Mathematical Q. about theoretical max boatspeed...

Discussion in 'Sailboats' started by Guest, Dec 28, 2001.

  1. Ollie Bell

    Ollie Bell Guest


    Hi every one, at the moment i am trying to complete my second piece of i.t coursework but i am having a problem. I need to find a mathamatical formula that will work out the speed of a boat when i have been given, The area of sail deployed, the angle of sail in comparison with the wind direction. If anyone has a segestion to help me with this problem could you please write back or email me on and title the subject of that e-mail mathmatical formula.
    thqanks everyone
  2. BrettM
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    BrettM Senior Member

    Einstein says objects can't go faster than the speed of light........:) now that's moving :)
  3. SailDesign
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    SailDesign Old Phart! Stay upwind..

    Guest, I challenge you to take a boat faster than the speed of sound. At that speed the pressure-wave from the pointy end will make such a big hole in the water ahead of the boat that you would fall in. Nasty!
    I know, I know, there is bouind to be some way to get around this, but no-one has got there yet so I'm safe for a few years :)

  4. fishboat
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    fishboat Junior Member

  5. gonzo
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    gonzo Senior Member

    A hull moving at the same speed as the wave can reach more speed with less power because the water surface is curved. It is the same as if the buttocks where straight.
  6. guest

    guest Guest

    maximum theoritical boat speed

    299,792,458 m/s ?.....
  7. yachtie2k4
    Joined: Jun 2004
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    yachtie2k4 Anarchist

    i will add wings to my boat & then it will be able to fly, break through the sound barrier & maybe the speed of light :p
  8. SeaDrive
    Joined: Feb 2004
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    SeaDrive Senior Member

    I was unable to view this link. However, an example from experience is the cruise ship Regal Princess, loa of 893. Sqrt(lwl) is probablyl about 28. Cruising speed is 22. S/L = 22/28 = 0.78. All very approximate. Of course, speed in getting to the destination is less important for cruise ships that for a ship delivering cargo. Fuel consumption is very important.

    For any commercial vessel, the computation is complex and depends on the interest cost $$ invested in the cargo, the fuel consumption, the number of cargos carried in a year, pervailing frieght rates, and whatever.
  9. Not A Guest
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    Not A Guest Junior Member

    Stephen Ditmore ---

    The 1.34 constant actually depends on hull length and shape. The values of .87 and 1.0 for the boats you mention are pretty close to what several sources give.
  10. Bighillwill
    Joined: Oct 2004
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    Bighillwill Junior Member


    "This also explains how heavy displacement keel boats can sail faster than hull speed without planing when sailing in swells longer than their waterline. A swell adding pressure to the skin near the stern can cancel out some of the pressure acting on the bow (in a trough). No planing or surfing required. "

    Please excuse my newbie-ness. Isn't that pretty much the definition of surfing?

  11. Bighillwill
    Joined: Oct 2004
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    Bighillwill Junior Member

    I apologize to be so abrupt, or interrupt impolitely. I am attempting to build a semi-displacement sailboat 20ft LWL, with cuddy, to plane. Many useful maths on this forum I have been studying. Some too complex for me, as I barely passed Dif. E. 20 years ago and haven't used since. However, some other maths very well presented for me, many by Mike D. in past threads. (MGRHS)

    It seems to me that, for any given hull, the planing mode would be entered after surface interactions between hull and water surface become stronger than buoyancy in providing lift. I suppose, also, that for this to happen with conventional (non-hydroplane) hulls, a speed surpassing about 1.34 L/S is reached, no matter the motive power, whether sail, engine, or hull surface force vector direction differential fore to aft, as in surfing.

    So, is surfing actually planing, just using an offboard power enhancement, such as gravity down the face of a wave, and the resulting hull surface force vector differential, as compared to planing using onboard power such as sails and/or engines, to reach the required speed for surface interactions to become dominant over buoyancy?
    Last edited: Oct 11, 2004
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