190
T126 Last Resource
containerization remains the single most important trend in inter—
national transport.
Building better s/zips
A model boat a few feet long seems far removed from ‘jumbo
tankers’, but it is almost certain that without tests made on scale
models such ships would prove difcult, if not impossible, to design.
In fact, ship designers have long relied on the use of models to help
them devise satisfactory hull shapes. At rst, experiments with
models had only a qualitative value, and the results could not be
scaled up
to the full—sized model. Then, about 1870, William Froude,
a British engineer, discovered that surface wave patterns created by
a ship and by a geometrically similar model are identical at certain
speeds, depending on the ship speed and the scale of the model.
From this concept, now embodied in the modelling parameter called
the Fronde Number, he was able to show how the resistance, or
hydrodynamic drag, of a ship could be directly deduced from
experiments with a model towed at the appropriate speed. Models
a much more important role in ship design, and ship
model laboratories have progressed from Froude’s rst laboratory
in a eld beside his home in Torquay, to a stage where few problems
of a ship’s performance at sea cannot be investigated in them.
The model testing tank built by Fronde was a primitive affair
little more than 200 feet long, in which wax and wooden hull
models and planks could be towed and their resistances measured
over a range of controlled speeds. Compare this with the facilities
available in modern laboratories such as the Ship Division of the
National Physical Laboratory (NFL) at Feltham near London.
The largest towing tank of the Ship Division is 1,300 feet long
48 feet broad and 25 feet deep. Spanning the channel is a carriage
which can travel at speeds of up
to 50 feet per second, providing an
instrument and observation platform from which models over 30
feet long can be towed or propelled, while a wave—making machine
at one end creates realistic sea states. There are also wavemakers
along the sides of the large sea—keeping tanks in which stationary or
remote—controlled, free—moving models are tested. Apart from
such ‘indoor oceans’, water—tunnels, the marine equivalents of
wind—tunnels, are used to study models, particularly various designs
of propellers and stabiliZing ns. Finally, the Ship Division has one
of the most up—to-date circulating water—channels in the world. The
T126 Last Resource
containerization remains the single most important trend in inter—
national transport.
Building better s/zips
A model boat a few feet long seems far removed from ‘jumbo
tankers’, but it is almost certain that without tests made on scale
models such ships would prove difcult, if not impossible, to design.
In fact, ship designers have long relied on the use of models to help
them devise satisfactory hull shapes. At rst, experiments with
models had only a qualitative value, and the results could not be
scaled up
to the full—sized model. Then, about 1870, William Froude,
a British engineer, discovered that surface wave patterns created by
a ship and by a geometrically similar model are identical at certain
speeds, depending on the ship speed and the scale of the model.
From this concept, now embodied in the modelling parameter called
the Fronde Number, he was able to show how the resistance, or
hydrodynamic drag, of a ship could be directly deduced from
experiments with a model towed at the appropriate speed. Models
a much more important role in ship design, and ship
model laboratories have progressed from Froude’s rst laboratory
in a eld beside his home in Torquay, to a stage where few problems
of a ship’s performance at sea cannot be investigated in them.
The model testing tank built by Fronde was a primitive affair
little more than 200 feet long, in which wax and wooden hull
models and planks could be towed and their resistances measured
over a range of controlled speeds. Compare this with the facilities
available in modern laboratories such as the Ship Division of the
National Physical Laboratory (NFL) at Feltham near London.
The largest towing tank of the Ship Division is 1,300 feet long
48 feet broad and 25 feet deep. Spanning the channel is a carriage
which can travel at speeds of up
to 50 feet per second, providing an
instrument and observation platform from which models over 30
feet long can be towed or propelled, while a wave—making machine
at one end creates realistic sea states. There are also wavemakers
along the sides of the large sea—keeping tanks in which stationary or
remote—controlled, free—moving models are tested. Apart from
such ‘indoor oceans’, water—tunnels, the marine equivalents of
wind—tunnels, are used to study models, particularly various designs
of propellers and stabiliZing ns. Finally, the Ship Division has one
of the most up—to-date circulating water—channels in the world. The