U.S. patent application number 12/548538 was filed with the patent office on 2011-03-03 for hydrofoil stabilizer of list, pitch and roll for sail vessels.
Invention is credited to Eduard Leonidovych Zvenyhorodskyy.
Application Number | 20110048306 12/548538 |
Document ID | / |
Family ID | 43622954 |
Filed Date | 2011-03-03 |
United States Patent
Application |
20110048306 |
Kind Code |
A1 |
Zvenyhorodskyy; Eduard
Leonidovych |
March 3, 2011 |
Hydrofoil stabilizer of list, pitch and roll for sail vessels
Abstract
A sailboat having a hull, a sail assembly and a keel is
additionally equipped with an assembly of stationary or pivoted
hydrofoils--the object of the present invention. The foils are
mounted on both sides of the hull and placed above and below center
of mass (C.G.) of a sailboat in a biplane manner that allows
efficiently compensating yacht's roll. The assembly of stationary
hydrofoils of the present invention, which upper foils can go out
of water when a yacht is heeling over also develop momentums
efficiently compensating wind list. Another embodiment of the
present invention, which comprises hydrofoils assembled in a
triplane manner, allows efficiently compensating wind list at low
sailboat speed. Biplane assembly of pivoted hydrofoils of the
present invention allows compensation all adverse momentum
affecting a sailing vessel.
Inventors: |
Zvenyhorodskyy; Eduard
Leonidovych; (Toronto, CA) |
Family ID: |
43622954 |
Appl. No.: |
12/548538 |
Filed: |
August 27, 2009 |
Current U.S.
Class: |
114/39.24 |
Current CPC
Class: |
B63B 39/06 20130101 |
Class at
Publication: |
114/39.24 |
International
Class: |
B63B 39/06 20060101
B63B039/06; B63B 35/00 20060101 B63B035/00 |
Claims
1. A sailboat comprising: a displacement hull, a sail assembly
mounted to said hull, a keel mounted beneath said hull, a one or
more submerged hydrofoils mounted on said keel, wherein the
improvement, which allows said hydrofoils counteracts sailboat roll
without adverse momentums, comprises: an upper hydrofoil assembly
and a lower hydrofoil assembly rigidly mounted on both sides of
said hull above and below center of gravity (C.G.) of said sailboat
in a biplane manner, wherein said upper hydrofoil assembly consists
of a two rows--right and left--containing two or more
hydrodinamically profiled hydrofoils each, and said lower hydrofoil
assembly consists of a two rows--right and left--containing two or
more hydrodinamically profiled hydrofoils each; and said upper
hydrofoil assembly generates upward lifting forces, whereas said
lower hydrofoil assembly generates downward lifting forces; wherein
surfaces of the hydrofoils are equal that allows compensating
hydrofoil upward and downward lifting forces so vertically
stabilizing said sailboat, compensating yaw momentum and
counteracting sailboat roll.
2. The sailboat of claim 1 having the upper hydrofoil assembly of
claim 1 and the lower hydrofoil assembly of claim 1 containing two
rows of the submerged hydrofoils of claim 1 each, wherein distance
between said two rows of the upper hydrofoil assembly of claim 1
and sailboat waterline is low that allows one of said rows of said
upper hydrofoil assembly, which is positioned on one sailboat side,
rising from water when the sailboat is heeling over, whereas
another said row of said upper hydrofoil assembly, which is
positioned on opposite side of the boat, stills in water; therefore
said hydrofoils that still in water continue producing upward
lifting forces, whereas said hydrofoils that completely rise from
water do not produces any lifting forces; thus said upper hydrofoil
assembly generates rotating momentum counteracting sailboat list,
whereas said lower hydrofoil assembly stills generating downward
lifting force so stabilizing said sailboat.
3. The sailboat of claim 1 containing the upper and lower hydrofoil
assemblies of claim 1 mounted on the sailboat hull in a biplane
manner, wherein each of said hydrofoils is a pivoted one driven by
a manual or computer-controlled actuator that allows efficiently
counteracting all adverse momentum affecting said sailboat; wherein
said actuator of each said hydrofoil is mounted inside said
hydrofoil and comprises: a. a rigidly mounted inside said hydrofoil
reversible electromotor having a shaft that is profiled as a
worm-gear, b. a second shaft rigidly mounted on sailboat hull and
supported inside said hydrofoil by bearings, so said hydrofoil can
rotate about said second shaft, wherein a part of said second shaft
is profiled as a gear that is engaged to said worm-gear; and said
second shaft has a channel where an electrical cable is placed that
allows feeding said electromotor from a source placed inside
sailboat hull; therefore, when the power is on, said electromotor
together with said hydrofoil starts rotating about said second
shaft in a direction depending on polarity of voltage applied to
said electromotor.
4. The sailboat of claim 2 having the hydrofoil assemblies of claim
2, which comprises additional upper hydrofoil assembly consisting
of two rows of hydrofoils--a right and a left--positioned above
sailboat waterline, so configuration of said hydrofoil assemblies
is a triplane containing two rows of upper hydrofoils positioned
above sailboat waterline, two rows of middle hydrofoils shallow
submerged below waterline and two rows of lower hydrofoils that
still submerged at any list angle; therefore, when the sailboat is
heeling over, for example, to left side, said left row of said
upper hydrofoils goes under water, whereas said right upper row
stills above water; said right row of said middle hydrofoils rises
from water, whereas said left middle row stills in water; thus,
said upper row of hydrofoils that enters water starts producing
upward lifting forces, whereas said upper row of hydrofoils that
still above water do not produces any lifting forces; said middle
row of hydrofoils that stills in water continue producing upward
lifting forces, whereas said middle row of hydrofoils that rises
from water do not produces any lifting forces; therefore, this
configuration of hydrofoil assemblies allows to said upper and
middle hydrofoil rows generating momentum strongly counteracting
sailboat wind list even at low sailboat speed, whereas said lower
rows of hydrofoils still compensating upward lifting force of said
upper and middle rows of hydrofoils so stabilizing said
sailboat.
5. The sailboat of claim 1 with the hydrofoils of claim 1 having an
internal part and an external part each, wherein said external part
of each said foil is angled about said internal part of said foil
in a manner of "seagull wing"; wherein plane of said internal part
passes through sailboat's C.G and plane of said external part is in
parallel to horizontal plane of the sailboat; therefore, said
internal part of said foil compensates sailboat's roll; and said
external part of said foil, which is in parallel to horizontal
plane of said sailboat, compensates sailboat's pitch.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] Not Applicable.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] Not Applicable.
THE NAMES OF THE PARTIES TO A JOINT RESEARCH AGREEMENT
[0003] Not Applicable.
INCORPORATED-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT
DISK
[0004] Not Applicable.
FIELD OF THE INVENTION
[0005] The present invention relates to sailboats, and more
particularly to improved hydrofoil list, roll and pitch stabilizers
for a sailboat.
DESCRIPTION OF THE RELATED ART
[0006] A type of conventional sailing boat is one, which comprises
a hull, a sail assembly, and a keel structure, wherein the function
of the keel is to operate as a vertical hydrofoil which resists
lateral movement of the boat partially compensating wind and turn
list so the boat can travel on an angled course in an upwind
direction. For this, the keel has to be weighted so as to add
ballast and lower the center of gravity of the boat to provide the
stability of the boat. Despite of many modifications introduced in
sailing boats, this basic design of sailing boats has for many
centuries been the one most commonly used; but, the practice
reveals that this solution is not enough to compensate wind and
turn list, roll, pitch and yaw, which affect speeding yachts.
Therefore, there were numerous attempts to solve this problem by
means of underwater wings--hydrofoils--installed in different parts
of yachts. Today it becomes even more important, because ship
designer try to utilize "green energy"--the well-known power of
wind--not only for small yachts, but also for large ships.
[0007] It is known in the prior art a number of applications of
hydrofoils in boats. One of the oldest hydrofoils, which is known
from beginning of XX century, is the bilge keel--the long
underwater hydrofoil placed along a hull. Although not as effective
at reducing roll, bilge keels are cheaper, easier to install, and
do not require special internal space inside the hull.
[0008] One of the best known applications of hydrofoils is to lift
the hull of the boat out of the water in such a way that the hull
is being supported entirely by the lifting force provided by such
hydrofoils--underwater wings--traveling through the water in high
speed. This application is perfectly working in motor boat, but it
can not be utilize in sail boat because of dangerous list that can
turn the sailboat over keel.
[0009] There have been other proposed applications of
hydrofoils--underwater fins--in boats to provide stability. One
such application is shown in U.S. Pat. No. 1,499,900 issued to
Zukucker, wherein a plurality of hydrofoils are mounted on two
sides of a power boat. These fins may be adjusted both upwardly and
downwardly to improve the stability of the boat. In two other
patents, U.S. Pat. Nos. 3,377,975, Field, and 3,842,777 issued to
Larsh, laterally extending fins are provided on opposite sides of a
ship to alleviate any roll condition of the ship.
[0010] There have also been other various attempts in the prior art
to stabilize sailing vessels by the use of hydrofoils. For example,
in U.S. Pat. No. 1,356,300 issued to McIntire there are pair of
bulky "stabilizing planes" mounted at the outer end of outrigger
arms. Each stabilizing plane is slopped at a downward and inward
inclination so, according to the author, compensating forces
causing boat's list and yaw.
[0011] The similar solution dedicated to multi-hull boats is shown
in U.S. Pat. No. 3,949,695 issued to Pless, which comprises pair of
hydrofoil members mounted at the outer ends of outrigger arms on
opposite sides of the hull.
[0012] As was noted above, hydrofoil members proposed in these
patents are bulky, significantly increase width of the vessel and,
because of this, useless.
[0013] U.S. Pat. No. 4,058,076 issued to Danahy shows hydrofoil
members functioning in the similar way as those in the previous
patents. In this patent the hydrofoil members look like triangle
extending downwardly to end of the keel.
[0014] This solution has obvious disadvantages: the strange shape
of hydrofoil members proposed in U.S. Pat. No. 4,058,076 makes the
yacht ugly, and, because the hydrofoils is extended below the
center of gravity of the yacht, the hydrodynamic forces applied to
parts of such hydrofoils above and below the center of gravity
produce momentums applied in opposite direction which can not
effectively compensate the list.
[0015] U.S. Pat. No. 4,193,366 issued to Salminen proposes a single
hydrofoil--underwater wing--profiled in such a way that provides
vertical downward forces that, according to the author, have to
compensate lateral aerodynamic force component exerted by wind
against the sail assembly, thus diminishing the list and yaw angle
in the travel of the boat. Analysis of forces and momentums (see
FIG. 1) applied to hydrofoil proposed in U.S. Pat. No. 4,193,366
shows that the hydrofoil does not produce any total momentum that
compensates the list, because symmetric hydrofoil positioning (on
the yacht) about center of gravity (C.G.) produces two equal
momentums (in vertical plane passing the transversal axis) that
compensate each other. Moreover, it causes yacht yaw. When such
yacht travels without list (or roll), no rotational momentum is
applied to the yacht. But when it starts listing, the center of
hydrodynamic drag forces applied to the hydrofoil stills in the
middle of the foil, but, because of the list, it is shifted at the
distance of .delta. about vertical line passing through C.G. of the
yacht. Therefore, hydrodynamic drag F.sub.drag applied to the
hydrofoil causes momentum M.sub.drag turning the yacht in
horizontal plane--the yaw. Moreover, wind forces F.sub.W applied to
the center of pressure of yacht's sail try to turn the yacht in the
same direction; so the hydrofoil proposed in U.S. Pat. No.
4,193,366 can not compensate the list and yaw, but, just the
reverse, cause significant yaw directly depending on angle of list
of the yacht.
[0016] There have been other attempts in the prior art to utilize
hydrofoils in combination with a set of "ailerons" lifting the hull
of the sailing vessel totally out of the water. One of such devices
is shown in U.S. Pat. No. 3,373,710 issued to Steinberg, in which a
hydrofoil is positioned beneath the boat, wherein the "ailerons"
are works as ailerons on an aircraft to maintain the sailboat in an
upright position.
[0017] The similar, but more complex arrangement is proposed in
U.S. Pat. No. 3,800,724 issued to Tracy. It shows a "winged sailing
craft" which has a vertical airfoil to provide a force for forward
travel, and a horizontal airfoil to provide stability. In addition,
there are provided upper and lower hydrofoils. The upper hydrofoil
lifts the vessel out of the water at lower speeds, and the lower
hydrofoil provides either positive or negative lifting forces as
required.
[0018] As was noted above, solution proposed in these two patents
can not be applied to sail vessels, unlike to motor boats. All sail
vessels are affected by wind forces applied high above the center
of gravity of the vessel. These forces power the vessel, but also
generate high momentum that is heeling over the vessel and tries to
turn it upside down. To make sail vessel stable, a heavy ballast is
placed below its center of gravity. Because of this, hydrofoils
lifting a sail vessel from water make it very unstable. Analysis
shows that it is necessary to install large hydrofoils or airfoils
(having size of a sail) to stabilize such vessel. Obviously, such
solution can not be utilized in yacht design.
[0019] Another solution is represented in U.S. Pat. No. 3,505,968
issued to Gorman and U.S. Pat. No. 3,968,765 issued to Menegus.
They show a hydrofoil mounted below a hull of a sailboat and
working as a conventional keel, but rotating about a horizontal
longitudinal axis so that its lifting force can be exerted
laterally to one side or another one. In one of embodiments, the
hydrofoil is turned in such a way that provides an upward dynamic
lifting force.
[0020] The task of vessel stability is a complex one, where all
forces, --static and dynamic ones--affecting the vessel,
particularly, sailing vessel, have to be taken in account.
Moreover, because vectors of these forces do not pass through the
center of gravity of the vessel, they produce momentums that try to
turn the vessel in all three planes that in many cases decrease the
vessel stability. As analysis of the prior art shows that the
authors of the prior art miss some forces and momentums; in the
result, the task of eliminating of adverse factors affecting
sailing vessels has not been solved yet. Also, the hydrofoils
proposed in the previous art affect yacht stability causing
unnecessary vertical lifting and yaw.
SUMMARY OF THE INVENTION
[0021] In the present invention, there is a sailing vessel
comprising a hull and a sail assembly that is mounted to the hull
and arranged to be positioned relative to wind which is blowing at
an angle to the longitudinal axis of the hull so that the sail
develops an aerodynamic force having a lateral aerodynamic force
component and a forward aerodynamic force component. The lateral
aerodynamic force component causes list and yaw--the adverse
factors affecting sailing vessels. The solution proposed in the
present invention is based on analyses of all momentums affecting a
sailing vessel; therefore it overcomes the unsolved problems of the
prior art by means of utilization of specially positioned above and
below the center of gravity of the vessel stationary and pivoted
hydrofoils--the object of the present invention--which compensate
forces causing wind list and yaw also minimizing roll and
pitch.
DESCRIPTION OF THE DRAWINGS
[0022] FIG. 1 depicts diagram of forces and momentums applied to
sailing vessel having hydrofoils of the prior art.
[0023] FIG. 2 depicts the preferred embodiment of the present
invention--the scheme of sailing yacht having completely submerged
biplane hydrofoils.
[0024] FIG. 3 depicts diagram of forces and momentums applied to
sailing vessel having biplane hydrofoils of the preferred
embodiment.
[0025] FIG. 4 depicts variant of hydrofoil having shape of "seagull
wing",
[0026] FIG. 5 depicts variant of the preferred embodiment of the
present invention--the scheme of double-hull sailing yacht
employing biplane hydrofoil assembly,
[0027] FIG. 6 depicts variant of the preferred embodiment of the
present invention--the scheme of sailing yacht having partially
submerged upper foils--and diagram of forces and momentums applied
to sailing vessel having hydrofoils of this embodiment.
[0028] FIG. 7 shows example of positioning of the hydrofoils on
Alberg 30 yacht.
[0029] FIG. 8 depicts the scheme of another embodiment of sailing
yacht that comprises assembly of pivoted hydrofoils, where FIG. 8b
shows possible design of the foil-mounted actuator.
[0030] FIG. 9 depicts the scheme of another embodiment of sailing
yacht that comprises partially submerged hydrofoils assembled in a
triplane manner.
DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION
Biplane Hydrofoils
[0031] The scheme of sailboat of the preferred embodiment of the
present invention is shown in FIG. 2. This boat comprises a hull 1,
a sail assembly 21 and 22, a keel 3, a rudder 4, a mast and
hydrofoil members 6, 7, 8, 9, 10, 11, 12 and 13. The arrangement of
the hydrofoil members 6, 7, 8, 9 10, 11, 12 and 13 is of particular
significance in the present invention and will be discussed in
detail below. It also can comprise a small engine that is used when
wind speed is not enough to power said boat.
[0032] The sail assembly is or may be of conventional design, and
as shown on FIG. 2 comprises a mast 5 to which a head sail 22 and a
mainsail 21 are mounted. The hull 1 has a conventional design of a
sailing yacht--a rounded, elongate configuration symmetrical about
its longitudinal center axis.
Description of the First Variant of the Preferred Embodiments of
the Present Invention
A Biplane Assembly of Submerged Hydrofoils Counteracting Vessel's
Roll and Pitch
[0033] As shown on FIG. 2, the assembly of static (non-pivoted)
hydrofoil members 6, 7, 8, 9, 10, 11, 12 and 13 is rigidly mounted
on the hull 1 from both sides as four rows above and below the
center of gravity (C.G.) of the yacht in such a manner that the
vertical distance between plain of upper rows containing hydrofoils
6, 8, 10 and 12 to C.G. is equal to the vertical distance between
plane of lower rows containing hydrofoils 7, 9, 11 and 13 and C.G.;
so planes of the upper and lower hydrofoils are symmetrical about
horizontal plane passing through C.G., wherein effective surfaces
of the hydrofoils are equal. Also, distance between the pair of
hydrofoils 6 and 7 (10 and 11) and C.G. is equal to distanced from
the hydrofoils 8 and 9 (12 and 13) and C.G.; therefore these pairs
of hydrofoils are symmetric about transverse axis passing through
C.G.
[0034] The hydrofoils 6, 7, 8, 9, 10, 11, 12 and 13 are placed
below vessel's waterline and hydrodynamically profiled to provide a
carrying power, wherein the hydrofoils 6, 10 and 8, 12 provide
upward lifting forces and the hydrofoils 7, 11 and 9, 13 provide
downward forces. This arrangement of the hydrofoils of the
preferred embodiment together with the hydrofoil shape provides
compensation of adverse momentums affecting a sailing vessel
equipped with the hydrofoils of the previous art; also, the
assembly proposed in the preferred embodiment of the present
invention develops momentum compensating roll and pitch (working as
a shock absorber).
[0035] Diagram of forces and momentums applied to sailing vessel
having biplane hydrofoils of the preferred embodiment is depicted
in FIG. 3.
[0036] The diagram shows that all momentums and lifting forces
developed by the hydrofoils compensate each other. Therefore, the
arrangement of the symmetrically-positioned biplane hydrofoils
proposed in the present invention utilizes hydrodynamic drag
forces; it works as a shock absorber to compensate roll and pitch
without other dynamic momentums and forces affecting a sailing
vessel.
[0037] The shock absorption force (hydrodynamic drag) of a
hydrofoil depends on surface of the hydrofoils and relative
water-hydrofoil velocity.
[0038] This force is determined by formula:
F=C.sub.x.times.s.times..rho..times.V.sup.2/2 [1],
where C.sub.x--coefficient depending on shape of hydrofoil (for
rectangular flat plate C.sub.x.apprxeq.1.1), s--projection of the
surface of hydrofoil on the plane that is in perpendicular to
vector of velocity, V--relative water-hydrofoil velocity,
.rho.--density of water.
[0039] When a yacht rolling, vector of water-foil velocity is lying
on tangent to circumference having the center in C.G; so projection
of the surface of hydrofoil on the plane that is in perpendicular
to vector of velocity can be calculated by the formula:
s=S.times.cos .beta. [2],
Where:
[0040] .beta.--angle between radius connecting C.G to geometrical
center of the foil and horizontal plane of the yacht (see FIG. 3),
S--hydrofoil surface.
[0041] For periodical roll with amplitude of A (maximal movement of
the foil about horizontal plane) and period T, the force will be
approximately determined by the following formula:
F=4.pi..sup.2.times.s.times..rho..times.A.sup.2/T.sup.2
cos.sup.2(2.pi.t/T).
[0042] According to this formula, this drag force is a periodical
function. Amplitude and mean value of the force--F.sub.a and
F.sub.m respectively--applied to the hydrofoil will be determined
by the formulas:
F.sub.a=4.pi..sup.2.times.s.times..rho..times.A.sup.2/T.sup.2 and
F.sub.m=1/2F.sub.a=2.pi..sup.2.times.s.times..rho..times.A.sup.2/T.sup.2.
[0043] Thus, mean value of momentum developed by the single foil
can be determined by approximate formula:
M.sub.m=2.pi..sup.2.times.(a-L).times.s.times..rho..times.A.sup.2/T.sup.-
2 [3],
where a--1/2 of wing (foil) span, L--width of the foil.
[0044] Therefore, all 8 foils of this assembly will produce the
compensating momentum of 8 M.sub.m.
[0045] As an example, if amplitude of pitch is 1 m and period of
the pitch is 10 sec, the single hydrofoil having surface of 0.5
m.sup.2 produces the amplitude of the resistance force F.sub.a of
2200 N or 440 lbs; the mean value of this force producing by all
hydrofoils will be about 1,760 lbs (800 kg), and mean value of the
momentum determined by formula [3] (for large racing yacht with
B=28 ft) will be about 24,600 lbs-ft (3,300 kg-m).
[0046] The hydrofoils of the present embodiment can be additionally
profiled in such a way that plane of each foil is bent and have
shape of "seagull wing" as depicted in FIG. 4, wherein plane of
internal part of said foil passes yacht's C.G and plane of external
part of said foil is in parallel to horizontal plane of the yacht.
Therefore, internal part of said foil efficiently compensate
yacht's roll (cos .beta.=1 in formula [2]); and external part of
said foil, which is in parallel to horizontal plane of the yacht,
efficiently compensate yacht's pitch.
[0047] The hydrofoils of the present embodiment can be utilized in
"combined yachts"--yachts jointed together in the process of
utilization of old-model yachts. The scheme of such yachts and
position of the hydrofoils on the hull of such yachts are shown on
FIG. 5. The yacht shown on FIG. 5 is a combination of two separate
medium-size yachts, which hulls 41 and 42 were cut in such a way
that allows said hulls to be jointed together. Such solution allows
not only utilizing such yachts, but also enlarging its size so
transforming it into higher-category yachts. For example, using
this way of utilization for two medium-size yachts, such as Alberg
30 and similar, allows transforming them into single double-size
yacht. Because such combined yachts has doubled average length
(LOA), but keeps original beam (B), its roll an pitch stabilization
is even more important than stabilization of a conventional
yacht.
[0048] The hydrofoil assembly of this embodiment comprises two
pairs of rows of hydrofoils--upper and lower ones--positioned in
biplane manner, wherein upper rows (left and right) are positioned
on both sides of the yacht above and below yacht's C.G on equal
distances from said C.G. Each row contains three hydrofoils--front
43, middle 44 and rear 45, wherein the middle foil 44 is positioned
in the place where the two hulls 41 and 42 are jointed. This
position of hydrofoils allows compensating momentum bending yacht's
hull that is important in the case of high pitch. The solution of
this embodiment becomes even more efficient when the hydrofoils are
pivoted and computer-controlled ones as described below in the
following embodiment.
Description of the Second Variant of the Preferred Embodiments of
the Present Invention
Biplane Assembly of Partially Submerged Hydrofoils Counteracting
Vessel's List
[0049] The static hydrofoil assembly of the first variant of the
previous embodiment can stabilize a sail boat in the cases of roll
and pitch, but does not compensate wind and turn lists and yaw.
This problem can be solved by means of a static hydrofoil assembly
arranged in such a way that one of upper foils can be partially
submerged (or completely out of water) when a sailing vessel is
heeling over. In this case momentums generated by upper foils do
not compensate each other and the resulting momentum is applied in
opposite direction to the momentum generated by lateral wind so
compensating wind list.
[0050] Scheme of hydrofoil assembly and diagram of forces and
momentums applied to sailing vessel having biplane hydrofoils of
this embodiment is depicted in FIG. 6. Here, the hydrofoil assembly
is a submerged biplane one that is similar to the hydrofoil
assembly of the first variant of the preferred embodiment so
comprising two upper rows of profiled hydrofoil that produce upward
lifting force, and two lower rows of profiled hydrofoils that
produce equal downward lifting forces, wherein planes of upper
hydrofoils and lower hydrofoils positioned on equal distances from
C.G. of the yacht, and, unlike the hydrofoil assembly of the first
variant, depth of the upper hydrofoils allow one row of said upper
hydrofoils rising above water when vessel's list exceeds some
predetermined value.
[0051] As was noted above, the conventional way of yacht
stabilization is the hydrostatic one utilizing heavy keel, when
C.G. of the yacht is positioned maximally below waterline. In the
case, when a yacht is heeling over, the center of buoyancy (C.B.)
of the yacht is shifted horizontally about its center of gravity
(C.G.) on the distance named Righting Arm (G.Z.), so hydrostatic
forces provide momentum compensating yacht's list and pitch. Even
though exact calculation of G.Z is difficult, for small angle of
list the hydrostatic compensating momentum can be defined by the
approximate formula:
M.sub.h=Disp.times.G.Z=Disp.times.sin .phi..times.(b+.delta.)
[4],
where: (b+.delta.)--distance from waterline to C.G.,
Disp--displacement (weight of the yacht), .phi.--angle of roll
(list).
[0052] Maximal angle of roll (list) for racing yachts is known as
LPS (Limit of Positive Stability). It is the roll angle at which a
boat will no longer right itself and become inverted (capsized).
All racing yachts is designed for LPS of about 100-120 arc degrees.
LPS roll angle is the extreme limit and the practical value of
maximal roll (list) can be determined by the condition when yacht's
deck touches water. It is approximately described by the
formula:
.phi..sub.m=arctan(2h/B) [5],
where: h--elevation of yacht deck above waterline, B--yacht's
overall beam.
[0053] Therefore, for the yacht with LOA (Length Overall) of 141
ft, B (Overall Beam) of 28 ft, D (Draft) of 19 ft, when height of
yacht's deck of fully loaded yacht is 5 ft, the maximal list will
be about 20 arc degrees.
[0054] As depicted in FIG. 6, upper hydrofoils are positioned below
waterline on depth of .delta.. Thus, when the yacht is listing,
hydrofoils positioned on one side of the hull are going up, whereas
the hydrofoils positioned on the opposite side of the hull are
going down. When ascending foils start going out of water, the
lifting force of the foils declines because just part of these
foils contacts with water.
[0055] Height of end of the foil rising above water can be
determined by the formula:
H=a-b.times.(1-cos h)/sin .phi.-.delta./sin .phi.,
where: a--1/2 of wing span of the hydrofoil (wing), b--distance
from C.G to hydrofoil plane, .delta.--depth of the hydrofoil plane,
.phi.--angle of the list.
[0056] Dry width of the hydrofoil (width of part of the foil that
is out of water), can be determined by the formula:
w.sub.dry=a-(b+.delta.)/sin .phi.+b/tg.phi. [6].
[0057] The dry width w.sub.dry may be larger than real width W of
the hydrofoil. It means that all surface of the hydrofoil is above
water. When it happens, only hydrofoils, which still in water
produce the lifting force and compensating momentum.
[0058] For the large racing yacht (mentioned above) with LOA=141
ft, B=28 ft, D=19 ft, which is equipped with hydrofoil assembly of
the present embodiment and having depth of the upper wing plane
.delta.=2 ft, distance from C.G to wing plane b=6.7 ft, 1/2 of wing
span of the hydrofoil a 32 14 ft, the possible dry length w.sub.dry
of the foil determined by formula [6] is shown on the Table 1:
TABLE-US-00001 TABLE 1 Angle of list .phi. Dry width w.sub.dry (arc
degrees) (ft) 20 6.96 10 1.89 8 -0.84 5 -9.2
[0059] The calculation shows that end of the foil starts going out
of water at .phi.=9 arc degrees.
[0060] The lifting force F.sub.1 of this foils declines because
only part of the foil stills in water, so the lifting force can be
determined by the formula:
F.sub.1=F.sub.y.times.(1-w.sub.dry/W) [7],
where: F.sub.y--total lifting force of the underwater foil,
w.sub.dry--dry width of the foil, W--width (lateral dimension) of
the foil.
[0061] Total lifting force of a wing is determined by the
formula:
F.sub.y=C.sub.y.times.S.times..rho..times.V.sup.2/2 [8],
where: C.sub.y--lifting coefficient, P--density of media,
V--water-foil velocity, S--surface of the foil.
[0062] Coefficient C.sub.y depends on many factors and can be
determined by approximate formulas or by the graphs in
textbooks.
[0063] For non-profiled foil (thin plate) C.sub.y can be determined
by the formula:
C.sub.y=2.pi..times.sin .alpha. [9],
where: .alpha.--angle of attack.
[0064] For airplane-like wing coefficient C.sub.y can be estimated
as shown on the Table 2.
TABLE-US-00002 TABLE 2 .alpha. (arc degrees) C.sub.y -4.5 0 -3 0.3
0 0.5 5 0.8 6 1.0 9 1.15 12 1.3
[0065] Below it is the example of operation of the hydrofoil
assembly of the present embodiment dedicated to the large racing
yacht mentioned above.
[0066] Thus, for single profiled foil having surface of 1.5 m.sup.2
the upward lifting force will be about 6,360 N (918 kg of force or
1,890 lbs) at V=10 kt (18.5 km/hour) and .alpha.=0.
[0067] If two upper foils are dry (>10 arc degree list) and two
opposite foils still in water, the total lifting force compensating
wind list will be about 1840 kg and produce the compensating
momentum of 7730 kg-m. Hydrostatic momentum M.sub.h (see formula
[4]) will be around 18,000 kg-m.
[0068] Lateral wind of 20 kt (37 km/hour) produces listing momentum
of 24,000 kg-m (at SA=400 sq.m. and height of center of wind
pressure of 12 m).
[0069] Thus, the compensating momentum of the hydrofoils (7,730
kg-m) together with hydrostatic compensating momentum of the yacht
(18,000 kg-m) provides total compensating momentum exceeding 25,000
kg-m that can successfully counteract wind listing momentum keeping
the yacht at the list not exceeding 10 arc degrees (at mentioned
above conditions).
[0070] Another example of calculation is dedicated to medium-size
Alberg 30 yacht having Displacement=9,000 lbs, LOA=30.2 ft, D=4.2
ft, Beam=8.8 ft and SA=410 sq.ft. Maximal roll (list) will be
.phi..sub.m=40 arc degrees (see formula [5]).
[0071] For the upper hydrofoils positioned 1.5 ft below waterline,
wing (hydrofoil) span of 8.8 ft and the distance from C.G. to wing
(hydrofoil) plane of 1 ft (.delta.=1 ft, a=4.4 ft, b=1 ft, see
formula [6]) the value of the dry width w.sub.dry of hydrofoil for
different angles of the list is shown on TABLE 3.
TABLE-US-00003 TABLE 3 Angle of list .phi. Dry width w.sub.dry (arc
degrees) (ft) 10 -1.4 15 0.4 18 1.0 20 1.3 25 1.8 28 2.0
[0072] As Table 3 shows, the hydrofoil with width W=2 ft is
completely above water at 28-degree list.
[0073] For single profiled foil having surface of 10.8 sq.ft (1
m.sup.2) the lifting force will be about 1260 lbs (612 kg) at V=10
kt and .alpha.=0.
[0074] If the row of two upper foils is dry (>28 arc degree
list) and the opposite row stills in water, the total lifting force
will be about 1220 kg that produces the compensating momentum of
1610 kg-m. Hydrostatic momentum M.sub.h determined by the formula
[4] will be about 1,150 kg-m at list of 28 arc degrees.
[0075] Lateral wind of 20 kt (37 km/hour) produces listing momentum
of about 2,000 kg-m at SA=410 sq.ft (38.1 m.sup.2) and height of
the center of wind pressure of 14 ft (4.2 m).
[0076] Thus, the hydrodynamic compensating momentum of hydrofoils
(1,614 kg-m) together with hydrostatic compensating momentum of the
yacht (1,150 kg-m) provides total compensating momentum of 2,764
kg-m that can successfully counteract the wind listing
momentum.
[0077] At the list angle of 20 arc degrees only part of hydrofoils
is involved in wind list compensation. Here, the hydrostatic
compensation momentum determined by formula [4] will be about 837
kg-m; and hydrodynamic compensation momentum will be about 1,047
kg-m (at yacht speed of 10 kt.). Totally they provide 1,900 kg-m
compensating momentum counteracting wind listing momentum of 2,000
kg-m. Thus, complete compensation will be achieved at list angle of
about 21 arc degrees.
[0078] Thus, at the list below 15 degrees, the hydrofoils do not
works as list compensator, but still working as roll and pitch
stabilizer; and list compensation is provided by conventional
hydrostatic forces. The lifting force of the hydrofoils starts
counteracting listing momentum at list angle of 15 degrees and
produce full compensating momentum at list angle of 28 degrees.
Therefore, such hydrofoil assembly protects the yacht from the list
exceeding 21 degrees. The lower hydrofoils positioned below C.G
produce downward lifting force, which stabilizes the yacht.
[0079] The hydrofoil assembly can be installed on a yacht when it
is on service in a dry dock; the foils can be rigidly mounted on
yacht's hull, or the foils can be clipped to a harness that is
attached to yacht's hull. The possible position of hydrofoil
assembly of the present embodiment on Alberg 30 yacht is shown on
FIG. 7.
[0080] The symmetrical position of the hydrofoils is the preferable
one, but for some sailing vessels having shallow C.G and
complicated underwater shape it is difficult to keep upper and
lower foils on the same distance from C.G. In this case these
distances can be different, but lifting forces of upper foils and
lower foils have to be equal.
Description of Another Embodiment of the Present Invention
Biplane Assembly of Pivoted Hydrofoils
[0081] Unlike the first embodiment of this invention--biplane
assembly of static (non-pivoted) completely submerged (never out of
water) hydrofoil members rigidly mounted on the hull above and
below C.G.--that can partially compensate roll and pitch, but can
not compensate wind list, an assembly of similar pivoted hydrofoils
allows compensating all adverse momentums caused by roll, pinch and
lateral wind.
[0082] The scheme of assembly of the pivoted hydrofoils is depicted
in FIG. 8.
[0083] Here, the assembly of submerged hydrofoils is the similar to
one shown on FIG. 2, but, in this embodiment, the hydrofoils can
change its angle of attack by means of actuators. Variation of
angle of attack alters coefficient C.sub.y; therefore lifting force
of the hydrofoil changes too (see formula [8]). According to Table
2, coefficient C.sub.y varies from 0 at the angle of attack of -4.5
degrees and 0.5 at the angle of attack of 0 degrees up to 1.15 at
the angle of attack of 9 degrees.
[0084] Thus, the lifting force of the single foil proposed above
for Alberg 30 yacht (at yacht speed of 10 kt) will vary from 1260
lbs (612 kg) at .alpha.=0 up to 2,900 lbs (1,400 kg) at .alpha.=9
degrees. In this case, momentum (in vertical lateral plane)
developed by the single foil will vary from 805 kg-m up to 1,850
kg-m respectively; and the lifting force is equal to 0 at the angle
of attack of -4.5 degrees.
[0085] Also, the foil develops momentum in vertical longitude
plane. If each foil is positioned on the horizontal longitude
distance of 12 ft from C.G, the foil produces momentum that varies
from 2,200 kg-m (.alpha.=0) up to 5,060 kg-m (.alpha.=9).
[0086] In the first embodiment all foils are submerged ones and
have pre-installed angle of attack of 0 degree; and upper foils
provide upward lifting, whereas the lower foils provide downward
lifting force. Thus, such hydrofoil assembly works as a roll
compensator, but does not produce any rotating momentum because the
momentums developed by the hydrofoils compensate each other.
[0087] In the case of pivoted foils, they can produce rotating
momentums that can be used to compensate roll, pitch and wind list.
For roll and pitch compensation, the foils have to be turned
synchronically with movements of yacht's hull, but counteracting
them. So, the lifting forces have to be in opposite direction to
vector of velocity of yacht's hull.
[0088] To compensate wind listing, the foils have to develop
rotating momentums counteracting listing momentum caused by wind.
This compensation can be estimated for the hydrofoil assembly
proposed above for Alberg 30 yacht.
[0089] As was noted above, the lateral wind of 20 kt (37 km/hour)
produces listing momentum of about 2,000 kg-m at SA=38.1 m.sup.2
(410 sq.ft) and height of the center of wind pressure of 4.2 m (14
ft). Hydrostatic compensating momentum of the yacht calculated by
the formula [4] is 690 kg-m at 10-degree list. So, the hydrofoil
assembly has to develop additional 1,310 kg-m momentum. If the
assembly is symmetrical about C.G and the yacht is heeling to left
side, the left upper and right lower foils have to be turned on the
same angle of attack of 5 arc degrees (see formula [8] and Table
2). It provides additional upward (for upper foils) and downward
(for lower foils) forces developing momentum that, together with
hydrostatic momentum, compensates the wind list.
[0090] Because the lifting forces produced by hydrofoils are
dynamic ones that depend on yacht speed
(F.sub..gamma..about.V.sup.2), angle of attack of the foils has to
be regulated according to the vessel's speed. In the case of low
speed when the lifting forces of the mentioned above foils are not
enough to compensate the wind list, other hydrofoils can be
involved. So (see example above), if the yacht is heeling to left
side at low speed, the right upper and left lower foils have to be
turned on the negative angle of attack of -4.5 arc degrees (see
formula [8] and Table 2) where C.sub.y=0. Hydrostatic compensating
momentum of the yacht calculated by the formula [4] is 690 kg-m at
10-degree list. The lateral wind of 20 kt produces listing momentum
of 2,000 kg-m. So, the hydrofoil assembly has to develop 1,310 kg-m
momentum. At the yacht speed of 5 kt the compensating momentum
produced by these four foils (at the same angle of attack of 5
degrees) will be only 327 kg-m that is not enough. So, if the left
upper and right lower foils is turned on the angle of attack of 9
arc degrees (see formula [8] and Table 2) and the right upper and
left lower foils are turned on the angle of attack of -4.5 arc
degrees, the hydrofoil assembly produce rotating momentum of 3,500
kg-m counteracting with the wind list. This momentum will be enough
to compensate lateral wind of 28 kt at the vessel speed of 5 kt.
Also these hydrofoils (at the angles of attack mentioned above) can
compensate lateral wind of 20 kt at the yacht speed of 3 kt.
[0091] The pivoted foils of this embodiment can be controlled by
electromechanical or hydraulic actuators placed inside of the hull
(FIG. 8a), or the actuators can be mounted inside of the foil as
depicted in FIG. 8b. Example of such foil-mounted actuator is shown
on FIG. 8b. Here, a reversible electromotor 33 is firmly mounted
inside of foil 32, wherein the shaft 34 of the electromotor 33 is a
worm-gear. Another shaft 35 is firmly mounted on yacht's hull 1 and
supported in the foil 32 by bearings 36 and 37 in such a way that
the foil 32 can rotate about the shaft 35. The part of the shaft 35
is a gear, which is engaged to said worm-gear. To feed the
electromotor 33, the shaft 35 has a channel 38 where an electrical
cable 39 is placed. Seal 310 protects interior of the hydrofoil 32
from water.
[0092] Therefore, when the power is on, the electromotor 33
together with foil 32 starts rotating about the shaft 35 in the
direction depending on polarity of voltage applied to the
electromotor 33.
[0093] This hydrofoil-mounted actuator can be also utilized in
pivoted "seagull wing" hydrofoils (see FIG. 4) turning whole
hydrofoil or just its external part.
[0094] For the accurate compensation of wind list, the actuators
have to be computer-controlled ones, wherein the controlling
computer 311 has to have information about yacht's speed, wind
speed and direction (FIG. 8c). This information can be obtained by
means of special sensors 312 and 313 connected to the computer 311.
Basing on this information, the controlling computer 311 according
to special algorithm incorporating formula [8] and Table 2 develops
commands to turn each foil on the specific angle of attack.
[0095] If the actuators are fast enough (time response is less than
about 2 seconds), this hydrofoil assembly can be utilize to
compensate not only the wind list, but also other adverse momentums
affecting the yacht, such as roll, pitch and yaw. In this case, the
controlling computer has to have additional real-time information
about position of the vessel and its dynamic, which can be obtain
from onboard gyroscope 314. To achieve fast and reliable response,
advanced fuzzy logic expert system and processors can be
utilized.
Description of Another Embodiment of the Present Invention
Passive Triplane Assembly of Hydrofoils
[0096] The scheme of the hydrofoil assembly of the present
embodiment is depicted in FIG. 9. Here, the partially submerged
biplane hydrofoil assembly of the embodiment depicted in FIG. 6 is
additionally equipped with two other upper rows of the foils 20,
23, 26 and 28 positioned above yacht waterline in such a manner
that allow the foils placed on one side of a vessel entering water
when the vessel is heeling over. These additional foils are
hyrodynamically profiled to generate upward lifting force.
Therefore, the assembly comprises said upper rows of the foils 20,
23, 26 and 28 providing upward force (when they in water), the
middle rows of the foils 6, 8, 10 and 12 (see FIG. 9) providing
upward force and the lower rows of the foils 7, 9, 11 and 13
providing downward force, wherein, when a yacht is in vertical
position, the upper row is above waterline, the middle row is below
waterline and above C.G, the lower row is below waterline and below
C.G; the distance between the middle row and C.G is equal to the
distance between the lower row and C.G, and height of the upper row
above waterline is equal to the depth of the middle row below
waterline.
[0097] The assembly works as follows:
[0098] When a yacht is heeling over (for example to left side), the
left upper row of foils 26 and 28 enters water providing upward
lifting force. The right middle row of the foils 10 and 12 (see
FIGS. 9 and 6) is going out of water, so the left row foils 6 and 8
stills in water also generating upward lifting force. The lower
rows of foils 7, 9, 11 and 13 still in water providing downward
lifting force that counteracts total lifting forces and does not
allow the yacht lifting up.
[0099] The assembly of the present embodiment is the passive one;
it does not require any foil alignment and computer-controlled
rotation. This solution allows significantly increasing momentum
counteracting wind list that is especially important at the
conditions of low yacht's speed. Below is an example of such
assembly dedicated to Alberg 30 yacht. For single profiled foil
having surface of 10.8 sq.ft the lifting force will be about 1260
lbs (612 kg) at V=10 kt and angle of attack of .alpha.=0.
[0100] If two upper foils enter in water, the total lifting force
compensating wind list will be about 2,690 lbs (1 220 kg) and
produce the compensating momentum of 11,820 lbs-ft (1610 kg-m).
[0101] If two middle foils are out of water and two opposite foils
still in water, the total lifting force compensating wind list will
be about 1220 kg and produce the compensating momentum of 1610
kg-m.
[0102] Hydrostatic momentum M.sub.h determined by the formula [4]
will be about 690 kg-m at list angle of 13 arc degrees, 427 kg-m at
8 degrees and 267 kg-m at 5 degrees. Lateral wind of 20 kt (37
km/hour) produces listing momentum of about 2,000 kg-m at SA=38.1
m.sup.2 (410 sq.ft) and height of the center of wind pressure of
4.2 m (14 ft).
[0103] Thus, the maximally possible hydrodynamic compensating
momentum of hydrofoils (3,200 kg-m) achieved at yacht's speed of 10
kt together with hydrostatic compensating momentum provides the
rotating momentum that is well enough for wind list compensation.
Because the list momentum and compensating momentum have to be in
balance, the upper and middle foils can be partially submerged to
provide together with hydrostatics the total value of rotating
momentum of 2,000 kg-m.
[0104] If the yacht is traveling with lower speed, such as 6 kt,
the hydrodynamic momentum of foil assembly will decline to 1,300
kg-m; so the complete compensation of the lateral wind will be
achieved when the left foils of upper row are completely in water
and the right foils of the middle row are completely out of
water.
[0105] Optionally, the distance between the upper row and waterline
can differ from the distance between the middle row and waterline;
so, for example, the right middle foils can leave water at lower
list and the left upper foils enters water at higher list. Such
solution provides smoother regulation of yacht's position.
[0106] Thus, if yacht's list is less than some angle (depending on
upper and middle hydrofoils position), the hydrofoil assembly does
not work as a list compensator, but still working as roll and pitch
stabilizer; here the list compensation is provided by conventional
hydrostatic forces. The lifting force of the hydrofoils starts
counteracting listing momentum at list angle when the upper foils
touch water and middle foils leave water; and the assembly produces
full compensating momentum at list angle when the left upper foils
are completely in water and right middle foils leave water
completely. The lower hydrofoils positioned below C.G produce
downward lifting force, which counteracts upward lifting forces
(not the momentums) generated by upper and middle hydrofoils so
stabilizes the yacht in vertical direction.
* * * * *