Ships – Hull or hull adjunct employing fluid dynamic forces to... – Having fluid channeling or entrapping configuration
Reexamination Certificate
1999-09-20
2001-06-26
Avila, Stephen (Department: 3617)
Ships
Hull or hull adjunct employing fluid dynamic forces to...
Having fluid channeling or entrapping configuration
Reexamination Certificate
active
06250245
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an “M-shaped” hull design for a watercraft (e.g., motorboat or sailboat) which suppresses wave action compared to conventional hull designs.
BACKGROUND OF THE INVENTION
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 stem-mounted internal combustion engines include:
1. Conventional power boats are designed as either: (a) displacement boats, efficient at low speeds but subject to 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 stem waves plus stem-mounted propeller wave action generated by boats operating at high speed can cause serious damage to other boats and to foundations at the water/land 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.
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 waterbome 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.
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Calcott, J., Fighting Waves in Venice,Hors Ligne, pp. 54-60.
Stanley, A., Boat Gobbles Waves, but Bobbles in Political Seas,New York Times International, Jan. 14, 1999.
Weil, L., Depths in Venice,Boston Globe Online, p. A01, Jul. 7, 1999.
Burns, III William F.
Robinson Charles W.
Avila Stephen
Hanson Loyal McKinley
Mangia Onda Co., LLC
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