The Wind Powered Sail-less Boat

Discussion in 'Boat Design' started by DuncanRox, Oct 20, 2008.

  1. spork

    spork Previous Member

    If you said anything confrontational it must've been pretty darn minor. I don't recall anything at all. And on this topic there's PLENTY of confrontational to choose from.
     
  2. chabrenas
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    chabrenas Mike K-H

    Rick: I know small diameter airscrews are less efficient than big ones, but have you looked at the effect of using 4 or 5 and halving the height of your design?

    That would make it a lot more stable...
     
  3. Guest625101138

    Guest625101138 Previous Member

    I would do many more iterations of this before I felt I had something near the best design just to prove a point.

    I started out with the idea it needed to be quite big to achieve the required efficiencies but was then surprised that it looks like it performs well at high speed.

    My next iteration would be a smaller boat for unmanned operation and intended for operation in stronger wind. Design condition would be say 10kts and boat would be designed to do 15kts in this wind. I expect I could then use a much smaller prop.

    Reducing the size of the prop would make it more practical. The large area of the current prop is a result of aiming for a 1m/s apparent wind speed. If I was to go for apparent windspeed of 2.5m/s, the energy in the airsteam goes up 6 times for the same area or I could reduce the area to 1/6. Having a smaller boat further reduces the area required.

    I only did the design to give realistic numbers and actual losses. Mark Drela's analysis does not give actual value for the losses although he discusses all the sources of loss. His power analysis was instrumental in me being able to understand one of the apparent inconsistencies in my model data but I have resolved that now.

    I have not fully modeled the Buggy design. I have done a couple of prop designs for it but this was not intended to be realistic. The aim was to prove a point but I have failed miserably with IRK. Very hard to have an open mind and clear thinking when the starting premise is that it cannot possibly work and he has dug such a deep hole showing that he really has no idea about basic physics.

    Rick W
     
  4. chabrenas
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    chabrenas Mike K-H

    'Twas aye thus. I always wonder how the first internal combustion engine ever got built. Surprising that doesn't seem to figure in history books.
     
  5. Guillermo
    Joined: Mar 2005
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    Guillermo Ingeniero Naval

    I'm not in dissacordance with what you say, and what you say is not in contradiction with what I say. To get energy whatever sailing craft needs to take it from the wind, specifically from the kinetic energy of the wind. For a given wind speed the way to get more energy from it is to take it from a bigger mass of air. That's what sailcrafts do by traveling to an angle with the wind. Lift, drag, etc are secondary to this principle and only affect efficiency.


    Yes, of course, but I was talking about the theoretical craft with the tacking boat inside it. That was a simplification. I would appreciate if you avoid terms such as 'rubbish' etc. Just give your opinion, please.

    Yes, but my questions still remains. Is there enough power transmitted from the water turbine for the air rotor to overpass the vortex ring situation? If the boat can speed up (and the rotor turn) to a point where the blades of the rotor begin to see usable apparent wind, the craft can then go FTTW, but, can it reach that point? That's what I'm not sure about.

    Not the treadmill because it doesn't address the transition point (vortex ring situation) in my opinion, as the energy applied to the wheels is external to the system (the power from the motor), so we can increase it all we need to overpass it.

    Cheers.

    P.S.
    Rick:
    I'm not questioning your numbers at all. I'm just talking about the vortex ring situation. All the best.
     
  6. Guest625101138

    Guest625101138 Previous Member

    Guillermo
    If this is your only issue then the very beginning of this video will show how readily the cart takes off and continues to accelerate.
    http://www.youtube.com/watch?v=kWSan2CMgos


    There is no impervious barrier. Once the vehicle gets moving and is spinning the propeller it will continue to accelerate. If the prop has reasonable efficiency it will reach equilibrium well above wind speed.

    Rick W
     
  7. spork

    spork Previous Member

    How can we convince you that the principle of equivalence of inertial frames is real - and applies to treadmills? This is one of the most basic tenets of physics.
     
  8. Guest625101138

    Guest625101138 Previous Member

    I think he now accepts that it can exceed windspeed but he is stuck on it getting through the impervious "vortex" ring state that he sees occurring. It means something full scale would not be able to get through a certain point.

    If you want to prove this condition with the treadmill you would need to have the treadmill running and just drop the vehicle on it. I don't think your treadmill is long enough to demonstrate that it will eventually move forward rather than just being flung backwards initially.

    Rick W
     
  9. Tcubed
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    Tcubed Boat Designer

    I see a new video soon , using the treadmills you see in airports . They're plenty long enough, if you can get past the absurd safety regs.
     
  10. ThinAirDesigns
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    ThinAirDesigns Senior Member

    We have several outside of security here at SFO. Unfortunately, they all run too slow for my cart. Would absolutely love to throw our cart on a long level conveyor, let it self-start and then climb off the front. We need around 5-6mph to get it done.

    Anyone find the spot and I'll provide the cart.

    JB
     
  11. Tcubed
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    Tcubed Boat Designer

    5-6 mph... i thought that is about how fast those things go. Walking speed.

    Ok why not modify the cart so it needs even less wind to get going?

    Bigger prop , even better bearings , a bit lighter , possibly larger wheels to reduce friction even more.
     
  12. ThinAirDesigns
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    ThinAirDesigns Senior Member


    My best cart will run faster than the wind in as little as 2.7mph. It will not self start at those speeds however.

    Bigger prop didn't have the effect we wished for. Already using excellent bearings with the dust seals removed -- cleaned and siliconed just before test. It weighs less than 6oz -- only a fair chunk of money (custom carbon prop, gears, etc) will reduce that by much. Larger wheels requires custom gearing/prop.

    I would love that video, but there's a limit to how much I'll spend to get it. You are more than welcome build on our experience (or your own) and put together a cart with all the pricey features you desire.

    JB
     
  13. Tcubed
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    Tcubed Boat Designer

    Seeing as you've already highly optimized things , my thought on lowering treshold self start air/ground speed without $$; Use the indoor model airplane technology with a lightweight frame and plastic film to make an oversize prop. I'm sure you know what i mean.
     
  14. Guillermo
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    Guillermo Ingeniero Naval

    Thanks Rick,
    Talking about the open air test, how is it possible for the rotor to change sense of turning? :confused:

    Cheers.
     

  15. Tcubed
    Joined: Sep 2008
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    Tcubed Boat Designer

    Looking at spinning things on video can be totally misleading due to phase effects of the flashing slides.
     
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