How to Determine the Curve of the Transom

To determine the curve or radius of the transom it is not enough to draw this curve on the drawing paper, for this reason: there are always variations in the finished transom due to errors in production in the yacht yard, some distortion in the stock after the hull is done and the stresses are applied to the transom when the various braces are removed.

To take off the true profile of the stern transom I use a thin piece of pine, usually a long, pine clapboard. Hold the thin edge of the board against the center, horizontally, of the transom and with the carpenter's scribe run a line along the face of the board. The pencil marker will make this line so that it corresponds with the irregularities of the transom. Cut the stock out along this line with the draw shave, finishing off with the spoke shave so that when this template is held against the transom in the same place where it was scribed, all faces of the curve of the template touch the face of the transom.

Then try the template at the upper part of the transom, note any discrepancies with the scribe; then do the same thing with the bottom of the transom. If the discrepancies are less than an eighth of an inch, do not try to correct them. It is not necessary. If they are greater, try to hit a happy medium as this profile is for the mocked-up or temporary transom you will build for use in your shop.

The second step is to take off the outline (or profile) of the transom as it exists on the yacht. I do this by placing large sheets of brown paper over the transom so they cover the piece with some overlapping of the edges. I fasten the paper to the hull with masking tape. It comes off the paint work without leaving any gum. If two or more pieces of paper are required to cover the transom, I usually lay the upper sheet over the lower and lay on two or three pencil lines so they cross the overlaps, one in the center and one at either side. Then I use a soft pencil and trace off the profile of the transom, using great care to see that I get it as exact as I can.

To make the mock-up, lay the piece of stock you used to get the radius of the transom on a wide pine board. Trace the curve on the face of the board. Repeat this process until three boards are scribed. Then develop the curve, being sure that the bottom edges of all the boards to be profiled out are straight. Remove the stock with the draw and spoke shaves. Check the curve against the template.

Draw a line one quarter inch below the curve and finish to that line. Assemble the profiled boards in such manner that they are held firmly in a vertical position. Apply a piece of %-inch plywood to the curved faces of the boards and nail in place with lath nails. Before nailing, put the template on the face of the plywood to be sure that it fits snugly. This, then, becomes the surface to which you will back-cut the carving and on which the outline of the transom is drawn as well as the design for the carving.