Nov, 20, 1897.] 
FOREST AND STREAM, 
415 
misunderstanding. In my conversation with you I said that 
"Division Representation" was based on a rulina: made by 
the Executive CommUtee, not the Board of Governors, and 
that my authority was Mr Robert J. Wilkin, to whom I re- 
ferred you at the time. Kindly give this correction space in 
your next issue, and oblipre. 
Fkank L. Dunnbll, Commodore. 
[We are under the impression that the statement as 
originally made to us, mentioned the Board of Governors 
and not the Executive Committee, but as the business of the 
meeting had just begun, there was no time then for a discus- 
sion or for obtaining particulars of the reported decision. 
It would now appear that no decision has been made by 
either body.] ' 
At a special meeting, on Nov. 11, the Massachusetts Y. B. 
A. decided to abolish time allowance at once, and not to 
allow time for another year to the older boats. 
The Society of Naval Architects and Marine Engineers 
held its annual meeting in New York, on Nov. 11-1^, a num- 
ber of interesting papers being read and discussed. 
Having disposed of Britannia, the Prince of Wales has 
very naturally ordered a new racing cutter, to be desigufd 
by Watson, built by D. & W. Henderson, and sailed by 
Capt. John Carter, all of these experts having done their 
parts toward the wonderful success of the old boat. The 
new one will be much smaller than Britannia, about the 
size of Mr. Watson's snccessful Bona, built this year; she 
being 75.80ft. l.w 1., 18 10ft beam, and carrying 7,606-q ft. of 
sail, making her linear rating 82 11 The size itself is enough 
to settle the authenticity of any wil'd rumors as to inten- 
tions to challenge for the America's Cup, with the prospect 
of meeting Defender; or of the latter crossing the Atlantic 
to meet the new boat. 
The change of size marks, we hope, the abandonment of 
the so-called "90ft. class" on the other side of the ocean, and 
on this side as well. The experience on both sides has fully 
proved that there is no demand on the part of even the 
wealthiest of racing yachtsmen for such large and expensive 
racing craft; and that, if built at all, it is only by royalty or 
or by syndicates of wealthy men who are not always yachts- 
men. The influence of the class on yacht racing at large has 
been distinctly bad; and is one of the great reasons for the 
abandonment of yachts of racing build in the large and 
medium sizes and the rush for very small racing machines 
or one-design classes. 
There is very little possibility of the building of racing 
yachts of even 75ft. l.w.l. in America to-day; but the estab- 
lishment of such a class would do more than anything else 
to bring about a restoration of international races on large 
yachts. 
The Principles of Measurement. 
Editor Forest and Stream: 
Answering Sextant in your issue of Nov. 6 briefly, for no 
new points seem to be adduced. First head (a). Instead of 
all, I should have said most. As illustrative, the 21ft. class, 
the 30ft. clas« and the 34ft. class, all built under speciflc re- 
strictions, failed to produce the type of yacht the class was 
intended to produce. 
The success of several designs for commercial purposes by 
naval architects whose reputations were gained from the de- 
sign of yachts, is evidence of the commercial value of the 
lessons thus learned. Sextant says: "Measurement rules are 
based on the fact that large boats are faster than small ones." 
He will probobly desire to qualify this statement in some 
way in view of the recently reported speeds of above eleven 
knots by 20-footers, speeds that few larger boats have ex- 
ceeded. 
As I have stated already, if (a) fails of proof then C is 
correct. I am simply taking what seems to be an existing 
opinion and suggesting a means of measuring or comparing 
yachts, (h) When I wrote, "Sail area is not in the least a 
factor in the speed that co'mesfrom length," I had reference 
to the reduction in retarding forces, which, with a constant 
displacement, comes from added length and consequently 
decreased breadth, and therefore less disturbance Asa prac- 
tical illustration, I have sailed in a yacht in which the in- 
crease of length, with increase of heel, amounted to a maxi- 
mum of about 30 per cent., and with each increase of heel 
came increased speed. 
(d) Concerning freedom of design. The English girth 
rule, the French rule, the English tonnage rule, all were un- 
satisfactory. The rules proposed both by A. Gary Smith and 
Cox seem to have been dropped. In all of these the designer 
was limited, either dirpctly or indirectly, In none was there 
an attempt to do more than approximate. In the proposed 
rule all of the elements are derived directly and leave an 
open choice with the designer to take any combination he 
likes to win prizes. Not by speed alone, but by a combina- 
tion of speed with other desirable qualities. I know that 
this is desired by the majority of yachtsmen whom I have 
the pleasure of knowing. 
Fourth: The various points here raised are in the main 
practical and must be decided by practical men. I must ob- 
ject, however, to the use of the word control where I used 
encourage. 
The statement, "the allowance of time to a small yacht by 
a larger one, both having the same lengih and sail area, is so 
illogical that it is not surprisiug that the author dodges the 
concrete question." Now compare two yachts: 
L W. L Lengtti Bpam. 
^ .over, ■ — — , Displace- 
Erect Heeled, all. Krect. Heel'd. Dft. menc Onhe 
A .80 as 45 10 7 r 1V,0L10 10.000 
B 30 3-i 45 10 9 5 SO.CO'D 20.000 
Sail 
Area. 
1,800 
According to Sextant and C, these yachts should race on 
even terms, though A has less of accommodation than B , is 
in fact a racing machine, while B. is a roomy safe cruiser. 
By the proposed rule, A. measures for racing 88.68; b! 
measures 32 28, and any yachtsman of practical experience 
will say that this is fair. 
It is by no means unprecedented to give a prize to a yacht 
finishing other than first. 
Finally: As to the theoretical and practical accuracy of 
the time allowance tables. The speeds given by C. were all 
made in strong winds, and therefore favorable to the larger 
yacht. Compare them. 
Speed. Length. 
Ratio. Acmal Actual, ^L. Ratio. 66^ oC 
Glencain and Momo.. 11 33 5.74 
Thirty-footers 1.18 13 4-<J e.48 1.13 67 
Dorotty 1.18 IS 31 5.5(5 0.67 "ss 
Defender ......1.45 16 So 9.74 1.70 j'.O-j 
They do not agree very well under the lengths stated by 
C. Now comparie again by the actual L.W.L., that the rule 
contemplates. 
Speed. Length. 
Actual. Eailo. Actual. ^L. Ratio. 60!<of 
Glencairn 11 17 4.12 
Thirties , 13 l.IG aO 5,47 1..33 
Dorothy ,...,,...,13 I.IS 2.-) 5.00 l.ai 
Defender 16 1.45 90 9.48 ^,30 
The agreement here is still bad. Practically, over long 
courses there is no chance for the smaller yacht, even when 
the allowances are doubled. The allowance table states, 
"opportunities for speed vary with the square root of the 
length, and for light winds .0(5 is allowed." 
We must subdivide otir yachts for racing purposes into 
many classes, and either legislate to give the cruiser a chance 
or else adopt C.'s sugge-<tion. 
The writer will welcome almost any rule that has actual 
dimensions where length is an element and displacement or 
cubic contents is another, or where actual area of midship 
section below L.W.L. is used with L.W.L , but is opposed to 
any rule in which breadth and depth appear as the equiva- 
lent of the midship section, where the overhangs are arbi- 
trarily taxed or where any special type is aimed at. 
Let us try to abolish approximations, and if we want dis- 
placement, ask for it; if speed, ask for speed; and whatever 
elements wetise, take them from the draft of the designer, 
and. take them as they exist when the yacht is sailing. A. 
Notes on the ITacht Defender and the Use of 
Aluminum in Marine Construction. 
BY RICHMOND PEARSOM nOBSON, ASSISTANT NAVAL 
COSrSTBUCTOR, UNITED STATES NAVY. 
Reprinted by permission from tb'* Proceedings of the United 
Sfcate.s Naml Institute. 
Copyrighted by the U. S. Naval Institute. 
{Continuerl from page 395.) 
Abroad a number of experiments have been made. 
In connection with the building of the torpedo-boat 
.79 
.73 
1.86 
Foudre, Mr. A. P. Yarrow carried on a series of experiments, 
the results of which he describes as follows: "With refer- 
ence to corrosion from sea water, we have tried a series of 
experiments, extending over twelve months, and we find, 
provided there is no galvanic action due to other metals 
being in contact with aluminum, the corrosion may be taken 
at under 4 per cent, for aluminum for plates about Xin. thick, 
the surface being unpainted." * 
This rate is not unfavorable in comparison with the usual 
rate for steel. 
As a result of investigations of corrosion incident to the 
subsequent condidon of the Foudre, M. Le Chatelier, Naval 
Constructor, French Navy, , pronounced that aluminum is 
oxidizable in proportion to its impurities; that salt water 
affects the aluminum of commerce, but not pure alumi- 
num; that pure aluminum re.sists oxidation as well as gold 
and platinum, and is not attacked by nitric and sulphuric 
acids, though dissolving in alkalies and hydrochloric acid. 
_M. Besson, Naval Constructor, French Navy, arrived at 
similar conclusions after investigations in connection with 
the building of the Davou.st for African service, stating that 
corrodibility diminished aa the quantity of copper impurities 
diminished, pure aluminum being practically incorrodible, 
the impurities most instrumental in causing the corrosion 
being aluminum oxide, iron, carbon and silicon. 
M, Guilloux, Nav^l Constructor, French Navy, designer and 
superintending constructor for the Vendenesse, who also in- 
spected the Foudre after her corrosion, and who investigated 
the subject in conjunction with M. Minet, of the Eeole des 
Arts et Metiers of Paris, found that the usual assemblages 
of aluminum, taken at random, are liable to create batteries 
within themselves, and found that the more aluminum is 
electro-positive the better it resists .salt water, and enjoined 
the following rules in the itse of aluminum: 1. Choose alu- 
minum as pure as possible. 2. Have the ingots mixed by 
fractional fusion to insure homogeneity, 3. Subject the ma- 
terial to galvanometric test and require it to be electro-posi- 
tive to a piece already tried and found to give satisfactory 
resistance to corrosion. Take careful precautions during 
construction. Paint all surfaces and avoid absolutely all 
contact with copper, 
In the paper in which these investigations were described, 
read before the Association Technique Maritime, whicti had 
been preceded by a paper on investigations in connection 
with the Vendenesse, M. Guilloux stated in conclusion that 
he regarded the metal as well adapted to marine construc- 
tion, though delicate and as yet of irregular composition 
in production, while but slightly understood and insuf- 
ficiently tried. 
Experiments conducted at Neuhausen, Switzerland, in 
1895, showed that pure aluminum was not attactced, while 
they showed that the copper alloys were badly attacked. 
In connection with the application of aluminum to uses in 
the arts and industries ashore, various experiments have 
been made in the Uuited States and abroad on its resistance 
to the usual agents that attack metals, noted among which 
experiments are those conducted by Prof. Richards, of 
Lehigh University. The uniform result has been the estab- 
lishment of the fact that aluminum offers particularly great 
resistance, except in the case of alkalies and the chlorine 
group. 
The experienc** in actual service and the experiments 
made, as outlined above, are inadequate to a definite and 
final conclusion as to the corrosion of aluminum in salt air 
and salt water. 
The consensus, however, would lead to the following gen- 
eral conclusions: 
1. When isolated, pure aluminum is not attacked. 
2. When isolated, the usual alloys of aluminitm and com- 
mercial aluminum are attacked in a measure more or less 
proportional to the amount or per cent, of the alloy or im- 
purities. Among the alloys, copper and zinc seem the most 
corrodible. 
3. When in contact or in communication with other 
uietals below it in electro chemical scale, galvanic action 
sets in and aluminum and its alloys are rapidly corroded. 
The action takes place when the contact is between different 
alloys of aluminum, and even between different pieces of 
the same alloy, when not homogeneous; and there is indica- 
tion that the corrosion of isolated alloys is probably due, 
in large measure, to the galvanic act;ion between the par- 
ticles of the two metals in the body of the alloy. Copper is 
again the metal whose contact causes most accentuated 
action, and the copper alloy is the alloy in which galvanic 
action is most marked. 
4. The conditions of corrosion can be ^^.raeliorated by the 
application of coatings and coverings. The usual coatings 
for iron and steel, however, are not adapted to aluminum, 
particularly red lead. In case of special coatings, as yet 
prepared, special care and frequency of application are re- 
quired. It would seem that the special characteristic to be 
sought is impermeability. 
While drawing the above conclusions on corrosion, the 
imperfect behavior of steel and iron should be borne in 
mind. With full appreciation of this imperfection, however, 
the comparison of the two metals gives the following gen- 
eral results: 
1. At the present stage, structural aluminum is materi- 
ally more subject to corrosion than steel. The marked cor- 
rosion, however, must be attributed to galvanic action due 
to the high electro-positive character of aluminum, the pure 
metal itself, practically incorrodible, being far ahead of steel, 
and to this galvanic action must be atttibuted the corrosion 
of alloys and the usual commercial aluminum where even 
there ia no external contact with other metals, the action 
taking place in the body of the metal from the intimate con- 
tict of the molecules of aluminum with the molecules of the 
alloying metals or impurities. 
2. This feature of inferiority must therefore be regarded 
* See paper by Mr. Y.irrow in the Transactions of the Institution of 
Naval Architects, Vol. XXXVl., 1895, 
as subject to future amelioration from increase of knowl- 
edge and selection in the preparation of the alloys and from 
improvement in conditions of insulation and protection. 
Substantial amelioration has already heen found in the use 
of nickel for the alloy, without entailing loss of strength, 
while further amelioration seems prorhised in the use of 
tungsten for the all or. 
Special measures toward insulation seem not to have been 
taken or tested in any case. 
3. The coatings used for painting steel are not effective in 
protecting aluminum, and the special coatings as yet pre- 
pared are but partially effective, and then only on condition 
of special care and frequent renewal. 
4. This feature of inferiority must likewise be regarded as 
subject to future amelioration with further experiment and 
increasp of knowledge. It could scarcely be expected to find 
a suitable coating without research, particularly when the 
usual coatings for steel are composed so largely of oxides 
of metals whose contact with aluminum sets up galvanic 
action. 
5. The degree of importance of the inferiority of aluminum 
to steel in the question of corrosion varies with the condi- 
tions of exposure and is disqualifying when the exposure to 
salt water and spray is constant and where frequent visita- 
tion is difficult or impracticable. 
_ The cost of maintenance and care and the length of life 
identify themselves, as seen above, with the question of cor- 
ro.sion. Without being able, evidently, to assign definite 
values, the cost of maintenance and care at the present 
moment must be taken as appreciably greater for aluminum 
than for steel. The cost of additional care is not of great 
consequence for parts easily accessible, provided the ex- 
posure is not great and the coatings applied or the other pro- 
cess of care are at all effective. For parts constantly ex- 
posed multiply the frequency of visitation, the additional 
co.st is considerable, particularly where the parts are diffi- 
cult of access. In such cases of exposure and difficulty of 
visitation, the inferior conditions of preservation reduce the 
length of life, which, under good conditions even, must be 
considered as shorter than the life of steel. This factor of 
cost takes on large proportions, and, at the present moment, 
must be considered prohibitory for water-washed surfaces 
and parts in contact with bilge water, while still of large 
consequence for all outside parts, topsides, upper works, 
and upper deck fittings. 
F. —Applications. 
With the conclusions thus arrived at for cost of mainten- 
ance and length of life and the results of calculations for 
strength, weight and first cost, assembled in the table ad- 
joined, a basis exists for judging between the two metals for 
adaptability to the various purposes of marine construction. 
For the present purpose, and in keeping with the necessitated 
method of broad treatment, examination will be limited to 
salient features only. 
1. AdajMibility for sliell platinrj. 
(a) For plating below water. 
(1) Bottom plating requires, besides elastic strength for 
structural stresses, special ultimate resistance to dynamic 
strains incident to grounding or even docking or moving 
alongside of wharves. 
Wnile adequate to the first requirement, aluminum, as 
seen, is altogether lacking in the second; an aluminum bot- 
tom would be penetrated and torn open where a steel 
bottom would only be deformed without perhaps springing 
a leak. 
A torpedo explosion on the bilge or flank would shatter 
aluminum plating over a large area, bilging in all probabili- 
ties a larger number of compartments. 
From considerations of strength, aluminum is thus un- 
adapted for bottom plating of large vessels unless reinforced 
by sheathing. 
(2) Bottom plating is necessarily in constant exposure to 
salt water and beyonri the reach of visiting, except at long 
intervals when in dry dock. Considerations of corrosion, of 
care and shortness of life also unfit aluminum for bottom 
plating of vessels keeping the sea, unle.ss they are sheathed. 
Notwithstanding its advantages of lightness, aluminum is 
therefore doubly barred from use for bottom plating of un- 
sheathed vessels keeping the sea. 
(3) The application of aheating to prevent fouling gives to 
steel bottoms an excess of resistanee to penetration; its appli- 
cation to an aluminum bottom would supply the deficiency 
of resistance, and at the same time give protection from the 
contact of sea water. 
TABLE OF RATIOS, ALUMINL'M TO STEEL. 
STKENSTH. 
Tension 
j Corn- 
pan.'! on 
Bending 
.9a 
Simple resistance, 
per square incu , 
Square Sections, 
equal tension, eiah- 
llc 
Square Sections, 
tqual tension, ulti- 
mate 
Square Sections, 
compression, eias-; 
tic , . 
Square Sec ions, 
uompiession, uKi 
male 
Square Sections, 
stieariDg 
Square Sections, 
equal weights. . . 
Rectangular plates,' 
equal tension, elas- 
tic 
Rec angular plates, 
equal lension, ulti-| 
mate .... I 1 
Rectangular plates, 
equal weights 
I tseaoas, proper 
ticnal dimensions, 
fqual weishcp 
I Beams, fqual bending mo 
menis, elastic 
I Beams, equal binding mo 
ments, ultimate 
Angle bars, equal weishtS;.. 
Aofjle bars, equal bending 
moment, elasiic 
Angle bars, equal bend ins 
moment, ultimate 
.66 .8, 
.5; 
61 
a 
M 
|i,6 
I. or 
a.03 
• * 
4. 50 
.99 
1 94 
4,45 
1 
1.04 
1.33 
2 % 
.6 
1. 6 
3.9J 
1 
.£6 
Costs. 
.44. 
1.C3 
,41 
l.U 
9 
3.08 
.at 
.8 
.S( 
.36 
.Si 
.Si 
AS 
,36 
1 
.35 
.46 
i 
.4 
.5^1 
00 
I 
1,0 
1.4 
1.1 
1.7 
i,s 
2.9 I 1.0 
3.3 1.4 
K.6 
10.^ 
3 9 
4.t 
10.4 
4.2 
2.S 
3.6 
1.4 
1.7 
3 ti 
1.5 
3.1 
Dynamic resistance in tension, elaslie, ratio of, per sq in, ,261, -weight 
rado .-iS. 
Dynamic resistance in tension, uPimate. ratio very small, approxi- 
mately inversely propcrtional to length. 
Having a weight ratio of but ,43, the aluminum bottom 
would realize a large saving amounting in a 9,000-ton vessel 
