Boats have several places where two surfaces come together at an angle, and special pieces—breasthooks and knees—are used join them together and add strength. Breasthooks are V-shaped blocks at the acute angle at the bow and, on double-enders, at the stern as well. Knees are supports closer to a right angle, and on open boats they’re most often quarter knees joining gunwales to a transom or seat knees supporting the topsides at the thwarts.
Knees and breasthooks made of solid blocks of straight-grained wood can be serviceable, but if the toes (the knee’s extremities) are fattened up too much to make up for the weakness of the cross-grain there, they don’t do much for a boat’s appearance. Pieces made from grown crooks are stronger because the grain runs with the loads, and much handsomer because they didn’t need to be bulky. Indeed, when carefully shaped they elevate the boat’s structure from “good enough” to art.
In former days when open boats commonly went alongside larger boats, seat knees were essential to the boat’s structure and were sometimes massive, keeping the sides from being stove in. Tenders and ship’s boats typically had two seat knees at each end of a thwart. With today’s light, glued-lapstrake construction they can be equally important in reinforcing the structure.
The traditional thwart knee was a marvel of simple joinery. The part that supports the sheer plank was often carefully locked into the gunwale structure. Some were set on top of the thwart, either parallel to its edge or at an angle to it. Their toes might have decorative points cut at their ends. Others were fastened to the vertical edge of a thwart and carefully shaped in a show of lightness and elegance.L-shaped grown crooks were prized pieces of wood, but as they became scarce, many boatbuilders who built substantial numbers of boats went to metal knees. Today it is hard for most boatbuilders to find grown stock needed for traditional knees. Aside from requiring the trees to harvest, the crooks have to be cured without developing splits and sawn into flat pieces prior to shaping.
In knees sawn from straight-grained stock, the toes are often blunt and thick, their length limited by the width of the stock used and their height, making up for weak cross-grain, requiring screw-fastening from underneath the thwart. It doesn’t have to be that way. With laminations and reliable glued joints, it isn’t hard to recapture the look and strength of natural knees. Steam-bent knees can provide a sweeping curve and slender toes, but they require blocking to provide the support of a solid knee. Stock can be created by laminating narrow strips of wood; knees can be built with half-lapped or splined pieces much the way that today’s builders emulate the natural crooks once used on dory frames.
Looking at these details on boats from an earlier time will train your eye. Spend the same kind of time on these details that you do on the rest of the boat; they’re what you’ll see every day. When master boatbuilder Joe Liener used to encourage novice boatbuilders to make parts like knees and breasthooks a little lighter, he wasn’t talking about trimming a few ounces of wood. It was his way of encouraging boatbuilders to consider grace and beauty in the work they do.
Ben Fuller, curator of the Penobscot Marine Museum in Searsport, Maine, has been messing about in small boats for a very long time. He is owned by a dozen or more boats ranging from an International Canoe to a faering.
A Gallery of Breasthooks and Knees
You can share your tricks of the trade with other Small Boats Monthly readers by sending us an email.