U.S. patent number 3,897,744 [Application Number 05/238,681] was granted by the patent office on 1975-08-05 for high speed semisubmerged ship with four struts.
Invention is credited to Thomas G. Lang.
United States Patent |
3,897,744 |
Lang |
August 5, 1975 |
High speed semisubmerged ship with four struts
Abstract
A high speed ship is formed of at least one elongate hull
section submerged completely beneath the water's surface supporting
a platform above the surface waves by a plurality of struts
dependent from the platform to provide support and stabilization by
reason of their configuration and location. High speed dynamic
pitch stability is ensured by including a stabilizer member on the
aft portion of the submerged hull having a horizontally oriented
control surface sufficiently sized to locate the greatest
composite, vertical pressure surface substantially aft of the
ship's centroid. Controlling the angle of the stabilizer member in
accordance with changing wave conditions and speed provides a
highly stable cargo transport capability as well as a superior
weapons platform.
Inventors: |
Lang; Thomas G. (San Diego,
CA) |
Family
ID: |
26895610 |
Appl.
No.: |
05/238,681 |
Filed: |
March 27, 1972 |
Related U.S. Patent Documents
|
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
200252 |
Nov 18, 1971 |
|
|
|
|
20204 |
Mar 17, 1970 |
3623444 |
Nov 30, 1971 |
|
|
Current U.S.
Class: |
114/61.14;
114/277; 114/278 |
Current CPC
Class: |
B63B
1/107 (20130101); B63B 1/288 (20130101); B63B
39/06 (20130101); B63B 1/286 (20130101) |
Current International
Class: |
B63B
39/00 (20060101); B63B 39/06 (20060101); B63B
1/24 (20060101); B63B 1/16 (20060101); B63B
001/12 () |
Field of
Search: |
;114/61,66.5H,126,152,43.5,.5D,16F |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Blix; Trygve M.
Assistant Examiner: Goldstein; Stuart M.
Attorney, Agent or Firm: Sciascia; Richard S. Johnston;
Ervin F. Keough; Thomas Glenn
Government Interests
STATEMENT OF GOVERNMENT INTEREST
The invention described herein may be manufactured and used by or
for the Government of the United States of America for governmental
purposes without the payment of any royalties thereon or therefor.
Parent Case Text
This is a division, of application Ser. No. 200,252, filed Nov. 18,
1971 of Thomas G. Lang for "High Speed Ship with Submerged Hull"
which was a copending divisional of Ser. No. 20,204, filed 3-17-70
now issued U.S. Pat. No. 3,623,444 issued Nov. 30, 1971 of Thomas
G. Lang for "High Speed Ship with Submerged Hulls."
Claims
What is claimed is:
1. A high speed marine vessel having a static and dynamic stability
comprising:
a platform member;
two parallel elongate hulls operationally disposed below the level
of surface waves laterally separated a distance equal to at least
two hull diameters each hull is provided with a canard fin mounted
on the forward portion of each hull for improving said
stability;
a first water surface piercing strut member shaped with a hydrofoil
cross-sectional configuration for reduced spray and wave drag and
reaching from the forwardmost extensions of each elongate hull and
a second water surface piercing strut member shaped with a
hydrofoil cross-sectional configuration for reduced spray and wave
drag and reaching from the aftmost extensions of each elongate hull
to support said platform member, both of the first strut members
lie in the same forward lateral projection and both of the second
strut members lie in the same aft lateral projection, said first
strut members and said second strut members are sized to present a
reduced lateral water projection area and are sufficiently
longitudinally separated to enhance said stability; and
a pair of opposed cantilevered vanes reaching toward one another
from separate ones of said elongate ulls operationally disposed
below the level of said surface waves mechanically coupled to said
hulls and longitudinally disposed to ensure the creation of the
vanes' dynamic center of vertically exerted pressure substantially
aft the centroid of said marine vessel to yet further improve said
stability.
Description
BACKGROUND OF THE INVENTION
In relatively calm seas, conventionally designed ships attain a
rate of speed satisfactory for most requirements. As higher speeds
are called for, wave drag and water surface drag impose maximum
speed limitations. As the sea state varies, or more precisely, as
increased wave activity is encountered, speed and stability of
surface ships fall off markedly due to their inherent pitch, heave,
and roll tendencies. One well known way of avoiding wave drag to
achieve higher speeds is to construct a submarine configured ship
having a large sized hull portion disposed beneath the surface of
the waves with some sort of a control tower extending above the
water's surface. Another approach for increasing speed by limiting
water surface drag is to employ a pair of shallow draft,
semisubmerged hull portions in a catamaran-like fashion supporting
a platform above the surface of the water. While, in part, these
designs have been successful, they have not eliminated the major
speed and stability reducing limitations, that is, at high speed
under adverse sea conditions, dynamic pitch, heave, yaw, and roll
motions are not checked by the aforementioned designs. One attempt
at damping these objected-to motions combines the previous
teachings by separating a pair of submerged hulls, catamaran-like
fashion, by a rectangular cross-member extending between the
submerged hulls their entire length. However, as is readily
apparent, the effect of such a manner of construction is to magnify
pitching and heaving motions at high speeds in high sea states
since the aggregate of the total, vertically reacting, stabilizing
control surfaces, provided by the cross-member, is forward, or at
best, at the ship's centroid. To elaborate, wave action causing
upward or downward pressures ahead of, or near to, the centroid
magnifies pitch and heave. Another endeavor to achieve high speed
stability modifies a single, bulbous submerged hull with a pair of
dihedrally oriented struts supporting a control room above the
surface of the water and with a pair of nominally sized fins
carried on the rear of the hull. Although the mall fins provide a
marginal vertically reacting stabilizing surface, the aggregate of
the vertically reacting control surfaces is substantially at the
centroid of the vessel and high speed dynamic pitch, roll, and, in
particular, yaw remain an obstacle to acceptable performance. The
state-of-the-art does not ensure the markedly improved dynamic
stability achieved by including a large horizontally oriented
stabilizer on the aftmost extension of submerged hull portions,
hydrodynamically functioning in much the same manner as do the
vanes or feathers which aerodynamically stabilize the flight of an
arrow.
SUMMARY OF THE INVENTION
The present invention is directed to providing a high speed marine
vessel having improved static and dynamic stability including a
platform member and an elongate, submerged buoying means
interconnected by at least two water surface piercing strut
members. The strut members are disposed with sufficient lateral
spacing to ensure partial stability and with a sufficient
longitudinal reach to provide additional stability and are
configured in accordance with basic hydrodynamic design
considerations. Mounted on the elongate buoying means, a
horizontally oriented stabilizer sized to ensure the location of
the greatest vertically reacting control surface aft of the
centroid of the vessel, greatly increases the stability of the
marine vessel irrespective of the relative speed or surrounding sea
state.
Therefore, it is the prime object of the invention to provide a
marine vessel having superior dynamic stability over wide ranges of
speed under adverse sea states.
Yet another object is to provide a horizontally disposed stabilizer
sized and positioned to ensure the location of the vertically
reacting stabilizing surface substantially aft of the vessel's
centroid.
A further object of the invention is to provide a marine vessel
having a submerged hull portion supporting a platform by struts
configured to minimize surface wave reaction and to provide static
pitch, heave, and roll stability.
Still another object is to provide a high speed ship having
angularly controllable flaps sized and positioned to ensure
improved dynamic pitch, heave, and roll stability.
Another object is to provide a semisubmerged high speed ship having
submerged, selectively vented, horizontally disposed control
surfaces to ensure immediate correction for pitch, roll, and have
motions at high speeds under adverse sea states.
Another object is to provide a pair of elongate hulls sufficiently
laterally separated beneath the surface of the water supporting a
platform with a plurality of struts, all being configured for
minimal hydrodynamic drag and maximum hydrodynamic stability and
separated by a laterally extending stabilizer carried between the
hull's aft portions for markedly increasing dynamic stability.
Another object is to provide a high speed ship having a high speed
burst capability by including a system for ejecting drag reducing
polymers in a complete layer over a buoying submerged hull.
Still another object is to provide a high speed ship having a hull
portion disposed beneath the water surface including a plurality of
ballasting chambers, upon the selective evacuation thereof,
reducing the ship's draft to enable shallow water operation.
Still another object is to provide a high speed ship having means
for raising and lowering a platform section to provide both a
further reduced draft and a variable silhouette.
Another object is to provide a high speed ship configured to induce
minimal hydrodynamic turbulence making the ship adaptable for use
as a relatively silent sonar platform.
Yet another object is to provide a high speed vessel having the
dynamic and static stability to ensure reliable delivery of
ordnance.
An ultimate object of the instant invention is to provide a large
stable platform having an aircraft accommodation capability formed
from a plurality of the high speed ships.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an isometric view of a preferred form of the invention in
high speed, dynamic pitch, heave, and yaw stability.
FIG. 2a is a schematic top view taken along lines 2--2 in FIG.
1.
FIG. 2b is a schematic top view generally taken along lines 2--2 in
FIG. 1 showing high speed yaw correction.
FIG. 2c is a schematic top view taken along lines 2--2 in FIG. 1
also showing yaw correction.
FIG. 3a is a schematic top view taken along lines 3--3 in FIG.
1.
FIG. 3b is a schematic view generally taken along lines 3--3 in
FIG. 1 showing pitch correction.
FIG. 3c is a schematic, view taken along lines 3--3 in FIG. 1 also
showing pitch correction.
FIG. 4a is a top depiction of a variation of the rearwardly
disposed stabilizing means.
FIG. 4b is a top depiction of another variation of the stabilizing
means.
FIG. 5a is an isometric view of a stabilizer means having a single
variable single flap portion for imparting dynamic pitch
correction.
FIG. 5b is an isometric view of a stabilizer means having an
aileron capability for imparting dynamic pitch and roll
correction.
FIG. 5c is an isometric depiction of a vented stabilizer means.
FIG. 5d is an end view of the stabilizer means taken generally
along line 5de--5de in FIG. 5c, showing the creation of a
vertically exerted, pitch stabilizing force.
FIG. 5e is an end view of the stabilizer means taken generally
along line 5de--5de in FIG. 5c showing the creation of a
counterclockwise exerted, roll stabilizing force.
FIG. 5f depicts uninterrupted water flow over a vented hydrofoil
taken along line 5f--5f in FIG. 5c.
FIG. 5f' depicts creation of a downward lifting force over a vented
hydrofoil taken along line 5f--5f in FIG. 5c.
FIG. 5g is a top view of the vented stabilizer.
FIG. 6 is a bottom view of a modified form of the invention
additionally including a forwardly located lateral vane and a
longitudinally extending storage pod.
FIG. 6a is a variation of the embodiment shown in FIG. 6 having a
pair of delta-shaped vanes in place of a single forward vane.
FIG. 7 is a side view of the invention showing the longitudinal
location of the ballasting chambers, water level sensors, and the
viewing ports.
FIG. 8 is a cross-sectional view of a nose section of one of the
submerged hulls schematically showing a polymer ejection
system.
FIG. 9 is a front view schematically depicting an optionally
included variable height platform.
FIG. 10 is an alternate form of the preferred embodiment.
FIG. 11 is a frontal view of a variation of the preferred
embodiment of the invention showing a smaller platform supported by
angularly disposed struts.
FIG. 12 is a side view of a variation of the invention having only
a single, elongate hull.
FIG. 13 is a frontal view of the variation set forth in FIG.
12.
FIG. 14 is yet another variation having the supporting strut
depending from the platform to the aftmost extension of the
elongate hull.
FIG. 15 sets forth still another embodiment having a pair of
dihedrally oriented aft struts.
FIG. 16 is a frontal view of the embodiment set forth in FIG.
15.
FIG. 17 is a top view of several marine vessels secured together to
form a large stable platform.
FIG. 18 is a front view of the stable platform shown in FIG.
17.
FIG. 18a is a frontal view of a modified large stable platform.
FIGS. 19a, b, and c are typical types of hydrofoils employed in the
construction of the invention to minimize drag and turbulence
according to the overall design requirements of the vessel and the
conditions expected to be encountered.
FIG. 19d depicts creation of a lifting force by a fully wetted
hydrofoil.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Marine designers have long known that surface wave drag as well as
high sea states severely limit the maximum speeds and stability of
oceangoing vessels. Thus, a ship's efficiency, a scaler function of
the product of displacement and maximum speed divided by the
installed power, sharply falls off as surface wave drag is
intensified by high sea states.
Realizing this, the current state-of-the-art shows semisubmerged
ships that reduce, to some extent, a ship's surface wave drag and
static reaction to increasing sea states by locating substantially
all of the bulky, heavy machinery, fuel, supplies, etc. in a hull
section beneath the surface of the water as far as practically
possible since wave action caused by increasing sea states
diminishes exponentially as the depth below the surface
increases.
However, merely locating a bulky hull beneath the surface of the
water does not, by itself, materially provide for increased dynamic
stability, especially at high speeds in high sea states.
The configuration of the present invention ensures high speed
stability by strategically locating hydrodynamically designed
struts and stabilizers. In the preferred form depicted in FIG. 1, a
pair of essentially tubular-shaped parallel submerged hulls 40 and
50 provide a buoying support for a platform hull 20 through four
vertically extending struts 30, 31, 32, and 33.
Each of the hulls is formed in the shape of a torpedo and
advantageously incorporates the advancements of this particular
technology, for example, choice of the optimum width-to-length
ratios, weight distributions, power plant requirements, etc. Hulls,
having a circular cross-sectional area, are selected as being the
most suitable since this shape best resists water pressure when the
hulls are submerged several hull diameters below the surface,
although other shapes are optionally used.
Individual propellers 41 or 51 are connected through a suitable
transmission to individual power plants to provide the forward and
reverse thrust for locomotion and a rudder member 41a or 51a is
carried immediately aft each screw to ensure a responsive means for
controlling the marine vessel's heading. In the alternative to
having a massive transmission connected to each of the propellers,
they are of a variable pitch type enabling bidirectional thrust. In
either case, the blades are optionally streamlined blades,
base-vented blades, or super-cavitating blades depending on the
cruise, operational, and dash speeds desired. Although not shown in
the drawings, a pair of counterrotating propellers is included in
lieu of each single propeller, or a hydrojet propulsion nozzle is
carried on the aftmost end of each hull for propulsion and steering
purposes.
By mounting the rudders in line with the variable pitch propellers,
the marine vessel has a selective 360.degree. vectored motion
capability while substantially at rest and while. maintaining a
pre-established heading. With such a capability, cargo and
passenger transfer operations are facilitated as well as where a
precise hovering control is required to negate drift attributed to
ocean currents.
Platform 20, depicted in FIG. 1, has a typical commercial
superstructure for storing materials or supplies and, because of
its large flat area and inherent stability, includes a helo-landing
pad. The platform is constructed with watertight bulkheads, this
being especially desirable when modified for military applications
to provide emergency flotation if the elongate hulls become damaged
or ruptured. At this point, let it suffice to say that the platform
is fabricated to provide crews quarters, storage holds, ordnance
mountings, etc. in accordance with sound shipbuilding practices.
Novel modifications of the platform will be pointed out later in
the specification.
The supporting struts are in keeping with contemporary strength of
materials and hydrodynamic design criteria while providing a
minimal drag and noise producing turbulence. FIG. 19 sets forth
three representative sets of hydrofoils which are used as guides in
fabricating struts 30, 31, 32, and 33 to minimize drag and
noise-producing cavitation.
Cavitation is characterized by the formation of small cavities
filled with water vapor which appear and collapse in the low
pressure region of a hydrofoil surface. As cavitation increases,
there is a corresponding increase in the number and degree of such
undesirable noise characteristics such as noise, drag, surface
pitting, reduction in the lift, and unsteady performance.
Cavitation is avoided by reducing speed, in particular, but since a
highly stable, high speed marine vessel is the desired end,
cavitation with its attendant noise, unsteady performance, and drag
must be eliminated or brought within tolerable limits by the proper
choice of hydrofoils.
The hydrofoils in set 19a shows streamlined, fully wetted
hydrofoils having excellent performance characteristics, such as
freedom from noise and drag, at speeds up to the beginning of
cavitation. However, cavitation begins at moderate speed when these
foils are surrounded by a nominal pressure. Fully wetted hydrofoil
sections are quite satisfactory on the lower portion of the struts
when the water depth causes a considerable ambient pressure to
contain cavitation tendencies at higher speeds.
Other types are superventilated hydrofoils, see set 19b. These
hydrofoils operate with their surfaces entirely covered by a gas
such as air or engine exhaust, except for their water-breaking nose
portions. Having the strut sides covered by the gas cavity reduces
drag.
Fur sustained performance at high speeds, a third type hydrofoil, a
base-vented hydrofoil, see FIG. 19c, feeds gas from the atmosphere,
or from a centrally disposed duct, through a plurality of trailing
vent ports to create a steady gas envelope adjacent to the trailing
surface. The overall effect is to create a steady cavity of
noncondensing, noncollapsing gas in contact with its surface to
eliminate drag and noise produced by otherwise cavitating
hydrofoils. Thus, a routineer is free to choose a hydrofoil having
only one cross-sectional configuration or a composite hydrofoil
suitably stressed for the speed ranges expected and tolerable
noise. Since cavitation is more prone to occur at shallow depth
where there is less ambient presssure, a vertical strut which
varies from a streamlined strut at the bottom to a base-vented or
fully-vented strut at the top is a preferred form for very high
speed ships.
While struts composed of the three types of hydrofoils referred to
above are selected primarily as a weighted product of strength,
speed, and noise considerations, they all experience substantially
identical, composite forces when passing through water. No
resultant lateral force is created when the velocity of the ambient
water flow is equal on opposite sides and when the hydrofoil's
angle of attack is parallel with the direction of water flow.
Rotating a fixed hydrofoil angularly to cut across the direction of
water flow, schematically represented in FIG. 19 d by water flow
arrows, creates a positive pressure area on the upstream side of
the hydrofoil nose portion, shown as + signs, and further creates
an area of lower pressure on the downstream side of the hydrofoil
nose portion, indicated by the - signs. Hydrodynamic engineers have
mathematically and empirically established that a rigidly held
hydrofoil's center of pressure, under such flow conditions, is
approximately one-quarter of the hydrofoil's length behind its
leading edge. Therefore, the area of high pressure on the upstream
side of the hydrofoil and the area of low pressure on the
downstream side of the hydrofoil additively create a lifting force,
represented by the large arrow LIFT in FIG. 19d, on the hydrofoil's
center of pressure.
Thus, irrespective of the use of the hydrofoil, as a strut or as a
stabilizer, laws of hydrodynamics dictate that substantially
identical forces are created, the controlling factors being the
velocity and the angle of impingement of the surrounding water.
Conventional ships as well as catamaran-type ships experience
random forces which initiate yawing motions. These forces arise
from wave and wind action as well as the water medium's reaction to
the ship's propulsion plant.
A close examination of FIGS. 2a, 2b, and 2c shows how the
strategically located struts eliminate yaw. By looking downward
below the platform, the ship's centroid, or center of gravity, 25,
is located in the same lateral plane as are main supporting struts
30 and 31.
In calm seas with no lateral forces applied, as the marine vessel
travels at high speed in the direction indicated by the arrow in
FIG. 2a, no clockwise or counterclockwise yawing motions about
centroid 25 are experienced. Wave and water surface drag on the
vertically extending pressure surfaces, forming the lateral
surfaces of struts 32 and 33, produce equal and opposite,
self-cancelling moments about the centroid and the ship's heading
remains constant.
A possible yawing action, caused by wind and waves, imparts a
greatly exaggerated clockwise rotation, shown in FIG. 2b. With the
ship's direction of travel as indicated by the large arrow, the
passage of the struts through the water differential pressures to
be built up along the vertically extending pressure surfaces
forming on the lateral sides of all the struts. Forces, created by
the angularly impinging water, represented by subarrows struts 30a
and 31a on 30 and 31 respectively, increase the clockwise yawing
rotation. However, a yaw-correcting, counterclockwise moment is
produced by forces exerted on the trailing struts 32 and 33,
schematically represented by subarrows 32a and 33a. The initial
clockwise yawing motion, augmented by the clockwise moments
produced by forces generally indicated at 30a and 31a, is overcome
by the much greater counterclockwise moments produced by forces 32a
and 33a acting on struts 32 and 33. These latter forces, 32a and
33a, are transferred through a lever arm reaching from the struts
to the centroid to create a yaw-correcting counterclockwise moment
greatly in excess of the opposing torsional forces. Thus, the
marine vessel automatically realigns itself on the direction of
travel indicated by the large arrow.
In a similar manner, the marine vessel self-initiates the automatic
correction of a counterclockwise yawing motion, shown greatly
exaggerated in FIG. 2c. A counterclockwise torgue-producing force
acts on struts 30 and 31, noting subarrows 30b and 31b, and tends
to increase counterclockwise yaw. Rapid realignment of the marine
vessel to its arrow direction of travel results from additive
clockwise moment-producing forces, generally indicated by the
subarrows 32b and 33b, which rotate the ship in a clockwise
direction. Because of the lengthy lever arm reaching between the
centroid and vertical pressure responsive surfaces on struts 32 and
33 the yaw correcting forces in this case clockwise moments,
quickly overwhelm the opposing moments to realign the vessel.
The rapid realignment of the marine vessel is owed to the strategic
mounting of the vertical struts to locate the aggregate,
rotation-imparting, horizontally exerted pressure surfaces aft of
the marine vessel's centroid to ensure high speed dynamic yaw
stability.
Inherent yaw correction is present in an alternate form of the
preferred embodiment, depicted in FIG. 10, having a single,
longitudinally extending strut 34 or 35 extending from each hull to
support the platform. Here again, the aggregate, vertically
extending pressure surfaces, the sides of the struts 34 and 35, are
disposed to ensure the location of the aggregate, horizontally
exerted pressure surfaces aft of the vessel's centroid 25a, noting
that the leading edges are backward near the lateral projection of
the vessel's centroid. Having a pair of struts joining each hull to
the platform, as depicted in the FIG. 1 embodiment, allows better
maneuverability than the FIG. 10 configuration since the forward
struts act like a keel and undergo smaller angles of attack in
turns which reduces drag and lessens the tendency to cavitate.
Also, the smaller surface area cutting through the waves reduces
wave and frictional drag, and reduces the vessel's wave
response.
The lateral, cross-sectional schematic representation of the marine
vessel of FIGS. 3a, 3b, and 3c gives insight into how the vessel's
superior, high speed, dynamic pitch stability is achieved by a
substantially horizontally oriented stablizer 60. While the
drawings show the stabilizer reaching between and somewhat forward
of the aftmost end portions of the hulls, the stabilizer is
optionally located at any longitudinal position behind the centroid
25; however, the greatest stabilizing force is created when the
stabilizer is carried between the aftmost end portions of the
hulls.
The stabilizer, in its least sophisticated form, is a rigid member
having an overall rectangular shape secured at opposite ends
between the two parallel elongate hulls. The cross-sectional
configuration of stabilizer 60, optionally, is no more than a
rectangularly-shaped vane, but preferably is one of the hydrofoils
set forth in FIG. 19. During operational speeds below that at which
cavitation occurs, the fully wetted hydrofoils shown in FIG. 19a
are best because of their low drag and low noise. When high speeds
are anticipated, base-vented hydrofoils shown in FIG. 19c are
employed to reduce drag and noise. Irrespective of the
cross-sectional configuration, stabilizer 60 is fabricated to
provide additional structural rigidity between the aftmose portions
of the hulls and to effectively transmit upward and downward forces
to stabilize the vessel's attitude.
In FIG. 3a a ship, traveling at a high rate of speed through a
relatively calm sea, maintains a level attitude in accordance with
predetermined ballasting and trimming with little or no rocking
motions about the lateral projection of centroid 25.
When the ship encounters high sea states, the vessel experiences
pitching and heaving tendencies, shown greatly exaggerated in FIG.
3b for the purposes of explanation. The bow of the vessel is
pitched upward and the stern is plunged downward by a bow-on, the
combined motion defining a clockwise angular displacement generally
about the centroid 25. The crest 26 of the wave submerges a much
greater portion of strut 30 and strut 31, the latter not shown,
producing a buoying, upward pitching force on the bow. The trough
of the wave, indicated by reference character 27, laterally
contains the parallel rear struts 32 and 33, 33 not being shown,
and causes an additive clockwise dipping motion generally about
centroid 25. The clockwise motion is, in turn, augmented by another
rotational force, generally shown as subarrows 30c, created as
flowing water bears against strut 30 as it is being plowed deeper
into wave crest 26.
With the direction of travel generally indicated by the large
arrow, a vertical heaving force additionally is created by water
pressure exerted on the submerged hulls, schematically represented
by subarrow 50a, as the vessel travels through the water. This
heaving force, is a composite force substantially the same as the
LIFT force shown in FIG. 19d, having a first component generally
attributed to a positive upward pushing force exerted by the water
on the lower half of the rounded nose section of each hull. The
other component is attributed to a lifting force produced as the
water flow velocity is increased over the upper half of the rounded
nose section of each hull creating an area of lower pressure, or a
negative pulling force. Together, all the components impart a
combined upwaard heaving motion and pitching motion.
Due to the unique configuration of the instant invention, the
aforedescribed pitching and heaving motion normally experienced by,
for that matter, any oceangoing vessel traveling at a high rate of
speed through high sea states, is dampened and nullified by the
reacting forces acting on substantially horizontally oriented
stabilizer 60.
As the vessel travels through the bow-on wave in the direction
indicated by the large arrow, a vertical lifting force due to
impinging water and indicated by subarrow 60a is generated on
stabilizer 60, to rotate the entire marine vessel generally about
centroid 25 in a counterclockwise direction. Rotation in the
counterclockwise direction relieves water flow pressure from the
nose portions of the hulls to eliminate the upwardly heaving force
and, simultaneously, the pitching motion of the vessel, its
previous clockwise motion, is also negated.
In the opposite extreme, when the bow dips into a wave trough
following a bow-on wave as depicted in FIG. 3c in a greatly
exaggerated excursion, immediate compensation again begins by the
rearwardly mounted stabilizer. The bow-dipping-pitching motion is
augmented by water flow pressure, represented by subarrow 50b,
pushing downward on both the hulls creating a sinking motion.
Struts 30 and 31, now being in trough 27 and aftstruts 32 and 33
being on crest 26 of the wave, generate a generally additive
counterclockwise dipping, pitching motion about centroid 25.
Stabilizer 60 immediately rectifies the sinking and pitching
tendencies of the vessel to ensure stable high speed operation by
its reaction to downward force 60b produced as water flows over it.
This downward force exerts a clockwise torque about centroid 25
that is much greater than the counterclockwise, pitch-producing
forces, due to the fact that the force is transmitted about the
centroid through the considerable longitudinal lever arm extending
from the stabilizer to the centroid. Thus, correction for a
simultaneous, bow-dipping, pitching motion and sinking motion
immediately commences. When the vessel encounters following seas,
the sequence depicted by FIGS. 3b and 3c is reversed but with
substantially the same hydrodynamic stabilizing forces
involved.
In conclusion, superior stability is ensured in dynamic yaw by the
relative size and location of the vertically extending struts 30,
31, 32, and 33, and superior dynamic heaving and pitching stability
is provided by a horizontally oriented stabilizer 60, to
respectively place the aggregate vertically oriented stabilizing
surfaces and horizontally oriented stabilizing surfaces
substantially aft of the vessel's centroid to function in much the
same, if not identical, manner as do the vanes or feathers
stabilize the trajectory of an arrow.
Static stability, freedom from pitching, heaving, and rolling
motions while the vessel is at rest, is also optimized by the
configuration and spatial orientation of struts and hulls with
respect to the platform. The transverse spacing of the struts and
their fore and aft reach are designed using conventional
engineering formulae to provide static stability. Because of the
hulls' considerable mass coupled with their being disposed more
than one hull diameter beneath the surface of the water and
separated a distance equal to several hull diameters, reaction to
surface wave action is small when the vessel is at rest.
A slight tendency to pitch and roll is created by the waves buoying
alternate ones of the struts. This tendency is reduced in the
preferred embodiment, already described, by shaping the struts with
cross-sectional areas in the form of one of the hydrofoils
schematically represented in FIG. 19, to present a low surface wave
drag and to reduce the vessel's power-consuming wave making drag.
The cross-sectional areas are designed to ensure static stability
and structural rigidity yet displace a minimum volume of water to
reduce unstabilizing buoying forces when the struts becomes more or
less completely immersed in water with repeat of each other.
Considering, therefore, the total volumes of all the struts
piercing the water's surface and their relative lateral and
longitudinal spacing, it is obvious that surface wave reactions are
small when, for example, the volume of change in strut displacement
due to fluctuating waves is small.
If slight pitching and rolling motions are created by the waves,
the relatively broad horizontally projected surfaces of stabilizer
60 and hulls 40 and 50 inertially produces opposing, damping
forces. Thus, having a large sized, rearwardly mounted stabilizer,
in addition to ensuring superior dynamic stability, also helps to
maintain static stability.
As alternates to the basic rectangular, horizontally oriented
stabilizer 60, FIG. 4a sets forth a pair of opposing delta-shaped
stabilizing fins 60c and 60d mounted on either side of the aftmost
extersions of each of the hulls, although these fins are optionally
carried on the outside of the hulls extending in opposite
directions. Still another modification of the stabilizer takes the
form of pairs of diametrically opposed double deltas 60e and 60f,
shown in FIG. 4b, carried on each of the hulls for increasing the
stabilizer effect as well as permitting greater reliability due to
redundancy of stabilizing surfaces.
One of the drawbacks of having a completely rigid stabilizer
becomes apparent when it is noted that correction of the vesssel's
attitude follows the vessel's becoming slightly off course; that
is, with respect to dynamic pitching upward and downward motions,
stabilizing forces exerted on the stabilizer result from the
vessel's experiencing a pitching motion beforehand. It is obvious,
therefore, that providing a means for anticipating, or immediately
monitoring, wind and wave conditions to accelerate and augment the
production of counteracting stabilizing forces by the stabilizer
results in a more stable oceangoing vehicle.
Looking ahead to FIG. 7, a means for anticipating ambient
conditions takes to form of a source of command-control signals,
schematically represented by a block 69 carried on the platform.
The source is, for example, electrically switched representations
of a helmeman's observations or attitude indications coming from a
gyrostabilized navigational device fed to a command-control lead
69a.
If automatic sensor signals giving indications of ambient wave
conditions are desired, sonar, radar, or light sensors 70 are
mounted at longitudinal and lateral extremes of the hulls and
platform to provide sensor signals representative of relative
variations in the water's surface with respect to the location of
the sensor. The sensor signals are fed from each of the sensors,
via lines 70a, to a centrally located common command-sensor control
center 71 to generate and couple appropriate driving signals from
the center to a drive-control lead 71a.
The common-sensor control center, responsive to either
command-control signals or sensor signals, is, in its simplest
form, a visual readout interpreted by an operator who, by
electromechanical linkages, switches the proper driving signal to
drive-control lead 71a. Although, there is a time lag between
initiation of the command signals or sensor signals, and the
transfer of the proper driving signal, such an arrangement is
adequate to provide responsive control of a large marine vessel in
moderate seas. However, well-known automatic computer-like devices
or any of a number of servocontrols contemporarily widespread are
preferably adaptable to deliver a responsive driving signal upon
receipt of a discrete command or sensor signal. Due to the fact
that these computer-like devices and servo-controls are universally
known and employed, detailed examples are omitted in the
specification for the sake of simplicity.
In FIG. 5a, improved control of the dynamic pitch, heave, and roll
tendencies of the marine vessel is provided by modifying stabilizer
60 with a single, elongate flap portion 61 carried on its trailing
edge. Two rotation-imparting mechanisms 62 are separately secured
at opposite ends of the flap and are responsive to driving signals
appearing on drive-control lead 71a to impart a representative
angular displacement to the flap. In the alternative, stabilizer 60
and flap 61 are constructed as an integral unit with the shaft
extending through and journaled in the rotation-imparting
mechanisms 62 to be rotated as an entire unit to correct pitching
motions.
A more preferred mechanism for controlling the dynamic pitch
tendencies of the marine vessel while having a simultaneous
capability for controlling the dynamic roll tendencies of the
vessel calls for conventional fixed horizontally oriented
stabilizer 60 having a pair of aligned aileron-like flaps 63 and
64. These flaps are on the trailing edge of the stabilizer in a
coplanar relationship and are individually controllable by a
separate rotation imparting mechanism 62a or 62b see FIG. 5b.
When underway in bow-on or following seas, signals originating in
source 69 or sensors 70 are passed through the leads 69a or 70a to
center 71. Appropriate driving signals are generated to actuate the
independent rotation-imparting mechanisms 62a and 62b. The
aileron-like flaps 63 and 64 are rotationally displaced,
simultaneously, to function like an elevator (identical to the
operation of flap 61).
While turning, or when in beam or quartering seas, the vessel
exhibits a tendency to roll in addition to experiencing pitching
and heaving forces. Under these conditions, the aileron-like flaps
are angularly displaced oppositely producing a counteracting
banking rotational force since the laterally separated sensors 70,
or source 69, pass signals to center 71, to indicate that the ship
is canted or the surface of the water is higher on one side than on
the other.
In a beam sea, independent counteracting driving signals are fed to
the rotation-imparting mechanisms and opposite angular
displacements are imparted to the aileron-like flaps to maintain
roll stability.
In a quartering sea, sensor output signals cause the generation of
driving signals in the center driving the mechanisms to rotate the
flaps in a simultaneous aileron and elevator fashion to stabilize
the vessel with respect to the surrounding conditions.
During high speed operation, severe stresses are developed within
mechanically rotatable flaps when immediate, violent dynamic pitol,
heave, and roll compensations are demanded. In speeds over 35
knots, nonreinforced flaps and their rotation-imparting mechanisms
are prone to fail, such failure possibly having disastrous results,
especially in high seas. When the mechanically displaceable flaps
are strengthened to withstand high speed operation, the weight and
cost of bearings and suitable journaling mechanisms have been found
to be prohibitive.
Thus, it is that a third structure of maintaining high speed
dynamic stability in the instant marine vessel has been devised and
is set forth in the stabilizer depicted in FIGS. 5c, 5d, 5e, 5f,
5f', and 5g.
A low cost, highly reliable controllable stabilizer is provided
including two lined columns of vents 65 disposed on the dorsal and
ventral sides of the horizontally oriented stabilizer. One-half of
each of the vent columns is joined by a common lateral passageway
connecting them in groups in common fluid communication with each
other. Noting in particular FIGS. 5d and 5e, lateral passageways
66e, and 66f, are each connected to one-half of a separate column
of upwardly facing vents on the left side of the stabilizer, and
passageways 66g, and 66h are connected to separate columns
extending one-half the distance across the ventral side of the
stabilizer. In a mirror image of the stabilizer's left side, the
right side has passageways 66e' and 66f' linking columns of vents
disposed on the stabilizer's upper surface and passageways 66g' and
66h' joining downwardly facing vents on the right hand of the
stabilizer.
In each hull 40 or 50, a source of pressurized gas 66 or 66' is
provided with outlet ducts 66a, 66b, 66c, and 66d, or 66a', 66b',
66c', and 66d', respectively, connected to feed matered volumes of
pressurized gas to passageways 66e, 66f, 66g, and 66h, or 66e',
66f', 66g', and 66h'. Each of the sources of pressurized gas is a
conventional air compressor, bank of compressed gas bottles, or an
equivalent potential source of gas cable or being immediately
valved by a self-contained valving unit in substantial amounts to
the dorsally and ventrally facing vents.
Upon receiving driving signals from center 71, via driving control
lead 71a, suitable volumes of pressurized gas are valved through
selective ones of the outlet ducts to their interconnected discrete
traverse passageways and pressurized gas flows through the vents
creating a trailing cone of air as the high speed marine vessel
passes through the water.
Observing the schematic representations of water flow around vented
stabilizer 60 in FIGS. 5f and 5f', 5f shows uniform water flow as
long uninterrupted symmetrical flow arrows around the symmetrical
stabilizer as it passes through water at high speed. Equal upward
and downward pressure is exerted on the upper and lower sides of
the forward edge of the stabilizer as schematically represented by
the small +s.
However, when the driving signals valve pressurized gas through
traverse passageways 66e and 66f, a trailing cone-shaped volume of
pressurized gas 66k is extruded through the vents, over the upper
trailing surface of the stabilizer. Formation of the gas cone
causes disruption of the aforementioned uniform water flow and it
assumes essentially the shape of the flow arrows in FIG. 5f'
creating a composite shown by downward force, the LIFT arrow. This
composite force is mainly attributed to the area of low pressure,
generally designated by the - signs on the stabilizer's leading
lower edge and side, and the high pressure area, generally designed
by the + signs disposed about the stabilizer's leading upper edge
and side. Similarly, an overall upward LIFT force is created by
valving gas through the ventrally facing vents.
Thus, when driving signals, indicating an attitude correction for
pitching, are passed to both sources of pressurized gas 66 and 66',
pressurized gas is valved through upper traverse passageways 66e,
66f, 66e', and 66f'. A composite downward force is created,
schematically represented by a large arrow in FIG. 5d, by the
pressurized gas valve through all the dorsally facing vents.
On the other hand, if driving signals indicate that an immediate
counterclockwise roll compensating force be provided by the
stabilizer, then pressurized gas is selectively vented to the
dorsally facing vents on the stabilizer's left side and the
ventrally facing vents on the stabilizer's right side, noting that
FIG. 5e shows the creation of a counterclockwise moment by passing
pressurized gas through passageways 66e and 66f, and 66g' and 66h'
to their fluidly communicating vents.
The vertically upward and vertically downward forces on the
stabilizer are intensified when the entire trailing edge of the
stabilizer is completely covered by an envelope of pressurized gas.
However, a partial upward or downward force is selectively
generated by venting only one of the two parallel columns of vents
on either side of the stabilizer when a lesser force is needed to
ensure stability.
Directing attention toward FIG. 5g, in which both dorsal columns of
vents are passing pressurized gas on the left-hand side while only
the trailing column of dorsal vents passes pressurized gas on the
right side, reveals that a simultaneous, composite downward force
is exerted on the entire length of the stabilizer while a partial
counter-clockwise moment is created to enable simultaneous,
compensating correction for a pitching motion and a rolling motion
by the vented stabilizer.
As mentioned before, the advantage of having a stabilizer vented as
opposed to including rotatable vanes resides in the fact that
having no moving parts ensures inherent greater, higher reliability
and immediate response. Thus, high speed maneuvering and attitude
correction for a sustained period of time is provided when
employing a vented stabilizer to allow a full-time operational
capability for the superiorly designed marine vessel disclosed
herein.
A marine vessel constructed in accordance with the above teachings
with a displacement of 5,000 tons attains a speed of between 30 and
40 knots with conventional propellers and power plant. Higher
speeds are reached by mounting gas turbines in the hulls driving
sophisticated base-ventilated propellers or pumpjets for operation
in sea states up to, and beyond, sea state 6. At present, there is
no other surface vessel of this size capable of smooth, continuous
operation in such a high sea state; conventionally designed ships
must reduce their speed to a few knots in such seas simply to
survive.
Modifying the horizontally oriented stabilizer in accordance with
the teachings of FIGS. 5a, 5b, and 5c gives the marine vessel a
capability to weather sea states producing waves greatly in excess
of the vessel's overall height. The typical 5,000 ton displacement
marine vessel, referred to above, has supporting struts of 50 feet
in length. It naturally follows that in seas having waves less than
50 feet from crest to trough, the vessel can maintain a level
attitude by appropriately controlling the stabilizer. However, when
the sea states increase to galelike proportions, the controllable
stabilizer is best used not to hold the marine vessel in a
relatively level attitude, but is controlled to allow the vessel to
ride over huge waves which would otherwise swamp it. Riding over
huge waves is optionally controlled from a helmsman feeding
appropriate driving signals through driving leads 71a or by sensor
signals originating from the plurality of sensors 70.
Further control of the vessel's heaving tendencies is aided by
mounting a forwardly located control vane 68, see FIG. 6, on a
shaft 68a journaled at opposite ends in separate
rotation-imparting, vane control mechanisms 68b. The vane control
mechanism is controlled by driving signals, fed via leads 71a
emanating from center 71 to angularly displace the control vane in
a hydrodynamically cooperating relationship with horizontally
oriented stabilizer 60. The angular displacement of the vane is
coordinated with the rotation of flaps 63 and 64 to provide the
desired heaving and pitching control forces and moments. For
example, when extreme heave is encountered, both the vane and the
stabilizer are simultaneously rotated in the same direction to
produce a unidirectional upward or downward force to oppose the
heave. On the other hand, when extreme pitching needs correction,
the vane is angularly displaced in one direction to produce a pitch
counteracting force while the stabilizer is rotated in the opposite
direction to additionally help counteract the pitch. When no
control force is needed by the vane, the vane is feathered to align
itself with the water flow so as not to interfere with the
stabilizing action of stabilizer 60.
The spatial disposition of the hulls coupled with their location a
considerable distance beneath the surface of the water minimizes
wave making and eddy noise and, accordingly, provides an ideal
location for carrying backward-looking sonar, towed array sonar,
towed whip sonar, or a housing for submersibles, ordnance, etc. A
pod-like fairing 80 is mounted on the underside, or coplanar with
the stabilizer, and, as shown in FIG. 6 is connected between
stabilizer 60 and a traverse forwardly located control vane 68.
Being mounted a distance below the surface is particularly
desirable in military operations, aside from noise considerations,
since the package carried in pod 80 is not subject to scrutiny by
distant observers. The fairing pod, when connecting the control
vane to the stabilizer, is advantageously stressed to strengthen
the structural linkages between the two elongate hulls and, of
course, is streamlined to reduce drag and noise.
Modification of the forwardly mounted control vane in the shape of
a pair of opposing delta-shaped control vanes 68', necessitates
each being supported by a shaft journaled in a suitable
rotation-imparting control 68b' receiving driving signals over
individual driving leads 7a. The fairing pod optionally is joined
to the delta-shaped control vanes; however, cantilevering the pod
from the rear stabilizer is adequate, barring the creation of
extreme stresses, note FIG. 6a. As in the preceding example, the
delta-shaped control vanes and the stabilizer have hydrodynamically
coordinated angular displacements to enhance heave and pitch
dampening.
Placing the twin hulls several hull diameters below the surface of
the water gives the marine vessel a deep draft to prevent its entry
into most harbors and preclude shallow water operation. In FIG. 7,
ballasting chambers 20a and 20b, carried in the platform section,
ballasting chambers 40a and 40b in hull 40, and chambers 50a and
50b in hull 50, not shown, are included to permit their selective
evacuation allowing the hulls to be buoyed to the surface of the
water and enable shallow water ferrying of the vessel.
Further draft reduction is provided by adding a rack and
pinion-like mechanism 22 and 23 to the struts and platform, noting
in FIG. 9. In a first modification the pinion mechanism and its
controlling machinery are carried on platform 20 in a dependent
platform hull section 25 having a pair of longitudinal recesses 25a
and 25b. Upon lowering the platform hull with the machinery driving
the pinions downward along the racks, the lower portion of the
platform hull section is brought in contact with the surface of the
water and forced below. Forcing the hull section below the surface
creates an additional buoying force further reducing the overall
draft of the marine vessel. The longitudinal recesses are
configured to conform to the rounded outer surfaces of both hulls
40 and 50 when the platform hull section has been fully lowered,
platform hull section 25 shown schematically in FIG. 9. completely
lowered, and in phantom, completely raised.
With platform 20 carrying a topmost flat portion 24, along with a
dependent hull section 25, an elective modification is provided
using the lifting and lowering capabilities of the rack and pinion
mechanism. This modification permits the selective vertical
displacement of the flat portion along with or independent of the
hull section. Having the capability for raising and lowering the
entire platform enables smoother cargo transfer operations when
docks of different heights are encountered and, also provides a
variable silhouette capability which, from a military standpoint,
promises reduced vulnerability as well as facilitating camouflage
and concealment.
Because the struts extending upwardly from the submerged hulls
through the water's surface have only a minimal cross-sectional
area designed to provide a minimal surface wave drag and wave
making drag, the maximum speed limitation on the marine vessel is
generally stated as being a function of the propulsion plant's
power overcoming the water surface drag or frictional drag along
the outside of the two submerged hulls.
Speed is markedly increased, as shown in FIG. 8, by providing a
reservoir of water-soluble polymers 72 within each of the hulls and
a valved source of pressurized gas 73, or similar mechanism for
expelling a polymer layer 72a through a vented nose sieve 74. The
valve 73a is actuated by an ejection signal appearing on lead 73b
from center 71 and a polymer layer is ejected to cover the nose
section and the longitudinal reaches of each hull greatly reducing
the frictional drag and giving the marine vessel a high speed burst
capability with no increase in power plant output. Supplemental
slots 75 along the hull, also operatively connected to the
reservoir, ensure that the layer is not broken to keep down the
frictional drag.
In the twin hull configuration of FIG. 10, inclusion of a pair of
forward looking sonars 76 and 77 in each of the nose sections of
the hulls enables superior three-dimensional sonar resolution. In
addition, a planar, conformal sonar 78 is ideally adaptable for
mounting on the outside, outwardly facing submerged hulls. Both the
forward locking and the conformal sonars permit highly accurate
readouts since they are fixed on the relatively large hulls a
considerable distance below the area of noise-producing surface
waves and eddy vortex resulting in greater reliability in the
composite sonar systems. Including a fairing pod 69 housing a towed
sonar array or whip array along with forward locking sonars 76 and
77 and planar sonar 78 provides even greater resolution.
Forming a plurality of marine vessels with platforms 20 having an
essentially flat portion 24, schematically represented in FIG. 9,
permits a modular-like construction of a single, large, stable
floating platform 90, noting FIG. 17. Individual marine vessels are
joined by a mechanism as simple as a large U-shaped bolt 91
inserted in vertically disposed bores provided in each of the flat
portions. Such a platform 90, thusly constructed, accommodates
heavily loaded aircraft and supplies. If each marine vessel is
outfitted to serve a particular function, for example, one vessel
serving as a tanker while another is a command headquarters, crew
quarters, supply depot, etc., the vessels can be separately
deployed from widely separated supply points to rendesvous at a
predetermined point for a combined operation. In the alternative of
simply constructing a large stable floating platform from a
plurality of the marine vessels, the platform is an integral member
90a, see FIG. 18a, supported by struts anchored on elongate hulls
40 and 50, separated by a horizontally disposed stabilizer 60.
Employing the inventive concept of providing the submerged hulls
with strategically spaced struts and a large horizontally oriented
stabilizer located aft the vessels's centroid permits simple
reloaction of the struts to form the alternate embodiments shown in
FIGS. 12 through 16.
In the embodiment of FIGS. 12 and 13, a single elongate hull 90,
displacing an elliptical cross-sectional area, has a pair of
essentially delta-shaped stabilizers 91 carried on the aft portion
of the hull. The stabilizers are fixed or, if rotational, are
linked to a suitable driving mechanism used in the previous
embodiments, to eliminate dynamic pitch or heave. A single
supporting strut 92 supports a platform 93 and a pair of
outrigger-like water surface piercing struts 94 and 95 emplace the
aggregate vertically oriented, horizontal pressure control surfaces
substantially aft of the centroid of the vessel to eliminate yaw.
Struts 94 and 95 are preferably base-vented to aid in quiet high
speed operation and displace a sufficient volume of water to
maintain lateral and longitudinal static stability. Since the large
delta-shaped stabilizer locates the vertical pressure exerting
control surface considerably aft of the centroid, pitch, heave, and
roll stability is guaranteed.
A side view of an alternate embodiment of the modification of FIGS.
12 and 13 appears in FIG. 14. An elongate hull 90a supports a
platform 93a through a single strut 92a from its aft portion and a
pair of forwardly located water surface piercing struts 95a and
94a, the latter not shown, are laterally disposed with the same
separation as struts 94 and 95 shown in FIG. 13. The total
laterally exposed surface of rear strut 92a aft of centroid 25 is
considerably more than the wetted area of depending struts 95a and
94a (latter not shown) to stabilize the vessel in dynamic yaw. The
horizontally oriented stabilizer 91a, being optionally fixed or
controllable, ensures stability from dynamic pitch, heave, and roll
substantially in the same manner as disclosed above.
In FIGS. 15 and 16, a single vertically extending strut 92b
supports a platform 93b from an elongate hull 90b. The strut
supports the platform generally through the vessel's centroid 25,
but a pair of dependent struts 94b and 95b reach down from rearward
lateral extremes of the platform to form a dihedral angle at their
juncture point on the hull. A pair of controllable flaps 94c and
95c are optionally included on the dihedral sections of the struts
and, by an internal driving mechanism and sensors, the flaps are
displaced to correct for pitching, heaving, and rolling tendencies
of the vessel. Additional delta-shaped horizontal control vanes
(not shown) may be mounted near the nose of the hull for augmented
pitch and heave control. Here, again, consistent with the disclosed
inventive concept of locating the aggregate horizontal control
surfaces and the vertical control surfaces substantially aft of the
centroid of the marine vessel, in the instant embodiment, the
aggregate horizontal and vertical control surfaces are located
substantially aft of the centroid by strategically locating the
dihedral struts 94b and 95b, and, the dihedral portions mounting
the flaps 94c and 95c.
Obviously, many modifications and variations of the present
invention are possible in the light of the above teachings, and it
is therefore understood that within the scope of the disclosed
inventive concept, the invention may be practiced otherwise than as
specifically described.
* * * * *