2015 New York Safe Boating - 6

BOATING AND MOTORS

Directional Terms

Astern- behind the boat, or to move backwards.
Abaft- behind or toward the stern in the boat.

(Assume you are sitting in the boat facing the bow or front
of the boat)

Abeam- off the port or starboard side of the boat, at 90
degrees to the keel of a boat.

Forward- towards the bow of a boat.

Athwartship- across the boat at a right angle to the keel.

Aft- towards the stern of a boat.

Beam- at the sides of a boat.

Starboard- the right side of boat.

Broaching-	the	turning	of	a	vessel	to	expose	its	side	to	the	
oncoming waves.

Port-the left side of boat.
Ahead- in front of the boat or to move forward through the
water.

Roll- to rock from side to side.

Boat Design and Hull Types

Displacement Hull
A displacement hull displaces a volume of water equal
to the weight of the hull and its load whether the boat is
underway or at rest. As the boat cuts through the water,
the displacement hull creates its own wave system with two
wave crests (one at the bow and one at the stern) and a long
unbroken trough amidships.

Hull Shapes
There are two basic types of hulls: displacement hulls and
planing hulls. Each type has its own distinct features and
characteristics. A third type, semi-displacement, shares some
of the features of both planing and displacement hulls.

The hull essentially is trapped within these crests. The
wave	system	created	cannot	exceed	the	waterline	length	of	
the boat. Therefore, the waterline length determines the
displacement hull's top speed. The longer the waterline is,
the greater the potential top speed.

All boats are displacement boats when at rest because the
boat displaces water in order to float. It is what happens to
the hull when power is applied that ultimately determines
its type. In addition, each hull type is associated with some
basic shapes.

Displacement hulls require less power to move through
the water than planing hulls, and generally have a slower
top speed. This type of hull provides a very smooth and
comfortable ride.

The shape of the hull may also determine the wake that
a boat creates. A wake is the moving waves that a boat
generates when moving through the water. A displacement
hull	may	have	a	larger	wake	due	to	the	box	shape	of	the	hull.	
	
A boat that is on plane may have a smaller wake when on
plane because a good portion of the hull is above or near the
top of the water surface.

The most common shape for displacement hulls is the
round	bottom.		Examples	include	large	cruisers,	trawlers,	
houseboats, canal boats and sailboats. Most multi-hull craft,
such as catamarans, trimarans, and pontoon boats also have
displacement hulls.
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2015 New York Safe Boating

Table of Contents for the Digital Edition of 2015 New York Safe Boating
