Editing Hull (watercraft) (section)

==Hull shapes==
Hulls come in many varieties and can have composite shape, (e.g., a fine entry forward and inverted bell shape aft), but are grouped primarily as follows:
* Chined and hard-chined. Examples are the flat-bottom (chined), v-bottom, and multi-chine hull (several gentler hard chines, still not smooth). These types have at least one pronounced knuckle throughout all or most of their length.
* Moulded, round bilged or soft-[[chine (boating)|chined]]. These hull shapes all have smooth curves. Examples are the round bilge, semi-round bilge, and s-bottom hull.

===Planing and displacement hulls===
<!-- [[Waterline]] links to this section -->
[[File:Royal Navy MTB 5.jpg|thumb|[[Royal Navy]] World War II [[Motor Torpedo Boat|MTB]] planing at speed on calm water showing its [[Chine (boating)#Various types of chine hulls|hard chine hull]] with most of the forepart of the boat out of the water.]]
* Displacement hull: here the hull is supported exclusively or predominantly by [[buoyancy]]. Vessels that have this type of hull travel through the water at a limited rate that is defined by the waterline length except for especially narrow hulls such as sailing [[multihulls]] that are less limited this way.
* Planing hull: here, the [[Planing (boat)|planing]] hull form is configured to develop positive [[dynamic pressure]] so that its [[Draft (hull)|draft decreases]] with increasing speed. The dynamic lift reduces the wetted surface and therefore also the [[Drag (physics)|drag]]. Such hulls are sometimes flat-bottomed, sometimes V-bottomed and more rarely, round-bilged. The most common form is to have at least one chine, which makes for more efficient planing and can throw spray down. Planing hulls are more efficient at higher speeds<!-- Removed the suggestion that hull speed is a "maximum" speed which can't be overcome -- see [[Hull speed]] or <ref>{{cite web| url=http://www.boatdesign.net/forums/boat-design/hull-speed-1220.html| title=Hull speed}}</ref> for an explanation of this misconception -->, although they still require more energy to achieve these speeds. An effective planing hull must be as light as possible with flat surfaces that are consistent with good sea keeping. Sailboats that plane must also sail efficiently in displacement mode in light winds.
* Semi-displacement, or semi-planing: here the hull form is capable of developing a moderate amount of dynamic lift; however, most of the vessel's weight is still supported through buoyancy.

===Hull forms===
At present, the most widely used form is the round bilge hull.<ref>Zeilen: Van beginner tot gevorderde by Karel Heijnen</ref>

With a small payload, such a craft has less of its hull below the [[waterline]], giving less resistance and more speed. With a greater payload, resistance is greater and speed lower, but the hull's outward bend provides smoother performance in waves. As such, the inverted bell shape is a popular form used with planing hulls.{{citation needed|date=January 2022}}{{clarify|This description only applies to a minority of hull shapes|date=January 2022}}

====Chined and hard-chined hulls====
{{Further|Chine (boating)}}

A chined hull does not have a smooth rounded transition between bottom and sides. Instead, its contours are interrupted by sharp angles where predominantly longitudinal panels of the hull meet. The sharper the intersection (the more acute the angle), the "harder" the chine. More than one chine per side is possible.

The Cajun "pirogue" is an example of a craft with hard chines.

Benefits of this type of hull include potentially lower production cost and a (usually) fairly flat bottom, making the boat faster at [[Planing (sailing)|planing]]. A hard chined hull resists rolling (in smooth water) more than does a hull with rounded bilges (the chine creates turbulence and drag resisting the rolling motion, as it moves through the water, the rounded-bilge provides less flow resistance around the turn). In rough seas, this can make the boat roll more, as the motion drags first down, then up, on a chine: round-bilge boats are more seakindly in waves, as a result.

Chined hulls may have one of three shapes:
* Flat-bottom chined hulls
* Multi-chined hulls
* V-bottom chined hulls. Sometimes called hard chine.

Each of these chine hulls has its own unique characteristics and use. The flat-bottom hull has high initial stability but high drag. To counter the high drag, hull forms are narrow and sometimes severely tapered at bow and stern.{{citation needed|date=January 2022}} This leads to poor stability when heeled in a sailboat.{{citation needed|date=January 2022}} This is often countered by using heavy interior ballast on sailing versions. They are best suited to sheltered inshore waters. Early racing power boats were fine forward and flat aft. This produced maximum lift and a smooth, fast ride in flat water, but this hull form is easily unsettled in waves. The multi-chine hull approximates a curved hull form. It has less drag than a flat-bottom boat. Multi chines are more complex to build but produce a more seaworthy hull form. They are usually displacement hulls. V or arc-bottom chine boats have a V{{nbsp}}shape between 6°{{nbsp}}and 23°. This is called the {{nautical term|deadrise}} angle. The flatter shape of a 6-degree hull will plane with less wind or a lower-horsepower engine but will pound more in waves. The deep V{{nbsp}}form (between 18{{nbsp}}and 23{{nbsp}}degrees) is only suited to high-powered planing boats. They require more powerful engines to lift the boat onto the plane but give a faster, smoother ride in waves. Displacement chined hulls have more wetted surface area, hence more drag, than an equivalent round-hull form, for any given displacement.

====Smooth curve hulls====
{{Further|Smooth curve hull}}
{{See also|Boat building}}
{{cleanup translation|date=August 2022}}
Smooth curve hulls are hulls that use, just like the curved hulls, a centreboard, or an attached keel.{{citation needed|date=January 2022}}

Semi round bilge hulls are somewhat less round. The advantage of the semi-round is that it is a nice middle between the S-bottom{{clarify|explain, define, or link S-bottom, show that it is a term used in English|date=January 2022}} and chined hull. Typical examples of a semi-round bilge hull can be found in the [[Centaur (dinghy)|Centaur]] and [[Laser (dinghy)|Laser]] sailing [[dinghies]].

[[Image:Chine types.svg|thumb|right|Comparison of three types of hulls: {{ordered list | list-style-type = upper-alpha | 1 = S-bottom | 2 = hard chine  | 3 = soft chine }}]]

S-bottom hulls are sailing boat hulls with a midships transverse half-section shaped like an ''s''.{{clarify|date=March 2019}} In the s-bottom, the hull has round bilges and merges smoothly with the keel, and there are no sharp corners on the hull sides between the keel centreline and the sheer line. Boats with this hull form may have a long fixed deep keel, or a long shallow fixed keel with a centreboard swing keel inside. Ballast may be internal, external, or a combination. This hull form was most popular in the late 19th and early to mid 20th centuries.{{citation needed|date=March 2019}} Examples of small sailboats that use this s-shape are the [[Yngling (keelboat)|Yngling]] and [[Randmeer]].