Vol. 71, No.1 Spring 2026 12


3. Alberto Santos-Dumont in his workshop with Hydroplane Pontoon. Wikimedia Commons.


diameter of each hoop. Aſt er some experimentation, the wood was laid up in three layers, with the butt joint for each layer shiſt ed 120 degrees. (Figure 5)


Each former was brought back to the lathe to reduce the hoop thickness to 1 millimeter. A 0.25-inch hole was drilled in the middle of former and then a 3-millimeter section of the hoop and former was parted off . A building jig was created that supported each hoop. T e supports were made from 0.125-inch hardboard and had a semicircle cut in matching the exterior hoop diameters. T e supports were created so the center of each hoop would be at the same height. T e tops of the supports were cut so they could be used to locate positions for attaching the longitudinal stringers. (Figure 6)


A building board was set up to hold the supports in their respective positions. A 0.25-inch dowel could then be passed through the former-hoop pieces to


keep the these pieces aligned on the supports. (Figure 7)


Hooks and rubber bands were used to keep the hoops snugly in place for the operation of adding stringers. Also, slots were milled in the bottom of each support so that aſt er the fi rst two stringers were added, the pontoon could be rotated 90 degrees in the jig in


4. Reconstructed plans. All images by the author unless otherwise indicated.


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