Dec 27, 1902.] 
FORE Sir AND STREAM 
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ing water. Just where the forward motion of the 
water stops -and the sternward motion begins, must de- 
pend on the form of bow and length of entrance. Every 
vessel may be considered to have a Hue of nodes pecul- 
iar to itself, exteniling from the port and starboard 
bows along which all the particles of water are abso- 
lutely at rest relatively to the far outlying surfaces. 
With the sharp needle-like bow and long entrance as 
exemplified in the modern torpedo boat, the two lines 
of nodes will run forward at a sharp angle to the axis 
of advance and diverge but little from one another. 
On the other hand, when the bow is very blunted and 
the entrance short, the node lines will be greatly di- 
vergent. 
Generally speaking, the greater the displacement the 
greater will be the force absorbed in wave making, and 
also the nearer this displacement comes to the water 
surface, the greater will he the disturbance. A torpedo 
towed but partly immersed has a greater resistance 
than when towed far below the surface. It is a com- 
mon fallacy of belief that a bulb of lead retards a deep 
draft boat more than when placed near the surface of 
a shallower vessel. It is, in fact, most decidedly the 
reverse, other conditions being equal. 
Unlike a perfect fluid, molecules of water flow past 
one another with certain difficulty, and a surface ad- 
vancing in water will cause all the particles in imme- 
diate contact with it to move forward revolve in so- 
called frictional eddies and finally pass astern in a 
frictional wake. These eddies form a skin about the 
moving hull, whose thickness varies according to the 
velocity and length of the hull, and to the comparative 
roughness or smoothness of its surface. If a well var- 
nished plank is moved through water, the surface near- 
est its bow or leading edge will be found to have a fric- 
tional resistance of nearly 4-10 of a pound per square 
foot, but this resistance per square toot will be found 
to rapidly diminish as the distance from the leading 
edge increases, finally assuming a value for lengths of 
fifty feet and upward of but little over 2-10 of a pound. 
This diminishing resistance is easily accounted for 
when it is considered that as the plank passes through 
the water it sets all the particles in immediate contact 
with it in motion in a direction similar to its own, so 
that the relative difference in tiaotion is lessened as the 
distance from the leading edge increases, moreover, it 
has been determined experimentally that this decrease 
of friction no longr holds for lengths of surface over 
fifty feet. 
The forward propelling tendency of the stream lines 
under the afterbody was well illustrated in the experi- 
ence of the two triple screw cruisers, Columbia and 
Minneapolis. On these ships tlie two propellers were 
arranged, as is the ordinary custom, with twin screws 
and a third propeller in a well similar to that on the 
single screw vessel. Each propeller was driven by |a 
separate engine, all designed to be of about equal 
horsepower. It turned out, however, that the central 
engine developed slightly more power than the port 
and starboard engines; instead of giving an increased 
number of revolutions, as would at first sight be ejf- 
pected, there was, on the contrary, a decided decrease 
in the number of turns. The pitch and diameter of all 
three propellers being identical, the only explanation 
was that the forward moving stream lines and skin 
friction eddies about the center line of the afterbody 
was to account for the increased resistance, | 
With the victory of the Defender in 1895, and the 
successes at the same time of many of the fin-keeled 
racing boats of the season, a reaction took place 
against the centerboard type of boat, ^nd many made 
so bold as to state that the heavy ballasted type had 
once and for all vanquished the centerboard boats, in 
all classes above the diminutive half raters and other 
small skimming dishes. It was urged that the centeir- 
board was more of a mechanical than a nautical con- 
trivance, and even likened to shifting ballast device^, 
hinged hulls and even catamarans, and the great ad- 
vantages of its extremely light draft and easy lined 
hull being entirely lost sight of. To my mind the 
cumbrous lead bulb hung far below the hull proper 
is a far less ship-shape device than a moderate form of 
centerboard. . ■ j 
The heavily weighted centerboard ofifers an entirely 
different problem. With the exception of the Harpooli, 
in her second racing season, few of the larger racing 
boats have derived much benefit from the heavily 
weighted board, and it is a curious fact that the iiji- 
creased statical stability, which on paper it woul^ seem 
to afford, is not lived up to in practice. The hglH 
centerboard gives a decided capsizing moment 'to lee- 
ward, in fact it presses so hard on the lower windward 
edge and the upper portion of the leeward side of tlie 
centerboard box that it is usually impossible to raisje 
it except in staj^s. In the heavily weighted board this 
effect is so neutralized by the weight of the board it-; 
self that it will lie almost neutral in the box and often 
vibrate from side to side. [ 
We finally come to the questions of the most easily 
driven form and the form which offers the least wetted 
surface, always remembering that both ease of forfn 
and minimum of wetted surface have often to tje 
sacrificed to increased power of carrying sail, and with 
the best results. It is a favorite joke with the rule of 
thumb men that a boat cut away to a nicety as to h^r 
wetted surface, will often perform wretchedly, but the 
same boat, when hauled out and given an enormous 
scag or other unusual additions to her keel, will sail 
steadier and much faster. This does not mean that 
wetted surface is an overestimated factor, but rather 
that the art of balancing a boat to get the best results 
is beyond_ the present method of calculation. In the 
case of sailing merchantmen, the eai ly naval architects 
had to do with enormous slow-moving ships with pro- 
portionately insignificant sails and long, steadying keels. 
The rules which were deduced under these conditions 
for the so-called lead (that is the distance of the ceti- . 
ter of gravity of the planes of the sails forv/ard of the 
center of gravity, of the profile of the under water 
hull), worked very well. However, when we come to 
apply these rules to the quick turning racing boat with 
its pivot-like keel and' rudder almost amidships, we 
are. led to grievous error, .,,With later yachts it has 
