CERTAIN IMPROVED METHODS OF PROPELLING VESSELB
Year: 1839

page_text: RENNIE'S SPECIFICATION.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, GEORGE
RENNIE, of Holland Street, Blackfriars, in the County of Surrey, Civil
Engineer, send greeting.
WHEREAS Her present most Excellent Majesty Queen Victoria, by Her
Letters Patent under the Great Seal of the United Kingdom of Great Britain,
bearing date at Westminster, the Twenty-sixth day of November, in the third
year of Her reign, did, for Herself, Her heirs and successors, give and grant
unto me, the said George Rennie, my exors, adiiors, and assigns, Her especial
licence, full power, sole privilege and authority, that I, the said George Rennie,
my exors, admors, and assigns, and such others as I, the said George Rennie,
my exors, adñiors, and assigns, should at any time agree with, and no others,
from time to time and at all times during the term of years therein expressed,
should and lawfully might make, use, exercise, and vend, within that part of
Her said United Kingdom of Great Britain and Ireland called England, Her
Dominion of Wales, and the Town of Berwick-upon-Tweed, and also in all
Her Majesty's Colonies and Plantations abroad, my Invention of "CERTAIN
IMPROVED METHODS OF PROPELLING VESSELB;" in which said Letters Patent is
contained a proviso, that I, the said George Rennie, shall cause a particular
description of the nature of my said Invention, and the manner in which the
same is to be performed, to be inrolled in Her said Majesty's High Court of
Chancery within six calendar months next and immediately after the date
of the said in part recited Letters Patent, as in and by the same, reference
being thereunto had, will more fully and at large appear.

page_text: NOW KNOW YE, that, whereas common paddle wheels with their rectan-
gular floats have, on account of the great depth and bulk necessary to be
given to them in order that they may take a sufficient hold of the water, and
of the position necessarily assigned to them at the sides of any vessel to which
they are applied, a great tendency to increase the rolling of the vessel in heavy
seas, present a most inconvenient breadth of surface to opposing winds, and
when they happen to be deeply immersed, offer a degree of resistance which
the engines have difficulty in overcoming: And whereas also the common
paddle wheels cause, by the striking of the edges of the rectangular floats upon
the water, a strong vibratory motion in the vessel and machinery, and con-
sequently a great increase in the wear and tear of both: Now, the nature of
my said invented improvements consists, firstly, in applying to the common
paddle wheel a float of a new construction, by which the several defects
before mentioned are either obviated, or their retarding influence greatly
diminished; and, secondly, in substituting for the common paddle wheel a new
propeller, of an entirely different construction, which revolves in the water
without concussion, and may be fixed at the stem, at the stern, or at the
middle, as well as at the sides, of a vessel, and may be driven equally well,
whether submerged to no greater extent than to be merely covered by the
water, or to any greater depth.
And I declare that the manner in which my said invented improvements
are performed is fully represented and explained in the Drawings hereunto
annexed, and in the following description thereof, that is to say:
Figure 1 is a lateral section of one radius of a paddle wheel fitted with the
floats of my new construction; and Figure 2, a side view of the entire wheel.
The floats are of a trapezoidal instead of a rectangular form. I prefer that they
should have the form of a trapezium, such as is represented in the Drawing,
Figure 1, in which the diagonals are in the proportion to one another, of one
to one and a half, and that they should be so fixed that the greatest of these
diagonals shall be vertical, as is also shown in the said Figure; but they may
be of any other form which can result from the bisection of a cone, and
whether the faces of the same be plain, or convex, or concave.
Not only is
the propelling power to be obtained by floats of this trapezodial form greater
than what can be obtained from an equal amount of surface of a rectangular
shape, but they enter and leave the water more gradually and smoothly.
Figure 3 is a side view, and Figure 4 a transverse section, of the new pro-
peller, by which I propose to do away with common paddle wheels altogether.
It consists of two or more curvilineal leaves or. plyers, formed as follows, and
attached to a shaft or axis. The curves of which the leaves or plyers should

page_text: be formed are obtained by the descent of a tracer down the surface of a conc
or conoid caused to revolve on its axis. Curves so obtained have a constantly
varying inclination with their axis, and I find by experiment that a shaft, with
leaves or plyers formed after such curves, revolves in water with a greater
propelling power than a shaft with any other sort of curved leaves or curved
surfaces. The conoidal mould on which the lines are so traced may be of any
degree of inclination from the apex to the base, but I prefer that it shall be
of such a form that its abscisses shall increase or diminish in arithmetical
progression, while its ordinates increase or diminish in geometrical pro-
gression. The screw was employed of old by Archimedes to raise water, and
it has in more recent times been also employed as a means of propelling
vessels; but the screw differs altogether from a shaft, having attached to it
leaves or plyers of the peculiar curvilincal form, which I have just described,
inasmuch as the lines of the screw are obtained by the circumvolution of a
tracer round a cylinder, while the lines of my propeller are obtained by the
descent of a tracer down the surface of a cone or conoid caused to revolve on
its axis; and in this also, that the reactive force of the curves in the former
case is far greater, and consequently the propelling power much less, than in
the latter. To distinguish my propeller from the Archimedian screw propeller,
as well as from all others, and by a name which shall at once indicate the
distinctive and peculiar property from which it derives its superior efficiency,
I call it the conoidal propeller.
And having now described the nature of my said Invention, and the manner
in which the same is to be performed, I declare that, as regards the first of my
said Inventions, I claim as new none of the parts of which the paddle wheel is
composed, saving and excepting only the floats of the trapezoidal form, before
described; and that, as regards the second of my said Inventions, I claim as
new the conoidal propeller, before described, and every variety thereof, the
form or lines of which can be obtained from the descent of a tracer down
the surface of a cone or conoid caused to revolve on its axis, and whether the
faces of the leaves or plyers of such conoidal propeller in any of its varieties in
plain convex or concave. And such my invented improvements in propelling
vessels being, to the best of my knowledge and belief, entirely new, and never
used within that part of Her said Majesty's United Kingdom of Great Britain
and Ireland called England, Her Dominion of Wales, Town of Berwick-upon-
Tweed, and also in any of Her Majesty's Colonies and Plantations abroad, I
do hereby declare this to be my Specification of the same, and that I do verily
believe this my said Specification doth comply in all respects, fully and without
reserve or disguise, with the proviso in the said herein-before in part recited