Ships – Hull or hull adjunct employing fluid dynamic forces to... – Having fluid channeling or entrapping configuration
Reexamination Certificate
2000-12-27
2001-11-13
Avila, Stephen (Department: 3617)
Ships
Hull or hull adjunct employing fluid dynamic forces to...
Having fluid channeling or entrapping configuration
Reexamination Certificate
active
06314903
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
This invention relates generally to watercraft, and more particularly to a motorboat or sailboat form of watercraft having at least one displacement body that produces a bow wave.
2. Description of Related Art
Motor and sail powered displacement boats generate a bow wave, followed by a trough and stem wave, due to hull form and friction. For a displacement boat, the bow wave increases in amplitude with boat speed until propulsion power is insufficient to climb the wave (i.e., the hull speed limit). The bow wave, when generated, initially moves forward at the hull speed, but eventually loses speed and moves at an angle away from the hull. When the bow wave does so, it has sufficient energy to threaten other nearby boats and cause damage to foundations at the water/land interface in narrow waterways. In addition, engines mounted on the stem of the boat generate strong propeller wave action and noise pollution, which are especially objectionable to residences and/or commercial buildings located near the water/land interface. These problems are accentuated when boats operating at low speeds are required to make sharp-angle turns in narrow waterways, such as in the canals of Venice, Italy. Because a rudder is less effective under such conditions, an articulating outboard motor (or propeller), which accentuates the generation of waves and noise pollution, may be required.
The problems associated with the operation of smaller displacement boats powered by stern-mounted internal combustion engines include:
1. Conventional power boats are designed as either: (a) displacement boats, efficient at low speeds but with sufficient power and planing surface to transcend the hull speed limits; or (b) planing boats, inefficient at low speed but with sufficient power and planing surface to transcend the hull speed limits;
2. As mentioned above, bow waves generated by a boat move forward initially at the boat speed, but thereafter at decreasing speed due to friction, leading to potentially destructive bow waves moving laterally away from the boat;
3. A significant portion of propulsion energy is lost when converted into wave energy, leading to inefficiency;
4. Bow and stern waves plus stern-mounted propeller wave action generated by boats operating at high speed can cause serious damage to other boats and to foundations at the water/and interface in narrow waterways and small lakes; and
5. Wave, noise, and air pollution generated by conventional displacement boats powered by internal combustion engines are accentuated with an articulating outboard motor or propeller.
Conventional twin-hull catamarans, motor or sail powered, are also displacement boats that generate bow waves followed by troughs and stern waves due to hull form and friction. They offer certain advantages over conventional mono-hull watercraft in their high lateral stability and reduced form and friction drag. Although increasingly popular, both sail and motor powered conventional catamarans suffer important disadvantages. Among other things, motor powered catamarans generate large bow waves at high speeds which threaten other nearby boats and foundations at the water/land interface. In addition, they generate substantial external noise pollution. Furthermore, neither motor or sail powered catamarans recover energy from the bow waves and thus they remain displacement boats and this limits propulsion efficiency at higher speeds.
SUMMARY OF THE INVENTION
It is a general objective of the present invention to minimize damage to foundations at the water/land interface and to reduce the disruptive heaving motion to waterborne vessels and structures from boat-generated waves through operation of a watercraft having an approximately “M-shaped” hull that is designed to suppress such wave action.
It is a further objective in certain embodiments of the present invention to provide a powerboat having a relatively narrow central displacement body and planing wings to operate efficiently at low speed in the displacement mode, while requiring less power for efficient transfer into the planing mode, thereby providing efficient planing at high speed.
It is a further objective in other embodiments to recapture boat-generated waves through extension from the central displacement body of planing wings and parallel tapered outer skirts having vertical outboard and curved inboard surfaces to direct both the bow and skirt waves into channels in the planing wings.
It is a further objective to recover energy from the boat-generated waves (which are recaptured by the wing channels and tapered outer skirts) through planing on these waves, thereby recovering some portion of their contained energy.
It is a further objective in certain embodiments to provide improved stability at low boat speeds by installing at the outer edge of the planing wing a tapered outer skirt extending downward below the water line.
It is a further objective in certain embodiments to provide inner skirts attached to both sides of the displacement body to aerate the water along the hull to reduce frictional drag and to minimize wave energy behind the boat.
It is a further objective to increase dispersion of the wave energy exiting the boat by installing hydrodynamic serrations on the underside of the displacement body and/or the wing channels, preferably generally aligned with the outer and inner skirts and propeller discharge.
It is a further objective to reduce noise and air pollution by replacing transom-mounted engines with internal combustion, electric, or compressed air motors mounted in the wing channels and/or on the central displacement body.
It is a further objective to adapt the “M-shaped” hull to a sailboat with twin wing channels to provide righting moment from the higher lee-side bow wave and an automatic adjustment of side force with increasing immersion of the lee-side skirt.
The foregoing objectives are achieved by using an “M-shaped” watercraft hull. The present invention provides in certain embodiments a watercraft comprising a hull having a fore end, an aft end, and a longitudinal axis extending between the fore end and the aft end. The hull comprises a displacement body and two downwardly extending outer skirts. Each of the outer skirts is located outside of the displacement body and is connected thereto by a planing wing having a wing channel. The ceilings (i.e., apices) of the wing channels are above the static waterline in the fore end and extend downward below the static waterline in the aft end. Preferably, the displacement body is approximately centralized, extending substantially along the central longitudinal axis of the hull. The wing channels are preferably generally arcuate and concave with respect to the static waterline.
It is a general objective of another aspect of the invention to provide a multi-hull watercraft (e.g., a catamaran) with the advantages outlined above.
It is a further objective to use skirts to form two wing channels for each of the hulls (e.g., a total of four wing channels for a twin-hull catamaran) in order to recapture the bow waves and thereby protect nearby boats and structures at the water/land interface.
It is a further objective to create a concave bow shape for generating a spiral motion of the bow waves in order to entrap entering air and force it down the wing channels into the aft “pressure” section to form an air cushion for efficient boat planing. This converts a conventional multi-hull watercraft from a “displacement” boat to an “air cushion” watercraft for more efficient operation at higher speeds.
It is a further objective to utilize the air/water mixture flowing through the wing channels to dampen engine noise which is a source of increasing complaints from residents along restricted water ways.
It is a further objective to use the multi-hull catamaran with M-shaped hulls as a means of expanding the size of the single-hull watercraft with M-shaped hull described above without significant increase in the width and height of the wing channel entrance. This is important fo
Burns, III William F.
Robinson Charles W.
Avila Stephen
Loyal McKinley Hanson
Mangia Onda Co., LLC
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