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NON-SELF PROPELLED VESSELS
by
Mike Vaughn
When we think of non-self propelled vessels we usually think of barges. However, there
are a variety of other crafts that, for one reason or another, do not contain or use propulsion
units that are self contained.
Hotel Ships
A cruise ship or liner is merely a hotel with the ability to change locations, the Caribbean
in the winter and Alaska in the summer. When a cruise ship nears the end of its useful
life, it has the opportunity to become more or less permanently fixed in one position as a
hotel ship.
There are a number of reasons that this will occur. The international convention providing for
safety aboard cruise ships (SOLAS) is a changing set of rules. Many older ships are not
economically feasible to bring up to the newer fire and safety standards. Consequently,
they have little or not value as a cruise ship.
In many cases these ships are still very elegant craft with a history of international cruising
behind then. Such ships, like the Queen Mary, now serving as a hotel and tourist
attraction in Long Beach, California go on to long and worthwhile careers. Others, without
the history of the Queen Mary, find other occupations as restaurants and attractions,
accommodation platforms and temporary quarters.
Very often when special events require an active cruise ship will be temporarily docked as
several ships were so used in Barcelona during the Olympics.
In the United States, where the Jones Act requires that all passenger carrying vessels be
U.S. built and flagged, a hotel ship can avoid this requirement by removing its propellers
and propulsion equipment and become affixed to the shore.
It is important to realize that when this happens, the ships must then meet local and state
building codes, as well as requirements for handicap access and use. Even with these
requirements, a hotel ship can be on site and in service in a fraction of the time it takes to
construct a major hotel.
Floating Dry Docks
A floating dry dock is an essential tool in the maintenance of commercial and private
ships. All ships and boats must be periodically removed from the water and the hull must
be inspected, repaired and painted.
For small pleasure craft and small working craft, a travel lift or marine railway may be
sufficient to lift them out of the water.
However, large commercial ships which may weigh hundreds of thousands of tons can
only be lifted by a floating dry dock.
A floating dry dock, is merely a large tank with walls on each side, massive pumps and
compartmentalized floating chambers that can be filled and evacuated on demand. The
floating dry dock will have a lifting capacity based upon the amount of displacement of
water designed in the dry dock. The lifting capacity need only be greater than the weight
of the ship being lifted.
A 10,000 ton dry dock should be able to lift a 10,000 ton ship. Of course a margin of
safety is always employed.
A “blocking plan” is devised for each ship when it is constructed. This plan shows the
shipyard the stress points in the hull so that massive wooden or steel blocks can be
strategically placed so as to support the weight of the ship without damaging it.
The dry dock is then submerged deeper than the draft of the ship by pumping ballast water
into the chambers in the dry dock. The ship is then positioned very carefully into the dry dock by tugs to make certain that the ship will rest upon the blocks that are pre-positioned in
the floor of the dry dock.
The pumps in the dry dock pump out the ballast water and as the dry dock starts to rise it
lifts the ship completely out of the water.
Dredges
A dredge is one of those work-horses of the industry that no one talks about until you
really need it. The dredge is a giant vacuum cleaner that is used to deepen and clear
waterways.
Dredges come in all sizes, but all have the same basic characteristics. These include a
cutter head that cuts or disturbs the ocean bottom and a ladder device that brings the mud
or dredge spoil up to the surface for deposit in a barge or other vessel.
Dredge
Dredges vary in size from 25 or 30 feet up to several hundred feet in size. The
distinguishing factor is the depth of water in which it can work and the size of the dredge
pipe that it uses to extract the dredge spoil.
Barges
The barge is probably the oldest form of water transportation. Today they are used in
every waterway of the world, every port and for every conceivable purpose.
They will range in size from small floats to giant ocean-going platforms that will rival some
of the largest ships.
The common characteristics are the lack of self-propelling equipment and a generally
rectangular shape.
There are a variety of barges. The following are some of the more common uses:
1. Deck barges are used for transporting cargo stored on deck.
2. Tank barges are used for transporting cargo, generally liquid stored below
deck.
3. Bin barges have high perimeter walls that allow bulk cargo to be carried
on deck.
4. Accommodation barges have housing built on deck to provide living
quarters for work.
5. Crane barges have large mechanical cranes on deck and are used in a variety
of marine construction situations.
6. Notch barges are barges that, instead of a flat or square sterns, have a notch
designed in the middle so that a tug boat can position the bow of the tug in to
the center of the barge and more effectively control the movement of the barge.
You will see both tank and deck barges built this way.
7. A Spud Barge is built so that it can be positioned in one place in relatively shallow
water and not move. This is accomplished by the placement of two or more long
metal pipes or tubes called spuds, vertically on the side of the barge, that can
be raised or lowered at will. When the barge is correctly in position, the
captain sinks the spuds into the bottom and the piling then holds the barge in
position. This if very common for construction projects and is routinely found
on carne barges.
8. Jack Up Barge is the next step up from the spud barge. It is very similarly
constructed, except the spuds are more substantial and the mechanical
equipment more complex. When the barge is correctly positioned, the legs are
positioned on the bottom and the barge is elevated out of the water using the legs
as vertical support.
Working on the water requires innovation, good design and courage. Every type
of water borne device may fail with disastrous results so it is important to choose
good equipment that is designed and suitable for the project intended.
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