It became necessary, therefore,
to steady the vessel by having her towed by the _Winkelried_, which was
chartered for such a purpose, to the General Navigation Company. It
became possible to thus carry on observations on speeds up to 27
kilometers per hour.
Fig. 3 shows how the tractive stress varies with each speed in a
theoretic case (dotted curve) in which the stress is proportional to the
square of the speed, in Madame Rothschild's boat, the _Gitana_ (curve
E), and in the Pictet high speed vessel (curve B).
The _Gitana_ was tried with speeds varying between 0 and 4 kilometers.
The corresponding tractive stresses have been reduced to the same
transverse section as in the Pictet model in order to render the
observations comparable. At slight speeds, and up to 19.5 kilometers per
hour, the _Gitana_, which is the sharper, runs easier and requires a
slighter tractive stress. At such a speed there is an equality; but,
beyond this, the Pictet boat presents the greater advantages, and, at a
speed of 27 kilometers, requires a stress about half less than does the
_Gitana_. Such results explain themselves when we reflect that at these
great speeds the _Gitana_ sinks to such a degree that the afterside
planks are at the level of the water, while the Pictet model rises
simultaneously fore and aft, thus considerably diminishing the submerged
section.
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