What is a Vessel's Chine?

Extend Your Boating Knowledge by Learning About Different Kinds of Chines

Even Good Safety Practices Can Land You In a Tight Spot. Jon Sullivan

In terms of boating, the chine is the area of a vessel's hull where the bilge angles up to become the topsides of the hull. The hull is the watertight section of the vessel, above which is the deck and any other superstructure feature. The bilge is the lowest part of a vessel under the waterline. 

Hard and Soft Chines

A chine is described as being soft or hard depending on the measurement of the internal angle between the bilge to topside transition.

A hard chine has a smaller interior angle than a soft chine. There are no absolute values for determining a soft or hard chine construction, but angles less than 135 degrees (90/2)+90) are considered hard chines and angles greater than 135 degrees are considered soft chines. A vessel with a 90-degree angle between bilge and topside has a very hard chine. 

Types of Chines

Here are a few examples of chine types. A "V" shape chine is constructed by connecting two flat panels at the bottom-most point of the vessel, creating a "V" shape. This is also called a single chine hull. While a simple construction, it is not the most stable.

A 2 chine hull consists of a flat bottom and 90-degree angled sides on both sides. A hard chine model, a 2 chine hull vessel is very stable and features a large capacity for cargo. 

One of the more common chine builds, a 3 chine hull features a very wide "V" shape extending from the keel.

Then, over 90-degreed sides extend up from the end of the "V".

Multi-Chine Hulls

Multi-chine hulls are vessels 3 or more chines. Modern hulls on high-speed or rough water vessels might have multiple chine hulls. These can be seen on the hull near the bow.

Multi-chine hulls allow the cross section of the hull that is exposed to the water to be reduced when the vessel is lifted because of the resistance of water in front of the hull.

This is also known as planning hull. As a vessel is lifted, less of the hull contacts the water and it becomes laterally unstable. This instability allows a hull to pivot along its length to stabilize a high-speed turn.

Multiple chines are also valuable on larger crafts that operate in rough conditions. The multiple chine hull eases the boat into an oncoming wave more slowly by absorbing the shock, as opposed to a single flat surface which would transfer all of the wave energy to the hull at one time. Steps of the chine also suppress hull roll and heave by spreading out the impact of waves over a longer period of time.