Ships – Hull or hull adjunct employing fluid dynamic forces to... – Movably mounted hull portion or hull adjunct
Patent
1994-05-25
1995-11-14
Avila, Stephen
Ships
Hull or hull adjunct employing fluid dynamic forces to...
Movably mounted hull portion or hull adjunct
440 53, B63B 122
Patent
active
054656788
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to providing a boat, vessel or other construction designed to travel over water, with a second, not fixedly attached piece of hull, the aim of which is to produce a range of different advantages compared to known hull constructions. The invention is specially meant to be used in high-speed boats, vessels and vehicles designed for recreational activities on the water and can also advantageously be used in transport and fishing vessels and in stationary operating special-purpose vessels.
The vessels or the like where the invention can be used will hereinafter be referred to by the term `boat`. The hull and the construction of a boat have to meet different demands generated by e.g. the noise and vibration caused by the engine, power transmission and propeller, the shocks and violent movements caused by waves, the overturning forces caused by the action of waves and wind, the frictional forces between the water and the hull, and the threshold of planing.
The noise and vibration problems caused by the engine and the power transmission have in a known manner been solved by separating the engine and the power transmission from the hull by antivibrators and by fixing sound absorbing and insulating materials to the walls of the engine space and by tightening the through holes. In spite of these measures, noise levels of about 80 dB(A) are common in boats.
The smashes and violent movements caused by the waves at high speeds have in a known manner been solved by giving the bottom a V-shape, using narrow hull shapes, providing the boat with hydrofoils or suspensioned pontoons and by giving a special shape to the underwater portion of the hull. By a V-shaped bottom and a narrow wedge-shaped hull, an effective wave cutting effect is achieved and the motion of the boat is stabilized, but at the same time the wetted surface area and frictional forces are increased and the boat will easily become wet at high speeds. A boat provided with hydrofoils or suspensioned pontoons will ride smoothly in small waves. Such a boat is difficult to use because of the outwardly projecting parts. If the suspensioned pontoons are located close to the midline of the boat,they will cause improper working of the propeller at the stern. By giving the underwater portion of the hull a special shape, a reduced motion will be achieved, especially with trimarans, but the wetted surface area will be large and frictional forces great.
A negative feature of boating with light high-speed boats and racers for which no good solutions have been found, is the influence of forces exerted Jointly by wind and waves, tending to lift the bow of the boat up and with the contribution of the push forces of the propeller at the back seeking to turn the boat over lengthways. The frictional forces between the water and the boat have as known been reduced by friction reducing coatings, specially shaped bows and bottoms, hydrofoils or mechanically produced air cushions. The effect of the friction reducing coatings is marginal. By designing the bow and the bottom in such a manner that air is forced under the bottom, a friction reducing effect is created that is significant at high speeds. Hydrofoils may be used to reduce the wetted surface area and friction at high speeds. The solution is expensive and calls for effective power sources at the acceleration phase. Mechanically produced air cushions are exposed to disturbances in rough weather with high waves.
The problems with avoiding the uncomfortable and decelerating bow-up position of the boat occurring at slow speeds, and with making the boat plane, have been reduced in a known manner by means of fixed or adjustable trim planes or adjustable drive pitches and fixed trim surfaces or bulbs of the hull. These are all ways of improving or complementing the basic boat.
By means of the piece of hull according to the present invention the aim is to get an overall basic construction that will make boating comfortable, safe, and energy saving for professional, recreational as well as racing purpos
REFERENCES:
patent: 3815541 (1974-06-01), Hansen
patent: 4000712 (1977-01-01), Erikson et al.
patent: 4067286 (1978-01-01), Stout et al.
patent: 4351262 (1982-09-01), Matthews
patent: 4977845 (1990-12-01), Rundquist
Avila Stephen
White John P.
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