Ships – Watercraft with means used in providing sailpower – Having specifically defined hull shape
Patent
1982-10-29
1986-01-07
Blix, Trygve M.
Ships
Watercraft with means used in providing sailpower
Having specifically defined hull shape
114121, 114123, B63B 4314
Patent
active
045627851
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to trimaran type sailboats permitting from any position the automatic return to a stable equilibrium corresponding to a normal sailing position.
In known designs of this kind the central hull is equipped with two constant volume lateral floats which are submergible or insubmergible. These three members are connected by beams which are very often of considerable constant volume. In general, the assemblies are rigid or flexible or even with very slight displacement and the sole function of the mast is to carry the sails. Such sailing designs cause permanent torsional stresses and the risk of plunging the float or the central hull because the waves can conceivably urge them at the same time. It is also known that this type of boat has a stability curve which decreases, in order to tend toward a second stable equilibrium position, which is reached when the boat is overturned. This design means the axis of symmetry, which is necessary for sailing and the weight of the mast, both function as ballast. It is therefore impossible for it to return to its initial sailing position on its own.
The trimaran according to the invention permits these drawbacks to be avoided. It is characterized by the association, with the sails and the floats, of means forming fluidtight submergible volumes, creating potential energy capable of displacement by rotational movement to destroy the symmetry. Each float is submergible and has a variable volumetric displacement comprising a main fluidtight volume located at the level of the bow, a second minimum fluidtight volume included between the bottom of the hull and the planking, a hollow volume which may be filled through openings at the level of the deck, and a quick discharge valve located toward the stern, the base of which corresponds to the level of the planking. The float is fixed to connecting arms which are of as small a volume as possible, by a cylindrical shaft, which shaft permits only freedom of rotation between the two abutments so that it may fluctuate between an approximately horizontal position and an almost vertical position. The two abutments are obtained by the connecting arms, limiting the rotation of the float which may occur freely in both directions, while having a means for ensuring upward rotation to obtain the vertical position against the abutment. This axis of rotation is located close to the center of buoyancy of the hull where the heel obtained in sailing is included within the clearance.
The mast and the floats are placed so that the boat, during righting, effects rotation about the longitudinal volumes of the center hull containing, to a great extent, the resultant forces due to the weight of the different elements and the axis of rotation located in the plane of symmetry, this axis having to remain as parallel as possible to the surface of the water. When the boat has overturned, the position of the floats relative to the surface of the water is such that it can roll on its side.
According to a combination of modifications concerning the fluidtight volumes, they are nondeformable compartments which operate immediately, or they are casings which are deformable by inflation under pressure, or even a combination of nondeformable and deformable volumes.
According to a further variant concerning the rotation of the float upwards when the boat is recumbent on the water, such rotation is obtained automatically due to the lack of symmetry of the float's axis of rotation which, in a first case, forms an acute angle with a straight line parallel to the surface of the water, this angle lying in a vertical plane, perpendicular to the axis of rotation of the boat, so that the bow of the float moves toward the plane of symmetry of the boat and the surface of the water, which, in a second case, forms an acute angle with a straight line perpendicular to the axis of rotation of the boat, this angle lying in a horizontal plane parallel to the surface of the water, so that the bow of the float moves toward the plane of symmetry and the surface
REFERENCES:
patent: 4102287 (1978-07-01), Ferris
patent: 4117795 (1978-10-01), Ruiz
patent: 4227474 (1980-10-01), Ullrich
patent: 4441445 (1984-04-01), DeWeck
Blix Trygve M.
Koch Robert J.
Swinehart Edwin L.
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