Ground effect flying craft, wind powered

Discussion in 'Boat Design' started by Cloxxki, Nov 18, 2011.

  1. Cloxxki
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    Cloxxki Junior Member

    An continuation of my earlier thread:
    http://www.boatdesign.net/forums/propulsion/wind-powered-ground-effect-boat-craft-33363.html

    I'm back breaking my head over such a craft. Not at all thinking it will be easy to realize.

    The more I think about it, the more manouvrable the thing could be. Flying upwind would be relatively easy. It might be able to deal with crosswinds, and then turn downwind. In groundeffect mode, downwind is the hardest to accomplish, as the apparent headwind to generate lift on the body and likely required outer delta-style winds, is zero when going at balloon speed. It gets interesting at double balloon speed. For that, a super low friction catamaran, gradually lifting out and off as speed increases will be needed. A batterypack (stored wind energy) and engine may be required to boost the air prop to get to take-off speeds, after which the wind would self-sustain flight mode.

    Going against the wind, laying still would already generate lift. As any upwind cart, apparent wind could easily reach 1.5* wind speed. Serious lift potential.

    I'm now thinking a wide catamaran would actually be a great basis for my craft. It floats, which is a good start. Takes away a difficult-to-scale self floating tank track. I'm confident that plastic air pockets can be made to work on 1/10 scale, but full scale it will liekly prove very tender.

    Between the two hulls, the vaned tracks could be placed. The hulls nicely contain the incoming apparent wind laterally, needed for ground effect. The tracks, sitting close to the insides of the hulls, would need to reach below the waterline to be able to act for propulsion at low speeds, upwind or even in crosswind.
    The track would form the underside of the flat wing shape of the big bridge, the top would be inside it.

    On deck, apart from from the tall turbine slash propellor(s), I envision collapsable airfoils. Might even be inflatable. They'd be lined up, line 3 per hull. Not tall at all, as that would be cumbersome with the propellor which can turn arounds its axle.

    I hope it works without it, but an engine might be needed to more easily reach take-off. with it on board, able to power either the tracks or the propellor, it might as well get some energy from otherwise wasted solar nergy hitting the deck. So, solar panels there. It's got a huge surface to work with, and solar tech gets lighter every day. It's free green energy, so why refuse it? OK, in the night you'll be without. Just a few kickstarts from the battery packs.
    And yes, the solar surface can be vast. As outside of the hulls, likely large Delta wings will be required to get it all airborne, and place controls. So, more room for solar cells. Solar may not be viable yet for manned flight as sole energy source, I think it could offer a boost an an already flight crafts, with electric engine in place. Add weight for the panels, get maybe an average 100W per m² to be used for the propellor or topping off the batteries. Might be worth it in their weight, might not. It would be great to have some significant solar power for windless days, obviously. And surface area is good for groundeffect anyway.

    My main concetual concern is the efficiency of the vaned tracks for transferring water speed of the hulls into airprop motion. Of course only doubtful of the tracks are out of the water, and just trapping an air bubble. There will be losses, but how many gains? What shape(s) are ideal for extracted to output wind energy ratio? The wheels of the DDWFTTW cart are extremely efficient. How to get the most efficient extractor, when all you have it the very apparent wind you are fighting against, not just ground speed?

    In downwind mode:
    The tracks would need to be resisting water underneath until a significant >1* windspeed figure. Ground effect is not likely to happen until near 2*, and then, apparent wind is only 1* actual wind speed. Not a lot or air passing to extract energy from yet.

    In upwind mode:
    From ancors loose, there is already 1* true windspeed in apparent wind. An A4 paper plane will want to takeoff badly. A boat, not yet.
    Turbine is spinning well, and drives the tracks making it a bit of a waterwheel boat, but better. Say, 50% of wind speed is reached. That is 1.5 in apparent wind. Take-off is near. The boat generates lift from the large Deltawing shape, ground effect is building a bubble. At worst, you have a boat displacing much less water. The turbine does its job, the tracks take the role of waterwheel/prop. Very exciting if take-off speed will ever be reached. The wind under the boat is slowed, which helps the tracks. Lift aplenty, but wind drive...?

    While the hulls make the deisgn heavy, they also open up ways to make it more user-friendly. What do you think?

    Anyone have both a scrap scale catamaran and airplane to sacrifice?

    And some good inspiration: http://en.wikipedia.org/wiki/Ground_effect_vehicle
    Just think wide and stable, plus a huge propellor on top.
     
  2. HJS
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    HJS Member

    An old project from 1969
    calculated doing 60 knots
    maybe faster today

    ;-)
    js
     

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  3. Cloxxki
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    Cloxxki Junior Member

    Wow, thanks HJS!
    That looks like something i was never able to draw, but sortof vague "felt" in my brain at times.
    Is this supposed to be fully airborn? Launch on a rollertrackfrom the shore?
     
  4. HJS
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    HJS Member

    Not fully airborn, just the centerboard in the water, otherwise it will not work.

    js
     
  5. Doug Lord
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    Doug Lord Flight Ready

  6. river runner
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    river runner baker

    I remember seeing a ground effect powered airplane several years back. Looked a bit like the alien space ships from the original 'War of the Worlds" movie. Kind of like a hawk mantling it's prey. I would imagine a wind powered one (glider?) would also have very low aspect wings, rather than high aspect sailplane type wings. Something that would trap a high volume of air between the wing and water.
     
  7. Jeremy Harris
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    Jeremy Harris Senior Member

    Bear in mind that you need to generate a force from the wind in order to be able to extract useful power. This means that any unpowered WIG craft needs to have a connection to the water, so that it can be restrained and a relative wind allowed to develop. You cannot get energy from the wind (in a steady state) from a free-flying craft. Anyone who's slope soared a glider will tell you there is a sucker trap (I've experienced it once over the cliffs close to Lands End, Cornwall, in a glider). You can be stationary over the ground, in the uplift from the wind over the cliff, yet you will really be slowly descending down the gliders normal glide angle.

    Tie a winch wire to the glider and you could kite it all day in this situation (as long as the wind keeps blowing), just as the Wrights did with their gliders at Kittyhawk.
     
  8. yipster
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    yipster designer

    even with the centerboard in the water you most problaby have a hell of a time to make that design work I figure..
    but think it may fly, maybe making it a motorsailer makes it a bit easy'r?
     
  9. Doug Lord
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    Doug Lord Flight Ready

    Sailrocket 100% fly's-there is no lift from buoyancy whatsoever when the front module is flying. When the front module is not flying, it is planing. There is a picture of that on their site.There is no lift up from the hydrofoil either: their only vertical lifting foil pulls down! And the rudder is a vertical fin out of the forward module.
     
  10. Cloxxki
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    Cloxxki Junior Member

    I beg to differ.
    Surely, this will not be an easy feat.

    Let's suppose a super-advanced DDWFTTW boat were to reach 3* wind speed. Like the desert cart already managed.
    Now, if the boat has a ground effect shape, channeling air under itself, that could already reduce water drag by sitting higher in the water. This will likely be needed to reach such windspeed multiples anyway.
    Ok, so wind is slightly compressed under the craft. This is an opportunity to extract energy from the apparent headwind. It's moving under the craft 2 times faster than the water when the boat is going 3* wind speed. With a really big, low friction, high-traction turbine as I am proposing, in theory the water as contact point to transfer wind power to the airprop, becomes redundant.
    I now realize I need to amend my design. The waterwheel will need a different gearing with the prop than the air turbine.

    I can see ways why my basic concept won't work, but it will need more elaborate bedunking than just stating that it's not possible. It's never been tried as far as I know.
    First versions that work will certainly not be manned. I anticipate absolute cutting edge materials to be required to make it work. Certainly a type of on-board booster to reach ~3*wind speed and going airborn may be needed. Like the first water airplanes probably also didn't manage to reach take-off speeds on the water. Just flapping your arms won't make you fly. But with big enough wings, and a high enough hill to jump off, you might even glide for hours.
     
  11. daiquiri
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    daiquiri Engineering and Design

    What Jeremy is saying is that you cannot get energy from the wind if there is no contact with either water, ground, or a fluid layer moving relatively to the wind in which your craft is flying.
     
  12. Jeremy Harris
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    Jeremy Harris Senior Member

    When you see sea birds doing this they are not getting energy from the wind in a steady state, they are doing something called dynamic soaring. They are small enough to exploit the wave-induced updrafts and downdrafts to gain energy - effectively they are extracting wave energy from the wind. If you watch them, you can see their technique and the way they gain airspeed on the down slope of the wave and then turn and gain height going along the upslope, before turning down wave again and building speed.

    Gliders can do the same, in the right conditions, but it requires a bigger wave in the air to work well.

    What I wrote before is correct, if you want to extract energy from the wind then you have to create a differential velocity between the vehicle/aircraft/vessel and the wind. If the vehicle is free flying in a steady state then it will always be in the moving body of air and unable to extract energy from the wind.

    If you do a web search on dynamic soaring you may get some useful info.
     
  13. Cloxxki
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    Cloxxki Junior Member

    I want to try to use apparent wind to replace the road or water surface. Wind turbines work, and hopefully the conditions under the ground effect craft help bring it's efficiency in the ballpark of a waterwheel.
    The turbine would be specifically designed to exploit the conditions it's to operate in: slightly compressed air. It would see wind at 2* actual wind speed, where the air prop on top would only need to propel the craft to 1* above actual wind speed.
    If the craft could lift itself out of the water, and go from using waterwheels to using turbines, that's be beyond amazing. A kite with an ever extended line, on board!
    To cheat, the craft could have a lightweight but (from smart amendments) draggy line aboard. Let it hang in the water, and unroll a wheel replacing the air turbine. This we know, works for flight, as long as the line is long.
    It could be a hybrid kickstarter perhaps, more efficient than the waterwheel (near 100%), adding less weight, but having a limited action radius.
     
  14. Cloxxki
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    Cloxxki Junior Member

    DDWFTTW exploits the speed difference between craft/ground and wind/ground.
    I want to attempt one step harder: exploit speed difference between craft/apparentwind and wind/water (ground when airborn). Up river, a water wheel or draggy line would make it even easier, but having a wind turbine even kills even that bonus.

    Perhaps try and design an upwind ground effect vehicle first? Lower speeds, easier to deal with?
     

  15. Jeremy Harris
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    Jeremy Harris Senior Member

    No problem with extracting energy this way, but as I've said before, you need a connection to the ground or the water in order to make it work if you don't want to do something like dynamic soaring, where you go up and down all the time to extract energy from the wind.
     
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