There are two different elements to a keel. They are the hydrodynamic element and the structural element. In layman terms, the keel is the backbone. There many different hulls. When you speak of hulls, you have displacement hulls, semi-displacement hulls or planing hulls. Hulls come in different shapes like moulded or hard chined or simply chined.
Offshore patrol vessels have much deeper hulls, and tend to be larger vessels, overall. An offshore vessel has to deal with weather conditions a river patrol vessel will not have to, and generally stays out for longer periods of time.
Some examples of displacement hulls include sailboats, traditional fishing boats, and some types of canoes and kayaks. These hulls are designed to displace water and move through it efficiently at low to moderate speeds, making them suitable for leisurely cruising or fishing.
Two hulls - catamaran Three hulls - trimaran
There is no set answer as someone is always experimenting with some new way to "beat the wind". Mono-hulls would vary from multi-hulls, for example. Sail material can make a difference. Gross weight of the craft makes a difference. Amount of free-board makes a difference.
A trimaran has 3 hulls, a main hull and two smaller outrigger hulls.
Yes, the plural noun hulls is a common noun, a word for any hull or hulls. The word hulls is also a verb (hull, hulls, hulling, hulled). Example uses: Noun: The hulls are removed before the grain is ground. Verb: This is the machines that hulls the grain.
A trimaran has 3 hulls.
general cargo ships
The main three types are; arteries, veins and capillaries.
Most submarine hulls are built of steel. Recall that a submarine is not usually considered one of the little robotic undersea machines, or a manned vessel that is operated off a support vessel. We usually reserve the term for the military submarines (boats) that put to sea for extended periods of independent operation. The Russians built a few hulls from titanium, but these boats were horrendously expensive and in so many ways were not cost effective. The lion's share of modern military boats are steel hulls with steel decks (on special supports) and filled with tons of equipment built largely of steel or other metal alloys. The modern nuclear submarines include the reactor, which has a steel pressure vessel and steel plumbing pretty much throughout the ship.
The plural form of "hull" is "hulls."