March / April 2023

Steam-Bending Frames at the Bench

Using a chain gauge, compression strap, and bending table
Chain gauge

The chain gauge is made of wooden “links” joined together with 1⁄4” machine screws.

Years ago, in the midst of a difficult reframing job, I came across Barry Thomas’s excellent book, Building the Crosby Catboat. In it, Thomas describes his research into the Crosby method for fitting thick steam-bent frames into very tight bilges. He had had the good fortune to meet Horace Manley Crosby, Jr. aka “Bunk,” right when he needed him. Thomas tells of Bunk showing him and his team the tools and method for picking up the shape of a frame using a wooden chain-like “timber mold,” transferring the shape to a bending jig, and bending the frame away from the boat with the aid of a compression strap. The frame was then installed in the boat cold after it had cooled and set to its curve.

Back in our shop, which was then in Kingston, Massachusetts, we set up a bending jig pretty much as Thomas describes. We bought a compression strap from Lee Valley Tools. And we built the chain gauge—our term for the Crosby “timber mold.” We then bent our very tortured frames to their shapes with perfect control. Knowing that one can always slightly relax an overbent frame, and that one cannot add more bend once the frame has steamed, we added some overbend here and there on our mold. It took a bit of experimentation to get the feel for it, but soon enough we found we could massage and relax these timbers to lie in our hull so sweetly that we could barely slip a piece paper between the frame and the planking. And that was without any fastenings installed. Our frames lay in the boat with no residual tension, and perfectly to form.

We’ve used our chain gauge, along with the bending jig, for nearly 20 years, and learned its limitations and benefits. We don’t use it for all the bending we do, but when we restored ST. LOUIS, a 36' fantail Elco launch from 1896 (see WB No. 289), this system played a major role in the reframing.

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