Flybridge overloading

Discussion in 'Stability' started by maybeturbo, Aug 7, 2021.

  1. maybeturbo
    Joined: Aug 2021
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    Location: sweeden

    maybeturbo Junior Member

    I've been looking for a flybridge boat lately (planing hulls), and notice that some boats have a limit to how may persons that are allowed on the flybridge during driving that is fewer than the number of seats on the flybridge. My understanding is that it's ok to have more people on the flybridge when it's on anchor then during a drive. I even read a review (from 2003) where the journalist wrote that he understood the limit of 4 persons on the flybridge during driving (even thou there were 5 seats there) because the boat was leaning so much into the turns at plaining speed.
    I've been at a large ship (100ish meters long, 9 decks high) when doing sharp turns at high speed (15-20 knots). The ship leaned outwards during the turn, to the extent that it was hard to stand upright without holding onto something. That was scary! I wouldn't be surprised if to much weight high up on that ship would make it roll over, outwards, during a sharp turn.
    But the plaining hull leans inward. As I read the journalist, he thought the boat was leaning to much inward. So I started to wonder, will a plaining hull lean more into the turns as the weight on the flybridge increases, the opposite of what displacement hulls do? What what would be likely to happen if there is too much weight on the flybridge while turning? Would the boat roll? Would it roll inward or outward?
  2. Mr Efficiency
    Joined: Oct 2010
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    Mr Efficiency Senior Member

    Just abide by the manuufacturer's load limit for the flybridge and all should be OK, second guessing could lead to grief. As for which way the boat heals with more weight up there, I would say if it banks noticeably when not much weight there, it will be more with extra weight.
  3. maybeturbo
    Joined: Aug 2021
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    Location: sweeden

    maybeturbo Junior Member

    Well, some boats are equipped with heavy devices mounted high up, way higher than the flybridge seats, like radar, motorized search lights... And most boats does not have a sign telling what is max load up there. Max load might be written in some book, but you often don't have that book when you buy used boats. How do you know if you have too high center of gravity? What are the warning signs to look for?
  4. fallguy
    Joined: Dec 2016
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    Location: usa

    fallguy Senior Member

    I know a few that don't like a flybridge because it makes the boat too tippy no load.
  5. bajansailor
    Joined: Oct 2007
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    bajansailor Marine Surveyor

    If you do buy the Fairline 36 Turbo, you could carry out a practical experiment to find out.
    Invite a group of friends, and then gradually load up the flying bridge, one person at a time.
    Each time you add a person, get everybody on the flying bridge to move from one side to the other.
    As you load it up, you will notice a a change in the behaviour of the boat and the roll period will become longer.
    Bear in mind that you are doing this in flat water, probably in a marina, so the actual limit on passenger numbers on the flying bridge while out at sea will be less, especially so if it is rough.

  6. kapnD
    Joined: Jan 2003
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    Location: hawaii, usa

    kapnD Senior Member

    The weight of “persons” can vary radically, I’d prefer to see a number based on total weight allowed on the fly bridge than a number of persons.
    Brings to mind the capsize of that whale watching boat awhile back, where everyone rushed to one side of the upper deck to view the whale, causing the vessel to roll right over.
    bajansailor likes this.
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