Improvements in Navigable Vessels.
Year: 1898

page_text: Improvements in Navigable Vessels.
I, HENRI LOUIS JOSEPH CLEMENT TURC, of Castans, par Cannes (Aude), France,
Naval Sub-Lieutenant, do hereby declare the nature of this invention to be as
follows:-
:-
In the Specification of my Application for Patent No. 7850 of 1898, I have indicated
the possibility of producing vessels, constructed according to that Specification with
their bulls proper submerged, that have very long periods of pitching and long periods
of rolling and are consequently both non-pitching and non-rolling.
Now, the present invention has reference to the special arrangements and the con-
structional conditions of the floats that impart to a vessel whose hull proper is
submerged, the property of being non-pitching and non-rolling.
This characteristic construction and arrangement consists in surmounting the
spindle-shaped hull with a single float, or with a group of floats, such that the moment
of inertia, as to pitching, of the waterline-area will have a very small value-very
much smaller than for ships of ordinary shape of the same tonnage.
This special arrangement of float or of a group of floats has for objects to utilize the
known fact that if a vessel has a period of rolling which is appreciably greater than
the period of the sea-way, it does not roll, or only rolls very little on this sea-way, and;
more generally, if a vessel has, for a certain oscillatory movement, a period appre-
ciably greater than the period of the sea-way, it has very slight oscillations corre-
sponding to this movement. The rolling and pitching of a vessel can therefore be
prevented if there be imparted to the vessel periods of rolling and pitching which are
appreciably greater than the period of the sea-way in the seas which the vessel is
intended to navigate.
Now, the periods of rolling and of pitching for slight oscillations in calm water
are given by the known formulae :-

page_text: centre of gravity of the vessel above the centre of buoyancy of the upright vessel;
I the moment of inertia of the mass of the vessel relative to a horizontal axis
passing through the centre of gravity and situated in a longitudinal central plane;
I, the moment of inertia of the mass of the vessel relative to a horizontal axis
passing through the centre of gravity and perpendicular to the longitudinal central 5
plane; the distance of the latitudinal metacentre above the centre of buoyancy
the upright vessel; and R the distance of the longitudinal metacentre above the
centre of buoyancy of the upright vessel.
The values of o and R are given by the known formulae
in which V represents the volume of the immersed portion of the vessel, i, represents
the moment of inertia of the waterline-area of the vessel with reference to an axis
parallel to the axis in relation to which I, has been taken, and carried through the
point where the vertical line passing through the centre of gravity of the mass of
the vessel meets the waterline, and represents the moment of inertia of the water-
line-area of the vessel with reference to an axis parallel to the axis in relation to
which I has been taken, and carried through the point where the vertical line
passing through the centre of gravity of the mass of the vessel meets the waterline.
Therefore, in order to increase the period of rolling of a vessel of a given tonnage it
will be necessary to increase I, or to diminish p-a; and in order to increase the
period of pitching of a vessel of given tonnage, it will be necessary to increase I, or
to diminish R-a.
Now, on account of the shapes rendered necessary from reasons of construction, of
resistance to progression, and of the nature of the service to be done by the vessel,
the moment of inertia, to rolling, of the mass of the vessel, and especially the
moment of inertia as to pitching, can only vary in slight proportions; therefore, in
order to obtain long periods of rolling, and especially long periods of pitching, you
must either diminish p-a or R-a.
In certain ships such as in many of the French ironclads having ordinary shapes
of hull, by raising the centre of gravity in such a manner that the value of p-a
shall be as small as possible, and just sufficient to prevent the vessel from capsizing
when rolling, there have been obtained vessels which have long periods of rolling
and which consequently do not roll, but they pitch just like vessels of ordinary
shape.
of
This is easily understood. In fact, with the ordinary shapes of hull, the value
P will hardly be greater than from six to seven metres, and as, in order that the
boat shall not capsize, pa must be positive, and a can be at most equal to from six
to seven metres. Now, with the ordinary shapes of hull, R is very large; it amounts
to about 100 metres for a steamboat of 4000 to 5000 tons. Consequently, as a
cannot be greater than six to seven metres, R-a must be equal to about ninety
metres. In consequence of this great value of R-a, although the moment of inertia,
as to pitching, of the mass of the vessel is very great, the vessel will have very small
periods of pitching and consequently it will pitch in most seaways.
Now, the form of hull which I propose to employ has for object to suppress pitching
by giving to the vessel long periods of pitching. To this end, the waterline-area is
reduced and is collected towards the centre of the ship, in such a manner that its
moment of inertia as to pitching will be very small-very much smaller than for ships
of ordinary shape of the same tonnage-so as to diminish the value of R; thus, as an

page_text: example given for the sake of clearness, the value of R which, with the ordinary shapes
of hull would be about 100 metres for a tonnage of 5000 tons, will not be, for the
form which I propose, greater than from five to six metres at the maximum. This
property of constituting vessels having very long periods of pitching is the
characteristic property of the form of hull which I propose.
In order to obtain at the same time long periods of rolling, I construct my vessel in
such a manner as to render the value of p-a small; either, as in the ship shown in
Figs. 1, 2, and 3, the principal characteristic features of which will be hereinafter
given, by arranging the float (or the group of floats) in such a manner that the
moment of inertia, as to rolling, of the waterline-area will be very small, transverse
stability being then solely due to the weight and being insured, if necessary, by
means of ballast, arranged in such a manner as to increase the moment of inertia, as
to rolling, of the mass of the vessel; or as in the vessel shown in Figs. 4, 5 and 6, the
principal characteristic features of which will be hereinafter given, by arranging the
float, or the group of floats, in such a manner that the moment of inertia, as to
rolling, of the waterline-area will be rather large and will aid in insuring the trans-
verse stability of the vessel.
The vessel is symmetrical relatively to the longitudinal central plane which contains
the axis of oscillation for rolling, rr (Fig. 7) so that, according to known geometrical
properties, the period of oscillation of the vessel about a horizontal axis M M¹
passing through the centre of gravity and located between the axis of oscillation as to
rolling, r, and the axis of oscillation as to pitching, tt, will be between the period
of oscillation for rolling and the period of oscillation for pitching; consequently it
will be long if these two periods are long.
In order to enable the invention to be properly understood, there are illustrated
diagrammatically in the accompanying drawings, but by way of example only, two
vessels constructed according thereto.
Figs. 1, 2, and 3, relate to a non-rolling and non-pitching submerged vessel having
one float only, Fig. 1 being a longitudinal elevation, Fig. 2 a plan showing the float
in section, and Fig. 3 a section corresponding to the line 3-3 of Fig. 1.
Figs. 4, 5, and 6 show a non-rolling and non-pitching submerged vessel provided
with two floats, Fig. 4 being a longitudinal elevation thereof, Fig. 5 a plan showing
the floats in section, and Fig. 6 a section corresponding to the line 6-6 of Fig. 4.
In the vessels shown in these figures, F is a submerged spindle-shaped body con-
stituting the hull proper and containing the motive and propelling apparatus; f is a
float, or one of the floats, surmounting the said hull; P is a platform containing the
cabins for the passengers; Q is a double keel serving as ballast; care chimneys and
ventilators; A is a horizontal fixed float-board of large surface situated at the rear of
the vessel and having a function described in the aforesaid Specification No. 7850
of 1898; q is a horizontal fixed rudder capable of being varied and regulated as to
position; q is an ordinary horizontal rudder either automatic or non-automatic; X X
represents the axis of the spindle-shaped hull. The waterline for normal immersion
is indicated by xx. The parts filled with an obturating and bulky material for
stopping the water-passages and filling up the compartments that are most exposed to
collision are indicated by hatching. In order to show in a more striking manner still
the advantages of my invention, I will now, for each of the two vessels, but solely by
way of example, and without restricting thereby in any way the generality of the
application of the invention, give a table showing the principle weights and the cal-
culations of stability. It will be noted that the weights are in all cases calculated
with a large margin and are much greater than those which would be necessary in
practice for the construction of the ship, whilst the calculations are made with an
accuracy that is sufficient for practical work.

page_text: The two vessels have periods of rolling of about 22 seconds and 20 seconds, and
periods of pitching of about 30 seconds and 23 seconds respectively. These
periods are much longer than those of the swells of a seaway, the ordinary period of
which is rarely greater than 15 seconds.
It is only in large stretches of water such as the Pacific Ocean, the Indian Ocean,
the Atlantic Ocean, and the seas around the South Pole that seaways are met with
The two vessels
(and then only very rarely) having a period of nearly 20 seconds.
that are given as examples will hardly ever pitch or roll, and in certain seas such as
the Mediterranean they will never pitch or roll-consequently, on account of the
geometrical property above referred to, they will have an absolute immobility of
platform, whereas a vessel of ordinary shape of the same tonnage would frequently
meet, in all seas, with swells that would cause it to pitch.
The lower floor of the platform being about ten inetres in most cases above the
normal waterline (Figs. 1 and 3, 4 and 6), and a float or group of floats presenting
but a slight hold to the sea, even in heavy weather, the water will flow freely under
the platform which will be very comfortable to live on. These vessels will conse-
quently be extremely comfortable and will be particularly suitable for the purposes of
yachts and mail-steamers.
I may state that in the case of such vessels, the periods of rolling and pitching
will vary as the square root of the dimensions and consequently as the sixth root of
the displacement. A vessel of half the tonnage similar to one of the two vessels

page_text: above referred to, would have periods of pitching and periods of rolling such that in
the Mediterranean it would have an absolutely immovable platform.
These two examples will shew what a great improvement will be effected by the
shape of hull that I propose.
The property of the shape of hull that I propose giving to ships having a very
long period of rolling, is due to the fact that the moment of inertia as to pitching
of the waterline-area is very small. Consequently, this moment of inertia must not
increase, and for this purpose the hull must not come out of the water.
In my
opinion, the waterline-area indicated (sixty square metres for one of the vessels, and
120 square metres for the other) and the depth of immersion of the hull (four
metres) appear to be sufficient to maintain the hull under water even in a heavy
sea.
If practice shews that the float, or the group of floats, is insufficient to keep the
hull under water even in a heavy sea, the following expedients may be employed.
For the vessel with one float the width of the float may be greatly increased, and its
length be slightly diminished, in such a manner as to increase the waterline-area
without increasing the value of R; the value of p would always be very small. For
the vessel with two floats, the width of the two floats may be greatly increased and
their length be slightly diminished in such manner as to increase the waterline-area
without increasing the value of R; the same value of p will be retained on shifting
the two floats towards each other. Also, whilst maintaining the same section for the
floats, there might be provided in the boat a water-ballast which would be filled in
the case of a heavy sea, for the purpose of having a greater immersion of the hull.
The increase in the draught thereby produced would not by itself constitute a draw-
back, because the hull would be immersed to a greater depth only where there are
heavy seas and where the depth is very great. The platform would have to be
arranged at a higher level in order to be sheltered from the sea in all weathers.
The vessel would, of course, be provided with the following parts, which are
indicated on the drawings in Figs. 1 and 2, 4 and 5, the functions of which have
been explained in the aforesaid Specification No. 7850 of 1898, and which aid to
diminish the pitching:
-:
1. A fixed horizontal float-board of large surface (indicated by A in Figs. 1 and 2,
4 and 5) provided at the rear of the vessel and aiding to cause the vessel to resume
its longitudinal trim the more in proportion as it is more inclined. This float-board,
by preventing the hull from emerging from the water, will insure for the vessel a
small and compact waterline-area and will consequently insure for the vessel long
periods of pitching and will prevent it from pitching. Furthermore, the great
resistance which will be offered by the float-board in the oscillatory movements of the
longitudinal trim of the vessel will deaden these oscillations and will aid in rendering
the pitching inappreciable.
2. A horizontal rudder indicated by q (Figs. 1 and 2, 4 and 5) which is normally
fixed but is variable as to position, which may be modified according to the speed and
according to the immersion of the vessel.
3. An ordinary horizontal rudder, which may be automatic or may be operated' by
one man, for counteracting instantaneously any accidental deviation from the
longitudinal trim.
It is certain that this new form of hull, whilst contributing in a very great measure
to suppress the pitching, and in a less measure to suppress the rolling, does not
insure the suppression of the pitching and of the rolling whatever the tonnage may
be. By reason of the elongated form in the direction of progression, the moment of
inertia, as to pitching, of the mass of the boat is large for a small tonnage, and a
period of pitching of about 20 seconds can be obtained with a vessel of from 500 tons
to 1000 tons. For rolling, a greater tonnage is necessary, from 1500 tons to
3000 tons, in order to obtain with the forms that I propose, a vessel giving every
security against capsizing and having a period of rolling of about 20 seconds.
In constructing a vessel according to this invention I prefer to make the length
of the float or group of floats at most equal to about one third of the length of the

page_text: spindle-shaped hull, and the moment of inertia, as to pitching, of the waterline-area
at most equal to about one thirtieth of that of a vessel of ordinary form of the same
tonnage; if the transverse stability is to be due to weight only, and the moment of
inertia, as to rolling, of the waterline-area is consequently to be very small, I prefer to
make the width of the float or group of floats at most equal to about half the width
of the spindle-shaped hull (type illustrated in Figs. 1, 2, and 3), whilst if the
transverse stability is to be due to the greatness of the moment of inertia, as to
rolling, of the waterline-area, I prefer to make the width of the float or group of
floats at least equal to about two thirds of the width of the spindle-shaped hull (type
illustrated in Figs. 4, 5, and 6).
t 1000
I, HENRI LOUIS JOSEPH CLÉMENT TURC, of Castans, par Cannes (Aude), France,
Naval Sub-Lieutenant, do hereby declare the nature of this invention and in what
manner the same is to be performed, to be particularly described and ascertained
in and by the following statement:―
In the Specification of my Application for Patent No. 7850 of 1898,I have indicated
the possibility of producing vessels constructed according to that Specification with
their hulls proper submerged, that have very long periods of pitching and long
periods of rolling and are consequently both non-pitching and non-rolling.
Now the present invention has reference to the special arrangement and the
constructional conditions of the floats that impart to vessels whose hulls proper are
submerged, the property of being non-pitching and non-rolling.
This characteristic arrangement consists in surmounting the spindle shaped hull
with a single float, or with a group of floats, such that the moment of inertia, as to
pitching, of the water-line area will have a very small value-very much smaller
than for ships of ordinary shape of the same tonnage.
This special arrangement of float or of a group of floats has for object to utilize
the known fact that if a vessel has a period of rolling which is appreciably greater
than the period of the sea-way, it will not roll, or roll only very little on this sea-way,
and, more generally, if a vessel has, for a certain oscillatory movement, a period
appreciably greater than the period of the sea-way, it will have very slight oscillations
corresponding to this movement. The rolling and pitching of a vessel will therefore
be prevented if there be imparted to the vessel periods of rolling and pitching that
are appreciably greater than the period of the sea-ways in the seas that the vessel is
intended to navigate.
Now, the periods of rolling and of pitching for slight oscillations in calm water are
given by the known formulae :—

page_text: In these formulae, P represents the weight of the vessel; a the distance of the
centre of gravity of the vessel above the centre of buoyancy of the upright vessel;
I, the moment of inertia of the mass of the vessel relative to a horizontal axis passing
through the centre of gravity and situated in a longitudinal central plane; I, the
moment of inertia of the mass of the vessel relative to a horizontal axis passing
through the centre of gravity and perpendicular to the said longitudinal central
plane; p the distance of the lateral metacentre above the centre of buoyancy of the
upright vessel; and R the distance of the longitudinal metacentre above the centre
of buoyancy of the upright vessel.
The values of o and R are given by the known formulae
in which V represents the volume of the immersed portion of the vessel, i, represents
the moment of inertia of the water-line area of the vessel with reference to an axis
parallel to the axis in relation to which I, has been taken, and carried through the
point where the vertical line passing through the centre of gravity of the mass of the
vessel meets the water-line plane and it represents the moment of inertia of the
water-line area of the vessel with reference to an axis parallel to the axis in
relation to which I, has been taken, and carried through the point where the vertical
line passing through the centre of gravity of the mass of the vessel meets the water-
line plane.
Practical navigation has shown that for fairly large vessels of a greater displace-
ment than about 1000 tons, the periods of rolling and pitching in rough water have
very nearly the same values as in calm water.
Therefore, in order to increase the period of rolling of a vessel of a given tonnage
it is necessary to increase J, or to diminish p-a; and in order to increase the period
of pitching of a vessel of given tonnage, it is necessary to increase I or to
diminish R-a.
Now, on account of the shapes rendered necessary from reasons of construction, of
resistance to progression, and of the nature of the service to be done by the vessel,
the moment of inertia, as to rolling, of the mass of the vessel, and especially the
moment of inertia as to pitching, can vary only in slight proportions; therefore,
in order to obtain long periods of rolling, and especially long periods of pitching, one
must diminish either p-a or R-a.
In certain ships (as in many of the French ironclads) having ordinary shapes of
hull, by raising the centre of gravity in such a manner that the value of p-a would
be as small as possible, and just sufficient to prevent the vessel from capsizing when
rolling, there have been obtained vessels which have long periods of rolling and
which consequently do not roll; but such vessels pitch like vessels of ordinary
shape.
This is easily understood. In fact, with the ordinary shapes of hull, the value of p
is hardly greater than from six to seven metres; therefore, since, in order that the
boat may not capsize, p-a must be positive, a can be at most equal to from six to
seven metres. Now, with the ordinary shapes of hull, R is very large, amounting to
about 100 metres for a steamboat of 4000 to 5000 tons; consequently, as a cannot
be greater than from six to seven metres, R-a must be equal to about ninety metres.
In consequence of this great value of R-a, although the moment of inertia, as to
pitching, of the mass of the vessel may be very great, the vessel will have very small
periods of pitching and consequently it will pitch in most seaways.
Now, the form of hull that I propose has for object to suppress pitching by giving
to the vessel long periods of pitching. To this end, the water-line area is reduced
and is collected towards the centre of the ship, in such a manner that its moment of
inertia as to pitching will be very small-very much smaller than in the case of ships
of ordinary shape of the same tonnage-so as to diminish the value of R; thus, as an
example given for the sake of clearness, the value of R which, with the ordinary shapes
B

page_text: of hull would be about 100 metres for a tonnage of 5000 tons, will not be, for the
form which I propose, greater than from five to six metres at the maximum.
This property of constituting vessels having very long periods of pitching is the
characteristic property of the form of hull which I propose.
In order to obtain at the same time long periods of rolling, I construct my vessel
in such a manner as to render the value of p-a small; either, as in the ship shown
in Figs. 1, 2, and 3, the principal characteristic features of which will be herein-
after given, by arranging the float (or the group of floats) in such a manner that
the moment of inertia, as to rolling, of the water-line area will be very small, trans-
verse stability being then solely due to the weight and being insured, if necessary,
by means of ballast arranged in such a manner as to increase the moment of inertia,
as to rolling, of the mass of the vessel; or, as in the vessel shown in Figs. 4, 5, and 6,
the principal characteristic features of which will be hereinafter given, by arranging
the float, or the group of floats, in such a manner that the moment of inertia, as to
rolling, of the water-line area will be rather large and will insure the transverse
stability of the vessel.
The axes, with reference to which I, and I have been taken, are, owing to the
shape of the vessel and the distribution of the weights, principal axes of inertia of
the mass of the vessel; in the same way, the axes, with reference to which i, and it
have been taken, are, owing to the shape of the water-line area, the principal axes
of inertia of the water-line area. Consequently the period of oscillation about a
horizontal axis M M (Fig. 7) passing through the centre of gravity, located
between the axis of oscillation for rolling, rr, and the axis of oscillation for
pitching, tt, and making an angle a with the latter axis, will be expressed by:
of the second member varies constantly in the same direction; it remains therefore
between T, and T.; consequently the period of oscillation about the axis M M¹ will
be long if the two periods are long.
In order to enable the invention to be properly understood, there are illustrated
diagrammatically in the accompanying drawings, but by way of example only, two
vessels constructed according thereto.
Figs. 1, 2, and 3 relate to a non-rolling and non-pitching submerged vessel
having one float only.
Fig. 1 is a longitudinal elevation thereof; Fig. 2 is a plan, the starboard cabins
being supposed to be taken away; and Fig. 3 is a section corresponding to the
line 3-3 of Fig. 1.
Figs. 4, 5, and 6 show a non-rolling and non-pitching submerged vessel provided
with two floats. Fig. 4 is a longitudinal elevation thereof; Fig. 5 is a plan, the
starboard cabins being supposed to be taken away; and Fig. 6 is a section corre-
sponding to the line 6-6 of Fig. 4.
Fig. 7 is a geometrical diagram.
In the vessels shown in the drawings, F is a submerged spindle-shaped body
constituting the hull proper and containing the motive and propelling apparatus ;
f is the float, or one of the floats, surmounting this hull; P is a platform supporting
the cabins for the passengers; Q is a double keel serving as ballast; c are chimneys
and ventilators; d are passages placing the hull into communication with the
cabins; A is a horizontal fixed float-board of large surface situated at the rear of
the vessel and having a function described in the aforesaid Specification No. 7850
of 1898; q is a horizontal fixed rudder capable of being varied and regulated as to
position; q is an ordinary horizontal rudder either automatic or non-automatic ;
X X is the axis of the spindle-shaped hull; the water-line for normal immersion is

page_text: indicated at xx; the parts filled with an obturating and bulky material for stopping
the water-passages and filling up the compartments that are most exposed to
collision are indicated by a hatching of alternate dotted and full lines; and the parts
containing the water-ballast are indicated by a hatching of crossed lines.
In order to show in a more striking manner still the advantages of my invention, I
will now, for each of the two vessels, but solely by way of example, and without
restricting thereby in any way the generality of the application of the invention, give
a table showing the principal weights and the calculations of stability. It will be
noted that the weights are in all cases calculated with a large margin and are much
greater than those that would be necessary in practice for the construction of the
ship, whilst the calculations are made with an accuracy that is sufficient for practical
work.
The following table relates to the non-pitching and non-rolling submerged vessel
shown in Figs 12 and 3.—

page_text: The two vessels have periods of rolling of about 26 seconds and 22 seconds, and
periods of pitching of about 27 seconds and 26 seconds respectively. These periods
are much longer than those of the ordinary seaways, the period of which is rarely
greater than 15 seconds. It is only in large stretches of water such as the Pacific
Ocean, the Indian Ocean, the Atlantic Ocean, and the seas around the South Pole
that seaways are met with (and then only very rarely) having a period of nearly
20 seconds. The two vessels that are given as examples would hardly ever pitch or
roll, and in certain seas such as the Mediterranean they would never pitch or roll-
consequently, on account of the geometrical property above referred to, they will
have an absolute immobility of platform, whereas a vessel of ordinary shape of the
same tonnage would frequently meet in all seas, with seaways that would cause it to
pitch.

page_text: The platform P, being, in the vessel shown in Figs. 1, 2, and 3, about 10 metres,
and, in the vessel shown in Figs. 4, 5, and 6, about 14 metres, above the normal water-
line, and the float (or the group of floats) offering little hold to the sea, even in bad
weather, the water will circulate freely under the platform and the cabins will be
very habitable. These vessels will consequently be eminently comfortable and will
be particularly suitable as packet boats and yachts.
In the two-float vessel shown in Figs. 4, 5, and 6, transverse stability is insured by
the two floats, which are of very slight cross section, but which are placed at a great
distance from each other. Consequently it has been possible to omit the ballast
while placing the cabins at a greater height above the sea and making them heavier.
The security against capsizing when rolling, without being absolute as in the type
shown in Figs. 1, 2, and 3, the stability of which is due to the weights, is amply
sufficient; it is as large as in ordinary packet boats, and in practice I should give the
preference to the type shown in Figs. 4, 5, and 6 with two floats abreast of each other
and without ballast. I may state that in the case of such vessels the rolling and
pitching periods vary as the square root of the dimensions and therefore as the sixth
root of the displacement. A vessel of half the tonnage and otherwise like one of the
boats described and illustrated, would have rolling and pitching periods such that in
the Mediterranean it would have an absolutely motionless platform.
These two examples will show what a great improvement will be effected by the
shape of hull that I propose.
The property of the shape of hull that I propose, of giving to ships a very long
period of rolling, is due to the fact that the moment of inertia, as to pitching, of the
water-line area is very small.
Consequently, this moment of inertia must
In my
not increase, and for this purpose the hull must not come out of the water.
opinion, the water-line area indicated (120 square metres for one of the vessels, and
210 square metres for the other) and the depth of immersion of the hull (four
metres) appear to be sufficient to maintain the hull under water even in a heavy
sea.
If practice shewed that the float, or the group of floats, is insufficient to keep the
hull under water even in a heavy sea, one might either increase the water-line area
of the floats, or, leaving the floats of the same cross section, arrange a water-ballast
apparatus in the vessel to be filled in the case of a heavy sea for the purpose of further
submerging the hull. The increase in the draught thereby produced would not by
itself constitute a drawback, because the hull would be immersed to a greater depth
only where there are heavy seas and where the depth is very great. The cabins
would consequently have to be arranged at a higher level in order to be sheltered
from the sea in all weathers.
The platform P alone would be connected to the hull; the cabins would form a
certain number of water-tight compartments E-four for instance, as indicated in
Figs. 2 and 5.
These compartments would be simply laid on the platform and secured in such a
manner as not to become displaced in the event of any accidental rolling or pitching
which might be experienced by the vessel, but secured also in such a manner that
they could detach themselves from the vessel and form a raft in the event of the vessel's
foundering. The employment of floating cabins is not novel, but with the proposed
form of hull there would be much less fear than with the ordinary form of hull that
the floating cabins would be capsized or staved in by the vessel at the moment of
foundering. It is not, however, desired to lay any claim to the provision of floating
cabins in a vessel as herein described and shown, as such provision forms no part of
the present invention.
The coal-bunkers would be divided into water-tight compartments of small size.
These bunkers would be filled with water as the coal were consumed so
keep the vessel trimmed and to insure stability.
as to
Owing to the low value of R-a, the shifting of a light weight from forward
aft would vary the longitudinal trim to an appreciable degree. A special water-

page_text: ballast, which would be moved from forward aft by means of pumps or compressed
air, would enable a suitable trim to be easily maintained.
The vessel would be provided with the following parts, which are indicated on
the drawings in Figs. 1 and 2 and in Figs. 4 and 5, the functions of which have
been explained in the aforesaid Specification No. 7850 of 1898, and which aid in
diminishing the pitching:-
(1.) A fixed horizontal float-board of large surface (indicated by A in Figs. 1 and 2,
and in Figs. 4 and 5) arranged at the rear of the vessel and aiding in causing the
vessel to resume its longitudinal trim in proportion to its inclination. This float-
board, by preventing the hull from emerging from the water, will insure for the vessel
a small and compact water-line area and consequently will insure for the vessel long
periods of pitching and will prevent it from pitching. Furthermore, the great
resistance that will be offered by the float-board in the oscillatory movements of the
longitudinal trim of the vessel will deaden such oscillations and will aid in rendering
the pitching inappreciable.
(2.) A horizontal rudder (indicated by q in Figs. 1 and 2, and in Figs. 4 and 5)
which is normally fixed but is variable as to position and may be modified according
to the speed and according to the immersion of the vessel.
(3.) An ordinary horizontal rudder, which may be either automatic or operated by a
man, for counteracting instantaneously any accidental deviation from the longitudinal
trim.
It is certain that this new form of hull, whilst contributing in a very great measure
to suppress the pitching, and in a less measure to suppress the rolling, does not insure
the suppression of the pitching and of the rolling whatever the tonnage may be. By
reason of the elongated form in the direction of progression, the moment of inertia, as
to pitching, of the mass of the vessel is large for a small tonnage, and a period of
pitching of about 20 seconds can be obtained with a vessel of from 500 tons to
1000 tons.
For rolling, a greater tonnage is necessary-say, from 1200 tons to 3000 tons-in
order to obtain with the forms that I propose, a vessel giving every security against
capsizing and having a period of rolling of about 20 seconds.
In constructing a vessel according to this invention I make the length of the float
or group of floats at most equal to about one half or one third of the length of the
spindle-shaped hull, and the moment of inertia, as to pitching, of the water-line area
determined by the float or group of floats at most equal to about one thirtieth of that
of a vessel of ordinary form of the same tonnage; if the transverse stability is to be
due to weight only, and the moment of inertia, as to rolling, of the water-line area is
consequently to be very small, I prefer to make the width of the float or group of
floats at most equal to about half the width of the spindle-shaped hull (type
illustrated in Figs. 1, 2, and 3), whilst if the tranverse stability is to be due to the
greatness of the moment of inertia, as to rolling, of the water-line area, I prefer to
make the width of the float or group of floats at least equal to about two thirds of the
width of the spindle-shaped hull (type illustrated in Figs. 4, 5, and 6).
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
1. A navigable vessel comprising a submerged spindle-shaped body forming the hull
proper, and a float or group of floats which surmounts the hull proper, is arranged at
the centre of the hull, and has a cross section and a submerged depth sufficient to
insure the submersion of the hull, and whose length is at most equal to about one half
or one third of the length of the hull so that the moment of inertia, as to pitching,
of the water-line area determined by the float or group of floats which is not sub-
merged, will be very small-at most equal to about one thirtieth of that of a vessel of
ordinary form of the same tonnage--so as to give the vessel a very long period of
pitching of about 20 seconds, a period which results in the novel consequence that a
vessel of the form indicated will never pitch in certain seas in which vessels of the

page_text: ordinary shape and of the same tonnage often pitch, and that it will scarcely ever
pitch on any sea; the vessel comprising either a single float (Figs. 1, 2, 3), the
stability being then due to the weights, or two floats or a group of floats abreast
of each other (Figs. 4, 5, and 6), the stability being then insured by the floats;
the weights being in all cases arranged so that the value of p - a will be the
lowest possible so as to give the vessel also a long rolling period and as a conse-
quence an almost absolutely motionless platform, substantially as described.
2. Navigable vessels constructed and arranged (apart from the floating cabins E)
substantially as hereinbefore described with reference to and shown respectively in
Figs. 1, 2, and 3 and in Figs. 4, 5, and 6 of the accompanying drawings.
Dated this 31st day of May 1899.
F. WISE HOWORTH,
46, Lincoln's Inn Fields, London, W.C., Agent for the Applicant.