Improvements in Means for Decreasing the Violence of the Rolling of Ships.
Year: 1895

page_text: Date of Application (in United Kingdom), 29th June, 1895
Complete Specification Left, 29th June, 1895-Accepted, 3rd Aug., 1895
Improvements in Means for Decreasing the Violence of the
Rolling of Ships.
I, KARL JOHAN ALBERT ISAKSON, of Maria Hissbro 6, Stockholm, in the
Kingdom of Sweden, Ship- and Engineer Surveyor to Lloyd's Register of
Shipping, 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:
An inconvenience, generally attending the use of waterballast in double bottom
ships is the violence in the vessel's motion, caused by excessive stiffness, when the
vessel is either in ballast or loaded with, a light, perishable cargo and the ballast
tanks filled.
The damages caused by this excess of stiffness are numerous, in the form of
boats, bulwarks, deck houses and so on being crushed by the seas and carried away
and masts or rigging being broken.
A useful means of decreasing the angle of beel is, as is generally known, bilge
rolling chocks, but the nature of their action is not so much to counteract the
violence or rapidity of the motion attending too much stiffness, as by their
passive and gradual resistance to prevent the heeling from reaching a dangerous
degree; and at all events they in most cases have a notably retarding action on
the vessel's speed.
I
The object of this invention is to decrease and counteract the inconvenience,
attending an excess of stability either if due to waterballast being carried in the
bottom, to improper stowing of the cargo, to the vessel's form and construction or
to other causes.
This object is attained by arranging the masts for ballast, or in vessels without
masts, such as some passenger steamers, "whaleback" and "turret deck "
steamers and so on in arranging the funnels and the derrick-poles for the same
purpose, or even, ip any vessel, by erecting special ballast masts constructed either
purely for this purpose, or in combination with any other known purpose.
By these arrangements for fitting or placing ballast at a certain height above
the upper deck, the metacentric height is decreased, but at the same time, and this
is equally, if not more important, the radius of gyration of the whole ship with
cargo, and so on is. increased considerably; and to what extent this influences the
D77

page_text: period of rolling by decreasing its violence and rapidity is easily seen by referring
to the long known expression for this quantity:
gm
where t =
A
k
==
==
rolling period in seconds
the usually very small value of an infinite series, which varies with
the angle of heel,
the radius of gyration,
the acceleration of gravity,
m = the metacentric height.
In ordinary cargo steamers, where every ton of dead-weight has a certain money
value to the shipowner, when applying this invention, masts can be arranged,
having a diameter, large enough to admit of a ladder being fitted inside them, and
having manholes, and they can then be accessible in every part for cleaning and
repair. These masts will also have to be fitted with a waterfilling pipe, leading
from one of the steam pumps on board, or from a special pump for this purpose,
also with a discharge pipe, air escape pipe and a pressure gauge for showing the
height of water. These masts can then be filled with water to such height, as
will give to the ship an easy motion, and, as ordinary ballast tanks, they will
be emptied, when the cargo is of such a nature, as to render their service
superfluous.
These masts will of course have to be constructed with due regard to the
considerable stresses, to which they will be subjected, and will have to be fitted
with extra strong shrouds and stays accordingly. The strain on these and also
the weight of the whole mast will have to be distributed over a sufficiently large
area of the ship's structure. Besides ordinary longitudinal angle and bulb stays,
these masts can be fitted with diaphragm plates, each having a manhole on the
same side as the ladder. These plates are to prevent the water splashing too high
up when the ship is rolling and the mast only partly filled, and when the masts
are constructed of an oval or other section, these diaphragm plates will act as
stays.
But all such details, inclusive of the proper distribution of the considerable
weight, represented by the mast with contents, are left to the taste and judgment
of the designer or ship-builder, as well as the considerations of the dimensions and
the scantlings of the masts and the proportion between their size and the vessel's
inherent stability all of which will have to be regulated by the circumstances of
each particular case and so that the margin of necessary stability is not exceeded.
A simple calculation will show, how a mast, having only the dimensions of a
common ""military mast" on a modern battle ship, if filled with water in
accordance with this invention, will materially increase the rolling period of a
cargo steamer of moderate size, carrying waterballast in a double bottom. But
there will of course be no difficulty whatever in giving to such masts sufficient
size to contain say 50 or 75 tons of sea water, if required by the size of the ship or
other considerations.
On passenger steamers or on certain cargo steamers, where the dead weight
capacity is not of so primary importance, the masts can be arranged with one or
more weights of iron, lead, and so on, movable on guide rods within or outside the
mast and raised or lowered by means of some mechanical appliance. Where a
weight of 3 or 4 tons is considered sufficient, it can be placed inside the mast and
raised and lowered by means of a chain, leading from the weight, over a pulley in
the mast head and from thence to one of the steam-winches. Another simple
arrangement, suitable, when a large weight is carried within the mast, consists of
a screw spindle, passing through the weight and turned by means of a worm wheel
gearing at the deck. If the weight is arranged round the mast, it will be
preferable to have it moved by two or more screws, actuated simultaneously

page_text: by a common gearing. Also several smaller weights may be arranged on each
mast, movable each on its own guide rod by means of winch chains or the like, but,
if the weights are not moved by means of screws each of them should be fitted with
an automatic checking or brake-appliance in order to prevent them from suddenly
dropping down and thereby causing serious damage, or from being lifted from
their position, when the ship is rolling.
Masts of this description, including those, fitted for carrying water-ballast, may
be fitted with all or any other usual appliances of topmnasts, gaffs, booms, sails,
signals, and so on, in use on common masts.
If ballast is to be arranged on funnels, these must of course be constructed of
sufficient strength and efficiently connected to the ships structure.
Arrangements for carrying ballast are also applicable on derrick poles, or they
may be fitted on special ballast-masts, constructed solely for this purpose and not
combined with other arrangements in use on common mists, funnels, and so on.
As illustrating the application of this invention, reference is made to the
accompanying drawing in which
Figure 1 represents a mast, constructed for carrying waterballast, and
Figure 2 shows a mast, fitted with a movable ballast-weight. It must be clearly
understood, however that the main object of this invention does not consist of the
different mechanical appliances, shown on the drawing or referred to in the
Specification, which appliances may of course be varied infinitely and substituted
by hydraulic, pneumatic, electric or other known equivalents, without affecting the
main object of the invention.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
Arrangements for decreasing the violence of a vessel's rolling in a seaway,
consisting either in fitting the masts, derrick poles or funnels for carrying ballast,
solid or fluid, or in providing special ballast masts.
Dated this 29th day of June 1895.
HASELTINE, LAKE & Co.,
45 Southampton Buildings, London, W.C., Agents for the Applicant.