IMPROVEMENTS IN THE CONSTRUCTION OF BOATS AND VESSELS
Year: 1881

page_text: LETTERS PATENT to Sydney Pitt, of Sutton, in the County of Surrey, for
an Invention of "IMPROVEMENTS IN THE CONSTRUCTION OF BOATS AND
VESSELS." A communication from abroad by Raoul Pierre Pictet, of Geneva,
Switzerland.
PROVISIONAL SPECIFICATION left by the said Sydney Pitt at the Office
of the Commissioners of Patents on the 29th September 1881.
SYDNEY PITT, of Sutton, in the County of Surrey. "IMPROVEMENTS IN THE
CONSTRUCTION OF BOATS AND VESSELS.' [A communication from abroad by
Raoul Pierre Pictet, of Geneva, Switzerland.]
At the present time boats are all constructed upon the principle of Archimedes,
which is a principle of statical mechanics.
They all displace a weight of water equal to their own weight, and the different
speeds imparted to them only affect in an insignificant manner the volume of the
immersed part
To obtain high speeds investigations have been made as to what should be the
forms of the bottom to permit most easily the displacement of a certain volume of
water equal to the weight of the boat. It is by this study that people have been
led to adopt fine lines in the bottom. The boat is pointed at its two extremities,
and presents near the middle the maximum section of the midship frame.
Under these conditions the power for propulsion increases approximately as the
cube of the speed of the boat.
The improvement which I have made in the construction of boats consists in
availing myself of the principle of Archimedes and of a dynamical principle,
associated the one with the other to facilitate navigation and increase the speed.
In a general manner this application presents itself as follows:-
Suppose me to have a boat of which the bottom is constructed in the following
manner:
The keel is a parabolic curve, represented in the Figures I and II, at A, B.
L

page_text: The bottom of the boat is represented by a surface generated by a right
line R, S, Figure II., constrained to remain horizontal and to pass along the
curve A, B.
A series of ribs A, E, F, H, B, Figures I. and II., giving sufficient strength to the
bottom of the boat are fixed firmly to the keel.
These ribs have each a rectilinear part of a length equal to R, S, and then they
rise and unite with the gunwale of the boat C, V, U, K, D, L, Figures I. and II.
The flanks of the boat and the remainder of the bottom are supported by the
ribs, to which they are solidly fixed.
Thus the bottom of the boat is composed of two parts, which geometrically are
very different; a part which is flat in the direction transverse to the boat, and
parabolic in the direction of the length; and a second part with rounding curves
serving to connect the bottom of the boat with the gunwale.
Such a boat when it is at rest floats on the principle of Archimedes, and the
water line is at M., M.
The back of the boat being B, I will suppose that a screw or a propellor of any
sort gives to the boat a certain speed in the direction B, A. Two phenomina
present themselves concurrently. The still water on which the boat moves receives
a small acceleration from above downwards under the action of the bottom of the
boat; the reaction of this mechanical effect being opposed to the weight of the boat,
this will displace less water and will rise somewhat, the midship section diminishes.
If the speed increases, this reaction of the water also increases, and little by little
the boat tends to rise out of the water and to glide upon the surface.
-Under these conditions it is evident that the immersed midship section becomes
a function of the speed, hence the total resistance which is encountered by the boat-
in its progress is itself a function of the speed.
Calculation applied to a parabolic curve of the form (Figure 1.) y = μ x + + a x² +
(±α²x² +α µx² +µ³x), in which and a are two constants, shows that the boat
will rise progressively, and that for varying velocities from 0 to the maximum
velocity that the motor is able to give the water line is continually and gradually
displaced from the position ML, M, to the limit M, M, Figures I. and II.
This limiting position M, M, corresponds to the tangent to the curve E, F, H, B,
passing through the point A. Analysis shows also that the power expended by the
motor which operates the propellor is no longer proportional to the cube of the
speed; the power varies constantly with the speed, according to a function which 3
passes through a maximum. The derivative changes sign when the speed becomes
equal to a certain value special to each boat, and rigourously defined by the equation
of the surface of the bottom and the total weight of the said bont.
Starting from this speed an increase of speed is accompanied by a decrease of
the power exerted by the muotor. This is the principal result, which can only bc 4
attained by the special bottoms to which this Specification relates.
Thus if I take a boat at rest and I set the engines going I observo the two
following periods:-
1. In the first period it is necessary to increase the admission of steam, that is to
say, the power of the machine, to obtain an increase of speed.
2. Having passed a certain point the boat increases its speed with the diminution
of the power exerted by the motor.
One may calculate before hand the parabolic curves of the bottom which govern
the numerical value for the speed of the boat when the passage is made froin the
first period to the second.
The connecting curves between the bottom and the gunwale and the propellor
may take any form without affecting the progress of the boat in any way.
5

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Sydney Pitt in the Great Seal Patent Office on the 28th March
1882.
SYDNEY PITT, of Sutton, in the County of Surrey. "IMPROVEMENTS IN THE
CONSTRUCTION OF BOATS AND VESSELS." (A communication from abroad by
Raoul Pierre Pictet, of Geneva, Switzerland.)
At the present time boats are all constructed upon the principle of Archimedes,
which is a principle of statical mechanics.
They all displace a weight of water equal to their own weight, and the different
speeds imparted to them only affect in an insignificant manner the volume of the
immersed part.
To obtain high speeds investigations have been made as to what should be the
forms of the bottom to permit most easily the displacement of a certain volume of
water equal to the weight of the boat. It is by this study that people have been
led to adopt fine lines in the bottom. The boat is pointed at its two extremities,
and presents near the middle the maximum section of the midship frame.
Under these conditions the power for propulsion increases approximately as the
cube of the speed of the boat.
The improvement which my correspondent has made in the construction of bonts
consists in making use of the principle of Archimedes and of a dynamical
principle, associated the one with the other to facilitate navigation and increase
the speed.
In a general manner this application presents itself as follows:-
Suppose us to have a boat of which the bottom is constructed in the following
manner:
The keel is a parabolic curve, represented in the Figures I. and II. at A, B.
The concavity of the curve is directed downwards.
The bottom of the boat is represented by a surface generated by a right
line R, S, Figure II., constrained to remain horizontal and to pass along the
curve A, B.
A series of ribs A, E, F, H, B, Figures I. and II., giving sufficient strength to the
bottom of the boat are fixed firmly to the keel.
These ribs have each a rectilinear part of a length equal to R, S, and then they
rise and unite with the gunwale of the boat C, V, U, K, D, L, Figures I. and II.
The flanks of the boat and the remainder of the bottom are supported by the
ribs, to which they are solidly fixed.
Thus the bottom of the boat is composed of two parts, which geometrically are
very different; a part which is flat in the direction transverse to the boat, and
parabolic in the direction of the length; and a second part with rounding curves
serving to connect the bottom of the boat with the gunwale.
Such a boat when it is at rest floats on the principle of Archimedes, and the
water line is at M¹, M'.
The back of the boat being B, we will suppose that a screw or a propellor of any
sort gives to the boat a certain speed in the direction B, A. Two phenomena
present themselves concurrently. The still water on which the boat moves receives
a small acceleration from above downwards under the action of the bottom of the
boat; the reaction of this mechanical effect being opposed to the weight of the bont,
this will displace less water and will rise somewhat, the midship section diminishes.
If the speed increases, this reaction of the water also increases, and little by little
the boat tends to rise out of the water and to glide upon the surface.
Under these conditions it is evident that the immersed midship section becomes

page_text: 47
in its progress is itself a function of the speed.
Calculation applied to a parabolic curve of the form (Figure 1)
y=x+x+(± α²x²³ + α µ x² + µ³ x),
a
a
in which μ and a are two constants, shows that the boat will rise progressively,
and that for varying velocities from 0 to the maximum velocity that the motor is
able to give, the water line is continually and gradually displaced from the position
M³, M', to the limit M, M, Figures I. and II.
This limiting position M, M, corresponds to the tangent to the curve E, F, H, B,
passing through the point A. Analysis shows also that the power expended by the
motor which operates the propellor is no longer proportional to the cube of the
speed; the power varies constantly with the speed, according to a function which
passes through a maximum. The derivative changes sign when the speed becomes
equal to a certain value special to each boat, and rigorously defined by the equation
of the surface of the bottom and the total weight of the said boat.
Starting from this speed an increase of speed is accompanied by a decrease of
the power oxerted by the motor. This is the principle result, which can only be
attained by tho special bottoms to which this Specification relates.
Thus if we take a boat at rest and we set the engines going we observe the two
following periods :—
1. In the first period it is necessary to increase the admission of steam, that is to
Bay, the power of the machine, to obtain an increase of speed.
2. Having
passed-a-certain-point-the-boat-increases its speed with the diminution
of the power oxerted by the motor.
One may calculate before-hand the parabolic curves of the bottom-which-govern-
the numerical value for the speed of the boat when the passage is made from the
first period to the second.
Finally, what I claim under the Patent is the special form for the bottom of
boats constructed upon the principles above set forth. These curves are always
of the parabola family, with concavity directed downwards; this position is {
characteristic.
The connecting curves between the bottom and the gunwale and the propellor
may take any form without affecting the progress of the boat in any way.
In witness whereof, I, the said Sydney Pitt, have hereunto set my hand
and seal, this Twenty third day of March, in the year of our Lord One
thousand eight hundred and eighty two.