John Kelly Hydroplane

Founding Partner Ed Clapp, arranged for us to get this board from Scott Edrington in New Jersey

Aside from being credited along with Fran Heath, Woody Brown, and Wally Froiseth, for creating the Hot Curl style boards in 1937, John Kelly was also founder of the environmental group, Save Our Surf in 1961. The invention of the Hot Curl allowed surfers like Kelly to ride some of the more critical breaks on Oahu, such as Makaha. His father, John Melville Kelly, was well known for his etchings of Islanders and for his designs on the menu covers of the Royal Hawaiian Hotel. His mother, Katherine Harland, was a noted sculptor. His patented hydroplane board pictured above, was created in 1963 and is one of 250 that he made. Although it represents another of Kelly's design innovations, the model didn't ever really catch on, but Kelly continued to ride them for as long as he surfed (very few of them remain and are quite collectable). Kelly passed away at the age of 88 in 2009. Among his other accomplishments was the publishing of the book, Surf and Sea, in 1965. We have excerpted the section of the book that describes this innovation of his: 

A favorite dream of surfers has always been to own a single all-time surfboard that combines the best of all ex­isting designs, speed, maneuverability, stability; it should be a good paddler, easy to stall, slow to dig, yet good for nose-riding, stable and heavy-riding in rough water yet light to the touch in smooth. It should be impervious to dinging and able to yell "Stop thief!" when stolen. Whether or not such a board exists or will ever exist de­pends on the individual surfer's own standards of judging waves and riding skills. Nevertheless, the dream is there and many hold fast to it.

Whereas the flat deck was the sacred and inviolate ele­ment of surfboards until the late 1940's, the single bottom-line was its counterpart until 1962. Those who had pio­neered the rocker, the gun tail and the hot dog board had convinced themselves that curves and straight lines could never be harmonized. Hot doggers had un-curved tail sec­tions and gunners had bent their straight lines but always with compromising results. Again, the solution was so sim­ple as to have escaped attention. It consists of breaking the heretofore undifferentiated bottom surface into two sur­faces, a longitudinally flat one for high-speed planing and a curved one for high-drag, low-speed turning. The two sur­faces are separated by means of a hydroplane step,* the high-speed planing surface being located forward of the step and the curved one at the tail where the turning effect is located.

The results were startling: on first experimental rides the hydro went so fast the rider fell off the back end of the board; first attempts at turning in the conventional man­ner threw the rider off in a tangent while the board spun off the wave. There was no doubt that a breakthrough had been made, but it needed tempering. Early models em­ployed a transverse step which introduced an undesirable pitching around the step-fulcrum. This was eliminated by elongating the step and moving it aft. At high speeds the air-borne tail section allowed cavitation on the wave side of the skeg. The skeg was moved to the planing surface and the step moved still further aft; cavitation ceased.

In designing the first hydro models, each design element was pushed to its extreme. The planing surface had been flattened in all directions, the rails dropped fully for 100 per cent draglessness on sides and trailing edge, the scor­pion tail elevated or scooped higher than any hot dog board. The board was so hypersensitive that for full turns the rider needed only to lean with a moderate ankle move­ment. Restoring a degree of transverse curvature to the planing surface, but keeping all fore-and-aft lines parallel to the line of flight, made it possible to regain any amount of stability and turning stiffness desired without lessening the high-speed capability. The fully dropped rails could then be partially raised preserving a chine which caused the usual side spray to be deflected out at a low angle. This preserves draglessness and a clean, noiseless ride at the point where most guns and semi-guns still produce exces­sive spray and some drag. In high-speed planing position with riders properly trimmed the hydro passed guns; its ultra speed partly results from shortening the planing sur­face which makes the tail groove in the wave shallower thus lessening drag.

By varying the length and degree of upturn of the scor­pion tail and the amount of transverse curvature, it was found that any degree of maneuverability from hot to stiff can be produced without affecting the high-speed capabil­ity. High-speed models built to ride the heavies turned more easily in small waves than the most maneuverable hot dog board of comparable length. The chined, side rails aft and rounded rails forward help cut a clean shelf in the wave wall and enable a high-riding position. A high-drag trailing edge at the stern in combination with the latter's upward curvature enables stalling at low and intermediate speeds which is difficult, if not impossible, with a gun or concave. The curved scorpion tail tucks into the curved slope of the wave as with hot dog boards facilitating turn­ing on the smallest waves. The added thickness of the aft section to accommodate the step gives additional buoyancy aft. This, together with the streamlined deck plan (taper-length ratio), makes the hydro a superior paddler and early wave catcher.

When the hydro is planing at full speed, the scorpion tail is completely air-borne thus eliminating all contour drag. The only remaining drag is skin friction between the high-speed planing surface and the water. This capability is achieved by the rider taking the position that frees the tail from contact with the water. In this position the effec­tive length of the board is from the bow to the aft point of the step. For this reason, it is advisable in considering a hydro to add nearly a foot to the length of the conven­tional board the surfer ordinarily would ride; this extra length also provides additional paddling buoyancy for early catching as well as stability during takeoff on the larger waves while having no negative effect on turning in smaller waves due to the action of the scorpion tail.

By leaning or stepping back, the high-drag scorpion tail is brought into play. This not only brakes the board but brings the curved scorpion tail into play as a turning member. Since the scorpion tail is adapted to the shape o£ the turning circle, turning becomes much easier, especially for beginners. While the hydro can be made as stiff as any conventional board, the models with fairly loose turning capability may, in the long run, turn out to be preferred since they simply require less effort to ride and turn. This has been the trend in surfboard design since the earliest times. Experienced surfers, whose reflexes are tuned to stiff conventional boards and to turning at slower speeds, find that it takes a while to get used to the hydro's higher speeds and easier turning. After the adjustment, many question the logic of returning to the stiffer and slower responses of conventional boards.

On small waves hydro-users tend to take more chances because the extra speed enables them to make more critical tunnels and fast' breaking crests. In large surf, the hydro's gun capability serves the rider for the first part of the ride when the big wave calls for speed; as the wave diminishes in size the hydro can be hot dogged to the very end of the ride. Still another advantage is that the surfer makes a permanent muscular and psychological adjustment to one surfboard for all seasons and sizes of waves.

A series of carefully calibrated drag tests were run in 1962 as part of a study of the effect of elements of design on a number of representative surfboards including a full gun, a semi-gun, a hot dog board and a hydro. At slow speed (10 mph) with scorpion tail in contact with the water, the hydro had drag comparable to the hotdog (35 pounds) and the semi-gun (35 pounds), but more than the full gun (30 pounds). At intermediate speed (20 mph), with scorpion tail air-borne, the hydro had 20% less drag than the full gun, 38% less than the semi-gun and 57% less than the hot dog. At high speed (30 mph) the hydro had 7% less drag than the full gun, 37% less than the semi-gun and 43% less than the hot dog. The tests were duplicated with different riders with the same results; in each case, the readings were for the planing position that produced the least drag. While the drag tests were confined to that aspect alone, and it goes without saying that in wave riding many other factors are in operation, the tests under laboratory conditions confirmed the principles under study as well as the performance in real surf.

Although the idea originated in Hawaii, it was not Cali­fornia with its bull market and contented manufacturers, but the up and coming Australians who showed the keen­est interest after the hydro's first appearance and were the first to be licensed for commercial production outside of Hawaii.

* The hydroplane surfboard is protected by United States Patents 3111695, and 3160897, foreign patents pending. 

We carry a wonderful print made from a photo taken by Art Brewer of John Kelly that you can have for your very own. Click here to view.