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Strake

Strake

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A strake is part of the shell of the hull
Hull (watercraft)
A hull is the watertight body of a ship or boat. Above the hull is the superstructure and/or deckhouse, where present. The line where the hull meets the water surface is called the waterline.The structure of the hull varies depending on the vessel type...

 of a boat
Boat
A boat is a watercraft of any size designed to float or plane, to provide passage across water. Usually this water will be inland or in protected coastal areas. However, boats such as the whaleboat were designed to be operated from a ship in an offshore environment. In naval terms, a boat is a...

 or ship
Ship
Since the end of the age of sail a ship has been any large buoyant marine vessel. Ships are generally distinguished from boats based on size and cargo or passenger capacity. Ships are used on lakes, seas, and rivers for a variety of activities, such as the transport of people or goods, fishing,...

 which, in conjunction with the other strakes, keeps the sea out and the vessel afloat. It is a strip of planking in a wooden vessel or of plating in a metal one, running longitudinally along the vessel's side, bottom or the turn of the bilge, usually from one end of the vessel to the other.

Special strakes


The strake immediately adjacent to the keel
Keel
In boats and ships, keel can refer to either of two parts: a structural element, or a hydrodynamic element. These parts overlap. As the laying down of the keel is the initial step in construction of a ship, in British and American shipbuilding traditions the construction is dated from this event...

 is known as the garboard strake. The longest continuous strake at the top of the side of the vessel on the main deck is called the sheer strake.

In old vessels, a rubbing strake was built in just below a carvel
Carvel (boat building)
In boat building, carvel built or carvel planking is a method of constructing wooden boats and tall ships by fixing planks to a frame so that the planks butt up against each other, edge to edge, gaining support from the frame and forming a smooth hull...

 sheer strake. It was much less broad but thicker than other strakes so that it projected and took any rubbing against piers or other boats when the boat was in use. In clinker
Clinker (boat building)
Clinker building is a method of constructing hulls of boats and ships by fixing wooden planks and, in the early nineteenth century, iron plates to each other so that the planks overlap along their edges. The overlapping joint is called a land. In any but a very small boat, the individual planks...

 boats, the rubbing strake was applied to the outside of the sheer strake. Others have no special name other than bottom strakes, bilge strakes and topside strakes.

A stealer is a short strake employed to reduce the width of plank required where the girth of the hull increases. It is commonly employed in carvel and iron/steel shipbuilding, but there are very few, possibly only one type of, clinker craft that use them.

Construction


Where the transverse sections of the vessel's shape are fuller, the strakes are wider. They taper toward the ends. In many larger vessels, to avoid ending with very narrow strakes, two are normally converted to one toward their ends. This one is known as a stealer or stealer strake. It was one of these which was also shaped to fit the concave line of the hull, under the counter at the sternpost. Historically, these had to be shaped by carving from an especially thick plank of wood (known as a short strake or plank). When someone was describing the epitome
Epitome
An epitome is a summary or miniature form; an instance that represents a larger reality, also used as a synonym for embodiment....

 of thickness, he thought of the metaphor
Metaphor
A metaphor is a literary figure of speech that uses an image, story or tangible thing to represent a less tangible thing or some intangible quality or idea; e.g., "Her eyes were glistening jewels." Metaphor may also be used for any rhetorical figures of speech that achieve their effects via...

, thick as two short planks.

In very small boats, strakes can be made of one continuous piece of wood. Usually, they are made of more than one piece of wood or metal scarfed or butted together similar to brick wall construction. In metal vessels, the modern practice is to butt-weld them with full penetration welds.

In a riveted steel ship, the strakes were usually lapped and joggled, but where a smoother finish was sought, they too might be riveted on a butt strap, though this was weaker. In modern welded construction, the plates are normally butt-welded all round to adjoining plates within the strake and to adjoining strakes.

Wooden vessels


Wooden planks can be scarfed
Scarf joint
A scarf joint is a method of joining two members end to end in woodworking or metalworking. The scarf joint is used when the material being joined is not available in the length required...

 into a strake by suitably tapering the thickness of the adjoining ends. Traditionally, the adjoining faces were coated with mixed white lead and grease, then held together with copper rivets. It was important to not have the plank end as thin as a feather edge and to have the outboard thin edge at the after end of the joint. In later times, after adhesives had been developed by the aircraft industry, the joint might be made with resin glue and no rivets. In heavier carvel work, the joint would be a butt, riveted to a butt strap. Even large clinker vessels had scarfed strakes as in this form of construction; the strakes contribute a significant proportion of the structural strength of the boat as well as keeping it water-tight.

Assembling the strakes


Two methods used to plank a wooden hull are: carvel
Carvel (boat building)
In boat building, carvel built or carvel planking is a method of constructing wooden boats and tall ships by fixing planks to a frame so that the planks butt up against each other, edge to edge, gaining support from the frame and forming a smooth hull...

 in which the edges of the strakes butt against each other, using an internal frame structure to maintain the boat's shape and clinker
Clinker (boat building)
Clinker building is a method of constructing hulls of boats and ships by fixing wooden planks and, in the early nineteenth century, iron plates to each other so that the planks overlap along their edges. The overlapping joint is called a land. In any but a very small boat, the individual planks...

 in which the adjoining strakes are held together on an overlap. Their varying widths and angles of overlap determine the hull's shape.

In the former form of construction, one more traditional in the Mediterranean than in north Europe produces a relatively smooth hull surface but needs caulking
Caulking
Caulking is one of several different processes to seal joints or seams in various structures and certain types of piping. The oldest form of caulking is used to make the seams in wooden boats or ships watertight, by driving fibrous materials into the wedge-shaped seams between planks...

 to make it watertight and it is relatively heavy (due to the mass of the required internal framing). Carvel boats are planked up onto pre-erected frames which become part of the boat.

The second method is clinker. It is traditional in the north and produced relatively light but strong boats. Normally, the boats are built from the garboard up so that the upper plank overlaps (aka hems) the lower on the outside. That overlap is known as the land and it is held together by copper rivets. In the twentieth century, the boat may have been built of plywood and the strakes glued together without clenched nails. Medieval boats are more likely to have been riveted with iron nails. To rivet the lands, the planks in the two adjoining strakes are pierced, a nail inserted from the outside and a rove or rove punched over the inside end of the nail. The latter is then cut off a little proud of the rove. The nail is then clenched over the rove.

When the shell of the boat is complete, the strakes are stiffened by the insertion of steam-bent timbers. These too, are riveted to the planking through the lands. The timbers, which are sometimes miscalled ribs, spread the load on the strakes and tie them together reducing the tendency of the relatively thin strake to split. With glued ply clinker construction, the timbers are unnecessary.

At the hood-ends of the strakes, where they approach the stem, they are let into each other with geralds (aka chases or gains). In these, the land of the lower strake is tapered to a feather edge at the end of the land where it is supported by the rebate formed by the apron. The strakes then meet the stem flush, which is also referred to as being hooded.

Steel ships may be plated as clinker-built vessels but more usually, they were built with strakes alternately in and out. The modern method is to butt-weld the strakes to each other as well as the plates within them, end to end. This leaves a smoother finish and is lighter.


Straightedge


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The word strake also refers to a straightedge
Straightedge
A straightedge is a tool with an edge free from curves, or straight, used for transcribing straight lines, or checking the straightness of lines...

 used for levelling a bed of sand, or striking poured concrete
Concrete
Concrete is a composite construction material, composed of cement and other cementitious materials such as fly ash and slag cement, aggregate , water and chemical admixtures.The word concrete comes from the Latin word...

 or plaster
Plaster
Plaster is a building material used for coating walls and ceilings. Plaster starts as a dry powder similar to mortar or cement and like those materials it is mixed with water to form a paste which liberates heat and then hardens. Unlike mortar and cement, plaster remains quite soft after setting,...

 level with the edges of the formwork
Formwork
Formwork is the term given to either temporary or permanent molds into which concrete or similar materials are poured. In the context of concrete construction, the falsework supports the shuttering moulds.-Formwork and concrete form types:...

or mould into which it has been poured. A strake used for flooring or paving work is often called a 'screed'.