The Wind Powered Sail-less Boat

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

  1. Guest625101138

    Guest625101138 Previous Member

    Tcubed
    You even anticipated what I should have posted. You will find your rep has gained.

    I have attached solutions for all four cases. To hopefully make it easier for some to understand I have introduced the wheel rpm but it is eventually substituted.

    So I will need to back track and see if some of the earlier posters gave the correct answers to my forward geared problem and award points retrospectively. (Hopefully my 5th grade teacher would have forgiven me for having a sign incorrect.)

    The point of this exercise is that the vehicle can travel in the opposite direction to the plate and also move faster than the plate in the same direction.

    I will post the next stage of the problem shortly.

    Rick W
     

    Attached Files:

  2. Tcubed
    Joined: Sep 2008
    Posts: 435
    Likes: 18, Points: 0, Legacy Rep: 318
    Location: French Guyana

    Tcubed Boat Designer

    Thanks Rick.

    Boston, i'm starting to think either 1; if you laid off the beer awhile your mind might clear up a little bit and you could understand, or 2; you do actually understand and like to wind people up.

    It is true that in a turbine boat, if the air prop is turning the water prop then it cannot go faster than the wind downwind. However, if the water prop is turning the air prop then the boat can go faster than the wind downwind.

    You seem to understand that a sailyacht tacking downwind can have a VMG dead to leeward faster than the wind. You correctly point out that the ice boat at 135 degrees to the true wind needs to go 1.4142 times the real wind (cos45=sqrt2) , ice boats have been known to reach V/W of close to three, making for near twice the speed of the wind downwind..

    In a turbine boat, only the boat itself is going straight downwind, all the dynamically active parts are moving at angles to the real wind just like the boat tacking downwind (or upwind)

    Guillermo, The energy available is a function of the relative velocities of the two fluid mediums. The energy lost is a function of the aero/hydrodynamic functioning of the boat (+ a bit of mechanical losses in the case of the turbine boat) . There is nothing in the energy equations that categorically limits boat speed at any angle to always be less than the real wind velocity-or more accurately the velocity differences between the two fluids.

    Boston, your ambiguous images are intriguing, they could be some aerial shots of some kind...I'm trying to see what if any connection there might be with this thread.
     
  3. Guest625101138

    Guest625101138 Previous Member

    Curtis
    Do you agree with what Tcubed provided and my more detailed solutions?

    We need to move on now to introduce some real world losses in the system. Can you answer the attached question?

    Rick W
     

    Attached Files:

  4. Guest625101138

    Guest625101138 Previous Member

    TheUnlogicalOne
    You will find your rep enhanced. I believe you were the first to provide the correct answer to the original questions. My apologies for not recognising it sooner.

    It was not until Tcubed posted that I realised I needed the gearing reversed in my DDWFTTW analogy. My excuse is that I was thinking of the boat situation where there is no need to reverse gear unless the pitches are reversed and I was looking for -1 and 3.

    By all means have a go at the next stage of the problem. Hopefully by working through this logically more will understand it is not witchcraft, a trick or perpetual motion but very simple physics.

    Rick W
     
    1 person likes this.
  5. Tiny Turnip
    Joined: Mar 2008
    Posts: 865
    Likes: 274, Points: 63, Legacy Rep: 743
    Location: Huddersfield, UK

    Tiny Turnip Senior Member

    go on then- starter for ten.
    if vehicle velocity is constant, no +/- acceleration, system is in equilibrium.
    input force = total system losses, i.e. 6n.

    pictures are Microscopic: mould/fungi, spores, eggs, possibly.
     
  6. Guest625101138

    Guest625101138 Previous Member

    I do not have much knowledge on how rep points work but I will continue to award to correct answers as long as I have them available.

    I do not think I will be able to award Tcubed or TheUnligicalOne until I have awarded others. If you do feel inclined to answer, wait a day or so until others have had a go at the next step of the problem.

    I really appreciate your contribution as it helps others realise that those who can think logically have little difficulty understanding that sailing DDWFTTW is possible.

    Rick W
     
  7. clmanges
    Joined: Jul 2008
    Posts: 576
    Likes: 144, Points: 43, Legacy Rep: 32
    Location: Ohio

    clmanges Senior Member

    Yes; the solution was tying me in knots though (about 35 knots DDW, to be specific).

    I'd like to make clear here that I never doubted that DDWFTTW could be done; I just wasn't able to untangle the knot of how.

    Also -- and I haven't seen anyone else mention this -- that, if you can go DDWFTTW, you can also go directly upwind, because, once you are doing the first, you're already doing the second. Exceeding the tailwind automatically puts you into a headwind condition.

    On to the next thing.
     
  8. Tcubed
    Joined: Sep 2008
    Posts: 435
    Likes: 18, Points: 0, Legacy Rep: 318
    Location: French Guyana

    Tcubed Boat Designer

    Wait a couple of days for rep? um if you feel like i deserve them you can always give em in a couple of days......

    The reaction force of the top tyre against the ceiling is three times greater than the reaction force of the bottom tyre against the floor due to the gearing.

    Call it f So 3f-f = 6N

    Therefore f = 3 N

    So the force required to move the top plate is 9 N and the reaction force on the floor is -3 N .

    9-3 = 6 so we have equilibrium.

    I assumed the drag force to be acting independently of either plate.
     
  9. masalai
    Joined: Oct 2007
    Posts: 6,818
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    Location: cruising, Australia

    masalai masalai

    Not meaning to interrupt but this may help http://www.boatdesign.net/forums/forum-questions-suggestions/forum-rules-code-conduct-11083-14.html post 205....
    It's currently set for:

    * User Spread: (How many different users must you give reputation to before you can hit the same person again?) 25
    (there was a fear early on that the user reputation system would create a problem of cliques so this number was set fairly high to prevent this)
    * Daily Reputation Clicks Limit: 10
    *
    * Minimum Post Count: (How many posts must a user have before his reputation hits count on others?) 50
    (so new users to the forum can basically send you a note of approval or disapproval (over 5 posts needed for any negative) but only members with at least 50 posts will affect your numerical reputation number at all.)
     
  10. Guest625101138

    Guest625101138 Previous Member

    Curtis
    I know you have believed in the concept but there is a difference between seeing and believing and truly understanding. Hopefully by working through this logically will actually help you understand what is going on.

    So we are agreed that the vehicle can do 3m/s when the plate is only doing 2m/s! With the help of others we have finally got agreement on that even with my confusing the whole story with gear reversal.

    We already have two answers to the next part of the problem. They are different. Is either TT or Tcubed correct?

    We will move on once you have understood this part.

    Rick W
     
  11. clmanges
    Joined: Jul 2008
    Posts: 576
    Likes: 144, Points: 43, Legacy Rep: 32
    Location: Ohio

    clmanges Senior Member

    Okay, I agree with TT's statement:
    From there, I get lost. You know how things look smaller as you get farther away from them? Well, it's been over 35 years since I've done more than a few minutes at a time worth of math or physics . . . so, to your post #138, I meant to say, yes, I agree, but no, I can't answer the next question.
    Maybe it would be better for everyone else if I just step aside and watch for a while . . . just be thorough in showing your work, and maybe I'll catch up. (Creak, creak . . .)
    Your show, you call it.
     
  12. Tcubed
    Joined: Sep 2008
    Posts: 435
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    Location: French Guyana

    Tcubed Boat Designer

    I should probably clarify slightly about the signs in my last post. The top wheel is rotating ccw and exerting 9 N force to the left, which must therefore be countered by maintaining 9 N force to the right in the top plate.

    The bottom wheel is being turned by the ground cw with 3 N force

    Furthermore, energy analysis; work done by motion of machine 6*3=18 NM/s = 9*2=18 NM/s by moving plate. The bottom plate is not moving so it is not 'working'.
     
  13. Guest625101138

    Guest625101138 Previous Member

    Curtis
    I have attached the answer sheet to the force question.

    You will see that Tcubed has it right.

    The sheet also has the next question which Tcubed has already anticipated.

    Each of these little steps is intended to take you through the logic. Not much point though if you are not following it.

    Rick W
     

    Attached Files:

  14. Boston

    Boston Previous Member

    lmao
    thats great
    there is a light
    as for beer
    if Magueijo can work out variable light speed theory on a cocktail napkin
    three sheets to the wind on a night out with a few friends in the local pub
    ( oh it took him years to work out all the kinks but the basic idea he got while face down on the bar, not bad since it solves the need for the cosmological constant in the field equations )
    then I think I can ride this wind thing till anyone actually breaks down and mathematically explains the tread mill
    ( which is the only tangible albeit tentative piece of evidence Ive seen yet )

    I havnt tried to work it out yet but the basic formula should be easy for the tread mill trick
    I hate playing my own devils advocate
    its like debating both sides of a loosing argument

    bingo
    my point exactly
    we are talking wind powered not water powered aren't we

    of course it can
    if the water is already moving faster than the wind and in something like the same direction
    in which case you might as well float a balloon down a river in a dead calm

    and wouldn't that be a water powered craft going faster than the wind
    what about hydrothermal powered
    can we shoot a lab rat out of old faithfull faster than the wind
    course you can
    but thats not wind powered


    but we are talking a wind powered vehicle going directly down wind


    yes if the boat is traveling at some angle to the wind
    then the turban will power the boat
    not very efficiently
    but it will
    but set it on a dead run course and
    the turban on the boat is going to realize the same apparent wind reduction relative to down wind speed that no one is willing to address yet

    a platform traveling directly down wind
    with a device (wind turban) mounted on the platform angled to the wind
    will realize the same reduction of apparent wind relative to speed
    as the platform itself
    therefor the directly down wind traveling oscillating turban
    wont work
    you dont have the energy available to flap your arms fast enough

    if you are draggin a sled behind the ice boat
    and Swedish rowing the ice boat ahead of it
    then yup
    the sled may end up faster than the wind
    ( I can hear people gasping now )
    but
    your engine didnt meet the parameters
    the question is
    can a wind powered vehicle traveling directly down wind go faster than the wind
    and the engine isnt going directly down wind if its rowing away out front somewhere
    so that model doesnt meet the criteria of directly down wind


    if anyone wants to break parameters
    and now say that a lead ball can be dragged down wind faster than the wind by a wind powered engine going at some angle to the wind
    then I hang my head in shame
    but if we stick with the original of
    direct down wind faster than the wind, wind powered craft
    then Im still holding my breath


    I couldnt agree more
    ( but dont tell anybody )
    glad we could find some common ground

    however if I might add
    and Im totally giving it away here
    the energy available at the transition to faster than wind speeds will no longer be significantly dependent on the variation of the mediums relative velocities to one another but as a function of the friction variations of the systems driving components relative to the mediums upon who's friction those driving mechanisms are dependent
    given that at some point in order to pass this test the relative wind velocity must pass through zero
    I believe the system will find stability if going directly down wind before crossing the light speed barrier because the amount of energy available to the system is directly proportional to the variation in either mediums relative speed to the system
    not relative to one another
    and since water is significantly more dense than air
    it will win in a friction contest any day

    happy thought kids

    just tell me what you think the pictures look like
    and no its not that relevant
    but you will be dam surprised

    [​IMG]
     

  15. Boston

    Boston Previous Member

    turban ?
    given my goofy sense of humor
    you guys are sure being quiet about my grammar skills
     
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