词条 | Hull (watercraft) |
释义 |
A hull is the watertight body of a ship or boat. The hull may open at the top (such as a dinghy), or it may be fully or partially covered with a deck. Atop the deck may be a deckhouse and other superstructures, such as a funnel, derrick, or mast. The line where the hull meets the water surface is called the waterline. General featuresThere is a wide variety of hull types that are chosen for suitability for different usages, the hull shape being dependent upon the needs of the design. Shapes range from a nearly perfect box in the case of scow barges, to a needle-sharp surface of revolution in the case of a racing multihull sailboat. The shape is chosen to strike a balance between cost, hydrostatic considerations (accommodation, load carrying and stability), hydrodynamics (speed, power requirements, and motion and behavior in a seaway) and special considerations for the ship's role, such as the rounded bow of an icebreaker or the flat bottom of a landing craft. In a typical modern steel ship, the hull will have watertight decks, and major transverse members called bulkheads. There may also be intermediate members such as girders, stringers and webs, and minor members called ordinary transverse frames, frames, or longitudinals, depending on the structural arrangement. The uppermost continuous deck may be called the "upper deck", "weather deck", "spar deck", "main deck", or simply "deck". The particular name given depends on the context—the type of ship or boat, the arrangement, or even where it sails. In a typical wooden sailboat, the hull is constructed of wooden planking, supported by transverse frames (often referred to as ribs) and bulkheads, which are further tied together by longitudinal stringers or ceiling. Often but not always there is a centerline longitudinal member called a keel. In fiberglass or composite hulls, the structure may resemble wooden or steel vessels to some extent, or be of a monocoque arrangement. In many cases, composite hulls are built by sandwiching thin fiber-reinforced skins over a lightweight but reasonably rigid core of foam, balsa wood, impregnated paper honeycomb or other material. Perhaps the earliest proper hulls were built by the Ancient Egyptians, who by 3000 BC knew how to assemble wooden planks into ahull.[1] See also: Hull (ship)Hull shapesHulls 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:
Planing and displacement hulls
Hull formsAt present, the most widely used form is the round bilge hull.[3] In the inverted bell shape of the hull, with a smaller payload the waterline cross-section is less, hence the resistance is less and the speed is higher. With a higher payload the outward bend provides smoother performance in waves. As such, the inverted bell shape is a popular form used with planing hulls. Chined and hard-chined hulls{{Further|Chine (boating)}}A chined hull consists of straight, smooth, tall, long, or short plates, timbers or sheets of ply, which are set at an angle to each other when viewed in transverse section. The traditional chined hull is a simple hull shape because it works with only straight planks bent into a curve. These boards are often bent lengthwise. Plywood chined boats made of 8'{{nbsp}}x{{nbsp}}4' sheets have most bend along the long axis of the sheet. Only thin ply 3–6 mm can easily be shaped into a compound bend. Most home-made constructed boats are chined hull boats. Mass-produced chine powerboats are usually made of sprayed chop strand fibreglass over a wooden mold. The Cajun "pirogue" is an example of a craft with hard chines. Benefits of this type of hull is the low production cost and the (usually) fairly flat bottom, making the boat faster at planing. Sail boats with chined hull make use of a dagger board or keel. Chined hulls may have one of three shapes:
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. This leads to poor stability when heeled in a sail boat. 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{{nbsp}}degrees. This is called the deadrise angle. The flatter shape of a 6{{nbsp}}degrees hull will plane with less wind or a lower horse power engine but will pound more in waves. The deep V{{nbsp}}form (between 18{{nbsp}}and 23{{nbsp}}degrees) is only suited to high power 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}}Smooth curve hulls are hulls which use, just like the curved hulls, a sword or an attached keel. 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 and chined hull. Typical examples of a semi-round bilge hull can be found in the Centaur and Laser cruising dinghies. S-bottom hulls are hulls shaped like an s.{{clarify|date=March 2019}} In the s-bottom, the hull runs smooth to the keel. As there are no sharp corners in the fuselage.{{clarify|date=March 2019}} Boats with this hull have a fixed keel, or a kielmidzwaard (literally "keel with sword"). This is a short fixed keel, with a swing keel inside.{{cn|date=March 2019}} Examples of cruising dinghies that use this s-shape are the Yngling and Randmeer. See also: Boat buildingAppendages
Terms{{main|Glossary of nautical terms}}
MetricsHull forms are defined as follows:
1) Block coefficient (Cb) is the volume (V) divided by the LWLx BWL x TWL . If you draw a box around the submerged part of the ship, it is the ratio of the box volume occupied by the ship. It gives a sense of how much of the block defined by the LWL, beam (B) & draft (T) is filled by the hull. Full forms such as oil tankers will have a high Cb where fine shapes such as sailboats will have a low Cb. 2) Midship coefficient (Cm or Cx) is the cross-sectional area (Ax) of the slice at midships (or at the largest section for Cx) divided by beam x draft. It displays the ratio of the largest underwater section of the hull to a rectangle of the same overall width and depth as the underwater section of the hull. This defines the fullness of the underbody. A low Cm indicates a cut-away mid-section and a high Cm indicates a boxy section shape. Sailboats have a cut-away mid-section with low Cx whereas cargo vessels have a boxy section with high Cx to help increase the Cb. 3) Prismatic coefficient (Cp) is the volume (V) divided by LWLx Ax. It displays the ratio of the immersed volume of the hull to a volume of a prism with equal length to the ship and cross-sectional area equal to the largest underwater section of the hull (midship section). This is used to evaluate the distribution of the volume of the underbody. A low or fine Cp indicates a full mid-section and fine ends, a high or full Cp indicates a boat with fuller ends. Planing hulls and other highspeed hulls tend towards a higher Cp. Efficient displacement hulls travelling at a low Froude number will tend to have a low Cp. 4) Waterplane coefficient (Cw) is the waterplane area divided by LWL x BWL. The waterplane coefficient expresses the fullness of the waterplane, or the ratio of the waterplane area to a rectangle of the same length and width. A low Cw figure indicates fine ends and a high Cw figure indicates fuller ends. High Cw improves stability as well as handling behavior in rough conditions. Note: Computer-aided designUse of computer-aided design has superseded paper-based methods of ship design that relied on manual calculations and lines drawing. Since the early 1990s, a variety of commercial and freeware software packages specialized for naval architecture have been developed that provide 3D drafting capabilities combined with calculation modules for hydrostatics and hydrodynamics. These may be referred to as geometric modeling systems for naval architecture.[6] See also{{col-begin}}{{col-3}}
Notes1. ^Ward, Cheryl. "World's Oldest Planked Boats," in Archaeology (Volume 54, Number 3, May/June 2001). Archaeological Institute of America. Archaeology.org 2. ^{{cite web|url=http://www.boatdesign.net/forums/boat-design/hull-speed-1220.html|title=Hull speed|publisher=}} 3. ^Zeilen: Van beginner tot gevorderde by Karel Heijnen 4. ^{{cite web | title = International Convention on Tonnage Measurement of Ships, 1969|work =International Conventions | publisher = Admiralty and Maritime Law Guide | date = 1969-06-23|url =http://www.admiraltylawguide.com/conven/tonnage1969.html |accessdate = 2007-10-27 }}, Annex 1, Regulations for determining gross and net tonnages of ships, Reg. 2(2)(a). In ships with rounded gunwales, the upper measurement point is take to the point at which the planes of the deck and side plating intersect. Id., Reg. 2(2)(b). Ships with stepped decks are measured to a line parallel with the upper part. Id., Reg. 2(2)(c). 5. ^{{Cite book | last1=Rawson | first1=E.C. | last2=Tupper | title=Basic Ship Theory | volume=1 | publisher=Longman | edition=2nd | isbn=0-582-44523-X | date=1976 | pages=12–14 | postscript=}} 6. ^{{cite web|last1=Ventura|first1=Manuel|title=Geometric Modeling of the Hull Form|url=http://www.mar.ist.utl.pt/mventura/Projecto-Navios-I/EN/SD-1.5.3-Hull%20Geometric%20Modeling.pdf|website=Centre for Marine Technology and Ocean Engineering|accessdate=29 March 2018}} References{{commons category|Hull (watercraft)}}
7 : Shipbuilding|Watercraft components|Naval architecture|Structural system|Structural engineering|Ship measurements|Egyptian inventions |
随便看 |
|
开放百科全书收录14589846条英语、德语、日语等多语种百科知识,基本涵盖了大多数领域的百科知识,是一部内容自由、开放的电子版国际百科全书。