What is clinker boatbuilding?

Clinker boatbuilding, also called lapstrake, builds a wooden boat from planks that overlap one another and are fastened edge to edge, so the hull is a self-supporting shell before any internal frame goes in. It is the older of the two great wooden traditions - the way the Vikings built, and the way much of England’s working and pleasure river craft was built down to the present. I watched it at Dennett Boat Builders in Laleham, on the Thames, where the boats are built and restored the old way, and the thing that surprised me is the order of it: the outside of the boat exists, plank by plank, long before there is anything inside to hold it up.

There are two ways to plank a wooden boat, and the difference is fundamental. In clinker, the planks overlap like weatherboarding and are fastened to each other; the shell is built first, from the keel up, and the frames (the ribs) are fitted into the finished shell afterwards. In carvel, the planks lie flush and smooth, edge to edge, and they are fastened to a frame that is built first. Clinker is shell-first; carvel is frame-first.

That order of work changes everything about the boat. A clinker hull is light, springy and strong for its weight, with the characteristic ridged run of overlaps down its side; it is the natural way to build a small, lively river or inshore boat such as a Thames skiff. A carvel hull is smooth and is the usual way to build larger craft. The Dennett yard builds both, choosing the method to the boat - which is exactly why "clinker or carvel" is a real decision in a working yard rather than a museum distinction.

The land is the overlap where one plank meets the next - the defining feature of a clinker hull. A strake is a single line of planking running the length of the boat (lapstrake = overlapping strakes). The garboard is the first strake next to the keel; the sheerstrake the top one. The overlaps are riveted with copper nails turned over small washers called roves - to clench or rivet a land is to hammer the nail-end over the rove. The frames or timbers are the ribs fitted inside afterwards; the transom is the flat stern; the stem the upright at the bow.

The keel, stem and transom are set up first, and then the boat is planked from the keel upward. Each strake is shaped (or "spiled") to fit, steamed if it needs to take a curve, and laid so it overlaps the strake below along the land. The two are fastened together through the land - traditionally with copper nails clenched over roves - so the shell grows plank by plank into a watertight, self-supporting hull. There is no frame yet; the planks hold each other.

Only when the shell is complete are the frames fitted inside it, bent in and fastened to the planking to stiffen the hull. The boat is then fitted out. Because the planks are thin and the structure light, a clinker boat depends entirely on the accuracy of every land and every rivet - a poorly fitted land leaks or works loose - which is why the method rewards exactly the patient, eye-trained hand the Dennett yard has carried across three generations.

The archive documented traditional wooden boatbuilding at Dennett Boat Builders in Laleham, near Chertsey, a yard that has been building and restoring Thames craft since the twentieth century. It met Michael Dennett, the founder, still at the masts in his eighties, and his son Stephen, the working principal, taught at the yard from boyhood - a line that the family is now extending into a fourth generation. The full account of the yard and the Upper Thames boatbuilding tradition is the essay Upper Thames Boats.

The Dennett yard is also, in this archive’s terms, an apprenticeship story: it has a long practice of taking on and training young people other yards would not, which is part of why it still holds the skills at all. Clinker building survives where it is taught hand to hand, and that is what the yard does.

Traditional wooden boatbuilding is a small and pressured craft. Fibreglass and aluminium took the volume work decades ago, and a wooden boat is now a considered choice - restoration of historic craft, commissions from people who want the real thing - rather than the default. The skills are held by a thin scatter of yards and individual builders, and the supply of properly trained shipwrights is a standing concern. The clinker tradition in particular, light and demanding, depends on a small number of yards still building it.

It is learned in the yard, by years beside a shipwright. The archive’s Learn a Craft directory points to where boatbuilding is taught, and the craft essay sets out the Thames tradition in full.

What is the difference between clinker and carvel boatbuilding?
In clinker (or lapstrake) building the planks overlap and are fastened to each other, and the shell is built first with the frames fitted afterwards. In carvel building the planks lie flush, edge to edge, fastened to a frame that is built first. Clinker gives a light, flexible, ridged hull; carvel gives a smooth one.

Why do clinker boats have overlapping planks?
The overlap (the "land") is where each plank is fastened to the one below, usually with copper nails turned over small washers called roves. That overlapping, riveted shell is what gives the hull its strength and stiffness without a heavy internal frame, making clinker boats light for their size.

Is wooden boatbuilding still practised in England?
Yes, by a small number of yards. Traditional wooden boatbuilding survives building and restoring craft such as Thames skiffs and launches; the archive documented it at Dennett Boat Builders in Laleham, which builds and restores historic Thames boats in both clinker and carvel.