Carvel (boat Building) - Relationship Between Clinker and Carvel

Relationship Between Clinker and Carvel

The clinker form of construction is often 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 parts of the world outside of Europe. 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 transverse 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 design created a vessel which could twist and flex relative to the long axis of the vessel (from 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 the size of clinker built vessels. Later carvel-built sailing vessels exceeded the maximum size of clinker-built ships several times over. However, clinker construction remains to this day a valuable method of construction for small wooden vessels.

A number of boat building texts are available which describe the carvel planking process in detail.