How do I find out the force on a mast?

Discussion in 'Boat Design' started by Bookmaker, Jan 26, 2010.

  1. CaptBill
    Joined: Jan 2010
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    CaptBill CaptBill

    Have you considered instead of trying to power this motor. to instead let it be a generator of power? this power would be very large whatever it is. This power could be fed to say, the tiller, for an autopilot with alot left over. So in effect you could have, theoreticaly, a generator plus a sail that is dynamicly adjusting. You could varry the power not by APPLYING power but by CONSUMING it.
     
  2. Petros
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    Petros Senior Member

    You would need a wind mill on a generator, not a motor at the end of a mast. Also, any wind energy you extract from the wind will slow the forward motion of the boat by increasing the drag. So while it might save fuel to use a wind mill to recharge your batteries and power your equipment, it will not come for 'free' but at the expense of higher drag.
     
  3. yades
    Joined: Aug 2006
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    yades Senior Member

    I believe many answers have been given by the sail & rig assembly as provided for "Maltese Falcon" conceived mainly to have a self rotational sails on a rigless mast (as conceived by Prof. J. Djikstra). If you see carfeully, the leading principle is to rotate boom and sail rather then the whole mast. Why?
    Easy enough.......Because if you like to rotate the assembly mast-boom-sail then you have to envisage (as being far more efficient....) the whole structure as a "wing" and therefore to conceive a rig similar to the one applied to the AC trimaran "BMW Oracle".....a .....space shuttle of the seas....rather then a yacht ! On the other hand if we are talking ...as I presume...about .....S A I L I N G Y A C H T S as such then it is sufficient and far more efficient to have only the boom+sail rotating around a rigless mast rather then having must+boom rotating together...from an engineering point of view and for the purpose intended ......
    If I may say ..... to apply a..."WING" to a "normal" sailing yacht it would be an inefficient and pointless energy consuming structure, as not only a rotational force on the mast is to be envisaged but also the gravitational forces acting offset from the mast axis when the boat is heeling over plus the very havy frictional forces to overcome on the mast base due to mast compression force acting along the vertical axis. Which material would then have to be used to withstand that situation for a long time in order to mantain the same efficiency throughout...... and what about costwise involved....and for which purpose ? :D
    The ratio cost/efficiency will answer by itself....!
     
  4. CaptBill
    Joined: Jan 2010
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    CaptBill CaptBill

    Actually my point was this. Make her sail as if you were sheet steering like you might sail a dingy. (except the motor would be your "sheets")Instead of tiller action let the sheet out. Steer-by-sheet.This is MORE efficient. You are not restricting the air flow but the contrary. By letting the are spill in a controlled/metered way you are sailing better, on her prefered lines (maintaining heel angle), and without inducing drag from the tiller now. Power generated is from the excessive power, that which causes the rig to be over/underpowered during a puff or a lull. An autopilot that doubles as a generator when all you asked for was a sheetless rig. Plus you can take the windmill down which,yes, is inducing drag. Performance = power.
     
    Last edited: Feb 17, 2010
  5. jonr
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    jonr Senior Member

    Sounds like an aircraft wing that has the attachment point at the leading edge (instead of closer to 1/2 of the way back on the wing).

    I agree - put the mast towards the middle of the sail if you can.
     

  6. Bookmaker
    Joined: Jan 2010
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    Bookmaker Junior Member

    I think we're getting way off the point of this discussion. Perhaps if we got back to basics and talked. What is it that you believe shapes a sail by using a boom and sheet with a fixed mast? If you describe the basic movement that accomplishes this, then I can look at what my fixed boom and rotating mast is missing (rather than trying to change this into something else).

    Again, the goal is to take away the sheet as a means to adjust the angle of the sail to the wind. Instead I want to rotate the mast. If this is going to cause some problem with the shape the sail.... why? My first concern was whether the rotation force on the mast would be too great for a motor. I no longer think this is a problem, but now I need to figure out this discussion on sail shape. I'm a little confused, so help me out with small words ;)
     
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