New-York tribune., 1897-08-15
THE SPEED OF STEAMSHIPS.
SUGGESTION THAT THE LIMIT HAS
NEARLY BEEN REACHED.

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 pres
sures and engines that vere lighter in proper
ton to the horsepower developed are among the
causes which have contributed to such result
At present the limit for ocean liners and first
class cruisers is about 90 knots few private
yachts do better than this. But the best time at
sea Is made by torpedo-boat destroyers. Two
or three years ago p and 2S knots was the
maximum speed Of such craft France now has
two. and England five or six destroyers able to
make between 80 and 81 knots, and several
more have been projected which must attain
speed Of 81 in order TO be accepted. That marvel
Of marine architecture and engineering. the
Turbinia. has already exceeded this figure. how
ever. having spurted at the rate of "a 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 1882 was dis
cussed at length few weeks ago. at 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 Unaccountable waste Of power somewhere
Mr.. Barnaby diagnosed the case. reached GER
tain conclusion as to the nature 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 (or pitch) of the blades was un-
altered. But the blades were broadened. so that
the whole area Of each screw was increased
from trine under nine square feet to trifle
under thirteen. The speed Of the boat was thus
increased from - knots to 2S.4. with the same
expenditure Of power and the slip of the screws
was diminished from 80 to Tx per cent.
Mr Barnaby's theory was that the high speed
at which the screws were rotated formed caVl-
ties in the water on their front surfaces. and
that this "cavitation" fas he calls the phenome-
nom produced the increase of slip and waste
Of power Since that :ime he has made some
experiments of his that strengthen his
convictions and he also finds something in the
observations Of other men to confirm his views
as to the genuineness of the evil referred to. In
his recent address, therefore, he remarks:
THAT cavitation will be the cause OF trouble
In the future is, l think, certain. Already 1t is
becoming difficult to obtain the requisite area
in screws of destroyers without either resort
ing to an abnormal width Of blade or TO larger
diameter and pitch ratio than would otherwise
have been preferable. The one eXpedient gives
undue surface friction, and the other hecesSi-
tales a reduction in the rate o. rcfoluton' ana
therefore a heavier engine. In otner "oruS 'iie
line Of procedure which he advised IN regard 10
the Daring has already been followed as far as
Is practicable.
That there remains at least one o'her means
70 nrevent cavtation is evident from the sue
cess Of the Turbna. The remarkable speed oi
that boat is to be sure, due in large measure 10
the new type of engines. the steam turbines
which nropel her But another innovation was
made in her case in the number and arrange
mont Of her screws or these she has no less
than nine three being mounted On each shal'.
and her rudder being displaced to one siue Oh
vertical plane running fore-and-aft throuEh 'he
centre Of the boat Mr.. Barnahy says t'a' '"e
Turbirja's designer was Forced douptie"s
apainst his will to employ nine screws l"p'
;rg that there are serious objections TO such
n,an The obvious success Of 1t. however, anu
the possibility that still other remedies lor cav
tation will be discovered justify a nope 'iia' MI
Rarnabv's predictions may not be Ver''ieu De
eidas designers can greatly improve on the pres
ant eneed of the finest merchant s'e'ihSnp
,,i,bout reaching the limit which he 1e;irS VIII
o,, he encountered by tOrpeco-boat deStfo!eiS'
rur TyNTOWN CHURCHS PICNIC.