The morning call., 1893-12-03


:hesiune between any part of moving vessel
and another substance, even though that
be wafer: then either the point where
such adhesion takes pIacs or else point
between: the point of such adhesion and
the. point of the vessels center of gravity
becomes;the point upon which the vessel
WILL turn when being steeTed. Thus crcum-
stances: Invariably cause vessels to turn on
some other point in their length than their
center. OF gravity. The effect of the force
used for steering any vessel will have its
effective power in proportion to the lever
age its direction will give it over the CEN
ter point of turning. which the circum-
stances of adhesion of wind, water, etc,
{ may have produced. If the propelling
screw Qr:scfews OF vessel as they revolve
al the stern had no hold on the water they
could: not propel; but having really 10y
:theIr speed in turning) very considerable
hold Oh the water, they thus prevent the
lateral movement of the stern. causing the
center point Of turning $50 long as the
screw orscrews are kept at work) to be
considerably Gbaft the vessels center of
gravity. anc-' OF Course. at the same time
givino iorce produced by wind and
mead and fore part very con-
3: Lure power TO resist the power
:: the subject Of sails.
Ii S-propelled vessel having
spec -. shohld it be reeuired to
turn ne. snarpiy as in the caseof 81. M.
= ). S.:-Vitoria), her engines slould be
.. stopped fU~ the ime being, her rudder
only being USED. She would then turn on
APPOINT Corresponding with ber center OF
gravity, or upon one considerably nearer
:her h9Ws. owing to the adhesion from
e: friction of the water on her bows which
her speed was producing.
Her rudder having thus considerable
: leverage upon her center point of turning.
,fa1-1-
I" less: space than when her screw or screws
are kept at work during the evolution.
Many vessel that has been stranded
upon a lee shore could have been saved by
thus attending TO the mechanical laws of
: force and of adhesion which takes place
through the friction between the water
and her screw propeller owing to its rapid
:: revolution.
In:al the evidence OF the court-martial
that have had the opportunity Of reading
L did not notice aEy consideration as to the
direction OF the wind. The harder their
engines worked the more effect would
:: wind and wave have had for or against
.. their turning.
. Many of our vessels are not ships at ALL
They are machines afloat, and IL would be
' unreasonable TO expect a sailor to know
their management unless be also become
. an engineer.
=: Finally, do not mistake me. sir, and con-
slider that ] am saying one word against
twin. screw propulsion, or in this letter
either one word as advocating or running
down:this or that invention. l merely here
write ~ once more, after an Interval of
more than thirty years. again call attep-
tion 10 the engineering and mechanical
forces affecting the steering of vessels
when speed is on them, and which forces
are now at the present moment lat wild
under the command or the officers. Fur
ther. the correctness of this theory is easily
proved = there are plenty of screw
lsunches, tugs and other vessels afloat.
This experiment In steering entails no
special preparation and no additional ex-
pense.
: To make this important matter quickly
clear to yourself, sir, l here inclose you
four sketches, with short description of
each:
Reference.-The white spo. shows the
point in the vessels length upon which
she turns; L 81, screw turning ahead; rs,
screw turning astern; - direction of
power steering; @-> direction of princi-
pal natural forces retardng steering; P D.
paddle wheel r, rudder; the white cross
shows the point upon which the vessel
will turn; S S, screw or screws stopped
turning.
-. Figure IA vessel propelled aud
steered by twin screws and rudder. The
direction of the force of each screw has
here about ten feet leverage on the center
point of turning. the force acting on her
rudder leverage of some forty feet, while
the forces of wind, wave and water may
;: have a leverage of from naught to three
hundred feet along her length. acting
against her steering or turning.
Figure PA paddle-wheel steamer Ow-
ing te the hold of her paddles to the water
lwhea revolving her center point of turn
ing Will be near her center. Hence the
effect OF the force of wind or water along
. her length would be about equal for and
against steering, while the direction of the
force exerted by her rudder would have a
leverage FOR turning her of at least nearly
half her entire length.
Figure "a vessel propelled by the rev.
olntions OF single screw. the adhesion of
which TO the water would cause her center
point OF turning to be near her stern.
Hence the direction of the force exerted
by her rudder would have but a short lev
erage, and the power thus used be of but
small value as steering power, while that
power exerted by wind. wave or water
along the greater portion of her length
would have by leverage considers BILE power
to retard her turning.
Figure represents screw steamer with
her screw or screws stopped in order to
turn her sharply while speed is vet on
her. Her center point of turning would