Nautical Research Journal Bending over forms


A form of some sort usually is needed to ensure the bend will take up the correct shape. Steam is not always necessary but can be used for tight


bonding it in place. T e deeper the saw kerfs the easier the part will be to bend; the closer together they are, the tighter the possible bend. Experimenting is a good idea. T is process also can be used to make a fairly heavy plywood deck conform to its crown. Rip dadoes fairly close together down the length of the part. Again, the depth of cut and the spacing will determine how easily the plywood will bend. I always fi ll the grooves with epoxy before placing the decking. T is ensures the plywood will not crack over time and it makes it easy to adhere the plywood to its deck beams while the epoxy is still wet.


Edge bending 12. A deck with edge-bent planking in process.


bends. Forms can be an actual hull or building plug (Figure 9), a simple convex piece of wood, or a more complicated aff air incorporating both convex and concave shapes and/or twists. (Figure 10)


Kerf bending


Kerf bending usually is done when the part eventually will be covered and not seen, as in under-deck supports or similar members. (Figure 11) It involves sawing repetitive kerfs, usually in fairly heavy wood members, to make the wood more fl exible and then


Usually we bend wood in its thinner dimension but trouble can arise, for example, when one has to bend a wide deck plank across its width. T e wood will tend to buckle on the inside of the curve unless the ratio between its width and thickness is less than about three to one and the bend is quite gentle. Usually, a form is necessary, but it need not be exact. T e deck planks in Figure 12 are 1/8-inch wide and 1/16-inch thick cedar and were pre-bent to their approximate fi nal shape with the simple form shown in Figure 13. T e covering boards at the outside of the deck were installed fi rst and the outside planks were steam bent on the form. While still fl exible, they were hand sprung into the curve of the covering boards and bonded in place (I plank decks like this from the


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13. T e set-up for edge bending these planks. One end is held in a stop on the form while the plank is slowly steamed and maneuvered over its curve, being held level all the while. T is is not a particularly hard operation but it can be challenging.


14. A complex tiller for a sailboat model made with bent laminations and steam bending. T e width of the part across the “eye” is about 2 inches.


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