AN IMPROVED METHOD OF REDUCING THE FRICTION OF VISSELS WHEN TRAVELLING ON THE WATER
Year: 1877

page_text: LETTERS PATENT to John Isaac Thornycroft, of the Firm of John I.
Thornycroft and Co, Steam Yacht and Launch Builders, of Church Wharf,
Chiswick, in the County of Middlesex, for the Invention of "AN IMPROVED
METHOD OF REDUCING THE FRICTION OF VISSELS WHEN TRAVELLING ON
THE WATER”
Sealed the 17th July 1877, and dated the 31st January 1877
PROVISIONAL SPECIFICATION left by the said John Isaac Thornycroft at
the Office of the Commissioners of Patents on the 31st January 1877
JOHN ISAAC THORNYCROFT, of the Firm of John I. Thornycroft and Co,
Steam Yacht and Launch Builders, of Church Wharf, Chiswick, in the County of
Middlesex "AN IMPROVED METHOD OF REDUCING THE FRICTION OF VESSELS
WHEN TRAVELLING ON THE WATER."
According to my Invention in order to reduce the friction of a vessel when
travelling on the water I interpose a layer or body of air between the bottom of
the vessel and the surface of the water, which air I confine within a cavity of the
bottom of the vessel so that the air shall be carried along with the vessel over the
surface of the water, the an being in direct contact with the exterior of the bottom
of the vessel and with the surface of the water below it To this end the bottom of
the vessel is formed with an external cavity into which air is forced so as to dis-
place water from the cavity, and the air is maintained at such pressure as to keep
the cavity filled, or nearly so, with an, such air as may escape being replaced
In some cases more than one cavity supplied with air as described may be
employed.

page_text: "AN IMPROVED METHOD OF REDUCING THE FRICTION OF VESSELS WHEN TRAVELLING
ON THE WATER
"
According to my Invention in order to reduce the friction of a vessel when
travelling on the water I interpose a layer or body of air between the bottom of the
vessel and the surface of the water, which an I confine within a cavity of the
bottom of the vessel so that the u shall be cared along with the vessel over
the surface of the water, the au being in -duect contact with the exterior of the
To this end the
bottom of the vessel and with the surface of the water below it
bottom of the vessel is formed with an external cavity into which air is forced so as
to displace water from the cavity, and the an is maintained at such pressure
as to keep the cavity filled, or nearly so, with an, such an as may escape being
replaced
In some cases more than one cavity supplied with air as described may be
einployed
Such being the nature of my said Invention I now proceed to describe the manner
of canying it into practical effect as illustrated in the accompanying Diawings, in
some views whereof dots are used to represent air
Fig 1 (Sheet 1) is a central longitudinal vertical section (in the line A, A, of
Fig 2) of a vessel according to my Invention, Fig 2 shews the bottom of the
vessel as seen from above
Fig 31epresents a number of half-sections taken transversely and marked with
letters of reference which agree with the letters applied to the corresponding section
lines in Figs 1, 2, 4, and 5, Fig 4 is a longitudinal vertical section in the line G, G,
of Fig 2, Fig 5 is a longitudinal vertical section in the line H, H, of Fig 2
The views are diawn to the scale of one-fourth of an inch to the foot
The form of this
a is the external cavity formed in the bottom of the vessel
cavity is clearly indicated in the Diawings At its forward part it is in communi-
cation with a channel b whose bottom is perforated by preference throughout the
length of the channel Into this channel an is forced by suitable means, such as
pumps, which may be of ordinary construction, so that the au escaping through the
perforations in the bottom of the channel shall displace water from the cavity a, for
which purpose the au should, as already explained, be maintained at such pressure
as to keep the cavity filled, or nearly so, with air. I prefer so to arrange the load
that the centre of gravity of the vessel shall be at or near to the centre (viewed in
plan) of the arca over which the layer of an interposed between the bottom of the
vessel and the surface of the water extends
It has often been proposed to make a vessel ise to near the surface of the water
by giving an extended inclined bottom and high speed, but the function of the
surface has so far as I know always rendered the proposition impracticable owing
to the magnitude of the force requied to overcome the fiction Now, my improve-
ment is designed to provide an extended supporting sui face almost without fiiction
with a view to the attainment of quick speeds In order to make a vessel which
should rise nearly to the surface at a moderate speed a large amount of water should
be acted on vertically and a downward motion impressed, the width of vessel
measures the surface acted on in a given distance, so the width of the vessel should
be as great as practicable The water should only be acted on for a short time so
the length of vessel (in the duection of intended motion) should be as little as
practicable From these considerations I have been induced to propose the vessel
for quick speed, about as broad as long, and of an elliptic or encular form in plan|
(not confining myself however to these forms), and as shallow as convenient
Fig 6 (Sheet 2) is a central longitudinal vertical section in the line I, I, of Fig 7
of a shallow draught vessel constructed according to my Invention and adapted for
calm waters, and intended to carry considerable loads at moderate speeds with great
economy of power
Fig 7 is a view partly shewing different horizontal sections, and partly represent-
ing the bottom of the vessel
Fir 8 represents a number of half sections taken transversely and marked with

page_text: letters of reference which agree with the letters applied to the corresponding section
lines in Figs 6 and 7.
Figs 6 to 8 inclusive are diawn to a scale of one-eighth of an inch to the foot.
a is the cavity in the bottom of the vessel supplied with air forced in as described
with reference to the preceding arrangement This vessel may be propelled by any
well known means If side paddles are used it will be desuable to keep them
farther than usual from the vessel's side, as indicated in the Drawing, to avoid too
great a disturbance of the water in proximity to the an cavity
Having described the nature of my said Invention, and explained the mode of
carrying the same into practical effect, I hereby declare that I clann as the Inven-
tion secured to me by the herein-before in part recited Letters Patent the method
substantially as herein-before described with reference to the accompanying Draw-
ings of reducing the friction of vessels when travelling on the water
In witness whereof, I, the said John Isaac Thornycroft, have hereunto set
my hand and seal, this Thirtieth day of July, in the year of our Lord
One thousand eight hundred and seventy-seven.
JOHN I THORNYCROFT, CE. (L.S.)