Clinker buildingBoat building, one of the oldest branches of engineering, is concerned with constructing the hulls of boats and, for sailboats, the masts, spars and rigging.-Parts:* Bow - the front and generally sharp end of the hull...
is a method of constructing
hullA hull is the watertight body of a ship or boat. Above the hull comes the superstructure and deckhouse. The line where the hull meets the water surface is called the waterline.The structure of the hull varies depending on the vessel type...
s of
boatA boat is a watercraft of modest 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...
s and
shipA ship is a large vessel that floats on water. Ships are generally distinguished from boats based on size and passenger capacity. Ships may be found on lakes, seas, and rivers and they allow for a variety of activities, such as the transport of people or goods, fishing, entertainment, public...
s by fixing
woodWood is an organic material; in the strict sense wood is produced as secondary xylem in the stems of trees . In a living tree it transfers water and nutrients to the leaves and other growing tissues, and has a support function, enabling woody plants to reach large sizes or to stand up for themselves...
en planks and, in the early nineteenth century,
ironthumb|The [[Eiffel tower]] is constructed from [[puddle iron]], a form of wrought ironWrought iron is an iron alloy with a very low carbon content, in comparison to steel, and has fibrous inclusions, known as slag. This is what gives it a "grain" resembling wood, which is visible when it is etched...
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 will also be joined end to end; the whole length of one of these composite planks is a
strakeA strake is:#part of a boat or ship. It is a horizontal strip of wooden planking or steel plating on the exterior hull of a vessel, running lengthwise along the vessel from the stem to the stern....
. The technique developed in northern
EuropeEurope is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally divided from Asia to its east by the water divide of the Ural Mountains, the Ural River, the Caspian Sea, the Caucasus Mountains , and the Black Sea to the southeast...
and was successfully used by the Vikings. The
TangThe Tang Dynasty was an imperial dynasty of China preceded by the Sui Dynasty and followed by the Five Dynasties and Ten Kingdoms Period. It was founded by the Li family, who seized power during the decline and collapse of the Sui Empire...
(7th century AD) and
SongThe Song Dynasty was a ruling dynasty in China between 960 and 1279; it succeeded the Five Dynasties and Ten Kingdoms Period, and was followed by the Yuan Dynasty. It was the first government in world history to issue banknotes or paper money, and the first Chinese government to establish a...
(9-11th century AD) Chinese developed the technique independently. The construction method is known in some places as
lapstrake.
Examples of clinker-built boats, and which are directly descended from those of the Viking shipbuilders, are the traditional round-bottomed
Thames skiffA Thames skiff is a traditional River Thames wooden rowing boat used for the activity of Skiffing. These boats evolved from Thames wherries in the Victorian era to meet a passion for river exploration and leisure outings on the water.-Construction of a skiff:...
s, built of mahogany, which can still be seen on the
River ThamesThe River Thames is a major river flowing through southern England. While best known because its lower reaches flow through central London, the river flows through several other towns and cities, including Oxford, Reading and Windsor....
in England, and the larger, (originally) cargo-carrying
Norfolk wherriesThe Norfolk wherry is a type of boat on The Broads in Norfolk, England. Three main types were developed over its life, all featuring the distinctive gaff rig with a single, high-peaked sail and the mast stepped well forward....
.
The Oldest clinker-built vessel
The oldest known clinker-built vessel has a
dendrochronologicalDendrochronology or tree-ring dating is the scientific method of dating based on the analysis of patterns of tree-rings. Dendrochronology can date the time at which tree rings were formed, in many types of wood, to the exact calendar year...
date of 190AD. This relates to fragments of an older boat found from more recent excavations at the site of the famous, and later, Nydam Boat, which is itself clinker-built.
Building a dinghy
Since the ninth century, perhaps culminating in the nineteenth, many ships were
clinker-built. Although it was developed primarily for use on wooden ships, some later iron ships also used this method. To give an understanding of what it involved, the best course is to describe the building of a pulling
dinghyA dinghy is a type of small boat, often carried or towed by a larger vessel. The term can also refer to small racing yachts or recreational open sailing boats. Utility dinghies are usually rowboats or have an outboard motor, but some are rigged for sailing...
(a rowboat). The reader should allow for the added complexity which comes from larger size.
Planking
In building a simple pulling boat, the
keelIn 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, the construction is dated from this event, with only the ship's launching considered more...
, hog, stem, apron, deadwoods,
sternpostA sternpost is the upright structural member or post at the stern of a ship or a boat, to which is attached the transoms and the rearmost left corner part of the stern. The Stern is traditionally the rear left corner of the ship however in mordern nautical terms the stern is considered the rear...
and perhaps
transomIn naval architecture, a transom is the surface that forms the stern of a vessel. Transoms may be flat or curved and they may be vertical, raked forward , or raked aft...
are assembled and securely set up. In normal practice, this will be the same way up as they will be in use. From the hog, the garboard, bottom, bilge, topside and sheer
strakeA strake is:#part of a boat or ship. It is a horizontal strip of wooden planking or steel plating on the exterior hull of a vessel, running lengthwise along the vessel from the stem to the stern....
s are planked up, held together along their lands by copper rivets. At the stem and in a double-ended boat, the sternpost, geralds are formed. That is, in each case, the land of the lower strake is tapered to a feather edge at the end of the strake where it meets the stem or stern-post. This allows the end of the strake to be screwed to the apron with the outside of the planking mutually flush at that point and flush with the stem. This means that the boat's passage through the water will not tend to lift the ends of the planking away from the stem. Before the next plank is laid up, the face of the land on the lower strake is bevelled to suit the angle at which the next strake will lie in relation with it. This varies all along the land.
GripesA gripe is a simple form of clamp used in building a clinker boat, for temporarily holding the strake which is being fitted onto the one to which it is to be attached. The strake is relatively thin and wide so that it is necessary for the tool to have a long reach while only a small movement is...
are used to hold the new strake in position on the preceding one before the fastening is done.
Timbering or framing out
Once the shell of planking is assembled, transverse battens of oak ash or elm, called timbers are steam-bent to fit the internal, concave, side. The timbers are frequently miscalled ribs. Elm species are not durable where the boat is used frequently in fresh water. As the timbers are bent in, they are copper riveted to the shell, through the lands of the planking.
On many clinker built craft, e.g. in Scandinavia, in
Thames skiffA Thames skiff is a traditional River Thames wooden rowing boat used for the activity of Skiffing. These boats evolved from Thames wherries in the Victorian era to meet a passion for river exploration and leisure outings on the water.-Construction of a skiff:...
s, and larger working craft like cobbles, sawn frames are used, assembled from floors and top timbers, joggled to fit the lands. Sometimes the timbers in larger craft were also
joggleThis is a glossary of nautical terms; some remain current, many date from the 17th-19th century. See also Wiktionary's nautical terms and :Category:Nautical terms.- A :* Above board – On or above the deck, in plain view, not hiding anything....
d before being steamed in.
With the timbers all fitted, longitudinal members are bent in. The
thwartA thwart is a strut placed crosswise in a ship or boat, to brace it crosswise.In rowboats it can also serve as a seat for a rower....
risings are fastened through the timbers with its upper edge on the level of the undersides of the thwarts. Bilge keels are added to the outside of the land on which the boat would lie on a hard to stiffen it and protect it from wear. A stringer is usually fitted round the inside of each bilge to strengthen it. In a small boat, this is usually arranged to serve also as a means of retaining the bottom boards. These are removable assemblies, shaped to lie over the bottom timbers and be walked upon. They spread the stresses from the crew's weight across the bottom structure.
Longitudinals
Inboard of the sheer strake the heavier
gunwaleThe gunwale is a nautical term describing the top edge of the side of a boat.Wale is the same word as the skin injury, a weal, which, too, forms a ridge. Originally the gunwale was the "Gun ridge" on a sailing warship...
is similarly bent in along the line of the sheer. This part of the work is finished by fitting the breast hook and quarter knees. Swivel or crutch chocks are fitted as appropriate to the gunwale, the thwarts fitted down onto the rising and held in position by knees up to the gunwale and perhaps down onto the stringer. The structure of gunwale, rising, thwart and thwart knees greatly stiffens and strengthens the shell and turns it into a boat. There are several ways of fixing the rubbing strake but in a clinker boat, it is applied to the outside of the sheer strake.
Fittings
Finally, the fittings such as swivels or crutch plate, painter ring, stretchers, keel and stem band are fitted and fixed with screws. In a sailing dinghy, there would be more fittings such as
fairleadA fairlead is a device to guide a line, rope or cable around an object or out of the way, or to stop it from moving laterally. Typically a fairlead will be a ring or hook. The fairlead may be a separate piece of hardware, or it could be a hole in the structure.A fairlead can also be used to stop...
s, horse, shroud plates, mast step, toe straps and so on.
Finishing
That more or less finishes the boatbuilder's work but the painter has yet to varnish or paint it. At stages along the way, he will have been called in to prime the timber. This is particularly so immediately before the timbering is done. The boatbuilder will clean up the inside of the planking and the painter will prime it and probably more, partly because it is easier that way and partly so as to put some preservative on the planking behind the timbers. Similarly, it is best to have the varnishing done after the fittings are fitted but before they are shipped. Thus, the keel band will be shaped and drilled and the screw holes drilled in the wood of keel and stem then the band will be put aside while the varnishing is done.
Fastenings
The planks may be fastened together in several ways:
- with copper
Copper is a chemical element with the symbol Cu and atomic number 29.It is a ductile metal with very high thermal and electrical conductivity. Pure copper is rather soft and malleable and a freshly-exposed surface has a pinkish or peachy color...
or ironIron is a metallic chemical element with the symbol Fe and atomic number 26. Iron is a group 8 and period 4 element and is therefore classified as a transition metal. Iron and iron alloys are by far the most common metals and the most common ferromagnetic materials in everyday use...
rivetA rivet is a permanent mechanical fastener. Before it is installed it consists of a smooth cylindrical shaft with a head on one end. The end opposite the head is called the buck-tail. On installation the rivet is placed in a punched or pre-drilled hole. Then the tail is "upset" A rivet is a...
s consisting of a square nailIn engineering, woodworking and construction, a nail is a pin-shaped, sharp object of hard metal or alloy used as a fastener. Formerly wrought iron, today's nails are typically of an alloy of steel, often be dipped or coated to prevent corrosion in harsh conditions or improve adhesion.Nails are...
and a dish shaped washer called a rove. The land is pierced, the nail knocked through from the outside, the rove punched on while the head is held up by a dollyA dolly is a portable anvil used to hold a rivet in position while it is being clenched with a "snapper". It is commonly cylindrical in shape and relies on its mass to work. The act of using it is known as holding up or holding on....
. The nail is cut off just proud of the rove and the cut end clenched over the rove while the dolly (a small portable anvil, usually of cylindrical shape) is used to hold the nail in place. In planking up clinker work, one man can hold both dolly and clenching hammer. Although this is common where sawn frames are to be used, boats intended for steamed timbers are usually nailed but not clenched until the timbering out is complete. As timbering is a two handed job it is more efficient to leave the clenching until help is at hand then the helper dollies up, whilst the builder sits inside the hull and clenches up.
- with iron
Iron is a metallic chemical element with the symbol Fe and atomic number 26. Iron is a group 8 and period 4 element and is therefore classified as a transition metal. Iron and iron alloys are by far the most common metals and the most common ferromagnetic materials in everyday use...
nails with the pointed nail ends protruding on the inside of the boat, bent over and back into the wood in the form of a hook. This is a cheap and cheerful technique maybe called clinching in some parts but usually, in England at least, "turnin'-em-over". It is the sort of thing which used to be found in Scandinavian-built boats but even with iron nails, on the lands, they were usually properly clenched over roves. Nails fastening timbers were sometimes turned over, particularly where removable bottom boards were to rest on the timbers. However, it was possible to tread the bottom boards onto the clenched nails and where marks were left, gouge out recesses to accommodate the clenched nails.
- screw
A screw, or bolt, is a type of fastener characterized by a helical ridge, known as an external thread or just thread, wrapped around a cylinder. Some screw threads are designed to mate with a complementary thread, known as an internal thread, often in the form of a nut or a object that has the...
s were used for fixing the ends of the strakes to apron and transom and in later times, knees to gunwale and thwarts, but traditionally, this last would be done with a clench bolt or a large copper nail, clenched.
- adhesive
Adhesive or glue is a compound in a liquid or semi-liquid state that adheres or bonds items together. Adhesives may come from either natural or synthetic sources. Some modern adhesives are extremely strong, and are becoming increasingly important in modern construction and industry...
, notably epoxyEpoxy or polyepoxide is a thermosetting polymer formed from reaction of an epoxide "resin" with polyamine "hardener". Epoxy has a wide range of applications, including fiber-reinforced plastic materials and general purpose adhesives.- Chemistry :...
. Traditionally, lands were neither glued nor was anything used to bed them. The garboard was bedded onto the hog and keel, and the ends of the strakes onto the stem and apron using a mixture of white lead and grease. During the World Wars new techniques and materials were developed by the aircraft industry. By the mid 1950s, these were well infiltrated into the boatbuilding trade. New boats in classes of racing dinghy with clinker hulls were built as glued clinker boats. The basic construction was the same but ply planking was used and the lands were glued with no fastenings, except that the ends and garboards were still screwed to apron and hog. The need to prevent the splitting of the planks was removed by the use of ply so no timbers were used. Except for a light gunwale and wide rubbing strake, the longitudinals were omitted too. A short thwart rising and knees were glued to the planking. These boats were all decked and that is how adequate stiffness was achieved. So that the liquid glue could be laid onto the land before the next plank was assembled onto it, they were built upside down.
Fastening the centre-line structure
In the last few years of wooden boat construction, glue and screws took over, but until the 1950s, the keel, hog, stem, apron, deadwoods, sternpost, and perhaps transom would be fastened together by bolts set in white lead and grease. There are three kinds of bolt, of which, nowadays, the
screwA screw, or bolt, is a type of fastener characterized by a helical ridge, known as an external thread or just thread, wrapped around a cylinder. Some screw threads are designed to mate with a complementary thread, known as an internal thread, often in the form of a nut or a object that has the...
bolt, with its nut and washer, is by far the most common. The second type of bolt is the
pin bolt or
cotter bolt, which, instead of a thread, has a tapered hole forged through the end away from the head, into which a tapered pin or cotter is knocked. The taper is in effect a straight thread. In conjunction with a washer, this draws the bolt tight, as a nut does on a screw bolt. The third type of bolt is the
clench bolt. It has some of the features of a rivet but was usually much longer than the normal rivet; in a wooden ship, perhaps a metre or more. For a shipwright's use, it is of copper. A head is formed by clenching it over a washer in a
swage plateSwaging is a forging process in which the dimensions of an item are altered using a die or dies, into which the item is forced...
. It is then knocked through a hole bored through the work to be fastened. The head is held up with a
dollyA dolly is a portable anvil used to hold a rivet in position while it is being clenched with a "snapper". It is commonly cylindrical in shape and relies on its mass to work. The act of using it is known as holding up or holding on....
and the other end is formed in the same way as the head but without the swage plate. Until well into the nineteenth century, this is what held the great ships of the world together, though some may have used iron. Until the late 1950s, the centre-line assembly of British
AdmiraltyThe Admiralty was formerly the authority in the United Kingdom responsible for the command of the Royal Navy. Originally exercised by a single person, the office of Lord High Admiral was from the 18th century onward almost invariably put "in commission", and was exercised by a Board of Admiralty.In...
twenty-five foot motor cutters were fastened this way.
Where suitable metal was not available, it was possible to use treenails (pronounced trennels). They were like clench bolts but made of wood, and instead of being clenched, they had a hardwood wedge knocked into each end to spread it. The surplus was then sawn off.
Relationship between clinker and carvel
The Clinker form of construction is linked in people's minds with the Vikings who used this method to build their famous
longshipLong-ships were ships made and used by the Vikings to raid coastal and inland settlements during the Viking Age. The vessels were also used for long distance trade and commerce, and for exploratory voyages to Iceland, Greenland, throughout the mediterranean etc. Longship design evolved over several...
s from riven timber (split wood) planks. Clinker is the
BritishBritish English, or UK English or English English , is the broad term used to distinguish the forms of the English language used in the United Kingdom from forms used elsewhere...
term, which is also used in Canada; it is known as
lapstrake in the USA. In general, the languages of other countries where the method was current use some version of the word clinker.
CarvelIn 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...
construction was probably invented earlier than clinker but in other parts of the world. In
EuropeEurope is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally divided from Asia to its east by the water divide of the Ural Mountains, the Ural River, the Caspian Sea, the Caucasus Mountains , and the Black Sea to the southeast...
carvel was the method of the south probably having spread though the Mediterranean from the
Middle EastThe Middle East is a region that spans southwestern Asia, southeastern Europe, and northeastern Africa. It has no clear boundaries, often used as a synonym to Near East, in opposition to Far East...
. Clinker was the method of north Europe having developed, apparently, in the Baltic.
The smoother surface of a carvel boat gives the impression at first sight that it is
hydrodynamicallyFluid mechanics is the study of how fluids move and the forces on them. Fluid mechanics can be divided into fluid statics, the study of fluids at rest, and fluid dynamics, the study of fluids in motion. It is a branch of continuum mechanics, a subject which models matter without using the...
more efficient. The lands of the planking are not there to disturb the
stream lineFluid flow is characterized by a velocity vector field in three-dimensional space, within the framework of continuum mechanics. Streamlines, streaklines and pathlines are field lines resulting from this vector field description of the flow...
. This distribution of relative efficiency between the two forms of construction is an illusion because for given hull strength, the clinker boat is lighter because it does not rely upon the compressive forces of the caulking and the resulting friction to bind the skin together. It therefore displaces less water so it has less to push aside while moving. The reduced displacement could be used to make the lines finer so as to make the passage through the water easier still. Of course, displacement was increased as cargo was loaded but still, the clinker vessel had the advantage in efficiency as the structure can be less bulky. Therefore, for a given internal volume, there was a smaller external one, meaning that a bulkier cargo could be carried if need be, given sufficient
freeboardFreeboard commonly refers to:* Freeboard , a six-wheeled skateboard designed to act like a snowboard.* Freeboard , the height of a ship's deck above the water level.Freeboard may also refer to:...
.
Additionally, the clinker built method as used by the Vikings created a vessel which could twist and flex relative to the line extending length of the vessel, bow to stern. This gave it an advantage in North Atlantic rollers so long as the vessel was small in overall displacement. Increasing the beam, due to the light nature of the method, did not commensurately increase the vessels survivability under the torsional forces of rolling waves, and greater beam widths may have made the resultant vessels more vulnerable.
There is an upper limit on size of clinker built vessels, which could be and was exceeded by several orders of magnitude in later large sailing vessels incorporating carvel built construction. Clinker requires relatively wide planking stock compared to carvel, as carvel can employ
stealersA strake is:#part of a boat or ship. It is a horizontal strip of wooden planking or steel plating on the exterior hull of a vessel, running lengthwise along the vessel from the stem to the stern....
to reduce plank widths amidships where the girth is greatest. The need for sufficient lap to accept the clench fastenings drives towards wider planks in proportion to thickness that can be employed in carvel. In all other areas of construction including framing, deck, etc clinker is as capable as carvel. Clinker construction remains to this day a valuable method of construction for small wooden vessels.