New York Safe Boating - 2020 - 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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New York Safe Boating - 2020

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