U.S. patent application number 12/454098 was filed with the patent office on 2010-02-11 for stabilizer of ship rolling.
Invention is credited to Alexander Segal, Zelik Segal.
Application Number | 20100031861 12/454098 |
Document ID | / |
Family ID | 41651726 |
Filed Date | 2010-02-11 |
United States Patent
Application |
20100031861 |
Kind Code |
A1 |
Segal; Alexander ; et
al. |
February 11, 2010 |
Stabilizer of ship rolling
Abstract
The roll-stabilizer consist of short wings, with aspect ratio
r=0.5-0.75, fastened immovably to the ship hull in staggered rows
or in lines along the bilges, at port and starboard sides. The
height of the wings is such that they do not protrude the maximum
breadth and base line of the ship. The transverse distance between
two wing lines of the staggered row is 0.5-0.7 of the wing's chord,
and the stagger between wings of the two lines is equal to the
chord. The wing profiles are parallel to the longitudinal axis of
the ship or form a small angle of 2-4.degree. with this axis. At
zero forward speed the roll damping moment of the staggered
stabilizer is almost equal to that of continuous bilge keels having
the same height and area. During motion of the ship ahead the lift
forces of the wings produce a large damping moment, considerably
reducing the ship rolling.
Inventors: |
Segal; Alexander; (Akko,
IL) ; Segal; Zelik; (Akko, IL) |
Correspondence
Address: |
Zelik Segal
Ben-Guzion st. 470/5
Akko
24602
IL
|
Family ID: |
41651726 |
Appl. No.: |
12/454098 |
Filed: |
May 13, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61133755 |
Jul 3, 2008 |
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Current U.S.
Class: |
114/126 |
Current CPC
Class: |
B63B 3/44 20130101; B63B
39/06 20130101 |
Class at
Publication: |
114/126 |
International
Class: |
B63B 39/06 20060101
B63B039/06 |
Claims
1. Stabilizer of ship rolling, consisting of wings, immovably
fastened to the ship hull in longitudinal lines or in staggered
rows, on the port and starboard sides, characterized so, that for
the purpose of considerable decreasing the roll amplitudes of the
ship in sea-way conditions with a sufficient strength of the wings,
the aspect ratio of the wings is 0.5-0.75, the height of these
short wings is such that they do not protrude beyond the maximum
breadth and base line of the ship, the intervals between the wings
in each line equal to wing's chord, and in a staggered row the
stagger between wings of two lines is equal to the chord, while the
transverse distance between the lines is 0.5-0.7 of the chord.
2. Stabilizer of ship rolling according to claim 1, characterized
so, that for the purpose of reducing the injurious interaction of
wings in the staggered row, the wings form an angle of 2-4.degree.
with the longitudinal axis of the ship, so that the angle in the
one line of the staggered row is in opposite direction to the angle
in the other line.
Description
[0001] The invention belongs to sphere of shipbuilding, in
particular to stabilizers of ship rolling, which do not contain any
parts moving relatively the ship hull. It is known ordinary bilge
keels as narrow bars fastened to the ship's plating along the bilge
turn, at port and starboard sides. The length of the bilge keels is
0.3-0.6 of the ship length L. Complete area of the bilge keels is
about 4% of the product LAB, where B--is the maximum breadth of the
ship. The reduction of roll amplitudes, secured by continuous bilge
keels, at zero forward speed is 40-50%; however, during advance
motion of the ship in irregular waves with a speed of 10-20 knots
the reduction of rolling is not more than 15-20%.
[0002] It is known also roll stabilizing wings attached in
longitudinal lines to boards or bilges of the ship (patent GB
501081, 1936). Two wing lines can be provided on each side, then
the wings of one line can be staggered to those in other line. To
increase the strength of the wings, they are interconnected by a
plate, the ends of which are fastened to the ship hull. The length
of the wings, measured athwartships, and intervals between them are
more than 2-3 chords of the wing. At such aspect ratio the wings
extend beyond the ship cross-section, and at such large intervals
the wing's stagger has no effect on the roll damping of a stopped
ship. Decrease of intervals between the narrow wings to about one
chord is unacceptable since it extremely reduces their lift forces.
"A major disadvantage of this system is its vulnerability to damage
and a weak quenching effect when the ship is at anchor. Hence, the
system is definitely unacceptable"--H. E. Saunders, "Hydrodynamics
in Ship Design", New York, 1957, p. 553. Already 70 years the
arrangement is not applied in shipbuilding, and it has no prospects
in the future.
[0003] The aim of the suggested invention is a considerable
decrease of rolling both at stop and at forward motion of the ship
in sea-way conditions. This aim is attained by arrangement of short
wings (aspect ratio r<0.75) having a sufficient strength and
producing large roll-damping moments.
[0004] Description of the arrangement is explained by following
drawings:
[0005] FIG. 1--Transversal section of the ship in region of the
short wings roll-stabilizer;
[0006] FIG. 2--View on the staggered row of the short wings.
[0007] Wings 1 are fastened immovably in a staggered order to the
ship 2 along the bilge, at port and starboard sides (FIGS. 1 &
2). The wing profiles are parallel to the longitudinal axis of the
ship or form a small angle .beta. with this axis so, that the angle
.beta. in the one line of the staggered row is in opposite
direction to the angle .beta. in the other line.
[0008] To avoid damage of the wings 1, their height h is taken so
that the wings will be within clearences determined by maximum
breadth and base line of the ship (dotted lines in the FIG. 1). The
chord of the wing b exceeds its height, and the aspect ratio is in
limits r=0.5-0.75. Relative thickness of the wing profile is from
0.05 to 0.15 and can be varied along the wing's height. The length
of the wing row is 25-50% of the ship length L. The transverse
distance between two wing lines of the staggered row is d=(0.5-0.7)
b. The longitudinal interval between the wings in each line equals
to chord b. The stagger of wings in one line relative the wings of
other line is also equal to chord b (FIG. 2). Consequently, unlike
the above-mentioned stabilizer of GB 501081, having great intervals
between the wings, in the suggested stabilizer the adjacent wings
are separated one from the other only in transverse direction by a
small distance d, i.e. there are only small transverse gaps, and no
longitudinal gaps in the staggered row. Therefore, at zero advance
speed of the ship the roll damping moment of this stabilizer is
almost equal to that of continuous bilge keels having the same
height and area.
[0009] During motion of the ship with advance speed v and with
angular velocity of rolling .omega., the water flow relatively the
wing has an average velocity V=.nu.+.mu., where .mu.=.omega.R;
R--distance from the middle point of the wing to the roll axis G
(FIG. 1). The angle .alpha. between vectors V and .nu. together
with the angle .beta. form the angle of attack of the wing profile
(.alpha.+.beta.) or (.alpha.-.beta.) (FIG. 2). The moment M.sub.i
of the wing's lift force Y.sub.i about the roll axis is directed
against the angular velocity of the ship .omega. and thereby
decreases the ship rolling.
[0010] At forward speed about 20 knots and roll amplitudes
10-15.degree. the maximum angle .alpha.=.mu./.nu. is equal
3-5.degree.. Therefore it is useful to have the angle .beta. in
limits 2 -4.degree..
[0011] The lift coefficient C.sub.y depends on the angle of attack
and on the wing's aspect ratio r=h/b according to the formula
C.sub.y=5.8(.alpha..+-..beta.)r.sub.e/(2+ {square root over
(r.sub.e.sup.2+2)}), where the effective aspect ratio of the wing,
attached by one end to the hull, is equal r.sub.e=2r.
[0012] The aspect ratio of the wings r=0.5-0.75 secures enough
great values of the lift coefficient C.sub.y, unlike the ordinary
bilge keels having, as a rule, r<0.04.
[0013] The lift force of the wing Y.sub.i is proportional to the
lift coefficient C.sub.y, to square of the speed V and to wing's
area S.sub.i=h.cndot.b.
[0014] The lift forces of a wing line with angles of attack
(.alpha.+.beta.) will be much grater than the lift forces of the
other line, where the angle of attack at this time is
(.alpha.-.beta.). As a result, the injurious interaction of the two
wing lines of the staggered row considerably declines in comparison
with the case when .beta.=0.
[0015] The total area of all the wings S=.SIGMA. S.sub.i is about
0.04 L.cndot.B, therefore the stabilizer's drag does not decrease
essentially the advance speed of the ship.
[0016] The suggested stabilizer provides a summary roll damping
moment M=.SIGMA. M.sub.i which reduces 2-3 times the rolling
amplitudes during motion of the ship with considerable forward
speeds in sea-way conditions.
[0017] It is useful and convenient to install the staggered rows of
short wings on ships with small midship coefficients
(C.sub.M<0.9) and rounded bilges.
[0018] Ships with large midship coefficients (C.sub.M>0.95) or
with angular bilges have a fairly large damping moment of the bare
hull at zero forward speed. Therefore, the short wings
roll-stabilizer can be installed on these vessels without
staggering, i.e. by one wing line on each side of the ship, with
the angle .beta.=0 and longitudinal intervals between the wings
equal to the wing's chord.
* * * * *