Ships – Hull or hull adjunct employing fluid dynamic forces to... – Having airfoil
Patent
1997-02-19
1998-09-29
Swinehart, E. L.
Ships
Hull or hull adjunct employing fluid dynamic forces to...
Having airfoil
114271, 114 61, B63B 116
Patent
active
058133585
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a marine or naval craft provided with a triple trimaran-type hull.
2. Description of Related Art
At present naval crafts of the type called trimaran are known, consisting of a set of three hulls placed one in the middle and the other two on each side with their longitudinal axes parallel to each other, that make it possible to obtain very slender hull shapes with moderate total drag values at high speed, through the reduction in residuary resistance as a result of the reduction in Froude number, with respect to a hull of the same displacement; the transverse stability which becomes unacceptable for ships with very narrow shapes, in this case is assured by the two lateral hulls which, being a long way from the longitudinal symmetry plane, provide substantial stabilizing moments. Since trimarans are displacing or semidisplacing craft, however, the reduction in total drag is relative because the reduction in residuary resistance is accompanied by an increase in viscous drag due to the fact that by dividing the total displacement over more than one hull there is an increase in the wetted surface.
Land and naval vehicles are also known of the type called WIG (Wing in Ground Effect Vehicles), which, by means of appropriately distributed and proportioned lifting contours, allow the weight of the vehicle to be totally supported by aerodynamic effect, freeing itself completely from the ground, allowing the drag to be reduced compared with a naval or land vehicle of the same weight and speed because, in the case of the naval craft, aerodynamic drag, due to an air density of 1.29 kg/m.sup.3, replaces hydrodynamic drag, due to a water density of 1.026 kg/m.sup.3 (sea water) and, on the whole, of a much higher value. Craft whose lift depends solely on the above mentioned wing contours, however, having no physical contact with the water surface, present the well-known, hitherto unresolved problems that have prevented their practical exploitation. Of these drawbacks, the main ones are the poor response speed of the controls in the air which make it extremely dangerous to fly at a short distance from the water surface, as required to exploit the ground effect adequately (normally a distance of 5% less than the wing span), the poor lateral stability, the low propulsive efficiency due to the relatively low speed, even if very large, heavy and noisy propellers are used.
OBJECTS AND SUMMARY
An aim of the present invention is to create a craft of new conception consisting of elements characteristic of the two vehicles described above but organized so as to eliminate their limits, drawbacks and defects whilst exploiting their food qualities.
The essential characteristics of the naval craft claimed are stated in the attached claim 1.
The marine or naval craft of the invention has three hulls, a central main one and two lateral auxiliary ones that support a load platform shaped as an airfoil which, at speed, generates sufficient lift to almost completely support the craft; beneath the three aforementioned hulls project three ventral fins which, when the craft reaches the speed at which it almost supports itself and thus its hulls are no longer in contact with the water, remain partially immersed and pierce the free surface, maintaining contact between the craft and the see, in order to perform some functions that are typical of the craft and will be more fully illustrated below.
If one wished to describe the invention very briefly, one could say the craft of the invention is a hybrid resulting from the blending of a trimaran (three-hulled boat) and a WIG vehicle (Wing in Ground effect vehicle).
The new craft of the invention overcomes the disadvantages of the above mentioned craft belonging to prior art, has a low hydrodynamic drag having reduced the hull volumes and wetted surfaces to the minimum, has a much smaller total drag than a naval craft of the same weight because for its support it essentially exploits aerodynamic lift which is as
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