New-York tribune. [volume] (New York [N.Y.]) 1866-1924, 1897-11-21
THE DEFENDERS HULL
1T is ALREADY MUCH DErER1oRArkp
GALVANIc ACTION MAY BE IN PART TO BLAME
ALUMINIUM IN YACHT BUILDING NOT
AN CNMIXED SUCCESS.

'ALVANlc ACTION MAY BE IN PART TO BLAME
ALUMINIUM IN YACHT BUILDING NOT
AN CNMIXED SUCCESS
1t VIII cause regret to many that the fastest boat
10 wihdward that was built is now apparen,v
10 oe numbered among the things OF the past. The
results or the official examinations of the yacht De-
fender made both before and after her
racing are at last made public II appears thar
flchiru fearson Hobson. Assistant Naval Con-
structor OF the United States Navy acted under
directions from the Government when he made a
number OF examinations Of the yacht. and the re.
suits or MS work are set forth in an article pub.
lished In the proceedings Of the United States Naya,
institute.
Mr.. Hobson not only examined tho De,erdor h..
fore she was completed but also at intervals NJ
every few months since she was launched
About six weeks before the racing WITH Vol,
kyrie III Mr. Hooson made careful examination Of
the Defenders hull and found unmistakabo owl,
dences OF disnegraton along the lines where the
aluminium and bronze plates met II will be re-
membered that the hull of the Defender above the
water-lne Is covered with aluminium plates instead
OF wooden planking, and that the immersed part OF
the hull Is bronze plated. In this examination thu
paint was found TO be Off in places, and the DAM
age has been referred to as corroson II Is known
however that the hulls Of ships greatly suffer from
disnegrations due TO galvanic action set up by the
chemical properties OF water. and il is difficult
to understand how a boat well kept and frequent
ly painted as the Defender should exhibit, such
marked evidences of deterioration unless eubected
to influences further ard other than the mere cor.
rosion OF water.
After the international races a further examina.
ton was made, which showed that the damage
had increased. Then. after the lapse Of the winter
months, the boat was again visited by Mr. Hob.
son, and found to be in a still worse condit,on
Some OF the heads OF the rivets mad entirely dis.
appeared. and along the line OF contact between
the two metals, namely close to the water.linA
the corrosion visible without any scrapins
away Of paint The decks were also leaking thu
general decay appearing in the neighborhood OF
the chain plates AS the yachts plates were ry.
eted with bronze rivets, 1t IL almost impossible
TO suppose that the action OF sea water aon. could
have caused them TO fall apart in so short TINA
as one year. The Defender the first and Der.
haps. she may be called the last. yacht to he built
largely Of aluminium, and the OF this material
In her construction must 10 a considerable extent
be regarded a step in the dark. II AT that time
chemists knew the inevitable results OF bringing
bronze and aluminium together In sea water Il can
at least be seen that this knowledge not pur.
chased by the yachts TWO chief owners. More
over the fact that all the aluminium parts OF the
rigging and deck-fittngs at first given to her had
10 be removed as soon as their weakness under
many different metals were ignorant OF the tensile
strength of the material
Later another inspection was made by MI Hob
SON and the Defender was found TO be In such
condition that IL may now be sald Win some
safety that the OF aluminium In yacht building
has ended. The process OF disintegration. whether
due corroson Gavanic action, or both, had
now gone 50 far that the powder OF tie aluminium
was found lying loose IN the places where the DAM
age was most extensive Not only were the decays
visible along the water-line, where the two metals
came In contact but in the interior the parts made
of steel were receiving corrosion from the bronze
rivets connected with the aluminium plates. Inc
inside strengthening straps. deck beams and upper
fittings OF the Defender were all made OF alum.
mum as well as the outside plating, while the
stem and stern pieces and other parts OF the frame
were OF STEEL and If IL be true as some nave sus.
pected that aluminium resembles zinc IN some OF
its chemical qualities. the yacht may be regarded
as n large gavanic batterya Zinclike substance IN
contact with the copper of the bronze brought into
action nv the acids OF water. and commune
eating the disntegratons thus effected 10 the SUR
rounding steel work. 80, -,,, -
So completely has the newly used metal failed IN
its hoped-for abilities that the deckfttngS which
were ca OF 4, seemed 10 be rottlng away Ing
outside Of the so-called metal could be ruooed on
nv the hand. Some doubt still remains as 10
whether the yacht may yet be plated win nrohEs
or steel after all the aluminium has been removed
from her. and this question can only be answered.
by ascertaining the extent OF the damage her steer
FRA mes have received but even IL this may pc pos
sihle the addition OF the large amount or extra
dead weight 10 be lifted along will certainly make
a marked difference In the boats future speed