Gyroscopic Stabilisers

Written by Miquel Mallafré.Translation: Marco Benevento.Issue Nº 51

Technology

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In search for comfort

Gyroscopic stabilisers are taking increasing force as a means to improve the stability of medium sized yachts. Installed inside of the hull, they do not slow down the progress of the vessel. In this article we will review their advantages and disadvantages.

All vessels are subject to the rolling imposed by the sea, during navigation and at rest rest. The stabilisers are used to compensate this rolling and to keep the vessel on the most stable position as possible and to improve the comfort of the crew and the guests. There are various circumstances in which you would want to improve the stability of the yacht and each of the methods that can be used for this purpose have their advantages and disadvantages.
Traditionally work has been carried out on improving the comfort of the yacht during navigation, i.e. moving. The hull bottom design is the first factor to consider, but as there is no hull design that could assume the different load, wind, sea and speed conditions, stabilisers have been used traditionally. In leisure yachting, there are two basic methods to stabilise the boat during navigation. On the fast yachts, equipped with planning hull, the most popular method is the use of flaps. The flaps are appendages, usually in metal, usually located on the transom so that they can modify the water flow created by the forward movement of the boat itself. There are flaps designed as an extension of the hull - conventional flaps -, and others where the plate goes down vertically, intercepting the flow of water, that is why they are called interceptors. When the flaps are lowered the water exerts an upward pressure that lifts the stern and, consequently, lowers the bow. Lowering the port flap there is a consequent reaction, the bow descends to starboard and lowering the starboard flap the reaction is the descent of the port side. The use of the flaps not only allows to modify the trim of the yacht longitudinally (in the fore-aft direction), but also transversely. Currently there are automated systems, computer controlled, that automatically establish the best possible stability in terms of speed and condition of the sea. Obviously, the flaps have no effect when the yacht is at rest as the progress is needed to correct the yacht’s stability.
On displacement or semi displacement yachts the flaps are not used because the speed is not enough to cause a change in the trim with small appendages astern and often, this kind of yachts do not have a flat transom to support its installation. In these cases, conventional stabilisers are used, consisting of movable keels arranged on each side of the bilge, under water, so that it is the automatic movement of these large plates that compensates the movement of the vessel during its progress. These keels are moved by hydraulic pumps installed inside of the hull and perforating the hull is required to allow the passage of the shaft that moves each one.

However, the problem that was pending to be solved is the yacht’s stability when at rest, when it is anchored in a cove or on open waters. Often this is one of the most unpleasant aspects for guests that are not used, as the breeze or the passage of other vessels, causing a wave, not being important or compromising to the safety of the vessel, may cause dizziness or might prevent certain tasks to be carried out normally, such as cooking or eating on board.To solve this problem the “zero speed” stabilisers have come to the market, i.e. stabilisers that also move when the yacht is at rest, partly offsetting the swing produced by the sea, and the gyroscopic stabilisers
The use of conventional stabilisers has no limit on the length of the ship, but has the disadvantage of their own constitution, as they are submerged appendages that can be damaged if a collision with the bottom or a submerged object occurs, in addition to being an evident obstacle to progress on the boat and, consequently, a speed decrease. Moreover, the boat loses a small percentage of speed for the sake of having them installed and if the stabilisers are in operation it loses an additional percentage. However, nowadays, these appendages are made from lightweight materials, rigid and with very hydrodynamic profiles and there are also retractable ones, so they are set against a hollow on the hull when their operation is not required. Computer systems calculate the movements of the stabilisers and can differentiate navigation and anchoring situations outputting compensation movements to the balance required for each stabiliser as depending on how each stabiliser is oriented there will be a brake to the balance. There are many stabilisers manufacturers that differentiate from each other for the design of the appendages, for the systems used to move them or for the electronics used and may include the gyroscope to determine the position of the vessel in the same way as the gyroscope is also used in the manufacture of compasses.

Comments  

 

0 #1 FONTANA CARLO 2010-12-08 17:33

dove posso acquistare in italia il mitsubishi arg ?

wear I can by arg in Italy ?

grazie

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