U.S. patent number 3,804,048 [Application Number 05/341,682] was granted by the patent office on 1974-04-16 for hydrofoil watercraft.
This patent grant is currently assigned to Dynafoil, Inc.. Invention is credited to David J. Cline.
United States Patent |
3,804,048 |
Cline |
April 16, 1974 |
HYDROFOIL WATERCRAFT
Abstract
A hydrofoil watercraft utilizing forward and rearward struts and
foils configured and oriented to provide lateral stability. The
forward strut is freely rotatable about its longitudinal axis and
mounts the forward foils. The strut and foils are configured and
oriented such that the resultant of the lift, pressure, and drag
forces therein tends to stabilize the watercraft in a turn and
generate righting forces.
Inventors: |
Cline; David J. (Brea, CA) |
Assignee: |
Dynafoil, Inc. (Newport Beach,
CA)
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Family
ID: |
26928983 |
Appl.
No.: |
05/341,682 |
Filed: |
March 15, 1973 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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235517 |
Mar 17, 1972 |
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Current U.S.
Class: |
114/281 |
Current CPC
Class: |
B63B
1/283 (20130101) |
Current International
Class: |
B63B
1/28 (20060101); B63B 1/16 (20060101); B63b
001/26 () |
Field of
Search: |
;114/66.5H,162,164,169 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Wood, Jr.; M. Henson
Assistant Examiner: Mar; Michael Y.
Attorney, Agent or Firm: Fulwider Patton Rieber Lee &
Utecht
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATION
This is a continuation-in-part of United States patent application
Ser. No. 235,517, filed Mar. 17, 1972, now abandoned, and the
benefit of the filing date thereof is claimed for subject matter
common to that application and the present application.
Claims
I claim:
1. A hydrofoil watercraft comprising:
an elongated hull having a longitudinal center gravity axis;
propulsion means for driving said hull;
forward strut means mounted to the forward portion of said hull for
rotation about a support axis extending downwardly and forwardly
relative to said center of gravity axis, said forward strut means
being characterized by side surfaces having a center of pressure
located rearwardly of said support axis whereby, upon tipping of
said watercraft to one side during propulsion thereof, water
pressure acting upon said forward strut means tends to turn said
forward strut means in the direction of said one side;
non-surface piercing forward hydrofoil means carried by said
forward strut means and characterized by surfaces operative to
develop lift forces collectively acting upwardly along a lift axis
which intersects said support axis below said center of gravity
axis whereby turning of said forward strut means tends to develop a
righting force tending to move the watercraft to an upright
position;
rearward strut means mounted to the rearward portion of said hull;
and
rearward hydrofoil means carried by said rearward strut means.
2. A hydrofoil watercraft according to claim 1 and including
steering means coupled to said forward strut means and operable to
rotate said forward strut means about said support axis.
3. A hydrofoil watercraft according to claim 1 wherein said side
surfaces of said forward strut means are generally vertically
oriented, and said forward hydrofoil means comprise a pair of
laterally extending foils disposed substantially normal to said
side surfaces.
4. A hydrofoil watercraft according to claim 3 wherein said foils
are each generally delta-shaped in configuration whereby the
effective impact of foreign objects against the raked leading edge
thereof is lessened.
5. A hydrofoil watercraft according to claim 1 wherein said
rearward hydrofoil means comprise a pair of anhedral foils
extending laterally and downwardly from opposite sides of said
rearward strut means.
6. A hydrofoil watercraft according to claim 1 wherein said forward
and rearward strut means each comprise a depending fin-like strut
having generally vertically disposed sides, the rear said strut
lying generally in the plane which includes said longitudinal axis
of said hull and said support axis.
7. A hydrofoil watercraft according to claim 6 wherein said struts
each include a blunt trailing edge.
8. A hydrofoil watercraft according to claim 1 wherein said
rearward hydrofoil means comprise a pair of foils on opposite sides
of said rearward strut means and oriented to define an inverted
V-shape.
9. A hydrofoil watercraft according to claim 1 wherein said forward
hydrofoil means comprise a pair of delta-shaped foils extending
laterally of said forward strut means, the chord line of each of
said foils being shorter at its outer portion than at its inner
portion adjacent said forward strut means.
10. A hydrofoil watercraft according to claim 1 wherein at least a
portion of said rearward hydrofoil means is movable to aid in
turning the watercraft.
11. A hydrofoil watercraft according to claim 1 wherein said
rearward hydrofoil means comprise a pair of laterally extending
foils each of which includes an aileron portion; and including
steering means operative to oppositely move the aileron portions
and thereby aid in turning the watercraft.
12. A hydrofoil watercraft according to claim 11 and including
means coupling said steering means and said forward strut means
whereby rotation of said forward strut means is accompanied by
movement of said aileron portions.
13. A hydrofoil watercraft according to claim 1 wherein said hull
includes upper and lower substantially V-shaped hull portions, said
lower hull portion having a deeper and narrower V-shape section
than said upper hull portion.
14. A hydrofoil watercraft comprising:
an elongated hull adapted for propulsion through water;
forward strut means mounted to the forward portion of said hull and
including a generally flat-sided, vertically oriented forward strut
rotatable about a support axis extending downwardly and forwardly
relative to the longitudinal axis of said hull, a greater portion
of the side surface area of said forward strut being located
rearwardly of said support axis whereby upon tipping of said
watercraft to one side during propulsion thereof water pressure
acting upon said side surface area of said forward strut tends to
turn said forward strut means in the direction of said one
side;
forward hydrofoil means of the fully submerged type carried by said
forward strut and including a pair of forward foils extending
laterally from opposite sides of said forward strut, the surfaces
of said foils having centers of lift located rearwardly of said
support axis;
rearward strut means mounted to the rearward portion of said hull;
and
rearward hydrofoil means carried by said rearward strut means.
15. A hydrofoil watercraft according to claim 14 wherein said
rearward strut means includes a generally flat sided, vertically
oriented rearward strut and said rearward hydrofoil means are
mounted to said rearward strut.
16. A hydrofoil structure according to claim 15 wherein said
forward and rearward struts are longitudinally aligned during
straight, non-turning travel of the watercraft.
17. A hydrofoil structure according to claim 15 wherein said
rearward hydrofoil means include a pair of anhedral foils extending
from opposite sides of said rearward strut.
Description
BACKGROUND OF THE INVENTION
1. FIELD OF THE INVENTION
This invention relates generally to hydrofoil watercraft, and
particularly to a watercraft having strut and foil structure
providing improved lateral stability.
2. DESCRIPTION OF THE PRIOR ART
Providing adequate lateral stability for hydrofoil watercraft has
long been a problem and is the subject of continuing research.
Achievement of satisfactory lateral stability would result in more
extensive utilization of hydrofoil watercraft.
One prior art method of providing lateral stability utilizes three
or more struts supporting the foils and coupled with mechanical or
electronic wave sensors. The foils were of the surface piercing
type, arranged in either a ladder, dihedral, or anhedral
configuration. When the craft leans to one side the foil surfaces
on the opposite side partially come out of the water and lose some
of their lifting force. The lifting force of the more deeply
immersed foil surfaces on the opposite side of the craft furnish a
righting torque. An example of the ladder version of such a system
is described in U.S. Pat. No. 1,410,876. A dihedral version was
introduced by Crocco and Ricaldoni in approximately 1907, with a
variation thereof being disclosed in United States U. S. Pat. No.
1,766,700. In the latter patent the hydrofoils are of inverse
dihedral, or anhedral shape. Anhedral foils provide increased
stability as the speed of the craft increases and it rises out of
the water.
A serious drawback of all of these systems results from their use
of laterally spaced hydrofoils and support appendages. This spacing
causes the watercraft to tend to oscillate laterally as the craft
passes through disturbed water. More violent reactions are
encountered in high seas, with their high differential wavefronts,
and this results in a harsh ride.
The use of surface piercing hydrofoils is also inefficient in that
air may be drawn onto the lifting surfaces of the hydrofoil at the
water level, destroying smooth hydrodynamic flow and disrupting the
lift characteristics desired.
In contrast to the surface piercing foil systems, there are fully
submerged prior art hydrofoil systems which are relatively
successful, principally because of recent advances in electronic
and derivative devices to provide adequate lateral stability. For
example, projecting feelers or booms have been mounted to the front
and sides of the watercraft to sense rolling motions of the hull.
They generate signals which are used to change the foil
orientations and angles to establish a righting force which tends
to halt the rolling motion of the hull. These and similar devices
pg,4 utilize relatively sophisticated and expensive mechanical and
electronic interpretation systems to provide the desired degree of
stability during rapid travel over the water surface. The system of
U. S. Pat. No. 3,364,891 is typical in this regard.
Other prior art systems attempt to provide lateral stability for
submerged foils by using electronic devices mounted within the
watercraft hull. Thus, combinations of accelerometers and rate
gyros sense sideways leaning of the craft and initiate operation of
roll alerons or lift spoilers attached to the submerged hydrofoils
to provide the desired righting force. These systems are
sophisticated, expensive and very complex because of the multitude
of input data that must be handled to cope with changing sea
conditions.
Lateral stability is even more critical in watercraft having a two
point, fore and aft hydrofoil support system. This type of
watercraft is capable of achieving high speeds because of the
reduced resistance or drag of the struts supporting the foils.
SUMMARY
The present invention is a simple, effective and relatively
inexpensive watercraft which has good lateral stability. This is
provided by utilizing fully submerged forward and rearward
hydrofoils mounted to support struts, with the foils and struts
configured and oriented to stabilize the craft in a turn
immediately upon any tipping of the craft to one side or the other.
No extra appendages, internal electronics or artificial devices are
required for this purpose.
Two hydrofoil struts are preferably arranged in line along the keel
of the craft to eliminate the torsional effects which are
experienced by prior art craft utilizing widely spaced struts. The
center of pressure of the forward strut, the center of lift of the
forward foil, and the center of drag of said strut and hydrofoil
are located rearwardly of a steering axis about which the forward
strut is movable. These centers of pressure, lift, and drag develop
forces which automatically stabilize the craft upon any leaning or
tipping of the craft to one side or the other.
The present watercraft is economical to manufacture and operate, it
is efficient, and it is capable of high speed operation without
loss of stability or smooth riding, even in highly variable sea
conditions.
Other objects and features of the invention will become apparent
from consideration of the following description taken in connection
with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side elevational view of a hydrofoil watercraft
according to the present invention;
FIG. 1A is a view taken along the line 1A--1A of FIG. 1;
FIG. 2 is a front elevational view of the watercraft of FIG. 1;
FIG. 3 is a side elevational view of the front strut and foils of
the watercraft of FIG. 1, illustrating the dynamic forces acting
thereon;
FIG. 4 is a front elevational view of the front strut, in a tilted
condition of the watercraft, and illustrating the dynamic forces
acting thereon;
FIG. 5 is a perspective view of one form of steering mechanism
incorporated into the rear strut; and
FIG. 6 is a horizontal cross-sectional view illustrating the front
and rear strut configuration and orientation.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to FIG. 1 of the drawings, the present hydrofoil
watercraft comprises a hull 1 having a fin-like rear strut 2
attached generally along a keel line 3 of the hull and adjacent the
rear of the hull. The strut 2 is generally flat-sided and extends
downwardly from the hull 1. A pair of rear anhedral foils 4 are
affixed to the sides of the rear strut 2 adjacent the bottom edge
thereof, extending laterally outwardly and downwardly. A propulsion
unit or engine (not shown) for propelling the craft is preferably
mounted within the hull, although it could, if desired, be mounted
on top of or hung over the rear portion of the hull. The propulsion
unit can be of any standard design and power and its configuration
is not critical to its use in this invention, so long as it is
capable of driving a propeller 5 or similar water reaction device
located on the craft.
Referring particularly to FIG. 3, the present watercraft also
includes a forward or front strut 6 which is acted upon by the
forces indicated when the craft is underway at a speed sufficient
to make it completely foilborne. The forward strut 6 is
longitudinally aligned with the rearward strut 2, and is generally
fin-like and flat sided in configuration. The strut 6 includes a
steering shaft 7 which rotates freely in a collar 9 forming a part
of the hull 1. The strut 6 is rotated about a steering axis 8 by
means of any well known steering mechanism such as a wheel 10. The
wheel 10 is preferably attached directly to the steering shaft 7,
although it may be remotely located and connected to the steering
shaft 7 by means of usual and well known systems of gears and
pulleys. A pair of forward foils 11 are affixed on opposite sides
of the forward strut 6 adjacent the bottom edge. The foils 11
extend laterally of the strut 6 in a substantially horizontal
plane, that is, substantially normal to the vertical plane within
which the strut 6 lies in an upright position of the
watercraft.
The design of the forward strut 6 and the angle of the steering
axis 8 relative to the surface of the water are critical to achieve
the purposes and objects of this invention. The steering axis 8 is
inclined at some angle A with respect to the horizontal or plane of
the water surface. The angle is approximately sixty seven degrees
in the drawings, although this can be varied in accordance with the
principles described herein.
The weight of the watercraft when foilborne can be considered to be
concentrated at a center of gravity which lies on a longitudinal
center of gravity axis Gc extending generally parallel to the water
surface and in the same vertical plane as the keel line of the
hull. At a speed great enough for the craft to become fully
foilborne, there are three major forces acting on the front strut
in addition to the weight of the craft, which may be considered to
be concentrated at a center of gravity which lies on a center of
gravity axis Gc which extends generally parallel to the water
surface in the upright, foilborne position of the watercraft. These
forces are lift L, drag D, and static pressure S. The center of
lift Lc for each foil 11 is the imaginary point on the foil from
which the lift force vector of the foil can be considered to be
acting. The composite lift force of the two foils may be considered
to be acting upwardly through the plane of the strut 6 along a line
L. The center of drag Dc is the imaginary point at which the total
drag forces of the combination of the front strut 6 and foils 11
are considered to be acting, and is usually located toward the rear
of the front strut. The center of static pressure Sc is the point
at which the pressure of the water on each side of the front strut
is considered to be concentrated. An important feature of this
invention is that the forward strut 6 is designed and constructed
so that the centers of static pressure Sc, lift Lc, and drag Dc,
are located behind or rearwardly of the inclined steering axis 8,
as illustrated in FIG. 3.
As long as the hydrofoil craft is traveling in a straight line, the
lift L will be imparted directly up along a lift axis 17, through
the vertical plane in which lie the steering axis 8 and the
longitudinal center of gravity axis Gc of the hull. It is important
to note that the lift axis 17 intersects the steering axis 8 at a
point below the longitudinal center of gravity axis 18, as best
seen in FIG. 1. However, once the craft begins to lean to one side
or the other, this plane, in which the longitudinal center of
gravity axis 18 and the steering axis 8 lie, shifts to one side of
its previous vertical position. This shifting occurs generally
about a point located near the foils 11 on the front strut 6. With
the changed attitude of the watercraft, the water pressure now
exerts a force on the total submerged area of the forwad strut 6.
Since the area of the front strut located rearwardly of the
steering shaft 8 is greater than the portion located forwardly of
the steering axis, and since the front strut is free to rotate, the
resisting force of the water tends to cause the forward strut to
turn in the direction of leaning of the hull. The watercraft is
then drawn by the steering action of the front strut into a turn of
sufficient magnitude to produce an opposing centrifugal force on
the craft. This opposing centrifugal force produces a righting
force permitting the craft to remain stable in the lean while
turning in the direction of lean.
In such a turn, the lift force L of the front foils 11 remains
fairly constant in magnitude and acts upwardly in the plane of the
front strut 6 in a direction generally perpendicular to the foils
11. However, as best illustrated in FIG. 4, this lift force on the
front strut no longer acts upwardly in a plane which includes the
support axis 8 and the longitudinal center of gravity axis 18, but
instead acts upwardly along the axis 17 which intersects the
support axis 8 at a point below the axis 18. Thus, an extension of
the axis 17 disposes it on the side of the axis 18 toward which the
watercraft is leaning. This causes the lift force L to generate a
torque about the longitudinal center of gravity axis Gc, which adds
to the righting moment generated by the inward turning of the
craft.
The magnitude of the righting force produced by the lift L of the
forward foils during a turn is a function of various factors,
particularly the speed of the craft and the steering axis
inclination or angle A. The length of the torque arm between the
lift force L and the longitudinal center of gravity axis Gc becomes
longer as the degree of turn is greater, resulting in an increase
of the righting torque. Consequently, the height of the
longitudinal center of gravity axis Gc of the craft above the water
line may be raised, by increasing the load in the hull, without
impairing the stability of the hydrofoil watercraft and, in
general, a greater load will make the craft more stable.
The longitudinally aligned rear hydrofoil strut 2 supports the rear
of the hull upon the foils 4 and is constructed in such a manner
that it tends to fall into line with the front strut as the craft
moves through the water. This self-centering characteristic is a
function of the inclined or angled orientation of the steering axis
8 relative to the hull and the rear strut, the freedom of the front
strut 6 to pivot about its steering axis 8, and the location of the
center of pressure of the front strut 6.
The property of self-centering results from the dynamics of
movement of an object through a medium and its tendency to conserve
mementum. Such conservation is optimum in straight and level travel
of the body. For a vehicle which interacts with a drag producing
medium such as water, the vehicle will orient itself to experience
the lowest drag. In the present invention the placement of the
struts at each end of the hull in longitudinal alignment produces
minimum drag. The longitudinal axis of the hull is parallel to its
direction of propulsion, and any tendency for the hull to yaw out
of this orientation causes the hull to pivot about the steering
axis 8 of the front strut 6. That is, since the front strut is free
to rotate or swivel, it will tend to always align itself with the
general direction of movement of the watercraft. In a yaw the plane
of the rear strut is not parallel to the direction of travel, and
therefore more drag is induced compared to the parallel condition.
Greater drag occurs as the yaw angle increases, with minimum drag
at a zero yaw angle. Consequently, the craft always tends toward
the zero yaw angle condition.
Whenever the rear strut is at some yaw angle relative to the
direction of travel of the watercraft, the strut begins to act like
a hydrofoil and generates a lift force acting in a direction toward
a rearward extension of the plane of the front strut. This lift
pulls the rear strut back into longitudinal alignment with the
plane of the front strut and thereby contributes to the
self-centering phenomenon.
As previously stated, the front strut is designed to align itself
with the direction of travel of the watercraft. When the watercraft
heels over in a turn, the planes of the front strut and rear strut
are therefore no longer aligned. This situation is analagous to the
previously described yaw condition of the hydrofoil watercraft.
Thus, the watercraft will tend to return to its most stable,
dynamic position, that of zero turn angle, and bring itself toward
an upright position in a straight line.
The righting forces described become greater as the speed of the
craft increases. At some speed the craft is substantially totally
self-righting and can be turned only when the front strut is
deliberately turned by the operator. In fact, due to the
self-centering action of the rear strut and foils, and the righting
forces resulting from the front strut and foils, turning of the
watercraft becomes increasingly more difficult as the weight and
speed of the craft increases. Therefore, the craft tends to remain
in its most stable configuration, with its longitudinal center of
gravity axis located directly in vertical alignment with the planes
of the front and rear struts, unless changed by deliberately moving
the front strut through some steering angle.
A further embodiment of the invention is illustrated in FIG. 5.
This embodiment is designed to ease the difficulty of steering,
particularly at higher craft speeds. More particularly, a pair of
oppositely connected ailerons 12 are substituted for fixed trailing
edges in the anhedral foils 4 mounted to the rear strut 2. Only one
side of the strut 2 and its associated foil 4 are shown, the foil 4
and aileron 12 on the opposite side being the same in construction.
The ailerons 12 are connected to usual bevel gears 13 which are
rotatable in opposite directions. Rotation of the gears 13 is
achieved by a control rod 14 which is geared to the gears 13 and
connected by means of pulleys, belts, or other mechanisms to the
steering wheel 10 or other steering means, as indicated
diagrammatically by the line 19 in FIG. 5 and as will be apparent
to those skilled in the art. Alternatively, such connection can be
made to a pair of pedals (not shown). This would permit movement of
the control rod 14 and the ailerons 12 to be made independently of
operation of the front steering wheel 10.
Movement of the ailerons 12 causes a difference in lift on the pair
of foils 4, and this lift differential develops a torque acting
about the longitudinal center of gravity axis Gc of the hull.
Consequently, the craft leans in a direction opposite the direction
of such strut displacement. This leaning is accompanied by the
previously described self-righting and self-centering operation,
which establishes the craft in a stabilized turn.
The present watercraft preferably includes some means of water
surface sensing, and some means of stabilizing the hull at a proper
height above the sensed surface. However, satisfactory means for
accomplishing this are well known in the art, and a description
thereof is therefore omitted for brevity. Generally, it should be
noted that such surface sensing is needed only to locate the keel
axis in the vicinity of the front strut, and this can be
accomplished by strut mounted pressure sensors, electrically
sensitive height sensors, frequency prediction systems, or sonar or
lasar height finders.
The watercraft hull 1 is buoyant to support the watercraft in the
water, and is provided with multiple keel configurations to provide
planing at speeds less than foil support speeds. In this regard, as
the watercraft first picks up speed in the water, the forward and
rear foils begin to lift the hull out of the water. As the hull
rises it passes through a transitional, partially unstable
condition, until it becomes fully foilborne and the stabilizing
forces herein described begin to take effect. To provide additional
lateral and directional stability during this transitional phase,
the hull 1 is provided with a second keel 15 having a deeper and
sharper or more downwardly angularly inclined configuration
compared to the higher keel 16. These V-shaped keels 15 and 16 are
illustrated in FIGS. 1 and 2. The lower keel 15 is thinner and
deeper and provides lateral stability during the transition between
hullborne and foilborne modes. In addition, when the craft is in
full foilborne operation in heavy seas, the lower keel 15, in
combination with the parting effect of the front strut, softens the
shock of wave contact on the hull 1 and prevents damage from
unusually large waves.
As previously described, the rear strut is directly behind the
front strut and runs in its trail. The front strut is preferably
constructed with a transverse or blunt trailing edge, as shown in
FIG. 6, to provide a trailing air pocket within which the rear
strut 2 can run. This air pocket contributes to establishment of
self-centering forces by the rear strut and lowers the rear strut
and foil drag. As also seen in FIG. 6, the trailing edge of the
rear strut is also preferably made blunt for improved watercraft
performance.
The foils 4 and 11 are preferably substantially delta-shaped in
configuration, as seen in FIGS. 1, 3, 5 and 6. Delta-shaped foils
are less susceptible to damage and rupture at higher watercraft
speeds. At the high speeds attainable through use of the two point
hydrofoil system herein described, any object in the path of the
foils strikes them with great impact. However, the direction of
impact on delta-shaped foils is not perpendicular to the foil
leading edges, but is at an angle. Consequently, trash and flotsam
tend to be shed by the foil without damage. In general, however,
the shape of the foils 4 and 11 is not critical, the only important
criteria being to provide sufficient total area to provide the
desired lift.
To reduce generation of upsetting forces during a turn, the front
foils 4 preferably are horizontally oriented, that is, project
normally of the front strut sides. However, the rear foils 11 are
preferably anhedral in orientation to reduce the possibility that
their tips might pierce the surface of the water in a severe turn
and destroy the lift of the tip through entry of air along the foil
surface. This construction also provides greater directional
stability at the rear of the watercraft.
It will be apparent from the preceding description of the operation
of the present two-point self-stabilizing hydrofoil watercraft that
the watercraft is relatively simply constructed, primarily
requiring critical design attention only to the struts and foils
for achieving stability. The watercraft is inherently balanced and
dynamically stable, particularly laterally, and the shock of wave
action is transmitted directly through the keel line of the hull,
which permits utilization of lighter hull construction. All of
these factors enable the craft to operate at higher speeds, in
rougher seas, and with a smoother ride, compared to prior art
vehicles of analagous purpose.
The foregoing is illustrative of the principles of the present
invention and numerous modifications can be made without departing
from the scope of the invention as defined in the appended claims.
Thus, the embodiments illustrated are only preferred and the
hydrofoils 4 and 11 can be varied in shape and angle of
orientation; the front strut can be varied in shape; the steering
axis angle of inclination can be varied to suit the design criteria
of the particular application; the propulsion means can be varied,
even to include water reaction and air reaction devices; and the
steering mechanism may also take many forms, including automatic
computer controlled or manually operated mechanisms. It is not
intended to limit this invention to the exact construction and
operation shown and described, and equivalent modifications are
considered to be within the contemplation and scope of this
invention.
The principles and apparatus described in this invention are
applicable to all types of watercraft and are not necessarily
limited to hydrofoil watercraft. That is, the dynamic righting
forces created by a movable, partially or fully submerged front
strut, and the self-centering forces developed by the rear strut,
can also be used to provide lateral stability for watercraft in
which the hull remains partially submerged within the water, or
planes on the water's surface. The righting forces would take
effect as the hull leans to one side or the other and while the
watercraft is turning. Consequently, the present invention
encompasses planing watercraft as well as completely foilborne
watercraft.
* * * * *