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Stabilizers

Discussion in 'Stabs, Tabs & Gyros' started by John B, Jun 2, 2004.

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  1. John B

    John B Senior Member

    Joined:
    Jan 28, 2004
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    Location:
    New York
    I am curious about stabilizers and how they work.

    Are these all computer controlled these days?
    What size boats do they start appearing in?
    How basically do they work?
    Are there many different designs for these?
    Do they all work in forward/aft and roll side to side?
    How effective are they in reality?

    Conceptually "I think" I understand what these do, but it's an area where I would like to have a better grasp of what these are, how they work and different types.

    Hope this isn't too broad of a question!

    Thanks in advance,
    John
  2. mik-48

    mik-48 New Member

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    all stabilizers works on a principle of gyroscope.More specifically, the gyroscope tends to resist any power applied to it, but when it is applied it reacts so that its axes moves perpendicularly to the power applied.
    In case of boats the applied power is achieved thru movement of the boat ( rolling ).

    The whole staff, consists of a hydraulic plant, gyroscope and of coarse the fins.
    Rotation of the gyro is achieved thru the hydraulic turbine to which it is connected at one side,while the other side serve to control the valves in the hydraulic system in order to properly swing the fins. Basically as the boat rolls the gyro axes moves fore and aft and so opens and closes the appropriate valves.
    The only thing which can be controlled by the user, is synchronization of the movement of fins with rolling of the boat.

    All stabilizers are effective while rolling, they have no effect on pitching of the boat.

    Tough there are no specific limitations on the size of the boat where they should be installed, it make sense to install them on boats 60 feet and over
    ( my opinion only)
  3. JHA

    JHA Senior Member

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    More and more stab. systems have computer controllers which often eliminate the need for any user input. Also - I believe that a four-fin configuration (as found in many lazzaras) will help control pitch to an extent.
  4. John B

    John B Senior Member

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    JHA,

    That was my understanding that some of these can control pitch as well, but I'm really not sure.

    If it is not computer controlled, what is the 'user input'?

    John
  5. YachtForums

    YachtForums Publisher/Admin

    Joined:
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    South Florida
    Hi David,

    In the beginning of the thread, a gentleman asked "how do stabilizers work?"...

    I'm sorry you couldn't take a few moments to answer his question, as several hundred people may have learned from you and possibly... turned to your company for service.

    Quite often, people that follow a forum come to trust those who participate. Generally, it's not good forum "etiquette" to plug your own company without offering something in return... such as help, knowledge and information.

    I took a look at your website. With the exception of a plumbing diagram, it didn't really answer his question. Therefore, I would suggest our viewers take a look at these websites too (to be fair)...

    www.naiad.com
    www.quantumhydraulic.com
    www.wesmar.com
    www.gyrogalestabilizers.com
    www.mhi.co.jp/enews/e_0983.html (Mitsubishi Anti Roll Gyro)
  6. mareng

    mareng New Member

    Joined:
    Mar 11, 2005
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    New England
    A bit of digestable stabilizer info

    To understand the basics of how stabilizers work, it's probably best to break the systems down into the fundamental parts and functions. There are variations to what I'm going to describe but it's best to keep it simple for those who have no understanding of the principles and equipment.

    SIZE:
    Stabilizers are found on cruise ships as well as small yachts. 40 feet is usually the smallest vessel you will find them on, because of space and expense.

    FINS:
    Most all fins are configured for an efficient hydrodynamic flow. The shaft is located in the foward third of the length of the fin. This arrangement, as with rudders, is refered to as semi balanced. It allows the fin to trail in center position, which is almost always parallel to the keel, with out great effort from the actuator to hold it there or rotate it from side to side. The force of passing water on leading edge of the fin also aids somewhat when the fin rotates beyond 5 or 10 degrees. Fins generally rotate 30 degrees either direction from center. Fins are ideally located in the mid fifth of the waterline length of a vessel. This can go as far as 1/3rd in some cases. When the longitudinal position is determined, the most effective transverse location is as far outboard as you can get for the best moment arm. This is determined by an envelope area such that the fin will not hang below the keel, nor protrude transversely beyond the waterline edge of the hull. The fins will hang 'normal' to the hull so they won't hit the hull as it rotates.

    ACTUATORS:
    This is the device that provides motion to the fin. They have to be sufficiently secured to the hull with a method of spreading the load across an appropriate area. The securing is achieved by varying methods depending on the hull material and to varying degrees depending on the size of the system. Virtually all actuators are hydraulic. Hydraulic systems are roughly 80% efficient from pump to function; if designed and installed properly, they are very safe, usually operating at 1000psi to1500psi.

    CONTROLS:
    Control systems have gone through many evolutions through the years. The current day trend is electronic control. The three basic characteristics of a vessel roll to be monitored are angle, acceleration and velocity, refered to as 'three term'.
    Lesser systems monitor one or two terms. State of the art systems do not employ a rotating gyro, but use an angle sensor and accelerometer to sense vessel roll. The actual control unit (the best are digital) sends signals to a proportional/directional control valve that causes the actuators (in tandem) to move appropriately to the command, direction and velocity.

    SYSTEM SPECIFICATION:
    A fin size for any given vessel is specified by the vessels, length, beam, displacement, speed and GM or metacentric height. Once the fin size is known, the appropriate actuator is specified to drive it, and the hydraulic system to drive the actuator. The control ststems stay the same.

    Hope that answers some questions.
  7. Yachtguy

    Yachtguy New Member

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    Mitsubishi ANTI ROLLING GYRO or ARG

    I am looking for information on the Mitsubishi or similar ANTI ROLLING GYRO or ARG. This is not an active fin stabalizer system as has been primarily discussed in this thread.

    I followed the link above but it does not give too much information. I understand it is under demo with Ferretti group yachts now.
  8. Yachtguy

    Yachtguy New Member

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    I am going to start this as a new thread titled Mitsubishi ANTI ROLLING GYRO or ARG. I think this may get looked over in this old thread.