Float (nautical)

Floats(also calledpontoons) are airtight hollow structures, similar topressure vessels,designed to providebuoyancyin water. Their principal applications are inwatercraft hulls,aircraft floats,floating piers,pontoon rhinos,pontoon bridges,and marine engineering applications such assalvage.

The British racing seaplaneSupermarine S.6B(1931)

DuringWorld War IItheUnited States NavyCivil Engineer Corpsdeveloped a modular steel box (pontoon) for theSeabeesto use. It was a system of pre-drilled pre-cutangle ironand steel plate that could be assembled anywhere for which they became famous.They used them to facilitate amphibious landings. With the pontoons, Seabees assembled docks, causeways, andrhinosto whatever size needed. They allowedlandings on Sicilywhere no one thought possible. They ferriedPattonacross the Rhineand put Marines ashore onOkinawa.They would be used during theKorean Warin thelanding at Inchonin 1950 and again inLebanonduring the1958 Lebanon crisis.

Various objects that make use of floats are often referred tosynecdochicallyaspontoons.

Applications

Floats make up the multipart hulls ofcatamaransandtrimaransand provide buoyancy forfloatplanes,seaplanesandhouseboats.They are used in pontoon bridges, floating piers, and floats anchored to the seabed for recreation or dockage. They are also used inshipbuildingand marine salvage, often deployed uninflated then pressurized to raise a sunken object. In military, floats are used as pontoon bridges or transportation platforms for heavier vehicles or machinery.

In popular usage, the termpontooncan refer to any of several of the following objects that make use of nautical floats.

Pontoon boat

Main article:Pontoon (boat)

Apontoon boatis a flattish boat that relies on nautical floats for buoyancy. Common boat designs are a catamaran with two pontoons, or a trimaran with three.In many parts of the world, pontoon boats are used as small vehicle ferries to cross rivers and lakes.

An anchored raft-like platform used for diving, often referred to as a pontoon

Anchored recreational platform

Raft-like platforms used for diving and other recreational activities are sometimes anchored at beaches and lake shores, often seasonally. Such platforms may be supported by foam-filled plastic floats or air-filled pontoons, and are known simply as "pontoons" in Australia and New Zealand.They may also be called swim floats.

Floating dock

Main article:Floating dock (jetty)

Afloating dock,floating pierorfloating jettyconsists of a platform or ramp supported by nautical floats. It is sometimes joined to the shore with a gangway but can be laid out the whole way from the shore to the end. This type of pier maintains a fixed vertical relationship to watercraft secured to it.

Salvage pontoon

Asalvage pontoon,sometimes known as alift bag,is a pontoon used to raise a sunken watercraft, or provide additional buoyancy. Salvage pontoons can be either flexible and inflatable, or a fixed size. Usually cylindrical in shape, they can be used either in a ship's internal spaces, or externally. In addition to raising sunken vessels, they are also commonly used for long tows, for providing buoyancy to cables and so on.

Pontoon bridge

Main article:Pontoon bridge

Apontoon bridge(also known as aponton bridgeorfloating bridge) uses floats or shallow-draft boats to support a continuous deck for pedestrian and vehicle travel. Most, but not all, pontoon bridges are temporary, used in wartime and civil emergencies.Seattle in the US and Kelowna in British Columbia, Canada are two places with permanent pontoon bridges, seeWilliam R. Bennett Bridgein British Columbia and these in Seattle:Lacey V. Murrow Memorial Bridge,Evergreen Point Floating BridgeandHomer M. Hadley Memorial Bridge.

Amphibian floats on aCessna 208 Caravan1floatplane,Gloucestershire Airport,England (2017)

Floatplane

Main article:Floatplane

Afloatplane(float planeorpontoon plane) is a type of seaplane with one or more floats mounted under the fuselage to provide buoyancy.

Construction

Pontoons for marine industrial uses are usuallyfabricatedfrom steel.Pontoons as parts of watercraft and aircraft are more typically molded inglass-reinforced plastic.Other techniques include those of traditional wooden boatbuilding as well asplywoodover wooden ribs or metal sheets over metal ribs (aluminium or steel), reflecting the prevailing practice in aircraft and boats. In most cases, the decking surface on top of the pontoon is made from glass-reinforced plastic (GRP) orcomposite lumber. In model building, floats can easily be carved out of solid blocks or laminated sheets of foam.

Gallery

• 
  Small opencatamaran.
• 
  Foldable trimaranwith the floats in extended position.
• 
  Floats in a smallfloatplane.
• 
  A helicopter pontoon augmented by an inflatable emergency pontoon shown in black
• 
  The underside of a boat during construction

See also

• Buoy
• Caisson (lock gate)
• Navy lighterage pontoons
• Outrigger
• Raft
• Semi-submersible platform