Pleasure watercraft

A pleasure watercraft is provided which comprises a hull, sponsons, and support structures for the sponsons which have a shape of an airfoil. A cockpit for seating a pilot in the hull is located such that the distribution of mass elements in the craft positions the center of gravity of the craft within a select range along the longitudinal axis of the hull in substantially vertical alignment with seating position of the pilot, and preferably beneath the pilot. Hydrodynamic and aerodynamic forces acting on the craft as it accelerates converge within the select range to permit the pilot control of the attitude and roll of the craft.

FIELD OF THE INVENTION 
The invention presented herein relates to a recreational watercraft and in 
particular to a watercraft having an aerodynamic configuration which 
improves transitional and high speed performance, and having a select 
arrangement of mass distribution to enable a pilot to control the attitude 
of the watercraft through control elements and the position of the pilots 
body. 
BACKGROUND OF THE INVENTION 
For many years, designers of pleasure craft have been researching 
water-borne craft designs which have aerodynamic elements generating lift 
force on the craft structure when at speed to assist raising the craft 
above its at rest buoyant draft. This is desired to reduce viscous drag on 
the craft hull providing increase speed and/or efficiency over a craft 
with a conventional design having the same weight and power. Early designs 
effectuating this objective are evidenced by the hydroplane style boat 
which comprises a pair of structurally supported sponsons separated by a 
raised hull floor, which form an underlying tunnel through which air is 
flowed. The underflowing airstream may also provide a lift force through 
the force of the airstream against the hull floor or through compression 
of the entering air mass between the water surface and the hull floor of 
the boat, or both. 
The hull of a hydroplane is supported by buoyant force generally along its 
entire underside, including the hull floor and sponsons, when at rest. 
Under power the boat is substantially supported by hydrodynamic force 
acting against the outwardly and forwardly positioned sponsons, and by 
radial thrust from the prop extending from the rear of the null. This 
triangular footing provides good stability in smooth surfaces water, 
however, the wide beam of the sponsons and the airflow through the 
centrally defined tunnel can result in instability in rough surface 
conditions. 
Generally, hydroplane style boats are designed with the cockpit in 
opposition to the powerplant, i.e. the cockpit is in the front if the 
engine is in the rear and vice versa, for heavier designs. For lighter 
designs, for instance boats under fifteen foot in length, the cockpit is 
generally positioned in the stern so that the pilot is within reach of an 
outboard type motor mounted to the transom of the boat. 
Tri-hull boat designs exemplified for instance in U.S. Pat. No. 3,952,678, 
have been described as improvements over the basic hydroplane style hull. 
Such boat designs comprise a third water borne hull generally positioned 
centrally between the sponsons to assist in dynamic stability. The depths 
of the hull and sponsons are generally equal, as shown, to provide a 
uniform and broad base support for the hull in the water, with their 
underlying surfaces being flat and horizontally disposed. 
The third central hull is thought to provide additional stability in rough 
surface conditions or high wind conditions which may create an unstable 
situation for a hydroplane style boat. Additionally, a forwardly rising 
support structure for the sponsons is described which provides an upwardly 
and forwardly angled undersurface which is bounded by the central hull and 
the respective sponsons. This undersurface is used to compress an 
airstream received when the boat is in motion to provide aerodynamic lift 
force on the underside of the structure in addition to the hydrodynamic 
lift force generated on the hull when the boat is under power. The boat 
described in the referenced patent appears to be larger than 20 feet in 
length and has the cockpit positioned rearwardly with the engine placed in 
an opposing forward position. 
Another differing style craft which is substantially aerodynamic in design 
while utilizing both aerodynamic and hydrodynamic lift forces during the 
transitional period from standstill through surface departure, is 
described in U.S. Pat. No. 3,190,582 and related U.S. Pat. Nos. 3,627,235 
and 3,030,448. The aircraft disclosed therein is, at rest, supported on 
forwardly and outwardly extended sponsons joined to a central craft 
fuselage. The sponsons are joined to the fuselage by airfoil shaped 
structures or wings extending outwardly and downwardly to the sponsons 
from the fuselage to provide a reverse dihedral wing configuration. This 
design positions forward portions of the fuselage above the sponsons such 
that the forward portion of the fuselage cannot contact the surface of the 
water on which the craft is supported. The wing structures extend 
rearwardly from the outwardly and downwardly directed leading edge which 
extends substantially perpendicular with the longitudinal axis of the 
fuselage, to an inwardly swept back rearward converging at the tail of the 
fuselage. The rearward edge of the wing sections extend in a generally 
horizontal plane from the sponsons to the rear of the fuselage. This wing 
configuration provides a triangular shaped frontal opening from the nose 
of the fuselage to the interior side of each respective sponson to define 
an underlying space below the fuselage and wing structures which is closed 
at the rearward edge of the wing against the surface of the water. The 
rearward edge of the wing is generally at the same vertical height as the 
sponsons and meets the water surface at rest from the sponson to the rear 
of the fuselage. Thus at rest the craft rests on the sponsons and the 
rearward edge of the wing and the rearward end of the fuselage, all of 
which are in contact with the water to support the aircraft. 
When the aircraft begins operation and accelerates, the air flow into the 
triangular shaped frontal opening of the wing begins to build air pressure 
under the aircraft, between the undersurface of the wings and fuselage and 
the surface of the water. Maximum aerodynamic pressure builds at the 
rearward edge of the wings so that the rear of the aircraft lifts from the 
surface of the water first and the aircraft is supported by hydrodynamic 
pressure on the sponsons and aerodynamic pressure along the rearward edge 
of the wings. 
Operation of the aircraft as velocity increases becomes increasingly 
unstable however due to loss of aerodyanmic lift as the rear edges of the 
wings rise and the ram air and ground effects lift dissipate. This causes 
great difficulty in pitch or attitude control of the aircraft. Due to the 
reverse dihedral configuration of the wings roll of the craft in one 
direction or the other tends to increase rotation of the same direction. 
This is caused by increases lift on the rising (more horizontal) wing as 
compared to the other, a phenomena which additionally causes attitude and 
roll instability. 
If the aircraft is piloted through the transitional period, the aircraft 
attains a stable and substantially horizontal pitch attitude and airflow 
over the wings generates aerodynamic lift to raise the craft from the 
water surface into free flight. 
The aircraft fuselage is configured in a common design having the cockpit 
positioned as far forward as is practical in view of other major 
components contained in the fuselage, such as engine, avionics, etc. which 
are positioned in the nose structure of the craft. 
A watercraft comprising a singular water borne hull which additionally 
utilizes a wing(s) for stability and control in operation is known as a 
Ski Plane.RTM. which is manufactured by a concern known as Ski-Plane, Inc. 
of Newport Beach, Calif. The hull of the Ski Plane is a narrow 
cigar-shaped structure which has a primary substantially flat and narrow 
undersurface extending the length of the hull. A pair of secondary and 
adjacent horizontal undersurfaces are disposed on either side and are part 
of the hull, beginning with a raised surface portion approximately 1/3 
along the length of the hull from the front and curved downwardly and 
rearwardly to a flat undersurface contiguous with the primary undersurface 
approximately midway along the length of the hull. The secondary 
undersurfaces are generally provided to aid high speed stability while 
decreasing the area of undersurface in contact with the water to reduce 
viscous drag. 
A pair of wing structures extend laterally from the rear of the craft and 
exhibit a slight dihedral angle with the hull. Each wing structure ends 
with a downwardly curved portion or "drooping edge" which acts to restrict 
lateral flow of air from beneath the wing to improve stall 
characteristics, i.e. reduce the speed at which stall occurs. The wing 
structure ends do not, however, meet the water surface at level operation. 
Ailerons extend along the rearward edge of each wing structure to assist 
in rotational control of the craft when at speed. A fixed laterally 
extending winglet is also provided at the nose of the craft. The wing 
structures are thus characterized by a design common to an aircraft, 
rather than a waterborne vehicle. 
The Ski Plane is powered by a typical outboard motor mounted to the transom 
of the hull to propel the craft and generate primary rotational control 
through a driving propeller disposed below the surface of the water. A 
pair of cockpits are provided in a generally forward position of the hull. 
Major control, fuel and drive components are mounted within the stern in 
the area where the wing structures are attached. 
SUMMARY OF INVENTION 
A pleasure watercraft is presented which comprises a central hull and a 
pair of laterally disposed sponsons which are mounted to the hull through 
support of wing structures. The watercraft design positions the pair of 
sponsons equidistantly and laterally from the watercraft central hull, and 
rearwardly from the bow. The wing structures have an aerodynamically 
configured shape to generate lift force to improve transitional and high 
speed performance of the watercraft. Preferably, the wing structures 
mounting the sponsons to the hull are configured to have the shape of an 
airfoil with a relatively large radius leading edge to improve low speed 
lift and stall characteristics. Also, the wing structures extend upwardly 
and outwardly from the central hull to define a dihedral angle with a 
horizontal plane of the craft to provide roll stability. The inside 
surface of each sponson provides a barrier which prevents lateral flow of 
air from under each of the respective wing structures to further reduce 
stall airspeed, and to permit efficient utilization of the forces 
generated beneath the wing structures from the force of airflow. 
In a preferred embodiment, the central hull has a concave shaped 
undersurface which extends from the bow rearwardly underneath the craft to 
the stern to improve hydrodynamic lift. Each of the sponsons also have a 
concave shaped surface or inwardly formed scallop along its undersurface 
to improve performance and assist in obtaining directional stability of 
the watercraft. Preferably the concave undersurface of each sponson is 
directed slightly outwardly and downwardly from the center of the craft. 
The airfoil shaped wing structures have a leading edge which extends from 
the bow of the central hull to the front of each respective sponson. Since 
the sponsons are positioned rearwardly from the bow, the leading edge 
defines a sweptback wing configuration from the front of the craft to the 
front of the sponsons. Each of the sponsons preferable end at an 
approximately lateral position with the stern of the central hull. The 
wing structures extend from the rear of each sponson to the stern of the 
hull to define a trailing edge substantially orthogonal with the 
longitudinal axis of the watercraft. Preferably, each of the wing 
structures exhibit a slightly outwardly and downwardly curved upper 
surface while maintaining a dihedral angle of the undersurface with 
respect to the hull, with the undersurface near the lateral end of each 
wing structure curving downwardly to blend into the interior wall of each 
sponson. 
The watercraft is powered by a typical power plant which drives an air or 
water propulsion system to provide motive force. Additionally, typical 
aerodynamic and/or hydrodynamic (fluid) control means are provided to 
steer and control attitude of the craft. 
The watercraft is designed to have a mass distribution which enables a 
pilot to control the attitude of the watercraft through the fluid control 
elements and the positioning of the pilots body within a cockpit contained 
in a central hull. A cockpit is formed along the longitudinal axis of the 
central hull preferably forward of the mid position to provide a seating 
position for a pilot. The mass distribution of the craft is designed such 
that the center of gravity of the craft lies within a longitudinal range 
beneath a seating position for a pilot in the cockpit. This permits the 
pilot to utilize body movement to control the attitude of the watercraft 
when is operation. The mass elements of the craft are distributed in the 
central hull to place the center of gravity within the defined 
longitudinal range below the seating position of the pilot. In a preferred 
configuration, the power plant is positioned in the nose or bow of the 
watercraft and the propulsion system is positioned in the stern. Drive 
means are provided extending below the seating position of the pilot to 
transfer power from the powerplant to the propulsion system. Fuel storage 
is preferably positioned immediately below the seating position of the 
pilot within the longitudinal range of the center of gravity so that fuel 
usage will not disturb the mass distribution of the watercraft. 
The propulsion system is preferably a ducted fan position in the stern of 
the watercraft with an air intake immediately behind the seating position 
of the pilot in the cockpit. The ducted fan preferably includes torque 
control means to eliminate torque forces characteristic of the fan from 
acting on the watercraft. A rudder may be provided behind the outlet of 
the ducted fan to provide turning and yaw control. Additional horizontal 
control surfaces may be provided to obtain pitch control. 
The watercraft is preferably constructed in a one piece structure from a 
structurally molded foam composition which comprises a tough outer surface 
for durability. 
In operation as the watercraft accelerates hydrodynamic forces exerted 
against the forward portion of the central hull and against the sponsons 
pitch the craft upwardly. This raises the swept back leading edge of the 
wing sections supporting the sponsons to enlarge the frontal window 
between the undersurface of the wing sections and the surface of the 
water, while lowering the trailing edge of the wing sections close to or 
on the surface of the water to substantially close the passage for air at 
the trailing edge of each wing section. This forms an airpocket below each 
wing section which receives the airstream as the watercraft urges ahead to 
generate ram and ground effect lift on the under surface of each wing 
section. The center of the aerodynamic lift on the wing section is 
rearwardly positioned. 
As the watercraft increases in speed and begins to plane on the surface of 
the water, the center of hydrodynamic lift moves rearwardly along the 
undersurface of the hull permitting the watercraft to decrease its 
upwardly pitched attitude and become more horizontally disposed. 
Aerodynamic lift at the rearward portions of the wing sections assist in 
decreasing the upward pitch of the craft. As the watercraft noses forward 
and the upward pitch decreases not only does the center of hydrodynamic 
lift move rearward on the undersurface of the hull but airflow is 
permitted over the wing sections as the trailing edge of each wing section 
lifts from the surface of the water. This generates aerodynamic lift force 
on the wing sections. The center of aerodynamic and/or ground effect force 
generated on each of the wing sections moves forwardly. 
As the watercraft goes through transition and approaches operation speed 
the center of hydrodynamic lift force on the hull and the center of the 
aerodynamic and/or ground effect lift force on each of the wing sections 
converges longitudinally, i.e. the center of hydrodynamic force moves 
toward the rear of the craft and the center of aerodynamic and/or ground 
effect force moves toward the front of the craft, such that the summation 
of forces enters into the longitudinal range of the center of gravity of 
the craft. In other words viewing the longitudinal range of the center of 
gravity as bounded on a forward side by a first plane orthogonal along the 
longitudinal axis of the craft and bounded on the rearward side by a 
second plane orthogonal to said axis, the summed hydrodynamic and 
aerodynamic and/or ground effect forces will converge within the two 
bounding planes. Thus, when the watercraft is at speed not only is the 
center of gravity, which is the balance point of the craft, positioned 
within the defined longitudinal range at the center of gravity but the 
lift forces acting on the craft are also acting within this range to 
provide the pilot attitude control of the watercraft by shifting his 
weight with respect thereto. Attitude control is thus assisted by a pilot 
shifting their position in the cockpit, or leaning their body in a desired 
direction. This is possible because the longitudinal range bounding the 
center of gravity and lift forces is substantially within the seating 
position of the pilot in the craft and preferably with the fuel supply 
included so that the balance of forces is not upset by fuel usage. The 
pilot may thus shift his weight forward to nose the craft downwardly and 
shift his weight rearward to nose the craft upwardly. Additionally, since 
the center of gravity is positioned directly under the pilot, the pilot 
may lean to the left or right to rotate the craft to the left or right 
respectively. The watercraft may thus be controlled by the pilot through 
usage of the control elements of the watercraft, especially the rudder 
and/or horizontal stabilizers, and through shifting of their weight as is 
easily accomplished within the cockpit when the craft is in operation. 
Additionally power applied to the propulsion means can be utilized to 
control pitch of the craft.

BEST MODE OF THE INVENTION 
The presented watercraft can be viewed in FIGS. 1 through 3. The watercraft 
comprises central hull 10 forming a central portion of the craft. A pair 
of laterally disposed sponsons 12 and 14 respectively are positioned in 
parallel relationship with the longitudinal axis of the hull and are 
mounted to the central hull 10 by outwardly directed support or wing 
structures 16 and 18 respectively. The sponsons 12 and 14 are preferably 
aligned rearwardly of the bow of the central hubs 10. 
The wing structures 16 and 18 are identical in structure and configuration 
though the mirror image and will be described simultaneously with this 
understanding. The wing structures 16, 18 mounting their respective 
sponson 12, 14 extend from the side of the central hull 10 laterally to 
the sponson. The undersurface of the wing structure 16, 18 has an 
undersurface 20, 22 which is outwardly and upwardly directed to form a 
dihedral angle with a horizontal plane through the central hull 10 as it 
reaches out to its respected sponson 12, 14. Preferably the dihedral angle 
formed by the undersurfaces 20, 22 of the wing section 16, 18 is 
10.degree. relative to a horizontal plane through the central hull 10. The 
undersurfaces 20, 22 have a curved section 17, 19 to blend with the side 
surfaces of the central hull 10. At their outer end the undersurfaces 20, 
22 have outwardly and downwardly curved section 21, 23 to form a "drooping 
edge" bounding the undersurfaces 20, 22 of the wing section 16, 18 and 
blend into interior side wall of each of the respective sponsons 12, 14. 
The upper side of each of the wing structures 16, 18 extend outwardly and 
curve downwardly to blend into each of the outer surfaces of the sponsons 
12, 14 which they support. This wing structure design forms a smooth and 
continuous form for the upper and under surfaces which smoothly form into 
the supported sponsons 12, 14. 
Each of the wing structures 16, 18 have an aerodynamically configured 
shape, i.e. have the shape of an airfoil. This can be clearly seen in the 
cross sectional view of FIG. 5 for a section A--A is taken through wing 
structure 16 to show the curved uppersurface 25 extending from front to 
the rear of the wing section and the substantially flat undersurface 20 
extending from front to the rear of the wing section. 
Referring again to FIGS. 1 through 3 the leading edges of each wing section 
16 and 18 extend outwardly and rearwardly from the bow of the central hull 
10 to the front of the rearwardly positioned sponsons 12, 14 respectively 
which they support. Each of the sponsons 12 and 14 respective are 
positioned parallel with the longitudinal axis of the central hull 10 and 
begin rearwardly of bow of the central hull 10 ending at a point 
substantially equal with the stern of the central hull 10. The leading 
edges of the wing section 16, 18 thus form a sweptback wing configuration 
from the bow of the central hull 10. Preferably, the leading edges 36, 38 
of the wing section 16, 18 extend rearwardly with a 60.degree. angle with 
the longitudinal axis of the central hull 10 the leading edges 36 and 38 
respectively of the wing structures 16, 18 have a relatively large radius 
frontal surface, such as is shown in the cross section depicted in FIG. 5 
for leading edge 36. The trailing edges 40 and 42 of the wing structures 
16 and 18 respectively are generally narrow in width and extend 
perpendicularly to the rearward end of each sponson 12 and 14 to form a 
straight trailing edge. 
In preferred form, the central hull 10 has a concavity 24 inwardly formed 
along the length of its undersurface. The concavity 24 rises forwardly and 
upwardly into the lower portions of the bow of the central hull 10 to form 
a forwardly directed concave surface at the frontal portion of the bow 
bounded by edges 24a and 24b respectively. 
Similarly, each of the sponsons 12, 14 have a concave shaped undersurface 
13 and 15 respectively formed along their length with a forwardly and 
upwardly curved portion to form a forwardly directed concave frontal 
surface. Preferably, the concavities 13 and 15 formed into sponsons 12 and 
14 respective are slightly inwardly directed and preferably symmetrical 
about a plane formed an angle between 20.degree. and 30.degree. with 
vertical. 
A cockpit 28 is formed in the upper surface of the central hull 10 and is 
positioned approximately 1/3 along the longitudinal length of the central 
hull from the bow to the rear. The cockpit 28 contains a seating position 
30 for a pilot and also contains control elements, as for example steering 
handle 40. The upper surface of the bow of the central hull 10 is shown 
with an air inlet 42 formed to provide an airstream to radiator means (not 
shown) for cooling a power plant used to drive the watercraft. 
A ducted fan 32 is positioned rearwardly of the cockpit 28 to provide 
motive force for propelling the watercraft a rudder 34 is positioned 
behind the outlet 65 of the ducted fan 32 to direct the airflow from the 
ducted fan to provide directional control for the watercraft. The ducted 
fan 32 has an inlet 59 behind the cockpit 28 to receive air which is 
compressed by the rotating fan blade 62 to force compressed air at high 
speed out of the ducted fan outlet 65. Horizontal airflow control elements 
may also be provided. 
The mass distribution of the watercraft is designed so that the center of 
gravity of the craft lies within a longitudinal range along the 
longitudinal axis of the central hull 10, shown bounded by front plane P1 
and rear plane P2 extending perpendicularly with the longitudinal axis of 
the craft. The seating position 30 of the pilot within the cockpit 28 of 
the central hull 10 is positioned substantially between the planes P1 and 
P2 thus positioning the driver 29 substantially within the range of the 
center of gravity is below the seating position 30 of the pilot 29 so that 
the pilot is seated over the center of gravity. 
The mass elements mounted within central hull 10 are distributed within the 
hull to place the center of gravity within the defined longitudinal range 
between planes P1 and P2 and below the seating position of the pilot. The 
fuel tank 31 is positioned below the seating position 30 of the pilot 29 
to provide fuel storage within the range of the center of gravity between 
planes P1 and P2 so that fuel usage will not affect balance of the craft. 
A power plant 44 is positioned forwardly of the cockpit 28 in the bow of 
the craft and lower than the seating position of the pilot 30. The power 
plant may be a typical multi-cylinder 2-cycle marine engine such is 
commonly known by those in the art. The ducted fan 32 is positioned in the 
stern of the craft and is mounted to direct thrust of the airflow which is 
generates over the surface of the water on which the craft is supported. 
The ducted fan 32 generally comprises a hub 60 which mounts a plurality of 
fan blades 62 radially around the hub 60. The fan blades 62 are bounded by 
a cylindrical wall or fan duct 63. A fairing 66 extend rearwardly from the 
hub 60 to provide a smooth surface over which the airflow compressed by 
the fan blades 62 may pass. A torque control means to correct torque force 
generated by thrust of the ducted fan 32 is provided, such as curved vanes 
64 which slightly redirect the flow of air leaving the fan blades 62 as 
they are powered. The flow of air leaving the ducted fan passes by the 
rudder 34 for directional control. 
Power from the power plant 44 is transmitted to rotate the ducted fan 32 
through drive means comprising a first horizontally disposed shaft 46 
extending below the seating position 30 of the driver and through a formed 
opening in the fuel tank 32. The shaft is mounted for rotation by suitable 
bearing support means such as the engine 44 and a bearing support 47. At 
the rearward end of the shaft 46 a pulley 48 is mounted to drive a fan 
shaft 54 through pulley 50 mounted on such shaft 54 with a belt 52 
interconnecting the pulleys 48 and 50. The fan shaft 54 may support the 
ducted fan hub 60 and is mounted for rotation by suitable bearing support 
means (not shown). The power plant 44, the drive means comprising the 
shafts 46, 54 with the belt drive and the ducted fan 32 are all elements 
commonly known to those skilled in the art and can be selected from any 
one of a number of manufacturers. The power plant 44, the drive means and 
the ducted fan 32 are mounted within the hull 10 such that in combination 
with the mass of the hull, their individual masses combine to position the 
center of gravity for the watercraft within the longitudinal range between 
the planes P1 and P2 so that the seating position of the driver 30 is 
positioned above the center of gravity. 
Control means are provided for controlling the speed of the engine 44 (not 
shown) and for controlling the rudder 34 such as through control handle 40 
which communicates with the rudder 34 through a control linkage 41. 
It should be noted that the central hull 10, the wing section 16 and 18 and 
the sponsons 12 and 14 may be made as a one-piece structure out of 
structural foam material which has a relatively tough outer surface. 
However, other material with are sufficiently light while rigid may be 
used such as fiberglass or other plastics or laminations as would be 
selected by those generally skilled in the art of watercraft hull design.