A boats hull shape is important for a number of reason, safety, sea kindliness,
load carrying capacity, speed and efficiency in a particular speed range and operating
Hulls can be classified/categorized into three major
boat hull types based on intended
boat speed range per hull length:
Although this hull type is stable in calm weather it is, because of its flatter
bow, a comparatively rougher ride. This is typically a planing boat that rides on
top of rather than through the water. Due to issues with maneuverability and the
roughness of the ride these hulls are limited to the amount of horse power applied.
This hull type is typically used on calm waters.
This hull is easier to maneuver than the flat hull and moves efficiently though
the water at low speeds. These are displacement hulls, which are limited in speed
due to the bow wave they create while pushing though the water as opposed to a planning
hull that climbs on top of the water. This hull is usually used for ships, canoes/kayaks,
Most power boats have this hull shape. You can think of this hull as a hybrid of
the flat and round bottom hulls. This is generally associated with a semi-Displacement
vessel that can, at low speeds push though the water relatively efficiently like
a round bottom hull but it can also plain to a certain extent, but not at speeds
of a flat bottom hull. The V allows the boat to cut though the water to minimize
slapping and provide some grip in turns. The angle of the V is called the dead rise
and tends flattens out toward the stern where the angle of the boats run, the V
at the stern, will be a big factor in determining the boats planing capabilities.
Used for power boats, you can think of this as multiple v hulls on one boat hull.
This design provides more stability, better handling and some claim more lift, due
to the air pockets between the mini-hulls.
Tunnel hulls or catamaran tunnel hull boats are the go fast boats. This hull design
is used on the supper fast racers and now even on some fast dinghy’s. This
hull has a sharp inner corner or a 90 degree inside hull but is rounded to the outside.
This shape provides exceptional grip in tight turns and allows for fast planing.
The hull being a catamaran design also allows for good stability and the ability
to carry large motors.
This is a very simple hull design to allow for a flat deck to lounge around on.
It’s like a catamaran but think of it as a deck with a line of drums tied
to either side. This hull shape is not intended to plan and is not the most efficient
but it’s great for parties on calm water.
This term is generally associated with catamaran and trimaran sail boats which is
simply a boat with two or three of round bottom hulls respectively, placed apart
for additional stability. This additional stability gives multihulls a significant
advantage in that, unlike displacement monohulls (single round bottom), they do
not have to be weighed down at the keel to hold them upright. This makes them lighter
Boat hulls are designed by Naval Architects using sophisticated software and are
designed with a particular speed range, conditions and requirements in mind. For
example a high speed catamaran ferry’s hull, due to its size and operating
speed will look very different to a catamaran sail boat. Designing a boats hull
is an iterative process. A boat designer will use scantlings rules. Scantlings are
the dimensions of all parts that go into building a boat for example frames, stringers,
girders, etc. The scantling rules are currently set by Lloyds and American Bureau
of Ships for fiberglass boats.
Hulls are made with a number of materials and combinations of materials, the major
The size of the hull and the money available for the project are major factors in
determining what material and/or method to use.