Improvements in the Formation of Navigable Vessels.
Year: 1886

page_text: Date of Application, 3rd July, 1886.
Complete Left, 4th Apr., 1887.
Complete Accepted, 6th May, 1887.
Improvements in the Formation of Navigable Vessels.
I WILLIAM FORBES, of Newark, Ellon, Aberdeenshire, do hereby declare the nature
of this invention to be as follows:-
My invention has for object by means of improvements in the formation or
modelling of navigable vessels to economise power in the propulsion of the vessels
or to obtain greater speed without applying increased power; and to that end the
invention consists in the application of parabolic curves in the modelling in such a
manner that when the vessel is in motion the water in its course is parted and shed in
a lateral direction only, the water thus shed aside being replaced by water rising
vertically from below to restore the normal surface level.
In constructing a navigable vessel under my invention, the cross section at any part
near the stem approximates closely to the form of a parabola, the keel forming the
vertex of the curve and the cross section as taken amidships shows the sides nearly
vertical but rounding inwards towards the bottom which may be flat, or even curving
upwards to form a hollowed out portion on each side of the keel, while in proximity
to the stern the cross section shows vertical sides and a flattened bottom with rounded
curves at the junction of the sides and bottom. The bottom, on which the water from
below presses strongly in the act of filling up the space vacated by the moving vessel,
is also formed on a parabolic curve which may commence at any point from near the
bow or stein to within a short distance, say one fourth the vessel's length, from the
stern, according as great speed is more or less a desideratum, and ending at or above
the loadline at the stern.
"
The keel may be carried at the same depth throughout, but the "dead wood forms
a vertical rib projecting downwards a considerable distance from the true bottom of
the vessel, and of such thickness as may be required for strength to bear the weight
of the vessel when aground, and the lateral pressure of the water in resisting leeway.
In utilising my invention to its fullest extent in the construction of a short vessel,
of say a length equal to 3 lengths of the vessel's beam yet fitted for great speed, the
parabolic curves by which the water is shed aside, must be continued from the stem to
the broadest part of the vessel near the stern; and the parabolic rise on the bottom on

page_text: the vessel facilitating the replacement of the water in rear, must in like manner
commence near the bow or stem; in which case the sides of the vessel are apparently
a continuation of the bow for dividing the water throughout the whole length, and in
similar manner the parabolic rise of the bottom is at the same time restoring the dis-
placed water over its whole length. In this manner all violent disturbance of the
water is avoided, the displacement and replacement being accomplished gradually by a
diminishing rate of motion.
Where greater length in proportion to beam is desirable, or where bearing capacity
is of higher importance than the maximum of speed, these curves, as before stated,
may be applied with advantage to a limited portion of the length of the vessel.
Dated this Second day of July 1886.
CRUIKSHANK & FAIRWEATHER,
62, Saint Vincent Street, Glasgow,
Agents.
I, WILLIAM FORBES of Newark, Newburgh, Aberdeenshire, 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 :—
My invention has for object by means of improvements in the formation or
modelling of vavigable vessels to economise power in the propulsion of the vessels,
or to obtain greater speed without applying increased power, and at the same time
adapting them to be safely navigated at a speed likely to be dangerous to vessels of
less suitable model. To that end the invention consists in the application of parabolic
curves longitudinally, or both longitudinally and in cross section in the modelling in
such manner that when the vessel is in motion the water in its course is parted and
shed in a lateral direction only, the water thus shed aside being on the passing of the
vessel replaced by water rising vertically from below to restore the normal surface
.level.
In utilising my invention to its fullest extent in the construction of a short vessel,
of say a length equal to three lengths of the vessel's beam, yet fitted for great speed,
the parabolic curves by which the water is shed aside, must be continued from the
stem to the broadest part of the vessel near the stern; and the parabolic rise on 'the
bottom of the vessel facilitating the replacement of the water in rear, must in like manner
commence near the bow or stem, in which case the sides of the vessel are apparently
a continuation of the bow lines for dividing the water throughout the whole length

page_text: and in similar manner the parabolic rise of the bottom is at the same time restoring
the displaced water over its whole length. In this manner all violent disturbance of
the water is avoided, the displacement and replacement being accomplished gradually
by a diminishing rate of motion.
Where greater length in proportion to beam is desirable, or where bearing capacity
is of higher importance than the maximum of speed, the parabolic curves may be
applied with advantage to limited portions of the length of the vessel at bow and
stern.
In the accompanying drawings figure 1, is a sheer plan and figure 2 shows the
lines of a short vessel adapted for carrying cargo, and figures 3 and 4 are end
elevations or body plans of the bow and stern. Figures 5, 6, 7 and 8 are similar
views of a vessel of greater length in proportion to its breadth of beam and designed
to attain high speed in sailing with less regard to cargo carrying capacity. Figures 9,
10, 11 and 12, are similar views representing my invention as applied at the bow and
stem of a vessel the mid portion of the vessel whose sides may be carried to a greater
or less extent nearly parallel to each other being omitted. The vertical lines showing
the contour of the vessel are marked by the same numerals and the longitudinal lines
by the same reference letters in the several views.
In the modelling of these vessels, the planking or plating of the sides, follows the
line of a series of parabolic curves which extend in the longitudinal direction from the
stem to the vessels quarter, the greater part of the length of the vessel; the sides of
the vessel aft from the termination of the curves being carried to the stern by lines
nearly parallel to the axis of the vessel. At and above the load line to the deck level
the parabolic curves may be carried to their vertex at the bow, but as a vessel so
formed would be rather bluff bowed and of too great a breadth of beam proportionate
to its length, the portions of the parabolic curves used in modelling the sides com-
mencing from the stem, are taken from a point some distance from their vertices, the
curves upon each side of the vessel being made to intersect at the stem as indicated
by the diagrams, figures 2, 6 and 10, and cut-water being formed in front of the point
of intersection of the curves. The portions of the parabolic curve which are taken
for the lines at the different vertical heights also vary, the point in the curve applied
at the stem receding from the vertex in proportion as the vertical height from the
keel of the vessel becomes less. Thus, if at the loadline, the lines of the ships sides
are formed by parabolic curves intersecting at the stem at any given point some
distance from the vertices of the curves, all the lower lines will be formed by curves
intersecting at the stem at greater distances from the vertices, the curves being as it
were carried forward in modelling the lower lines of the vessel as more particularly
shown by figure 10. The lines of the true parabolic curves should be carried in
planes parallel with the load line of the vessel, and in general when the lines of the
ship are to be fine-in order that high speed may be attained with a minimum
expenditure of power-parabolic curves of greater focal length, or starting at points
receding farther from the vertex are employed, than when the vessel is to have larger
carrying capacity in proportion to its length and maximum breath of beam.
In modelling a vessel of large carrying capacity this invention can only be applied
to the bow and stern, as indicated by figures 9, 10, 11 and 12, in which case the
central portion of the hull will be formed with sides nearly parallel, and may be
vertical, at the bottom rounding off at the bilge into a flat bottom or may take any
form which may best suit the purposes for which the vessel is intended, but in every
case the parabolic curves intersecting at the stem will be, as it were, moved forward
until the curves meeting the parallel sides will join its lines without vitiating the
symmetry of the curve. At the stern the underlines curving upwards as before
mentioned will join the flat bottom of the central portion in the same manner giving
the greatest facility for the water rising from below to fill the space vacated by the
moving vessel. In some circumstances it is advisable to depart from the exact
parabola for a very short distance at the stem where the parabolic curves intersect, so
as to present a more acute angle at the cutwater, the angle at the intersection of the
curves being in every case under 60°. The stem of the vessel is a nearly vertical rib
°

page_text: and at any part near the stem, the cross section may with advantage take the form of
a parabola or the sides may be nearly vertical and rounded off at the bilge, and the
cross section as taken admidships also shows the sides nearly vertical but rounding
inwards at the bilge, the bottom being flat or even curving upwards to form a
hollowed out portion on each side of the keel, while in proximity to the stern the
cross section likewise shows the sides almost vertical and a flattened bottom with
rounded curves at the bilge. The after part of the bottom upon which the water
from below presses strongly in the act of filling up the space vacated by the moving
vessel is also curved upwards in a gradual bend or segment of an extended circle but
to obtain the fullest advantage of this invention it must be formed on a parabolic
curve which may commence at any point from near the bow or stem, and continued
to the load line or past it at the stern the portion of the after part of the ship's
bottom to which the parabolic curve is applied being lengthened or shortened,
according as great speed is more or less a desideratum. The position of the parabolic
curve so applied, may be taken at any suitable distance from the vertex, and carried
either well forward or commenced farther aft, but where the curve joins the portion
of the forward part of the vessel's bottom which is practically parallel with the keel,
it should inperceptibly merge into the straight line.
The keel and deadwood form a vertical rib projecting downwards a considerable
distance from the true bottom of the vessel and of such thickness as may be required
for strength to bear the weight of the vessel when aground and the lateral pressure of
the water in resisting leeway.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, I declare that what
I claim is:
A navigable vessel whose lines are formed by parabolic curves applied as described,
whose sides are approximately vertical and whose bottom flattened to a greater or less
extent in cross section curved from the lowest point forward to the load line at the
stern, substantially as described.
Dated this Second day of Al 1887