Past Examples of Long Tows 
It is of some interest to briefly consider towing floating 
structures as large as MOBS. Table 5.9 presents some data on tow boat 
requirements for objects of various displacements. It is assumed that 
the towed vessel is equipped with a fairing and is essentially ship- 
like in shape. 
During World War II a large number of dry docks were towed consid- 
erable distances. These dry docks varied in displacement for 1,000 to 
7,600 long tons. The overall average towing speed was 6.2 knots. For 
the large (7,600 long tons) dry docks, a 3,000 horsepower tug capable 
of towing at an average speed of 4.6 knots (slightly less than 8 feet/ 
second) was used. Table 5.10 presents some data on a few of these tows. 
The large columns which are used for buoyancy in the elevated 
platform concepts displace less than 2,000 long tons, so it is feasible 
to tow them (in the horizontal position) with relatively small tow boats. 
The larger, barge-like floating decks can displace greater than 30,000 
long tons. While the floating barges of this size can be towed, it is 
probably more practical to make the units considerably smaller so they 
could be towed by the smaller, readily available tug boats of the ATA 
class. 
If the sizes of the components or modules are in the neighborhood 
of 2,000 long tons, a towing speed of six knots is possible. If the 
modules are 5,000 long tons or more, a towing speed of four knots is 
probably all that is practical. As a consequence, it does not appear 
that speed on the order of that of a cargo ship is possible if the 
modules are to be towed by conventional means. 
