The sun., 1895-02-03

from the main coating. liy this any animal q
vegetable growth that has attached itself to tht
the marine parasites arc Killed Just before d
after they have attached themselves, IL IL
mootcd question MS to whether the anti-fouIlnS
properties Of copper, zinc, and yellow metal ar,
due to oxfolation or poisoning. In the opinion
OF Mr.. llollapfel, IL IL only from the fact thai
they exfollnto that they become anti-fouling
and IL is only metals and compositions which Ia
cxfQliatinp produce poisons that are effective
MY argument Is this" says Mr.. Holzapfel
that when the copper exfoliates IL produces q
poison Coxychlorlde OF copper which Is highly
destructive to tho lower animal and vegetable
life, and that this poison is the effective anti.
can attach itself Now, IL the extoliation OF
copper alone prevents fouling why does. not the
| may say that IL does so to very limited eX-
tent, but not because II cxfoliatcs. but lecause
by coming into contact with salt water tho sur
faco of the iron plate ia transformed into rust,
which also Ia to some extent poisonous, but not
sufficiently 80 To prevent fOuling in any but the
coolest climates. An iron plato when exposed
TO the action OF salt water for four years will
lose at least five times as much %: It's weight,
that is, will suffer FIVE times as much exloation,
as u copper or yellow metal plate. 1f. therefore.
exfoiation were the real and true factor which
prevents fouling. iron itself should bo "A much
more effective anti fuulcr than copper"
1t has been said that exfoiatiOn can only act
ns an ant l-fouler In regard to substances which
adhere lightly to the bottom OF ship, and not
In regard to barnac!es, vi hich seem to eat into
the protective coating and gain firm hold on
the bare iron of the hull. Tine poisoning princi-
pie of an ant-fouler Is that the anti i-fouinR ma
terial must surround the ship with II thin layer
of poisoned water to destroy any marine life
entering il. An animal cannot be poisoned ex-
cept by absorbing tho poisoned wafer. and tho
deadly layer OF water H. therefore. gradually
absorbed and must necessarily be replaced. In
copper shenthing and In anti i-fouling mixtures
this is accomplished hy gradual dissolution OF
the main material. The, substances most gem
mercury. zinc, and arsenic. They must be used
In the form of II paint which dissolvcs rapidly
enough to yield constant combination with
tain part of the coating until 1t Is time to re-
dock the ship, or, more generally speaking,
during the time emergency may demand the use
Ii has been found that even copper is not a
perfect Gnti-fouler, ms shells several inches long
have been seen on copper sheuthing when the
animals had undou6tedly. absorbed u great
amount OF poison. In closing his article, Mr..
liol2apfel says:
I'm an experience of over ten years have
absolutely satisfied myself that most mcrCural
varnish paints on competitive trials will invari-
ably show n better result than any other COM
pound. while the preservation OF the iron and
I he smoothncss of the surface are unCqualled.
The only Improvement, therefore. which may
be looked forward to might be the substitution
OF mercury hy some cheaper substance which
ter as mercury. All we can therefore expect
from the immediate future is comparative per-
fection within the radius in which we now
gums used in preparing varnishes and of the
various anti-fouling materials now known.
that the composition may be quite reliable even
in cases where the various paints now used
fail to fully answer their purpose"
The sh-athing Of vessels is practice Of great
age. At one time the bottoms of vessels were
Dreamed or charred. but such n course OF treat
mont afforded but slight protection. Lead as
plates being fastened TO the ship with copper
nails. This system In vogue until about
l770. when it was found that lead did not fulfil
the desired conditions. The British lne-ot- battle
ship Marlborough was lead sheathed. hut her
length of service was such as completely to
l. 737 was OF tar, pitch, and birthstone. Wooden
was used in the last century. and the
nails used were in some cases made with SUCH
large heads that they met and covered the
but iron had been used rs far back AS 1913 on n
Japanese junk of 500 tons burden.
For many years the principal nations OF Eu-
rope have constructed copper-shcathed vessels,
and there is no question as TO the utility of such
| method OF protecting steel hull. Sheathng
l ship consists in carefully plating her from
'tem to stern with stout wood and then coating
When the he's, second Naval Advisory Board be-
gan in 1852 its consideration of the Roach
phin the adyisa6iity i' of sheathing them was was
discussed. The method was not adopted be-
,ausc, OF the additional weight the sheathing
he sheathing of the Chicago would not only
'ost 1000, but tnat 255 tons would thereby
,e added to her weight. The increase to the
md TO. the Dolphin Il tons. Further than
his, the wooden plating would require the
,esn sheathed;. bu. from what naval con,
hsathed hef Hs Php
ani all sps sT9Fg or az"
emote waters. Constructor Frank l.. Fcrnald |
contends hat the detriment to the speed of the |
hip occasioned by the sheathnE hardly war |
ants such process in the case of all ships. He |
avors the sheathing of bark-rigged ships of |
bout 1900 tons displacement for use in the |
a
distances AS from Callao to samoa and in |
ruising, the ship Is far removed from docking |
he corrosive action of sea water. What method |
{ the many IN use should be adopted for our
nent vessel sheathed is the Fishhawk, which is
small vessel in the service Of the Fish Com
mission. She has an iron hull, plated with
curse 81 2lp-inch planking and copper coated.
'he is about sixteen years old and in fair con-
ition.
In the British navy all vessels intended for
uty in foreign waters are sheathed with copper.
r yellow metal, an alloy OF copper. some OF
quadron have been sheathcd apparently on
General Irinciples. IN explaining. The various
ays in the paper previously referred to:
The English Admiralty made the first eN-
Sns Hhe is m rms husa
nd class cruiser. In this ship more expensive
nd extraordinary precautions were taken to
revent the supposed disastrous effects of gal
anc action on the skin OF the ship than upon
ny subsequently built. She WAS lush plated.
.iih heavy seam straps ON the outside. Into
hese seam straps was tapped the fastening for
eak frames, which We're worked on the skin
lating. A course of plank was worked on the
utside Of these teak frames. fastened thereto
y lag screws, all fastenlngs having the heads
unk and covered ny insulating material. and
he whole covered by copper sheathing.
Ince then, up to 1852. tEirty-two vessels have
cen built with shoathiEg. Seven OF these,
uilt from 1869 To 1877 were sheathed with IA
ngle course OF plank. not cslked or insulated,
nd zinc. Experiments with HinC shcathing
ere however. abandoned, and all the others
ere fitted with two courses OF plank, worked
irectly on the skin Of the ship, the inner course
eug fastened thereto by iron bolts, tapped into
he skin plating and having nuts tied on the
lsde, and the outer course fastened to the IN
cr by lag screws, so fitted as not to reach the
sin plating. In spite 0f all efforts to insure
aier tightnes~ IN the wood sheathing ii has
cen found that more or less water obtains
cess to spaces between the inner course
sheathing and the skin plating, and
seems probable from experience that
Ost of this was admitted by the
g-scrrw fastening of the outer course The
feet Of the presence of this water has been
'oVed to be not at all disastrous, as the only
jury that has resulted in any cnse has been
ie partial or complete destruction Of many of
Ie iron bolt securing the inner course of
leathing, which seemed to 10 due To cOrrOsion
ther than to galvaniC action. In no case was
e skin plating of the ship i0upd Ia have been