Sunday, November 21, 2010

Hull types (ship & boat)

Hull types

A hull is the body of a ship or boat. It is a central concept in floating vessels as it provides the buoyancy that keeps the vessel from sinking [8].

In order to choose the correct hull types, many factors must be undertaken before built a boat.
Some types include:

Smooth curve hull

Generally for this types of hulls these vessels are rounded and don't usually have any chines or corners.

They can be round-bilged, soft-chined or molded. Examples are the s-bottom hull, semi-round bilge and round bilge.

Chined and hard chined hulls

These are hulls made up of flat panels (commonly made of plywood, or more traditionally with planking) which meet at a sharp angle known as the chine. Chined hulls range from simple flat-bottomed boats where the side and bottom are two distinct pieces (such as banks dories, sharpies and skiffs) to multichine boats. Multichine hulls allow a round hull shape to be approximated [5].
A chined hull consists of straight plates, which are set at an angle to each other. The chined hull is the most simple hull shape because it works with only straight planks. These boards are often bent lengthwise. Most home-made constructed boats are chined hull boats. A benefit of this type of boating activity is the low production cost and the (usually) fairly flat bottom, making the boat faster at planning. Chined hulls can also make use of a sword or attached keel [7].
Basically chined hulls can be divided up into three shapes: flat-bottom chined hulls, V-bottom chined hulls and multi-chined hulls.

Flat-bottomed hull

There are many advantages for flat-bottomed hull, such as the ability to travel in shallower water. But the disadvantage for this type of hull is less stable in choppy waters than other hull types.

It also an ideal type for the beginning amateur builder because it is simplest to build, goes together quickly and requires fewer tools and usually less money than more complex shape. Flat-bottom boats have a deserved reputation for pounding in head seas but intelligent design can reduce this substantially provided the vessel is used as intended [16].

V – Bottom hull

The "V"-bottom boat is probably the most common hull design. Most manufacturers of boats built today use modifications of this design. This design offers a good ride in rough water as the pointed bow slices forward and the "V"-shaped bottom softens the up-and-down movement of the boat. The degree of the angle of the "V" is called "deadrise." As the "V" shape extends to the back of the boat, it usually flattens out until it all but disappears at the transom. Some "V"-bottom boats have a flat surface at the very bottom called a "pad." This pad allows a little more planing surface and at the sacrifice of a little softness in the ride, but this addition increases top speed.

Displacement hulls

These are hulls which have a shape which does not promote planing. They travel through the water at a limited rate which is defined by the waterline length. They are often heavier than planing types, though not always [5].

Planing hull

These are hulls with a shape that allows the boat to rise higher and higher out of the water as the speed increases. They are sometimes flat-bottomed, sometimes V-bottomed and sometimes round-bilged. The most common form is to have at least one chine to allow for stability when cornering and for a supportive surface on which to ride while planing. Planing hulls allow higher speeds to be achieved, and are not limited by the waterline length the way displacement hulls are. They do require more energy to achieve these speeds.

No comments: