircraft).

The conclusion was finally reached after exhaustive studies by the international aviation authority who refused to accept that WIG craft could be classified as 'aircraft', (and thereby coming under their rules and authority). WIG are NOTaircraft (according to the rules and definitions of the FAA).

What is greatly misunderstood by most who have only limited
understanding of WIG principles is that WIG craft operating in
surface-effect (ground-effect) are not 'flying' in the conventional
sense as an aeroplane does. They are operating more akin to 'hovercraft'
principles... except that, they operate on a dynamic ram cushion of
compressed air as opposed to a static (contained) cushion.

All the talk about comparison of WIG with aircraft by those who
understand aeronautical theory is IMHO somewhat misguided. Although
aerodynamic theories come in to the question peripherally - to a great
extent they are irrelevant. It's like trying to compare hovercraft to
aircraft, and dissecting both through aerodynamic theory ad infinitum,
which leads nowhere except the conclusion that a hovercraft is a very
ineffecient 'aircraft' ... so what ??? An aircraft, conversly, is a very
ineffecient hovercraft (or WIG for that matter).

Designers of WIG are not attempting to create an efficient aircraft,
they are attempting to create an efficient mode of transport which
lies between the limitations of ships and aeroplanes.

 

Re hump drag,
I have just found your site so very much a new person, I am happy to make the tea. So you may have already found info on the above. Have a look @ http://superiorhulls.com/index.html Strange site and secretive but there may be something there. I am currently looking at improving flows in pipes, following research by Victor Schauberger -any one heard of him?

 

heliferry

I am all with you, foxxaero, on your comments on wig types and all.
Furthermore, I do not want to highjack this very interesting thread, but please review the heliferry site http://users.telenet.be/heliferry to see a wig design with a prerotated high inertia overhead rotor to overcome the hump drag and eliminating the pitch-heave problem while transitioning from water to air borne. Your comments and critiques are most welcome.
Luc

 

Wig

Foxxaero,

We find ourselves deeply into philosophical discussions. I fear we are coming from two different directions.To help me understand you better, please tell me a little about your involvement in this field.Why are you interested? Are you a designer of Wig craft? Other?
Returning to the IMO definitions. Please ignore the comment about "marine" being their middle name.It was a feeble attempt at a joke. There is nothing wrong with the definitions as far as they go. Everbody agrees(even me) that their type A craft are boats.Everybody agrees that type C craft are aircraft.
It is the B type craft definition that is problematic. But before I address this point,let me digress to A type craft.
I am well aware that these craft use various amounts of air lift to "supplement" planning lift.Some boats use no air lift.Small racing stock runabouts, for example, are specifically forbidden from using any air lift per APBA rules.Hydroplanes (including tunnel boats) use air lift from 20% to 75%
of their weight The remainder being derived from planning.The higher percentages are subject to potentilly dangerous pittch instability.The point of all this is that all these craft are designed for continuous contact with the water.That is not to say they don't periodically "jump" up momentarily out of the water if so driven by adverse wave conditions. By the way, it is not important to the definition (or to the craft itself) how the air lift is generated. Wig is merely a way of getting it with smaller foil areas and with a built-in means of altitude control.
Now to the nub of the problem,If I can generate enough air lift to completely lift the craft out of the water,not withstanding varying wind conditions, it will stay out of the water. In the case of conventional lift it will continue to rise to equilibrium altitude(sounds like a sea-plane to me) In the case of wig lift it will only rise until the falling lift/altitude function reaches equilibrium with the weight. In the absense of a disturbing force it will stay at this height ,locked in by the very steep lift/altitude relationship. This is the mode of operation of the Erakoplan. The point of all this is there is no type B craft. If I can build a craft to reliably come out of the water to avoid obstacles why not leave it there? The IMO has for whatever reason omitted the most inportant definition; that of a craft that comes out of contact with water and stays there.
Rather than speak about when and how long a craft comes out of the water one should consider where the lift derives from. If any lift derives from hydrodynamic forces ie planning, it is a boat. If 100 % of the lift derives from aerodynamic forces it is an aircraft. However even if all of the lift comes from aerodynamic forces I would still define it as a boat, if propullsion and steering is hydrodynamically generated.
I dont believe it is important to this discussion what government aircraft controlling bodies say.
I hope this long winded storey makes sense to you.

 

Wow !!!

Hi Luc, I've seen some of your posts over on the WIG Page, but could never understand what the heck you were talking about, until I saw the pictures on your site. Suddenly it all becomes clear. That has got to be one of the "Worlds Most Radical Boat Designs" ! Looks great on paper. Have you tried out any models, or are you planning on going straight to a manned operational prototype? I'd love to receive any Hi-res jpegs you could send for an article I'd like to add to the Worlds Most Radical Boat Designs http://foxxaero.homestead.com/newsplash.html

Thanks for posting the info on the Heliferry. Please keep me updated on your progress. You can find my email by clicking on my name above.