Wing in ground effect boat

Discussion in 'Aircraft Design / Aerodynamics / New Technology' started by Starman, May 20, 2010.

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  1. May 20, 2010 #1

    Starman

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    Wing in ground effect

    i have a new design project :) as some of the longer term members here know, I've built some welded aluminum boats and have a bunch of aluminum available. I also live in the Seattle which has great inland waterway access almost all the way up to Alaska.

    What I envision is a four seat craft with a lot of additional cargo capacity, and if possible making this cargo space useful for sleeping two people inside the plane while it's not moving. The cargo/sleeping space could be a partial 'trade' with the two rear seats.

    It also needs to have the removable wing tips that can be switched with longer wings in order to get better range. I want to ultimately have a 3000 mile range so I can use it to go to Hawaii, for example.

    Longer wings will allow flying within ground effect at a higher distance above the surface.

    I want it to have enough wing area so that it will fly slowly enough to be able to follow the contours of ocean swells and remain in ground effect. I think 50mph is a good ballpark figure.

    So far I envision a reverse delta with twin engines on pylons like the Russian BE-103 uses: http://cdn-www.airliners.net/aviation-photos/middle/3/7/7/1111773.jpg

    I realize that with longer wings it will be able to fly out of ground effect and so will need to be registered as an aircraft, but that's for later.

    I hope to initially use two 40 hp industrial (lawn mower) engines like the Kohler Command V twin. And initially use them with direct drive.

    Later, for long range, I might need to switch to larger water cooled engines, and of course, diesels would be ideal for the long range. I've done some preliminary spreadsheet calculations using rough assumed ballpark figures. With a gross weight of 3000lb and a span of 40 ft it needs to have 150+ hp to get a marginal climb rate, and marginal is OK for it when it is overloaded with fuel. This is assuming 1000lb of fuel, which will give a 3000+ mile range.

    However, those figures are for flying out of ground effect, and flying in ground effect can increase fuel efficiency up to 250% but for now I'm going to figure it as if there is no ground effect, which will provide a large fudge factor.

    There are two types of ground effect, span dominated ground effect, and chord dominated ground effect, and the chord dominated ground effect will provide better efficiency but requires flying lower (unless AR is less than 1, and this won't be)

    Chord dominated ground effect creates an unstable condition, which can be partly compensated for with use of a reverse delta with negative dihedral and a large horizontal tail: http://www.aerospaceweb.org/question/aerodynamics/ground-effect/flarecraft-l325.jpg

    On these types of WIGs the horizontal tail is normally a lifting surface because it helps to automatically prevent the unstable pitching up the occurs when the plane increases it's height above the surface. At low heights the center of lift moves back to about 50% chord so the tail lifts very little, but when higher the center of lift moves to around the 25% point, at which the tail must lift more.

    This site has some discussion of the stability issues and different airfoils used to help with that: aero
     
    Last edited: Jun 24, 2010
  2. May 20, 2010 #2

    Starman

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    Re: Wing in ground effect

    Here are some preliminary sketches of my idea. Showing a two step hull, I thought of using a hydroski, but if the plane contacted the water while the ski was retracted it would stick to the water and not bounce off.

    My plan is to use welded aluminum boat construction methods for the hull, engine mounts, and main spar and use foam and fiberglass for the top of the fuselage, wings, and tails. The wings will provide flotation.
     

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  3. May 20, 2010 #3

    addaon

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    Re: Wing in ground effect

    Is 80 hp going to be enough to get you up on step? Direct drive, your static thrust will be rather low.
     
  4. May 20, 2010 #4

    Starman

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    Re: Wing in ground effect

    It might not be enough, but I'll try direct drive first, mainly due to impatience :) I thought it wouldn't be enough but then I saw that the original Airfish 1 got airborne and went 100mph on 13 hp so there is hope. If I need a PSRU I'll make one out of V belts. The smaller diameter is good because it allows a lower thrust line but if I go from a 6ft to an 8ft prop it will only raise the thrust line one foot.

    Obviously when it is reconfigured for long range and a large fuel load it will need more power and thrust efficiency.

    I see that many planes with engines in pods have the prop in front (like the Be-103), but I would prefer it in the back because it allows a lower thrust line. Do they put the prop in front mainly for convenience sake? I guess it allows a shorter prop shaft.
     
  5. May 21, 2010 #5

    Dan Thomas

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    Re: Wing in ground effect

    On any waterborne aircraft, an aft prop ends up eating a lot of spray and splash. Water does terrible things to propellers, like splitting them apart and eroding them, and any big gulp of water can cause sudden deceleration of the crankshaft and damage things.

    So the pusher props we do see on amphibs tend to be mounted up high and above the wing or above some strakes to try to keep the water out of it.

    Dan
     
  6. May 21, 2010 #6

    Starman

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    Re: Wing in ground effect

    Thanks Dan, I'm aware of the importance of keeping water out of the prop. When I mentioned putting the prop in front I meant in front of the engines, which are still in back. On this design I'm relying on the prop being above the big fat wing root and hopefully once the craft gets going fast enough to cause some spray that it will rise up to where all the spray will go under the wing. The Be-103 accomplishes this by using a delta shaped wing root that reaches fairly far forward, Reverse delta WIG craft accomplish it by having the large wing root at a high incidence.

    In this case, whether the engines are oriented with the props in front of or behind them, it is still a pusher craft since the props and engines are behind the passenger compartment; and if water went over the wing it would hit the props no matter which way the engines are facing.

    I imagine that wood props would split and erode but that aluminum ones wouldn't split but may get eroded a little?
     
  7. May 23, 2010 #7

    GESchwarz

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    Re: Wing in ground effect

    Wing in Ground = Cartwheel Effect :ban:
     
  8. May 23, 2010 #8

    orion

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    Re: Wing in ground effect

    The biggest problem WIG craft continue to have in their development is simply that the hydrodynamic forces at play will drive the power requirement, more so than anything flight related. If we look at an idealized planing flat plate at a positive angle of attack, the optimum L/D occurs at or near 5 deg in relation to the waterline. The max L/D value at this point is approximately 5.5:1. But this is idealized and assumes a perfect flat surface. Introduce typical environmental issues and realistic hull design values, including things like dead-rise, the max L/D value will most likely be around 4.0:1 or even less. So, for your 3,000 pound craft you will be generating about 750 pounds of drag. Below this trim speed you will be in displacement and/or transition mode and after this point it'll be assumed that your wing will be providing lift thus reducing the weight the hull has to lift.

    Then your dynamic effects come into play - as a rule of thumb, it's a good idea to have a substantial thrust margin at this point so as to avoid porpoising. For the sake of discussion let's round off the thrust required to get off the water to be at about 1,000 pounds. Given your two 40 hp motors with moderately small props, it's doubtful that you'll generate more than about 250 pounds of static thrust, give or take a bit. Maybe with an optimized low pitch prop you can do a hair better, but you'll still be woefully short of the mark.

    And regarding your 250% increase in fuel efficiency in ground effect, simply stated, in your dreams. While it is true that a wing in ground effect does generate less drag and to a limited extent a bit more lift (requires very small h/c values) than in free air, remember that you're dealing with induced drag only. Because of speed and performance issues though, you generally have a large wing so your cruise lift coefficient is relatively small, thus making the induced drag number relatively small. You still have the fact that it's a low aspect ratio design and you are still carrying the rest of the vehicle. Those numbers do not change.

    But here's the basic problem, you need power to get off the water but you then don't really need it to cruise (BTW, I think a more realistic cruise speed goal for you will be around 80 to 100 mph). On a large scale craft like the Russian KM that means you carry ten large turbofans for take-off but then you idle eight of them for cruise.

    On a smaller vehicle like the failed Flarecraft you will then have a tendency to overpower the craft, which can greatly destabilize the vehicle (long story here and not a very pretty one).

    The difficult task in designing a WIG is simply that there is not enough reliable information out there to do a good job of it. If you're designing a plane there is tons of data, text books and reference papers that you can dig through to get just about anything you need. For WIGs there is virtually nothing. I've been doing WIG development consulting for over about fifteen years now so I've seen most of the programs in the Western hemisphere. Some have potential and some are downright scams but all have the same issues - not enough data and not enough money to do it right.

    The bottom line of this is that the project you have in mind is ambitious and there is a lot more to it than a cursory glance might reveal. I certainly do not wish to dishearten your effort but just want to make sure you understand what you're getting into. People and organizations have been after a functional WIG craft for years, especially a Class B. So far though, no luck. FlightShip came closest but it too ran out of money, mainly due to creative bookkeeping by the developer. That program did go through sea trials and certification but once the money got pulled, it just disappeared. Last I heard it was sold to someone in Turkey but there it seems to have gone nowhere.
     
    Last edited: May 24, 2010
  9. May 23, 2010 #9

    Kristoffon

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    Re: Wing in ground effect

    Did you even do the basic math? 3000 miles at 50 mph is a 60 hour trip! Do you plan to sleep in the middle of the ocean?
     
  10. May 23, 2010 #10

    orion

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    Re: Wing in ground effect

    One thing I forgot to note above: The hull L/D value is for an established planing configuration. To get there though you have to deal with your bow wave so getting up on plane requires a lot more thrust than the planing L/D value might suggest.
     
  11. May 24, 2010 #11

    Starman

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    Re: Wing in ground effect

    Yes, land in the middle of the ocean and put up a strobe light on a short mast to hopefully prevent being run over by an ocean liner. Actual distance between Seattle and Hilo is 2655 miles, from San Fran to Hilo is 2318 miles. But 3000 miles should be minimum potential range (for the long wing, long range version only).

    Anyway, 50 mph is more like hopeful minimum practical flying speed if I want to follow larger ocean swell contours but I envision the Pacific being pacific enough to allow flying at a planned long distance cruise of at least 100 mph while still benefiting from some ground effect. I expect to plan trips when the ocean is relatively calm and so allow faster speeds while flying low (watch out for rogue waves =). So that is 27 hours, meaning flying overnight or spending one night parked in the middle of the ocean.
     
    Last edited: May 24, 2010
  12. May 24, 2010 #12

    Starman

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    Re: Wing in ground effect

    Yes, I expect to put skis on the tips of the reverse delta to help prevent cartwheeling but I didn't draw them in there yet. With the long wings I'm on my own :) There won't be any skis on the tips of the long wings, but maybe some end plates.
     
  13. May 24, 2010 #13

    Starman

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    Re: Wing in ground effect

    It looks like I'll need some PSRUs then, keep in mind the two 40 hp engines are for a more lightly loaded, short wing, shorter range version and direct drive is mainly for first sea trials. The figuring I did suggests that I need at least 150 hp to get even a poor climb rate, which would be acceptable for this since there are so few mountains in the ocean.

    This is how I'm thinking of going at it, in very rough figures:

    First 'flight' attempt:
    1200 lb
    20 ft span
    150 ft wing area
    80 hp w direct drive

    Local cruising in Puget Sound and up behind Vancouver Island:
    2000 lb
    20 ft span
    150 ft area
    80 hp w PSRU (might need more hp)

    Going to Hawaii:
    3000 lb
    40 ft span
    250 ft wing area
    160 - 200 - 250 hp w PSRU

    Thank you for the planing boat L/D figures, that helps. One thing I wonder about is the ideal planing angle - are you pretty sure that the ideal angle is 5 degrees? Previously, and over a decade ago, I had read that the ideal angle is 10 degrees. Possible 5 to 10 is close and is the ideal range? 10 degrees though would mean a little bit less wetted area in a hypothetical ideal situation.

    I'll get back to the rest.

    I just edited the title to include the word 'boat' so expect a whole new bunch of lurkers here. =)
     
    Last edited: May 24, 2010
  14. May 24, 2010 #14

    orion

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    The ideal planing angle usually resides between 4.5 and 5.5 degrees. Yes, there is some variance as a function of Froude Number and finesse ratio but for a conventional hull, that's about it. Beyond that the drag rise is fairly substantial. Also keep in mind that the hull imposed trim angle will initially be much higher as you approach the planing speed so the actual amount thrust you'll need is dramatically greater.
     
  15. May 24, 2010 #15

    Starman

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    Re: Wing in ground effect

    Orion, I'll respond to your other statements here without quoting all of them.

    I got the 250% efficiency increase from the website I linked to, and I didn't believe that it's possible in a real world situation. Maybe it is possible on smooth water at very low h/c where the air under the wing completely stagnates and generates a full pressure recovery. In any case, when I figured the range I assumed no efficiency increase due to WIGE just to be on the safe side.
    I'm aware of the excess power situation that WIGs have, but could you state briefly what the source of the destabilization is when overpowered. High thrust line?

    I've had my eye on WIGs for about 25 years now and it seems there are plenty of them that have acceptable functionality. I have no desire to start a company and sell these, it's just for me, and so no scamming. In any case scamming is against my nature and ethics is very important to me due to my 'situation' Here's something I wrote about ethics on my website: The Way of the Immortal - Ethics

    The idea that there isn't a lot of design info is fine with me because I like seat of the pants designing and going into the unknown appeals to me a lot. I'll build scale models of this craft before cutting too much metal.

    I'm curious though about this website The WIG Page - information about Ekranoplan and Wing-In-Ground effect craft that I linked to earlier, which is a clearing house for the latest WIG design info. They require a fairly substantial membership payment to access the info. Have you heard of them and/or are you a member of it?

    I don't mind ambitious projects, and I like the challenge so don't concern yourself with disheartening me =)

    It's too bad that the Flightship was the victim of more scamming and went under as it looked very good to me.

    Also, keep in mind that with the longer wings this vehicle is intended to be an actual 100% aircraft (amphibian) able to fly out of ground effect - with a lifting tail.

    Now I need to find out how to make a good model that is waterproof, I suppose balsa wood doesn't fill the bill.
     
  16. May 24, 2010 #16

    Joe Fisher

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    Back in the 1960's there was an article in Popular Mechanics about a hybrid boat plane. They had a small boat with the outboard engine and a long boom forward with the seaplane attached.
     
  17. May 24, 2010 #17

    Starman

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    Do you mean the boat was to help accelerate the aircraft to flying speed and was then left behind? In that case the proper term is composite vehicle rather than hybrid.

    Short Mayo composite aircraft:
    [​IMG]
     
  18. May 25, 2010 #18

    orion

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    Re: Wing in ground effect

    If it's the case I'm thinking of, the number comes from a theoretical analysis of a wing-alone condition. The example is used to demonstrate the potential of ground effect flight however most folks seem to take a cursory glance at the example and assume that it means that somehow a WIG will be 25 times as efficient as a 747 in cruise. Nothing of course is further from the truth but in many cases the facts do not seem to deter the determined. Ground effect flight does add efficiency but the real comparison must use is one that compares transportation systems, not aircraft. Compared to high speed marine vessels, the potential of WIG operation is substantial. And herein lies the benefit of the WIG craft being classified as boats, not airplanes. In your case though I'd urge care since if you are going for free air flight you will not be a WIG - you will simply be an airplane that happens to fly really low. That then does put you in the jurisdiction of the FAA.

    It's a combination of things but simply said, the WIG craft must be able to achieve a trim and stable attitude that's a function of height. Since this condition is a function partly of speed, variances in power could cause the trimmed craft to climb, thus exceeding its trimmed attitude and thus go unstable. As you indicated in your post, the wing's resultant lift vector position changes dramatically between ground effect and free air and too much power at the wrong time is a guarantee of loud and wet noises. Yes, you also have the high thrust line issues and trim effects of the horizontal tail in the slipstream so all these things combined are a recipe for disaster, In the case of the Flarecraft, if I recall right there were two crashes, the last one fatal to the pilot.

    Actually none have any real domonstratable functionality. Pretty much every Russian WIG has crashed and has within the last decade been proven unstable and poor in function. Currently all Russian WIGs are grounded and mothballed with the exception of the Amphistar, but that one will be also (if it hasn't been already) since it can be herd coming for miles and no community I know of will allow that noise anywhere near its shores.

    More modern designs have also been proven ineffective (with the exception of the Airfisch series and of course the FS-8) - the German government had a fly-off about five years ago or so and all the functional WIGs were invited to the event. If I recall right almost a dozen came. On the morning of the demonstrations there was a light wind and the lake developed a light chop. That slight surface disturbance created enough of a problem that not one of the participants was able to lift off to flight mode. Not even the more hyped ones like Dr. Fischer's Hoverwing.

    I know it well - I was one of the founding members (although the real person behind it is Edwin van Opstal, who's one of the leading authorities in the field) and I provided the same type of technical support that I do here. After a few years though I stopped simply because there was very little new blood, the questions became repetitive and sometimes just plain dumb, and because no-one was really serious about the technology or the development of a real product. It was essentially just a bunch of amateurs playing around with toys and their pet theories, none of which really held much water. In short, it just became really disheartening so I and a few others who are into this end of things just faded from the group. I don't know its current status and I really don't want to pay so much to find out.
     
  19. May 25, 2010 #19

    Starman

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    Now that is disheartening :)

    My idea was to make a WIG and be under the jurisdiction of the Coast Guard and then after playing around with it for a couple of years adding longer wings and getting it FAA certified.

    I found some clear info on WIG design and potential titled: Australian Military Research and Studies on Wing in Ground Effect Craft. It is a pdf file that can be found on the wikipedia page on ground effect craft.

    So the story goes that by the time you add the gigantic rear wing and all the extra power that there isn't much gain in efficiency - in addition to the stability problems.

    It seems to me that the best way to get stability is to use a narrow chord wing, but then you have an aircraft, which still could utilize ground effect.

    I suppose a float plane or flying boat will need just as much power to get water plane as a WIG, but they can put the power to good use by going faster in the air.

    So, back to the drawing board.
     
    Last edited: May 25, 2010
  20. May 31, 2010 #20

    ekranoplan

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    Re: Wing in ground effect

    This is not true, they all had success, only drawback was lack of funding, as I will explain later.

    Not every one crashed, and reason was not in WIG concept, rather in human errors and continuosly smaller budget for program.
    All are landed and rotting only because then Soviet, and now Russian government, gave up from Ekranoplan program, and instead invested all money from Ekranoplan program, to nuclear submarine program. I have to add that, Hruščov's successor, Brežnjev, wasn't interested in program at all. So, as you see, Russian Ekranoplan program was placed a side only because of politics, and in early 1990's major political changes in ex USSR, now Russia.

    There are companies making ekranoplan's or WIG's as you want it.

    Russian ATTK ( Arctic Trade and Transport Company ) - you may call it one of successors of Russian Ekranoplan program, since many of engineers and designers ended here, and company uses some of facilities of the program:

    Products

    [video=youtube;LL3AC1LRRVk]http://www.youtube.com/watch?v=LL3AC1LRRVk[/video]

    Asian company ( Japanes or Thai, not sure ):

    [video=youtube;qk0HRShYbGU]http://www.youtube.com/watch?v=qk0HRShYbGU[/video]

    Korean company:

    [video=youtube;i-SLrAkYL3Y]http://www.youtube.com/watch?v=i-SLrAkYL3Y[/video]

    Singapore company:

    http://www.wigetworks.com/index.html

    Chinese company:

    Home | Sea Eagle

    [video=youtube;4pd8SFCuFpk]http://www.youtube.com/watch?v=4pd8SFCuFpk[/video]

    UK company:

    Flyboat,flying boat or WIG. Wing in ground effect fly boat for sale.

    [video=youtube;i4QguO9ti1c]http://www.youtube.com/watch?v=i4QguO9ti1c[/video]

    I must admit, that this is very niche market, unfortunately, and any info on internet is very, very hard to find. But still, in depths of internet abyss one can find little information on them.

    Honestly, it is surprise for me also, considering what kind of things people made in their homes, it seems that WIG is really, very rare.

    So, Starman, you have my support, as I'm also considering same thing as you, but, as for me, I think first couple of years will be in learning all about WIG's I can learn.
     
    Last edited by a moderator: Mar 20, 2019

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