Slamming loads on a small high speed craft

Discussion in 'Boat Design' started by nikezz, Jan 7, 2011.

  1. nikezz
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    nikezz Junior Member

    Hi all,
    From experience, does anyone know of the slamming loads if you travelled on a small HS craft?

    At
    25 knots
    Sea State 3

    The craft would be about
    12m length
    5 tonne displacement

    Edit: 5 tonne
     
    Last edited: Jan 9, 2011
  2. Mr Efficiency
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    Mr Efficiency Senior Member

    The biggest slam would come at the fuel pump, directly to your pocket ! Any 50 tonne, 12 metre length vessel would need to be jet propelled to reach 25 knots. :D
     
  3. rxcomposite
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    rxcomposite Senior Member

    That is not a HS craft. That is a displacement boat at 12 meter, 50 ton displacement. Is it an oil rig?
     
  4. PAR
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    PAR Yacht Designer/Builder

    Without considerably more data about what you want, the vessel and the context, you're not going to get much more the glib replies from the board members.
     
  5. nikezz
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    nikezz Junior Member

    I apologise. That was a typo. It was meant to be 5 tonnes.
     
  6. PAR
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    PAR Yacht Designer/Builder

    You can't possibly think that you've provided enough information to warrant a reasonable reply do you?

    The answer is . . . yes.
     
  7. Mr Efficiency
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    Mr Efficiency Senior Member

    This thread is making excellent progress, isn't it ? Keep up the good work, I say ! :D
     
  8. rxcomposite
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    rxcomposite Senior Member

    Probably because it is too easy. :p

    "The hydrodynamic load on the panel is
    calculated by dividing the panel into several
    strips. The flow over each strip and the
    corresponding pressure distribution is
    derived by a Wagner-type approach as
    described in [13]. The actual response of the
    panel is calculated by a modal approach.
    The generalised hydrodynamic forces are
    derived by integrating the pressure over
    each strip. The response and, in particular,
    the instantaneous velocities on each point of
    panel surface, are then obtained and
    summed to the overall rigid-body velocity to
    calculate the panel immersion and the
    hydrodynamic loads for the following time
    step. With a constant or decaying impact
    velocity, the maximum amplitude of
    response is attained during the first cycle of
    oscillation of the panel; hence the iteration is
    normally stopped after the first response
    peak is observed.":confused:

    An alternative approach to the design of structures exposed to
    slamming loads.
    P.F.Manganelli, M.A.Hobbs, SP Technologies, UK
     
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  9. PAR
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    PAR Yacht Designer/Builder

    The Wagner impact theorem has a low angle deviation that's unacceptable to most. Are you recording peak pressures during transitional impact or maximum strains on impact or averaging pressures at impact?
     
  10. Mr Efficiency
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    Mr Efficiency Senior Member

    As a rule of thumb, with slamming loads, the people break before the boats. :D
     

  11. nikezz
    Joined: Aug 2010
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    nikezz Junior Member

    I see. Quite different from what I've heard. Strangely, another someone told med "Most importantly, we need to know the boat speed, length and displacement and also a little bit about the shape of the boat." to estimate the g's.

    May I know how you guys do it instead and what information you require?
     
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