Improvements in Ships' Propellers.
Year: 1895

page_text: Date of Application, 23rd Nov., 1895
Complete Specification Left, 22nd Aug., 1896-Accepted, 3rd Oct., 1896
PROVISIONAL SPECIFICATION.
Improvements in Ships' Propellers.
I, FREDERICK FRIEDENTHAL, of Ribble Engine Works, Preston, in the
County of Lancaster, Engineer, do hereby declare the nature of this invention
to be as follows:-
This invention consists in forming the blades of ships' propellers with
corrugations concave on the driving or "go-ahead" side and convex on the back
or "go-astern" side. The said corrugations are composed of curves-concentric to
the axis of the propeller except as hereinafter explained-stepping out from the
driving face of the blade from the vertical to the horizontal in the form (in section)
of one quarter of a circle. The corrugations may vary in depth on different sizes
of propellers and may also be of various depths on the same blade. Thus they
may be deeper near the boss of the propeller and shallower towards the tip of the
blade. From the boss to the first corrugation and from the first corrugation to
the second and so on to the tip of the blade that portion of the blade may rise
vertically or diagonally to the axis of the propeller and may be either a true
helix or of increasing pitch from forward to alt. The corrugations may be made
at any distance apart from each other suitable to the size of the propeller and for
the particular purpose for which the propeller is intended. To compensate for the
diminished resistance that the above described shape of propeller blade would offer
for "going-astern" I design the tip of the blade with a curve from the last or
outermost corrugation straight at first and gradually diverting from the per-
pendicular line so as to lean towards the steru post. The above description
relates to the corrugations on the driving side of the blade as they would appear if
taken at a section drawn through the centre of the blade from boss to tip. With
reference to the direction or curvature of the corrugations across the face of the
blade "fore and aft" to commence with I find a true helix to correspond with the
particular diameter of the section being dealt with or the helical line that any
particular corrugation would describe if wound round a cylinder and draw this true
helix across the expanded view of the blade from fore to aft and to gain the
object I have in view namely to better confine on the driving side of the blade the
volume of water that is below the corrugation and to prevent it flying off at a
tangent or upwards of the blade I drop the curvature of the corrugation gradually
towards the after edge from five to ten per cent. or thereabouts and use this curve
line as the extreme or aftermost edge of the corrugation in order that a particle
of water met or touched by the corrugation on the leading edge will be depressed
from five to ten per cent. or thereabouts from the true pitch before it leaves the
alter edge of the blade.

page_text: Improvements in Ships' Propellers.
1, FREDERICK FRIEDENTHAL, of Ribble Engine Works, Preston, in the
County of Lancaster, Engineer, 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 :-
23
This invention consists in forming the blades of ships' propellers with corrugations
concave on the driving or "go-thead" side and convex on the back or "go-astern
side.
In order that my invention may be better understood I append a sheet of drawings
in which
and
Fig. 1 is a combined section and side view of a single blade of a ship's propeller
Fig. 2 an end view of an entire propeller constructed according to my said
invention.
"
The corrugations referred to are composed of curves a a concentric to the axis
of the propeller-except as hereinafter explained-stepping out from the driving
face of the blade from the vertical to the horizontal in the form (in section) of one
quarter of a circle. The corrugations may vary in depth on different sizes of
propellers and may also be of varying depths on the same blade. Thus they may
be deeper nearer the boss of the propeller and shallower towards the tip of the
blade. From the boss to the first corrugation and from the first corrugation to the
second and so on to the tip of the blade that portion of the blade may rise vertically
or diagonally to the axis of the propeller and may be either a true helix or of
increasing pitch from forward to aft or aft to forward. The corrugations may be
made at any distance apart from each other suitable to the size of the propeller
and for the particular purpose for which the propeller is intended. Thus for slow-
going engines the corrugations would be preferably much deeper than for high-
speed engines. To compensate for the diminished resistance that the above
described shape of propeller blade would offer for "guing astern I design the
tip of the blade with a curve from the last or outermost corrugation straight at
first and gradually diverting from the perpendicular line so as to lean towards the
stern post. The above description relates to the corrugations and tip on the
driving side of the blade as they would appear if taken at a section drawn through
the centre of the blade from boss to tip (see sectional part of Fig. 1).
reference to the direction or curvature of the corrugations across the face of the
blade "fore and aft "-to commence with I find a true helix to correspond with
the diameter of the section being dealt with or the helical line that any particular
corrugation would describe if helically wound round a cylin ler and draw this true
helix across the expanded view of the blade from fore to aft and to gain the object
I have in view namely to better confine on the driving side of the blade the volume
of water that is below the corrugations and to prevent it flying off at a tangent or
upwards of the blade I drop the curvature of the blade gradually towards the
after edge from five to ten per cent. or thereabouts and use this curve line as the
edge of the corrugation in order that a particle of water met or touched by
the corrugation on the leading edge will be depressed from five to ten per cent. or
thereabouts from the true pitch before it leaves the after edge of the blade.
Fig. 1 the broken line c shows the true curve line and the solid line the leading
edge of the corrugations depressed.
With
At
Although I prefer to drop the curvature of the leading edges of the corrugations
as just described the said leading edges may if desired be kept to the true curve
or pitch line.

page_text: 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. Forming the blades of ships' propellers with corrugations substantially as
herein described and shewn in the drawings.
2. In combination with corrugations on the blades of ships' propellers forming
the tips of the blades so as to lean towards the stern post substantially as described
and shewn in the drawings for the purpose specified.
Dated this 21st day of August 1806.
For the Applicant,
W. LLOYD WISE,
46 Lincoln's Inn Fields, London, W.C., Chartered Patent Agent.