The record-union., 1897-08-29
SPEED OF STEAMSHIPS.
A Suggestion That the Limit Has
Nearly Been Reached

Nearly Been Reached.
A slow but steady increase in the
speed of steamships has been effected
ever since that class of vessels first
came into existence Greater length,
finer models, higher boiler pressures
and engines that were lighter in pro-
portion 10 the horse power developed
are among the causes which have con-
tributed to such a result At present
the limit for ocean liners and first-class
cruisers is about twenty-five knots. A
few private yachts do better than tbs.
But the best time at sea is made by
torpedo boat destroyers. Two or three
ago tWenty-seven and twenty-eight
knots vas the maximum speed of such
craft. France now has two and Eng
land five or six destroyers able to make
between thirty and thirty-one knots,
and several more have been projected
which must attain a speed of thirty-two
in order to be accepted That marvel
of marine architecture and engineering
the Turbinia, has already exceeded
this figure, however, having spurted at
the rate of thirty-four knots, a record
not likely to be beaten for some months
at least; perhaps not for years.
possible obstacle to great advances
in speed in the future, dimly hinted at
in 1895, was discussed at length few
weeks ago at a scientific congress in
England by Sydney w. Barnaby. When
the torpedo boat destroyer Daring
made her first trial trip two years ago,
she failed to develop the speed which
had been expected by her designers and
builders. There seemed to be an un-
accountable waste of power somewhere.
Mr.. Barnaby diagnosed the case, reach
ed certain conclusion as to the ma
ture of the trouble, and prescribed a
remedy. He recommended some
changes in the screws, and his advice
was followed. The diameters remained
the same, and the slant Cor pitch) of the
blades was unaltered. But the blades
were broadened so that the whole area
of each screw was increased from a
trifie under nine square feet to a trifie
under thirteen. The speed of the boat
was thus increased from twenty-four
knots to twenty EIGHT and a quarter
with the same expenditure of power,
and the slip of the screws was dimin-
ished from 80 to 11% per cent.
Mr.. Barnaby's theory was that the
high speed at which the screws were
rotated formed cavities in the water
on their front surfaces, and that this
"cavitation" (as he calls the phenome-
nom produced the increase of slip
and waste of power. Since that time
he has made some experiments of his
own and strengthens his convictions,
and he also finds something in the OBJ
Servaticns of other men to confirm his
views as to the genuineness of the evil
referred 20. In his recent address,
therefore, he remarks:
THAT cavitation will be the cause of
trouble in the future is, / think GER
tain. Already it is becoming difficult
to obtain the requisite area, in screws
of destroyers without either resorting
to an abnormal width of blade or to a
larger diameter and pitch ratio than
would otherwise have been preferable.
The one eXpedient gives undue surface
friction, and the other necessitateS a
reduction in the rate of revolution, and
therefore a heavier engine" In other
words, the line of procedure which he
advised in regard to the Daring has
already been followed as far as is
practicable.
! That there remains at least one other
means to prevent cavitation is evident
| from the success of the Turbinia The
remarkable speed of that boat is, to be
sure due in large measure to the new
| type of engines, the steam turbines,
which propel her. But another innova-
! ton was made in her case, in the num-
Der and arrangement of her screws. OF
these she has no less than nine, three
! being mounted on each shaft, and her
rudder being displaced to one side of a
vertical plane running fore and aft
through the center of the boat Mr..
Barnaby says that the Turbinia's de-
signer was forced, doubtless against
his will, to employ nine screws" i'm
plying that there are serious objections
to such a plan. The obvious success
of it, however, and the possibility that
still other remedies for cavitation will
| he discovered justify a hope that Mr..
Barnaby's predictions may not be YER
flied. Resides designers can greatly i'm
prove on the present speed of the finest
| merchant steamship without reaching
the limit which he fears will soon be
| encountered by torpedo boat Destroy
ers.-New York Tribune.