An Improved Method of and Means for Increasing the Efficiency of Screw Propellers.
Year: 1899

page_text: Date of Application, 17th July, 1899
Complete Specification Left, 17th Apr., 1900-Accepted, 19th May, 1900
PROVISIONAL SPECIFICATION.
An Improved Method of and Means for Increasing the Efficiency of
Screw Propellers.
We, FREDERICK SEATON SNOWDON, of 1, Arundel Street, Strand, London, W.C.,
Technical Editor, and WILLIAM JARVIE ORR, of Ashburton House, Custom House,
London, E., Mariner, do hereby declare the nature of this invention to be as
follows:-
This invention relates to an improved form of attachment to the blades of
screw propellers, or to improvements in the formation of the blades themselves,
and has for its object to increase the efficiency of such propellers by preventing,
or greatly decreasing the amount of "slip."
In carrying out the invention each blade of the propeller is fitted on its
driving, or forward, face with one or more battens. The configuration of the
battens is such that their inner faces will lie snug" to the contour of the faces
of the blades of the propeller to which they are suitably secured, preferably by
screwed studs or bolts and nuts. The inner and outer edges of the battens are
curved so that they shall coincide with, or more or less approximate to, a cireum-
ferential line described from the axis of the propeller as a centre. Or the battens
may be straight with their inner and outer edges parallel, or not, in which form
they would lie more or less tangentially to the circumferential line. The outer
faces of the battens are of greater depth than the inner faces, and the inner
edges are bevelled away at any suitabfe angle to meet the forward faces of the
blades. Or the outer faces of the battens may be "flared" outwardly, from the
faces of the blades, the formation in either case being such that the projection
of the battens from the blades shall form projecting ledges from the faces of the
blades tending to prevent any water flying off circumferentially, or tangentially,
from the blades.
The proportions of the battens will be governed by the contour, pitch, and
diameter of the propeller to which they are to be applied, or of which they may
be made to form part either by casting or otherwise. By setting the leading
ends of the battens slightly beyond, or outside, the circumferential line and their
trailing ends slightly within that line the battens will form a helix tending to
throw the water inwards towards the boss, or axis, of the propeller. The distance
of the battens from the axis would also depend upon the form of propeller used,
and the outermost battens would project further from the faces of the blades so
as to give a step like formation to their arrangement.
Dated this 15th day of July 1899
SNOWDON.
F. SEATON
WILLIAM J. ORR.

page_text: An Improved Method of and Means for Increasing the Efficiency of
Screw Propellers.
We, FREDERICK SEATON SNOWDON, of 1, Arundel Street, Strand, London, W.C.,
Technical Editor, and WILLIAM JARVIE URR, now of Maheno, Oamaru, Otago,
New Zealand, Mariner, formerly of Ashburton House, .Custom House, London, E.,
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:―
This invention relates to an improved form of attachment to the blades of
screw propellers, and has for its object to increase the efficiency of such propellers
by preventing or greatly decreasing, the amount of "slip."
"
"
In carrying out the invention each blade of the propeller is fitted on its driving
face with one or more battens," the configuration of the battens being such
that their inner faces will lie snug" to the contour of the faces of the blades
of the propeller, to which they are suitably secured; preferably by screwed studs
or bolts and nuts. The inner and outer edges of the battens are curved so that
they shall coincide with, or more or less approximate to, a circumferential line
described from the axis of the propeller as a centre. Or the battens may be
straight with their inner and outer edges parallel or not, in which form they
would lie more or less tangentially to the circumferential line.
The battens project more or less from the face of the blades according to their
position thereon, those furthest from the axis of the propeller projecting most,
and their depth, as measured on a radius from the centre to the tip of the pro-
peller, also varies, the deeper battens being mounted outermost. The innermost
surfaces of the battens are cut away so as to form a channel like cavity between
them and the face of the blade, the battens thus forming projecting ledges which
tend to prevent any water flying off circumferentially or tangentially from the
blades.
By setting the leading ends of the battens slightly beyond, or outside, the
circumferential line and their trailing ends slightly within that line the battens
will form a helix tending to throw the water inwards towards the boss, or axis,
of the propeller. Thus the battens not only prevent the water slipping off the
blades but give the propeller more solid water to work in, as well as tending to
rope "the stream of water directly astern, a great advantage to vessels working
in canals where the dispersion of the water by the ordinary form of propeller
injures the banks.
It will be understood that the number of battens to be fixed to each blade and
their proportions and positions on the blade will be governed by the contour,
pitch, diameter and speed of the propeller to which they are to be applied.
In the accompanying drawings the driving face of a three bladed right handed
screw propeller is shown with two battens, 1, 2, mounted on each of the blades.
As will be seen from the figure representing the enlarged section the battens are
secured to the blades by screwed studs, 3, 3, but these may be replaced by bolts
and nuts or the battens may be rivetted in place. From this figure also it will
be seen that the outermost batten, 1, projects further from the face of the blade
than the batten 2, and is also deeper than the latter, while from the face view of
the propeller it will be seen that the leading ends, a, of the battens are further
from the axis of the propeller than are the trailing ends b, the relative positions
and dimensions of the battens being governed by the factors as herein before
indicated.

page_text: Having now particularly described and ascertained the nature of our said
invention, and in what manner the same is to be performed, we declare that what
we claim is:-
First The attachment of one or more battens to the driving face of each of
the blades of a screw propeller, the battens being so proportioned and disposed
relatively to the circumferential line that they shall tend to prevent the throwing
off, or slipping, of the water from the blades.
Second: The mounting of the battens, more or less tangentially to the cir-
cumferential line so that they shall act as helices to throw the water in towards
the axis of the propeller, so giving it more solid water to work in, and tending to
rope the stream of water directly astern with the minimum of sideway dis-
persion.
.
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