Sailors wrong for thousands of years?

Discussion in 'Sailboats' started by backyardbil, Feb 7, 2011.

  1. pjssailor
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    pjssailor Junior Member

    Rigged test

    Hey guys. I have what may be a stupid question. The video I see is a rigged test. The fans output is focused on the windmill. Why not put the little boat in my cana:)l and see if it will go directly upwind? A small lightweeight radio conrot will help you control it to stay pointed upwind. Not any rocket science to make a pretty true test and no BS to it. Cheers. Lloyd.
     
  2. jehardiman
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    jehardiman Senior Member

    Go to the first thread I linked in post #3, there is a model shown in open water. The issue with these things is not that they don't work, but that they have material scale issues that prevent them from being built to large useful sizes. In this respect they are similiar to inertial propulsors. They are cool toys, even small yacht sized, but of little comericial value in large sizes.
     
    Last edited: Feb 8, 2011
  3. Windmaster
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    Windmaster Senior Member

    Anyone who has doubts if they work can easily build one to satisfy themselves and also amaze their friends! The plans are on this webpage: http://www.sailwings.net/windspinner.html
     
  4. BATAAN
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    BATAAN Senior Member

    This simple gadget is illustrated with a photo in one of the Herreshoff books or articles, except placed on a model flat bottom skiff about 1890 or so. In the photo it seems similar scale to pop bottle catamaran in video.
    L.Francis was a child and his dad, Captain Nat, made it for his kids as a toy. Works straight upwind only as I recall LFH's comments, but I can't find the photo. Maybe someone else can, as it's definitely been around for 120 years. Capt Nat also built wicked fast catamaran racers in the same period but was banned from competition as being too radical.
     
  5. backyardbil
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    backyardbil Junior Member

    So we wonder why they never tried to develop the concept.
    Surely, the ability to sail directly to windward would seem an obvious advantage. It would be understandable if they had tried and failed or found it impracticable, but as far as I can see they didn't make any attempts at it until more recent times.
     
  6. BATAAN
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    BATAAN Senior Member

    They did try and found in impracticable, in model form. It will crank itself to windward but the forward propeller is the first thing to hit an obstruction, and don't think about going aground.
     
  7. jehardiman
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    jehardiman Senior Member

    As I pointed out earlier, it is a material issue, the same as with Herreshoff's cats. He himself described them as toys, never suitable for anything more that day sailers...and with the materials of the time he was correct. Just like you never saw a wooden ship much greater that 250 feet long until the advent of iron frames and strapping, or a large building (not tower) over 7 stories until rolled iron framing systems; large all ocean sailing cats and tris are tied to the advent of modern composites. Many designs sit around until suitable materials are developed to allow the design to be built in workable sizes. There are many things I could do if I had Unobtainium (infinitely light, strong and ridgid material), Spidercloth (infinitely light, strong and stretchless fiber), Bouyancyium (buoyancy with no volume or weight), or Ballastium (weight with no volume).

    It is important to really grasp the concept of scale effects as they apply to things like watercraft and aircraft. If I double the size of something I increase the dimensions by 2, areas by 4, and volumes by 8. If I am extracting power based upon area, like a blade/wing/sail I am losing specific power because the weight is increasing twice as fast as I gain power. Small models I can build out of balsa or 0.005 sheet plastic and have sufficient strength to weight, fullsize there is no material I can use. As I have pointed out in other threads there are real engineering limits to the size you can make certian hull and mast systems. This I think happens to be one of them, the cost to make it a useful size greatly exceedes the useful value.
     
  8. backyardbil
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    backyardbil Junior Member

    What parts do you think would not stand up to being increased in size? Old traditional windmills (like the ones in Holland) are many times bigger and they don't fall to bits.
    Also, if that's all they're suitable for, why not use them as day sailers?
     
  9. Windmaster
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    Windmaster Senior Member

    I think they can be configured in a more practical way, for example in this video:
    http://www.youtube.com/watch?v=NNbNNSDljGI
     
  10. jehardiman
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    jehardiman Senior Member

    Blades, torque tube, mast strength and hull stability. While there have been several "boat sized" windmill powered craft built, like Windmaster's and Revelation II they really never transitioned to a larger size and speed. While there have been many advancements made in blades recently, there are still material and transonic issues that limit rotational and tip speed. Additionally, while a small devices can be made strong enough to take motion loads, larger devices like the unit shown on the barge, need to have roll pitch and sway restricted to hold weight to a reasonable level. Dynamic loads at the mast head can reach 2-3 g's for a small to moderate vessel and though I haven't gone through the exercise I'm willing to bet a design study would lead you to structurally impossible vessel if you look at "yacht sized" paramaters and speed goals.

    There is a good looking thesis project for someone...
     
  11. Windmaster
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    Windmaster Senior Member

    Since you mention my boat - I can tell you that there was never any sign of the design not being strong enough and I had no failures of any kind. I see no reason why they can't be scaled up. Revelation II is a full sized catamaran.
    What about Bil's point about the old windmills, (which were only made of wood).
    I think you're taking an unduly pessimistic view here.
     
  12. Perm Stress
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    Perm Stress Senior Member

    Would be interesting to hear more about real-life use, speeds, achieved in certain conditions, handling issues, behavior in heavy weather, big sea, etc..
     
  13. Windmaster
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    Windmaster Senior Member

    Some personal circumstance curtailed the testing of my wind-turbine boat. True enough a lot more testing needs to be done. It's a development process, not just a question of coming up with the right perameters straight away. As it happens I am re-constructing the boat this year, plus a few updates, with the prospect of doing more testing.
     
  14. jehardiman
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    jehardiman Senior Member

    I consider it more realistic than pessimistic. I expect anyone with half decent mechanical skills build a rig like yours in thier garage and sail it in the conditions shown in the videos, sea conditions are effectively nil and winds less than 5 knots. The real issue is could the rig survive operational conditions like Perm Stress asked, that requires a factor of safety and material quality assurance on a level that I would not expect it being built to. What were the wind speed criteria and FoS did you design to?

    While we are seeing far fewer blade failures now than prevoiusly, for reasonable commericial marine applications an operational requirement of 50 knots (~26m/s, consistant with 46 CFR wind loading) with a FoS of 1.25-1.5 and 100 knts (~52m/s) survival load would with a FoS of 1.0+ would be prudent. This is before considering G loads due to motion. This also means that the stability of the vessel needs to adaquate to survive the survival over-turning moment, not just the 46 CFR 178.330 14 degree maximum heel loading case. Trying to design for this case may prove difficult, especially with a cat hull which is structurally inefficient as well as increasing masthead G loads.

    As I said, I'm willing to bet that when all the t's are crossed and i's dotted that you will not find a viable structural solution that exceedes existing soft-sail performance in a "yacht sized" or larger vessel in operational conditions.
     
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  15. Windmaster
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    Windmaster Senior Member

    No-one has suggested that they would exceed existing soft-sail (or wingsail) performance in all respects. Or said that they are suitable for "commercial marine applications". However, I have proved that for a small sized "daysailer" type boat they are perfectly practical, and quite possibly can be made larger.
    I am based on the "Norfolk Broads" - a system of rivers in the UK. For river transport they are ideal - by the way. There are thousands of miles of river in the world (particularly the US) where they would be very suitable.
     
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