Wingboat Design

Low Aspect Ratio Wings in Ground Effect

For application to powerboats, see Secrets of Tunnel Boat Design . Research based on Low Aspect Ratio Wings in Ground Effect at University of Michigan, and NRC water channel in Ottawa, Canada.

 

WIG Small Waterplane

Hi All, I've been following this thread with great interest. The idea of adding a wave-piercing small waterplane hull below the hull of a WIG craft is the means by which I intend to power-up my FX-1 'Ocean Mirage' prototype. (see photo on page 3 of this thread and more info at http://foxxaero.homestead.com/Update2.html ).

IMHO, the 'mistake' that MAP is making in their HYSWAS design is failure to utilize a WIG hull for the upper body of the craft.

Another developer is also working on a 'SWIG' . See photo below or their website at http://www.hydroski.com/index.htm

 

foxxaero

thanks for the links and info, great stuff!

i tend to agree now (thanks Doug!) that map can be a swig, been thinking of their pod and foilwing resistance as well here. a "normal" swath or hyswath's critirias are speed, comfort and economy; not very high speed i still belive... masterblasters wig IMO classification type A design (what other types are there?) i dont even know the design targets for, so before i swallow my tongue i best be back at my simple tricycle

yipster

 

I don't want anything of mine dragging in the water at 500 knots.

 

Re: Small Waterplane WIG

Hi guys.

Yipster - nice design ... it might just work, although personally (as I indicated previously I have an aversion to reverse-three-point-designs). In my view, the pilot in your craft is facing backwards - the two spread points should be forward.

Nevertheless, I would like to include your design to the Worlds Most Radical Boat Designs website - http://foxxaero.homestead.com/newsplash.html (if you are agreeable AND when I get around to it). You can find my contact e-mail on my website.

Doug, I agree ... I also would not want anything of mine dragging in the water at 500 knots! Richard Roake (hydroski international - designer of the Kestrel) is, (shall we say) somewhat given to wild claims regarding his designs which don't seem to stand the light of day ... C'mon... 500 KNots !?!.... MAYBE ... 100 Knots.

The true benefit of WIG vessels is not super high speed, but rather high lift at relatively high speed. The MAP project is missing out on the high lift capacity of WIG design, as well as suffering stability problems to keep the un-aerodynamic upper hull stabilized. Of course - these are all just my 'opinions'. Cheers

Russ Steffler - Foxxaero Marine Technologies

 

thanks Russ, whatdoyaknow!

to Doug and everyone interested; see Richard Roake's newest "wigswath" design at http://foxxaero.homestead.com/indrad_063.html
and do check the link to supercavitation!

 

Supercavitation

Yipster,

It seems to me that the negative effects of incidental ventilation, as experienced with keels and rudders that break the surface, would eliminate the possiblity of controlled supercavitation of a "wigswath".

I would think that a series of apertures along the submerged surfaces, linked to the ambient atmosphere through the above surface structures, would supply a not nearly so exciting but possibly useful surface bleeding effect even at the relatively low speeds we mere mortals and civilians might be interested in. These apertures might be controlled by reed valves or the like in a low tech application.

Doug Carlson

 

Project HYDROWING from Germany


Wing-in-Ground effect craft (WIG) incorporates properties of ship and aircraft. For fast sea transportation over distances of up to some hundred nautical miles WIG’s can be used as an alternative to existing means of sea transportation. For transport of persons and freight WIG’s are able to close the gap in speed and cost between fast ferries and regional aircraft.

Techno Trans e.V., MTE Ltd. and other partners started in 1994 with the HYDROWING-Project. The Department of Maritime Studies at Wismar University is involved in this project since 1995.



The HYDROWING concept is characterised by hydrofoil used as lift-off aid to reduce power requirement. Based on the results of experiments and calculations the manned test craft HYDROWING VT01 was designed and constructed and started to its maiden flight in summer 1997.



http://www.mte-germany.de/index2/NEWS/body_project_hydrowing.html

Video:

http://www.mte-germany.de/HYW-VT01.WMV

 

Wow!

I've been noodling and roaming the net for designs and ideas about wig-craft, ram-wings, etc. It's an exciting design concept. This one is simply beautiful. I no zip-zero-nada about boat design but that isn't going to stop me from making some models and building something for myself. Long on guts, short on brains.

 

A cad model from a wing boat by

Sudhir Padaki

http://www.3dcontentcentral.com/3DC...el.asp?model=part5&category=&subcategory=&ss=

 

Ahhrrr Matey!!! What about Cmdr Peter Ducane's ram-wing experiments? His ram-wing craft bears a decent resemblance to Masterblaster's. I'll do some digging in my bookshelf this weekend. I'm moving, and the wife wants me to start chucking books out......

 

Well hell!

I am not entirely sure what I have walked into here but, if you are designing a boat, it will leave the water and u will loose control, or if you are designing a WIG,GEV, there isnt much about that is right, other than it looks sorta pretty.
A GEV has anhedral (or neg dihedral) to optimise the tips location from the surface (yes the water), they usually also like to have forward swept wings because this reduces the spanwise flow around the wing. (same deal)

Among other features, they usually incorporate tails, becuse "this is not an aeroplane", were an aeroplane tends to find the right AoA according to speed, a GEV cant do this. A GEV must maintain a positive angle of attack of around 5 degrees +, if it where to become parallel with the surface of the water, a suction force could develop, leading to catastrphic events. Therefore the mission of the tail is to hold, most surely, the AoA of the mainplane. Beyond that, the tail carries the conventional aerodynamic controls.

 

There's a reason why all successful WIG craft have large T-tails - it's to counter unstable pitch-heave coupling.

All wings, and most especially low aspect ratio wings like you find on WIG's, leave a downward-moving wake behind them. The tail operates in this wake. A statically stable aircraft of typical proportion requires a down-load on the tail, and the negative angle of attack cause by the downwash in the wake assists in trimming the pitching moment from the wing. The strength of the downwash is proportional to the lift on the wing and inversely proportional to the flight speed.

As a flying vehicle approaches the surface, the downwash velocity is lessened. This is the whole point of flying in ground effect, because it's the downwash acting on the wing that causes induced drag. However, with a reduction in downwash comes a reduction in the trimming moment provided by the tail, and this leads to a nose-down pitching moment. The pitch-down tendency causes the aircraft to descend closer to the surface, reducing the downwash still more. And leading to more pitch-down. The opposite occurs as the craft rises from the surface - increasing downwash makes the craft pitch up, flying it out of ground effect and increasing the pitch-up even more. Unless countered by the pilot or an automatic control system, the craft is liable to zoom up, stall, and crash back down.

Mounting the tail on top of the vertical stabilizer lifts it away from the wake, lessening the effect of the downwash in the wake. And making the stabilizer large results in a greater stabilizing moment for a given change in angle of attack due to the pitching of the aircraft.

So you're right that the purpose of the tail is to maintain a more constant angle of attack, but there are some subtleties for WIG's (like the variation in the aerodynamics with height) that you don't get with a conventional aircraft.

 

Wingboat

Master blaster,
I have been working on a foil lifted hydroplane for 3 years. Built a prototype and am now working on the fourth modification to same. I only wish I knew as much about planing and air lift as I do now. I believed when I started that as much air lift as possible was benificial in reducing overall drag.I was striving for 100% (or else close to) air lift, thus "unloading" the planing surfaces. I now know this is not the holly grail of hydroplanes. First, the total drag of the boat consists of 3 forms of drag.1) Square law drag from air,2) square law drag from underwater and 3) drag due to lifting the boat,planing or air lift. It turns out that the three are sort of equal in magnitude(at least for the boat I am working on) Square law drag in air is mostly profile related and is minimized by reduction of frontal area and streamlining.Under water drag is both profile and friction ,helped in same way but ultimately is limited by the propulsion lower unit size and shape, and the need for a turning fin. The point here is these drags are caused by structural aspects from the size and weight of the craft and not the method of lift.

The drag component we are trying to minimize is that due to planing. This drag in turn has 2 sub-components, induced drag and frictional drag. The latter drag is generally the smaller of the two. Induced drag is geometrically related to lift ,which is essentially the weight of the boat. Induced drag comes about from air lift as well as hydrodynamic lift. So that all things being equal it makes no difference in induced drag to substitute air lift for planing lift.Frictional drag is another story. It can be helped by air lift but in a much smaller and complex way.

I can go into much more technical detail. Send me an E-mail if you so desire.

There is more one important principle to leave you with. In all foils air or planing, aspect ratio, plays a very important part. Short span foils with large chords are notoriously inefficient in providing lift. Unfortunately long span foils with sufficient area are impractical for boats.

I hope this gives you a little insight into the design problems you face.

 

Interesting Stuff, John !

I'd love to see some pics of your design (a picture speaks a thousand words and can save lots of typing

About your last paragraph ...

"There is more one important principle to leave you with. In all foils air or planing, aspect ratio, plays a very important part. Short span foils with large chords are notoriously inefficient in providing lift. Unfortunately long span foils with sufficient area are impractical for boats." ...

Please feel free to correct me, if I misunderstand here; but, it is my understanding that the upper foil shape is less important to WIGe craft than in air-craft because approximately 80 % of the lift created in WIG actually comes from the interaction between the lower foil shape and the surface and only approximately 20 % is derived from lift of the upper wing shape. So, although 'short span foils with large chords are notoriously ineffecient in providing lift' (in conventional aircraft), this may be far less important to WIGe boats.

I will try to add a picture below of the undersurface foil shape of the FX-1 'Ocean Mirage'

I look forward to hear more about the design you are working on, and seeing any sketches or pics you have.

Many Thanks in advance

Russ