16 October 2006

New Favorite Nautical Term: Tumblehome

I recently scored for a pittance--I'd like to say two pieces of eight--a castaway copy of a gem of a book, The Encyclopedia of Ships, in which I've been browsing around during lunchtime at work. I've always been intrigued by ships and sea tales and nautical terminology, but this book taught me a lovely old English term not found in abbreviated dictionaries: tumblehome, a word that fairly tumbles off the tongue, as if invented by A. A. Milne or J.R.R. Tolkien. Does anyone know the French, Dutch, Portuguese, or Japanese equivalent? It describes the inward curve of a ship's side above the waterline, at one time designed to make room for projections at deck level to clear the wharf, or to make boats easier to paddle, but also found in vessels like submarines designed to slice through the waves rather than ride over them. Its opposite is the V-shaped flare hull, like the bow of an aircraft carrier.

Another opposition of historical interest is that between clinker (or lapstrake) and carvel (or strip) planking in hulls, the former typical of northern Europe (like Viking ships), the latter spreading north from Iberia.
In the form that we would recognize it, ["carvel"] first appears in northern European languages to describe flush planking in the late 14th/early 15th century, at the same time that Iberian caravelas started visiting northern ports on a regular basis. When northern shipwrights started building ships with flush planks (c. 1430-1440) they referred to the new ships as "carvel-built" or just as "carvels" (or its equivalents). The Dutch "karviel-nagels" ... are derived this way. In late medieval Dutch, "karviel" or "karveel" referred to boats built in this new way, and was the same word applied to ships coming from Portugal or Britanny with salt and wine. It may have entered English via the Dutch, but the origin is ultimately the small seagoing craft of the Iberian coast.

On the matter of clinker planking, it is almost always caulked, either with tarred animal hair or moss. In Nordic ships, the caulking (usually hair) is laid into a groove in the seam when the planks are assembled, while in cogs and other Low German craft, the caulking is driven into the interior side of the seam, above the nails (there is a relatively wide overlap).

One reason that clinker was abandoned for large vessels in favor of carvel was purely a matter of expense. Eliminating the thousands of clinker nails (rivets) reduced the expense considerably. Something like 20% of the material cost of a cog (which only had clinker sides) was in the iron for it, mostly clinker nails, according to building accounts from the Netherlands in the late 1200s. Wood could also be used more efficiently, as carvel construction did not depend on such high quality wood and it could be more efficiently sawn from the log into plank. Not to mention the savings in labor from not having to drill and drive all the clinker nails. In boatbuilding practice, fitting clinker planks is not appreciably harder or more time-consuming than it is in carvel construction - the total amount of contact surface is about the same - and most of the other tasks are about the same in terms of time and difficulty, but eliminating the rivets saves a great deal in material and labor cost. These savings were more dramatic in larger vessels, and so it is no surprise that carvel construction first took hold in big ships and then trickled down to smaller craft. In Norway, clinker continued in use in bigger vessels until the early 20th century, when it became clear that it was not compatible with diesel engine power (rivets don't take the vibration so well).
Reader Aidan Kehoe notes that the French term for tumblehome is encabanement. Language Hat has further discussion.

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