The latest post on Far Outliers introduces me to a wonderful term which Joel cites (from his newly acquired Encyclopedia of Ships) as tumblehome, but which my own treasured copy of The Sailor’s Word-Book gives as tumbling-home “The opposite of wall-sided, or flaring out.” I decided to let the OED settle the issue; here’s their entry:
tumbling home: the inward inclination of the upper part of a ship’s sides; opposed to FLARE n.1 4: see TUMBLE v. 11. Also tumbling-in.
1664 E. BUSHNELL Compl. Shipwright 11 Then set off the Tumbling Home, at the Height of the two first Haanses. 1769 FALCONER Dict. Marine, Encabanement, the tumbling-home of a ship’s side from the lower-deck-beam upwards, to the gunnel. 1832 Encycl. Amer. XI. 367/2 Nothing can be urged in favor of tumbling in.. but that it brings the guns nearer the centre. c1850 Rudim. Navig. (Weale) 157 The topsides of three-decked ships have the greatest tumbling-home, for the purpose of clearing the upper works from the smoke and fire of the lower guns.
So I’m going with tumbling home for my post title. [From the comments, I learn that the current form is in fact tumblehome; I'm keeping the older form as my post title because I like the ring of it, but I don't want to mislead anyone. If you have a boat you want to describe, you should mention its tumblehome if you want to be au courant.] Joel adds that the curve was “at one time designed to make room for projections at deck level to clear the wharf, or to make boats easier to paddle, but [is] also found in vessels like submarines designed to slice through the waves rather than ride over them” and asks: “Does anyone know the French, Dutch, Portuguese, or Japanese equivalent?” The French equivalent, as you can see from the second OED cite, is encabanement, but I too would be curious to see equivalents in other languages (especially Russian). Such specialized terms are not found in general bilingual dictionaries, of course, and it’s possible that most languages don’t have an equivalent term (simply saying “inward-sloping” when the need arises), but I just thought I’d ask.
It turns out, by the way, that the verb tumble can also be used in this sense; the OED’s definition 11 is:
Of the sides of a ship: To incline or slope inwards, to contract above the point of extreme breadth; to batter. Usually tumble home. Opposed to FLARE v. 4a. Also transf.
a1687 PETTY Treat. Naval Philos. I. ii, Let the supernatant sides of a Ship so much tumble.. as that the said sides may remain perpendicular when the Ship stoops. 1711 W. SUTHERLAND Shipbuild. Assist. 165 Tumbling home; when the Ship-side declines from a Perpendicular upwards, or, as some call it, houses in. 1761 H. WALPOLE Let. to G. Montagu 28 Apr., Old Newcastle, whose teeth are tumbled out, and his mouth tumbled in. 1848 T. WHITE Ship Build. 39 The upper works usually incline towards the middle line, or as it is termed ‘tumble home’.