Page 12 - NAVAL FORCES 03/2017

Technology Spotlight

The US Navy is also building
Littoral Combat Ships with
relatively beamy, semi-planing
hulls. USS “Fort Worth”
is shown in the Sulu Sea.
Her relatively great beam allows
her to have a large helicopter
deck aft.

which the ship interacts with the sea. A con- of the older Small Waterplane Area Twin Hull the waterplane and hence both resistance
ventional hull has a considerable waterplane (SWATH) concept. and sensitivity to the motion of the sea.
area (the area of the hull at the waterline), The slenderness of the main hull reduces
which ties it to the motion of the surrounding Reducing the resistance: A trimaran of a given size and
sea. As it cuts through the sea that mass of hull Waterplane Area power output is faster than a comparable con-
penetrating the water generates waves, which ventional ship. That is certainly the case with
create resistance. If the waterplane can be Trimarans substitute a slender hull and the “Independence” class, which was bought
drastically shrunk, the ship ought to be less af- two outriggers for the usual displacement on the basis of extensive Australian experience
fected by wave motion and may also suffer less hull. The combination buys back the stabili- with fast car ferries. A SWATH also drama-
resi stance as it moves through the sea. That ty and steadi ness usually associated with the tically reduces waterplane area, in this case
perception is the basis of the trimaran and also beam of a ship’s hull, while sharply reducing by substituting a pair of underwater bodies

Accompanied by the trimaran
“Independence”, the missile destroyer
“Zumwalt” shows her backward-raked,
wave-piercing bow.

10 NAVAL FORCES III/2017