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. Such planking requires caulking between the joints over and above that needed by the clinker built technology, but gives a stronger hull capable of taking a variety of full-rigged sail plans, albeit one of greater weight. On the up side, "Carvel built" construction enables greater length and breadth of hull as well as superior sail rigs because of its strong framing, and is the most critical development that enabled the centuries long dominance of the powers of Northern Europe in the Age of Sail and beyond.

The technology was probably introduced to the west via the Muslim culture of Al-Andalus, and its explorers of the 13th century, before the Christians had triumphed in reunifying Spain. Until the new dynastic union merging the Crown of Aragon with the Crown of Castile in 1479, creating what would become the Kingdom of Spain the Portuguese were the premier explorers of the western cultures.

History

In western knowledge and culture, carvel construction originated in the Carrack and Caravel ships of the fourteenth–fifteenth centuries, the two types of ship both being invented in Iberia from which they were first used by the kingdoms of Portugal and Spain in the early trans-oceanic voyages of the Age of Exploration. At the same time as their appearance, the centuries long battles to expel the Muslims was gradually swinging to the Christian side represented by the Kingdom of Aragon and the Kingdom of Castile, which were not united into Spain until the time of Christopher Columbus. Their invention is generally credited to the Portuguese people, who first explored south along the coast of Africa searching for a trade route to the far east in order to avoid the costly middlemen of the Eastern Mediterranean civilizations who sat upon the routes of the spice trade. Spices in the era were not only luxuries, but preservatives when there were few means of preserving foods.

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 longships from riven timber (split wood) planks. Clinker is the British term, it is known as lapstrake in North America. In general, the languages of other countries where the method was current use some version of the word clinker.

Carvel construction was probably invented earlier than clinker but in other parts of the world. In Europe carvel was the method of the south probably having spread though the Mediterranean from the Middle 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 hydrodynamically more efficient. The lands of the planking are not there to disturb the stream line. 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 has far less heavy timber framing. 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 was less bulky therefore, for a given internal volume, there was a smaller external one. That means that a bulkier cargo could be carried if need be, given sufficient freeboard. Clinker built vessels are however not well suited to most types of sailing rigs because they lack the internal rigidity to anchor the vessel's stays against the traverse forces generated by sailing into or across the wind with either lateen or sloop rigging methods. They also lack the internal strength to support a center-board, as well as a deep keel, drastically limiting their ability to sail across or close to the wind.

Additionally, the clinker built method left 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. Thus, the greater rigidity of carvel built construction became necessary for larger non-coastal cargo vessels, as the twisting forces grew proportional to displaced (or cargo) weight. The physics of this imposed an upper limit on clinker built vessels, which could be and was exceeded by several orders of magnitude in later large sailing vessels incorporating carvel built construction. Clinker construction remains to this day a valuable method of construction for small wooden vessels.

References

ee also

* Clinker — by way of contrast, the predominant method of ship construction used in Northern Europe before the Carvel.