The
Feathering Sidewheel
The most unusual feature of the wreck site
is the pair of iron-framed, "feathering" sidewheels. Although such sidewheels
were relatively commonplace on steamships of the period, they are very distinctive and
strongly support the identification of the wreck as Denbigh.
The feathering sidewheel was perhaps the
most successful attempt to improve the efficiency of the conventional paddlewheel. The
idea was to continually adjust the paddle blades, or "floats," as the wheel
turned, to get the best, most effective use of the engine's power. In the feathering
wheel, each float was secured in an iron frame (shown in red, above) so that it could
pivot slightly. Attached to the rear face of each float was a short arm, which was itself
attached to second wheel (gray), attached to the outside frame of the paddlebox, and set
to pivot slightly forward of the main wheel. It was a complex arrangement, but it worked
well.
The main components of a "float," or paddle, from Denbigh's
feathering wheel.
The feathering paddlewheel was first
patented in England in 1829 by Elijah Galloway. In 1838 the rights to the design were
transferred to an attorney, James L. Lucena, who turned it over to his partner, William
Morgan, an engineer from Surrey. Morgan refined the design considerably, and by about 1850
feathering wheels were becoming increasingly commonplace. Although they were not widely
adopted by large transatlantic steamers, due to their cost and "likelihood of
derangement," they quickly became the standard for smaller vessels like excursion
boats and harbor tugs. Denbigh, which may have originally been built as a small
freight or excursion steamer, was equipped with feathering wheels at the Laird & Son
Yard in Birkenhead while under construction. Although they were not developed for blockade
running, feathering wheels did possess an additional advantage for smugglers -- because
the floats entered the water at a more efficient angle, they were quieter and kicked up
less spray than conventional wheels, an important consideration sneaking past Federal
warships.
Feathering sidewheels quickly lost favor
in the latter half of the 19th century as the efficiency of screw propulsion became
evident. For a few purposes, though, sidewheels retained an advantage. They were
especially useful for harborcraft that needed to maneuver in narrow channels and docks.
Frequently, a steam tug equipped with independently-controlled sidewheels could spin on
its own axis like a top. Paddlewheel steamers remained in widespread use into the 20th
century, particularly in the United Kingdom, where several examples were still in active
service in the years after World War II.
Much of the above is drawn from
Peter Allington and Basil Greenhill's The First Atlantic Liners: Seamanship in the Age
of Paddle Wheel, Sail and Screw (London, Conway Maritime Press, 1997). |
