Spray (sailing Vessel) - Self-steering Ability

Self-steering Ability

One of the most remarkable things about Spray was her ability to run before the wind under her regular fore-and-aft rig with the helm lashed, and hold her course for hours or days on end. If Spray had not had this ability, Slocum's performance would have been a physical impossibility.

On nearing the Cocos (Keeling) Islands, Slocum noted "I didn't touch the helm, for with the current and heave of the sea the sloop found herself at the end of the run absolutely in the fairway of the channel. ... Then I trimmed her sails by the wind, took the helm, and flogged her up the couple of miles or so abreast the harbour landing, where I cast anchor at 3.30 pm, July 17, 1897, twenty-three days from Thursday Island. The distance run was twenty-seven hundred miles as the crow flies. ... During those twenty-three days I had not spent altogether more than three hours at the helm, including the time occupied in beating into Keeling harbour. I just lashed the helm and let her go; whether the wind was abeam or dead aft, it was all the same: she always stayed on her course."

Iconoclast designer John G. Hanna, known as the sage of Dunedin but perhaps better known as the designer of the Tahiti ketch, said of Spray, "I hold that her peculiar merit as a single-hander was in her remarkable balance of all effective centres of effort and resistance on her midship section line." Hanna nevertheless felt it necessary to warn prospective circumnavigators looking for a suitable vessel that "Spray is the worst possible boat for anyone lacking the experience and resourcefulness of Slocum to take offshore."

Cipriano Andrade, Jr., engineer and yacht designer, said of Spray: “After a thorough analysis of Spray's lines, I found her to have a theoretically perfect balance. Her balance is marvelous — almost uncanny. Try as I would — one element after another — they all swung into the same identical line. I attacked her with proportional dividers, planimeter, rotameter, Simpson's rule, Froude's coefficients, Dixon Kemp's formulae, series, curves, differentials, and all the appliances of modern yacht designing, and she emerged from the ordeal a theoretically perfect boat. For when she is underway every element of resistance, stability, weight, heeling effort, and propulsive force is in one transverse plane, and that plane is the boat's midship section. I know of no similar case in the whole field of naval architecture, ancient or modern.”

Slocum himself said "I did not know the center of effort in her sails, except as it hit me in practice at sea, nor did I care a rope yarn about it. Mathematical calculations, however, are all right in a good boat, and Spray could have stood them. She was easily balanced and easily kept in trim."