U.S. patent application number 10/277186 was filed with the patent office on 2003-05-15 for pleasure craft.
This patent application is currently assigned to ARGONAUTIC. Invention is credited to Vos, Ronald Adriaan Gerrit.
Application Number | 20030089293 10/277186 |
Document ID | / |
Family ID | 19774193 |
Filed Date | 2003-05-15 |
United States Patent
Application |
20030089293 |
Kind Code |
A1 |
Vos, Ronald Adriaan Gerrit |
May 15, 2003 |
Pleasure craft
Abstract
The present invention relates to a craft comprising a surface
module, a single submerged body and a one strut for connecting the
body to the module, wherein said strut is operative for moving the
submerged body relative to the surface module from a extended
position of the body in which the surface module is arranged in
vertically spaced relation thereabove to a retracted position in
which the submerged body and the surface module together form a
displacement hull, wherein the hull of the surface module comprises
a hollow recess for receiving the submerged body in the retracted
position, wherein the recess and the upper part of the submerged
body have a mating form such that the hull of the craft in the
retracted position of the submerged body has a drag reducing
form.
Inventors: |
Vos, Ronald Adriaan Gerrit;
(Prinsenbeek, NL) |
Correspondence
Address: |
Richard L. Byrne
WEBB ZIESENHEIM LOGSDON ORKIN & HANSON, P.C.
700 Koppers Building
436 Seventh Avenue
Pittsburgh
PA
15219-1818
US
|
Assignee: |
ARGONAUTIC
Prinsenbeek
NL
|
Family ID: |
19774193 |
Appl. No.: |
10/277186 |
Filed: |
October 21, 2002 |
Current U.S.
Class: |
114/284 |
Current CPC
Class: |
B63B 2001/145 20130101;
B63B 1/107 20130101; B63B 39/00 20130101; B63B 1/042 20130101; B63B
1/244 20130101; B63B 1/246 20130101 |
Class at
Publication: |
114/284 |
International
Class: |
B63B 001/22 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 22, 2001 |
NL |
1019207 |
Claims
1. Craft comprising a surface module, a single submerged body and a
one strut for connecting the body to the module, wherein said strut
is operative for moving the submerged body relative to the surface
module from a extended position of the body in which the surface
module is arranged in vertically spaced relation thereabove to a
retracted position in which the submerged body and the surface
module together form a displacement hull, characterized in that the
hull of the surface module comprises a hollow recess for receiving
the submerged body in the retracted position, wherein the recess
and the upper part of the submerged body have a mating form such
that the hull of the craft in the retracted position of the
submerged body has a drag reducing form.
2. Craft according to claim 1, wherein a propeller is mounted to
the submerged body and wherein the recess in the surface module is
further recessed at the aft section thereof for receiving the
propeller in the retracted position of the submerged body.
3. Craft according to claim 2, wherein strakes are arranged along
the edges of the further recess in the hull.
4. Craft according to one of the preceding claims, wherein a rudder
is attached to the surface module, said rudder being located in the
wake of the propeller in the retracted position of the submerged
body.
5. Craft according to one of the preceding claims, wherein the
submerged body has a raised bow and a streamlined shape with a
flattened circular cross-section being axi-symmetrical at the
stern.
6. Craft according to one of the preceding claims, wherein the
submerged body comprises at least two pairs of hydrofoils being
mounted to the submerged body along the length thereof, the
hydrofoils of each pair lying on both sides of the submerged
body.
7. Craft according to claim 6, wherein the place of attachment of
each hydrofoil on the submerged body is determined dependent on the
pressure distribution generated by water flow along the submerged
body in extended position and/or vortex generation around the
hydrofoils.
8. Craft according to claim 6 or 7, wherein a winglet is fitted to
the tip of at least the aft pair of hydrofoils.
9. Craft according to one of the claims 6-9, wherein the hydrofoils
of each pair are placed in a negative dihedral.
10. Craft according to one of the claims 6-9, wherein each
hydrofoil is rotatable around its longitudinal axis.
11. Craft according to one of the preceding claims, wherein the bow
section of the submerged body plastically deforms when hitting a
obstacle.
12. Craft according to claim 11, wherein the bow section is
provided with a tank filled with water and bounded with a nozzle
shaped closure which opens at a predetermined pressure in the
tank.
13. Craft according to one of the claims, wherein the connection
between the strut on the one side and the submerged body and/or the
surface module on the other side fails at a predetermined impact
level upon hitting an obstacle.
14. Craft according to one of the claims 6-13, further comprising a
control unit for controlling the rotation of each hydrofoil.
15. Craft according to claim 14, further comprising xyz roll rate
sensors for providing xyz roll rate information of the craft.
16. Craft according to claim 15, further comprising a GPS for
providing Lat/Long, attitude and directional information of the
craft.
17. Craft according to claim 16, wherein the xyz roll rate
information is used as input signal and the GPS information is used
as reference signal of the control unit.
18. Craft according to claim 16, wherein the xyz roll rate
information is used as input signal of a rate input controller and
wherein the GPS information is used as input signal of an attitude
input controller, said controllers providing dual redundant input
signals for the control unit.
19. Craft according to claim 18, wherein the control unit averages
the input signals of the controllers for controlling the angles of
the hydrofoils between safety constraints.
20. Craft according to claim 19, wherein the control unit comprises
an actuator for each hydrofoil.
21. Craft according to claim 20, wherein the hydrofoil actuators
each comprise separate control and actuating elements supplied from
separate power sources integrated into a single unit.
Description
[0001] The present invention relates to craft comprising a surface
module, a single submerged body and a strut for connecting the body
to the module, wherein said strut is operative for moving the
submerged body relative to the surface module from a extended
position of the body in which the surface module is arranged in
vertically spaced relation thereabove to a retracted position in
which the submerged body and the surface module together form a
displacement hull.
[0002] Traditionally, ship hull shapes can be classified in three
categories: displacement designs, semi-displacement designs and
planing high speed designs. The maximum speed for displacement
designs is limited by the wave system generated, whereas
semi-displacement designs can enter the planing state using much
power and generating excessive waves. In the planing state, the
crests of surface waves will result in vertical acceleration of the
hull, which has a direct influence on passenger comfort. High speed
hull shapes have poor low speed efficiency in terms of kg fuel/m
and the efficiency at cruising speed is at best similar to the
efficiency at top speed. Innovative designs like hydrofoils or
small water area twin hull crafts enable high speeds without
compromising passenger comfort in a sea state but have important
disadvantages. The disadvantages are among others a notably
complicated propulsion, big exposed hydrofoils in case of the
hydrofoil designs and, in case of a twin hull craft, habitable
volume lost between the hulls and a beam that is less suited for
harbors with a traditional layout.
[0003] A combination of hydrofoils and a central submerged body,
i.e. a hydrofoil small water area ship, can result in a craft with
a propulsion of high efficiency because of the possibility to place
a propeller in a approximately uniform flow field of water
accelerated by surface drag. In such a craft the hydrofoils can be
designed not to extend beyond the beam of the hull, whereas no
habitable volume is lost. Such a design is known from U.S. Pat. No.
3,730,123. However an optimization of habitable volume and draught
as well as energy efficiency for the different speed ranges is not
achieved.
[0004] For ship carrying passengers, the required habitable volume
is directly related to the purpose of the ship (how many passengers
and crew, what kind of voyage at which comfort level) and in the
concept phase maximized within practical and aesthetic limits. A
shallow draught can dramatically increase the area of inland
waterways which can be navigated. Inland waterways are, for the
average passenger, much more attractive than the open sea. A
comparatively high cruise speed with a high comfort level in an
average sea state can increase the area of the globe that can be
reached within a constrained period (e.g. a holiday period). Thus,
the craft should ensure safety, passenger comfort or minimization
of wave generation for all speed ranges, energy efficiency and
exciting maneuverability.
[0005] According to the invention these objectives are met with a
craft characterized in that the hull of the surface module
comprises a hollow recess for receiving the submerged body in the
retracted position, wherein the recess and the upper part of the
submerged body have a mating form such that the hull of the craft
in the retracted position of the submerged body has a drag reducing
form.
[0006] In retracted position the surface area of the recess of the
surface module and the surface area of the upper part of the
submerged body and the surface area of the struts have no contact
with a boundary layer of water. As a consequence these area's have
no relevant contribution to surface drag and overall surface drag
is relatively low. Furthermore minimal draught is obtained with a
predetermined minimum standing height.
[0007] It is noticed that U.S. Pat. No. 3,590,765 discloses a
reconfigurable vessel comprising a surface hull module and a
submerged body connected thereto by means of two struts which can
be actuated to lower the surface hull module to seat on the water
surface in order to reduce draft of the vessel for navigating in
shoal water or for docking. This vessel however does not have a
conformal recess for receiving (part of) the submerged body.
[0008] Preferably the recess is further recessed at the aft section
of the surface module for receiving a propeller mounted to the
submerged body in the retracted position thereof. When the
submerged body is retracted, the massive flow disturbance for the
propeller caused by the hull can be prevented by incorporating a
streamlined further recessed part in the conformal recess enabling
an additional flow around the submerged body with the result of an
even flow-field for the propeller. The aft recess has a narrowing
part downstream of the propeller to ensure a positive pressure at
the top and to prevent ventilation of the propeller resulting in a
loss of thrust. Strakes arranged along the edges of the aft recess
in the hull prevent parasitic resistance due to water flowing into
the aft recess. For steering the craft in a slow speed mode a
rudder is attached to the surface module. The rudder is located in
the wake of the propeller in the retracted position of the
submerged body.
[0009] The submerged body has preferably a raised bow to improve
pressure distribution with a positive effect in the near surface
flow. Furthermore the body has a streamlined shape with a flattened
circular cross-section being axi-symmetrical at the stern. The
cross-section is flattened to ensure that the standing height and
draught constraints are not exceeded.
[0010] To enable different modes during navigation, the submerged
body comprises at least two pairs of hydrofoils, said pairs being
mounted to the submerged body along the length thereof, whereas the
hydrofoils of each pair are attached on both sides of the submerged
body. Next to a slow speed mode (or full displacement mode), a
planing mode and a foil born mode can be obtained. When changing
from slow speed mode to foil born mode, the submerged body is
extended by operation of the struts. The place of attachment of
each hydrofoil on the submerged body is determined dependent on the
pressure build-up generated by water flow along the submerged body
in extended position. The placement of the hydrofoils should be
such that they positively influence the wave pattern generated.
[0011] In a preferred embodiment a winglet is fitted to the tip of
at least the aft pair of hydrofoils to reinforce them. When the
hydrofoils of each pair are arranged in a negative dihedral, the
tips can be placed on the ground to support the craft on the ground
in a leveled dried up position or in shallow water harbors, e.g. to
raise the hull of the surface module above water level to prevent
bio-fouling.
[0012] In a further preferred embodiment each hydrofoil is
rotatable around its longitudinal axis. The rotatable hydrofoils
are set to optimum angles to minimize overall drag and reducing the
waves generated when the craft is not in a foil born mode.
[0013] Directional control for low speed conditions is ensured by a
low-speed rudder attached to the surface module in the wake of the
propeller when the submerged body is retracted. The helmsman can
select a switch so that at or above a predetermined transition
speed the control system can quickly select an angle of attack
setting for foil born mode. A fast selection limits the energy lost
in the transition where the hydrofoils have considerable profile
drag and induced drag and where the surface and pressure drag of
the surface module is still high. In foil born mode the hydrofoils
are controlled to retain straight and level "flight" or to
(partially) follow the contour of long (ocean) waves or to make
turns according to inputs from the helmsman or navigation system.
As a method to maximize the excitement of the ride, the control
system determines safety constraints of immersion and (aggressive)
bank following from joystick inputs. This system can even allow the
craft to jump. In the system, foil surface breaking with resulting
ventilation and loss of lift is monitored and predicted to
safeguard spin out situations.
[0014] The center of gravity and the floatation center for the
craft with an extended submerged body ensure a positive righting
arm for all positions. When a negative righting arm for a craft
with a retracted body is considered a problem, the craft can be
fitted with an emergency "extend" function. The control systems
furthermore monitors and predicts the breaking of the surface by
the propeller and regulates the power generated by the generators
and the excitation of the electric motor to prevent overspeed
conditions. Apart from that, the control system can select an angle
of attack for each hydrofoil pair that results in an emergency
stop. In such a situation the hull takes a nose up position so that
deceleration and gravity combine to an acceleration vector normal
to the deck which prevents passengers from falling or being
launched from their seats.
[0015] The nose of the submerged body is provided with an
integrated water tank having a closure shaped as a nozzle and
provided with a cap which breaks at a predetermined pressure. When
the submerged body of the craft hits an object the nose will
compress and the pressurized water passes through the nozzle shaped
closure to the surrounding. The outflow of high pressure water will
absorb the impact energy and prevent serious damage to the craft.
Also the attachment of the struts to submerged body is calculated
to break off at a predetermined strain level which can be absorbed
by the hull construction. This will further reduce the risk that
impacts at high speeds result in a loss of the craft.
[0016] To summarize, the invention can result in embodiments that
better meet the objectives than all previous hull shapes and
hydrofoil arrangements.
[0017] The present invention will be further elucidated with
reference to the accompanying drawings. In the drawings shows:
[0018] FIG. 1 a preferred embodiment of a craft comprising a
surface module and a retracted submerged body;
[0019] FIG. 2 the surface module of FIG. 1 with an extended
submerged body;
[0020] FIG. 3 a side view of the craft with the retracted submerged
body;
[0021] FIG. 4 a side view of the craft with the extended submerged
body;
[0022] FIG. 5A a front view, FIG. 5B a back view and FIG. 5C a
partially side view of the submerged body;
[0023] FIG. 6 a cross-section of the craft near the recessed aft
section;
[0024] FIG. 7 a longitudinal section of the recessed aft
section;
[0025] FIG. 8 wave patterns generated by the submerged body and the
hydrofoils in foil born mode;
[0026] FIG. 9 the hydrofoil dihedral in a banked turn;
[0027] FIG. 10 the craft in a dried up position;
[0028] FIG. 11 the craft with extended submerged body in a
harbor;
[0029] FIG. 12 wave patterns generated by the submerged body and
the hydrofoils in a low speed mode;
[0030] FIGS. 13A-D different angle settings of the hydrofoils;
[0031] FIGS. 14A en 14B side views of the submerged body with
crushable nose;
[0032] FIG. 15 a breakage of the connection between the struts and
the submerged body;
[0033] FIG. 16 an emergency stop maneuver;
[0034] FIG. 17 a jump maneuver;
[0035] FIG. 18 placement of sensors and input devices;
[0036] FIG. 19 a schematic overview of a navigation and control
system;
[0037] The shape of the craft according to the invention is
generally shown in FIGS. 1-4. The craft comprises a surface module
1, a single submerged body 2 and two struts 5 for connecting the
body 2 to the module 1. The struts 5 are operative for moving the
submerged body 2 relative to the surface module 1 from a retracted
position (FIGS. 1 and 3) to a extended position (FIGS. 2 and 4) of
the body 2.
[0038] The surface module 1 has a recess 6 conformal to the upper
section 3 of the submerged body 2. In the extended position of the
submerged body 2, the recess 6 is exposed to waves but will not
impair directional stability nor induce vertical loads (wave slam)
because of the linear edge and smooth curved shape. Two pairs of
hydrofoils 4, 12 are attached to the submerged body 2. One pair 12
at the front part and one pair 4 at the aft part of the submerged
body 2. The hydrofoils 4, 12 of each pair are located on both sides
of the submerged body 2.
[0039] The submerged body 2 has a central high-skew propeller 8
driven by an electrical motor which is powered by generators in the
surface module 1. The length of the submerged body 2 should be such
that the position of the two pairs of hydrofoils 4, 12 can have the
desired influence on the wave pattern induced by the submerged body
and that the influence on the flow field in front of the propeller
8 is not to much disturbed. Also the front of the submerged body
should be somewhat cut back from the bow of the surface module to
prevent damage when mooring. This will result in a submerged body 2
which is somewhat shorter than the surface module 1. The optimum
diameter/length ratio for a submerged body 2 with a given
displacement resulting in a minimum surface drag and pressure drag
will result in an unpractical large diameter. The diameter is
constrained by the requirement of a flat passenger's floor 9 being
as low as practical to ensure adequate vertical space without
gaining undesirable high deckhouses, and the requirement of a
shallow draught as determined by the water line 10 and the keel
line 11 of the craft (see FIG. 3). The submerged body 2 has a bow
and stern part connected by a long part with a parallel top line 13
and keel line 11.
[0040] When in foil born mode the control system will steer the
hydrofoils 4, 12 (FIG. 4). The level of the surface module 1 in
relation to the water surface (with an average water line 10 as
indicated in FIG. 4) is maintained in such a way that instances of
waves touching the hull of the surface module and ventilation of
hydrofoils 4, 12 or propeller in troughs between wave crests are
minimized. When the length and frequency of the waves, as sensed by
the control system, are suitable a wave contour "flight" path can
be followed.
[0041] An axi-symmetrical streamlined submerged body 2 can be an
optimal choice when optimizing for performance and endurance. A
streamlined submerged body with a bigger volume and better
(near-surface) pressure drag performance is shown in FIG. 5. The
submerged body retains the axi-symmetrical stern 19 (FIG. 5A) with
the integrated propeller and the bow 20 is raised (FIG. 5B and C)
to improve pressure distribution with a positive effect in near
surface flow. The submerged body 2 has a flattened circular
cross-section. Finally, placement of the front hydrofoils 12 can be
optimized for cruise speed so that the low drag laminar flow
conditions can extend for a significant part of the submerged
body.
[0042] The boundary of the recess 6 in the hull of the surface
module is indicated with reference number 24 in FIG. 6. The recess
8 is further recessed at the aft section of the craft (see upper
drawing in FIG. 6) such that a streamlined aft recess 23 is
obtained. This aft recess 23 enables an additional flow around the
streamlined body resulting in an even flow-field for the propeller
8. FIG. 6 shows a cross-section just in front of the propeller hub,
whereas FIG. 7 shows a longitudinal section just above the
centerline of the submerged body. The aft recess 23 has a narrowing
part 26 downstream of the propeller 8 to ensure a positive pressure
at the top of the aft recess 23 (which is at waterline level) and
prevent ventilation of the propeller. The hull is fitted with two
strakes 27 which prevent loss of dynamic pressure for the
downstream flat surfaces of the hull when the craft is in a (non
foil born) planing mode.
[0043] In foil born mode the flows around the submerged body and
the flows as influenced by the hydrofoils 4, 12 generating lift can
be influenced by the shapes and angle setting of these parts such
that their interaction has a positive result on the overall wave
drag (and wave energy causing damage and nuisance). This is
depicted in FIG. 8. Line 29 is a section through the wave pattern
as generated by the submerged body. Line 31 is a section through
the wave pattern as generated by the pairs of hydrofoils 4, 12 and
line 30 is a section through the wave pattern for the combination
of the submerged body 2 and the hydrofoils 4, 12.
[0044] To meet the objective for an exiting high-speed
maneuverability the hydrofoils 4, 12 are placed in a negative
dihedral to prevent ventilation when making steep turns. To make
the turn as steep as possible an edge 32 of the hull can touch the
water (see FIG. 9). The angles for the aft 4 and the front 12
hydrofoils are indicated with reference numbers 34 and 33
respectively. Furthermore the dihedral is used for small yaw
corrections.
[0045] The negative dihedral helps in providing support in drying
up conditions (see FIG. 10). The control system has an algorithm to
adjust hydrofoil angles and to move the submerged body relative to
the surface module when preparing for a dried up position. A
similar algorithm can be used in the harbor (see FIG. 11) to raise
the surface module above the water level. To increase the strength
of the hydrofoil tips a winglet shaped element 35 is fitted to each
aft hydrofoil 4. When properly shaped this winglet 35 has some
positive effect on hydrodynamic performance.
[0046] To minimize drag in the low-speed mode (see FIG. 11) the
angles of the hydrofoils 4, 12 are being set in such a way that the
interaction of the pressures generated by the hull of the surface
module in combination with the retracted submerged body and the
pressures generated by the hydrofoils at this determined setting is
optimized. These pressures result in waves. In FIG. 12 these waves
are indicated by section line 38 for the surface module with
submerged body, section line 40 for the hydrofoils at angles 41, 42
and the resulting section line 39. In this mode the control system
can give inputs to the hydrofoils to increase roll stability The
hydrofoils are movable around their longitudinal axes standing at
right angels to the submerged body. The front hydrofoils 12 and the
aft hydrofoils 4 are shown in FIG. 12.
[0047] The collapsible forward section of the submerged body is
shown in FIG. 13. When a hard object 51 hits the submerged body,
the front section 50 compresses and water 49 is forced through the
nozzle shaped closure 48. The forward bulkhead 47 is strong enough
to retain its integrity even when hitting objects at top speed.
However at top speed the loads on the structure will be such that
structural damage is inevitable. To prevent the connection between
the struts 5 and the surface module 1, which contains moving
elements, from failing and the underside of the hull potentially
tearing with a high risk of losing the craft, the connection
between the struts 5 and the submerged body 2 is designed such that
in case of high deceleration forces being transmitted to the
surface module 1 the struts 5 can rotate (see FIG. 15). This
rotation induces uneven shear forces to the shear-pins 52, 53 that
connect the struts 5 to the submerged body 54. As a result the
connection fails leading to a separation of the submerged body 2
and the surface module 1.
[0048] The control system enters an emergency stop sequence when
the throttles are slammed back in foil born mode (see FIG. 16). The
generators are throttled and the electric motor is slowed down
within limits to prevent damage to the motor or propeller. The aft
hydrofoils 4 are set to induce a pitched angle of the craft so that
the resulting vector 56 from the dynamic and static forces of the
water on the craft result in a force acting on the passengers not
deviating from normal gravity. The front hydrofoils 12 are set to
maintain a certain depth in the water to prevent ventilation. The
craft makes a planing "landing" on the rear end of the hull.
[0049] The control system sets limits to an envelope for radical
maneuvers under helmsman control. FIG. 17 shows a jump maneuver.
Coming from the normal "flight" depth 57, the helmsman lowers the
craft 58, makes an aggressive pull up 59 when there is enough
vertical speed to clear the water surface 60 and than make a splash
landing 61.
[0050] FIG. 18 indicates the location of the non-standard sensors
and the input devices. The four antennae 62, 63, 64, 65 of the
Global Positioning System (GPS) are placed on the roof of the
pilothouse in optimal view of overhead GPS satellites. The combined
three-axis angular rate sensor 66 is located near the center of
gravity at the level of passengers sitting in the craft. The
submerged body immersion (water surface distance) sensors 69, 81
are located near the tip of the submerged body facing towards the
surface. The input devices are a joystick 67 for bank (and
consequent turn) and depth input and a throttle 68 for revolutions
of the propeller and emergency stop input. The joystick 67 has a
trim button for trimming the craft in case of an unavailability of
the GPS attitude. Switches and buttons are not show.
[0051] FIG. 19 indicates the navigation and control system.
Extended or retracted mode is selectable in the control panel 89.
Using this control panel 89 also autopilot having different options
and the control parameters which determine comfort level and energy
use can be selected. The control parameters are for example
"comfort" meaning minimized accelerations, "economy" meaning
minimized hydrofoil angle changes, and "performance" meaning
maximised safe turn rate and jump capability. Also special
functions, such as levelling when drying up, can be selected and
system condition and maintenance information are presented in the
control panel. The control systems has a dual redundant
architecture with two controllers 87 and 88, each using different
input signals. Controller 87 obtains input signals from the
xyz-roll rate sensor 66, immersion sensor 69, speed sensor 86 and
joystick 67, whereas controller 87 obtains the input signals
GPS-attitude and speed from GPS antennae 62-65 and further input
signals from immersion sensor 81 and joystick 67. Both controllers
87, 88 are connected to the control unit fo controlling the four
hydrofoils 90-93. The control unit comprises four duplex integrated
servo actuator 94-97 which control the angular position of
hydrofoil 90-93 respectively. A processor 83 is used for the
man-machine interface, interfacing to other systems and system
monitoring. This processor 83 connects to the different system
elements through a network, schematically depicted as 98 and has a
standardised (NEMA) network interface 99. Both sides of each duplex
integrated servo actuator 94-97 have a separate power supply. The
control system is set up in such a way that failure of a single
controller 87, 88, the network 98, the processor 83 or one side of
a duplex integrated servo actuator 94-97 will not preclude foil
born navigation (with certain restrictions). For an extended
non-foil born mode, an extended foil born mode and retracted slow
speed mode different settings and limits are used. The joystick 67
has a "foil born" switch so that, when selected, the controllers
87, 88 switch the hydrofoils 90-93 settings when the speed through
the water reaches the predetermined transition speed. The
controller 88 monitors wave-height and wavelength measured by the
submerged body immersion sensor 81 in combination with GPS. When
wavelength, wave-height and periodicity are suitable, a "Soll"
flight path following a wave contour is established. The
information on the wave situation is monitored by the processor 83
and control limits are applied to the selection (or automatic
de-selection) of the performance settings.
[0052] The invention relates to a ship configuration which is
variable. There is provided a craft with a retractable submerged
body fitted with movable hydrofoils controlled by a full authority
control system to optimize three speed ranges, namely a low speed
displacement mode (with the submerged body retracted), a cruise
mode where the main hull is lifted above water surface and lift is
generated partly by flotation forces and partly by the hydrofoils,
and a high speed mode where the hydrofoils enable tight control on
safety margins and passenger comfort and high maneuverability.
[0053] While the foregoing description and accompanying drawings
represent preferred embodiments of the present invention, it will
be obvious to those skilled in the art that various changes and
modifications may be made therein without departing from the spirit
and scope of the present invention.
* * * * *