Hello to all. I bought this board a week ago for my brother in law. The board is 6’8’’ and about 20’’ wide shaped by luciano leao. the board costs me about 160 dlls, really cheap considering the overall conditions of the board. this board will be riden in 4’-6’ beach break waves. the outline seems like a mini gun to me, but the rider is 5’6’’ tall an weighs about 110 lbs. this board is gonna be like a longboard to him. i want someone to tell me what is the purpose of the little step in the tail of the board, just behind the fins. maybe the picture doesnt show it very well, but is the only pic i have. any advice/help will be welcome. Jack.
The hydrodynamics have been understood for quite awhile. Glenn Curtiss of Curtiss-Wright Corporation probably deserves more credit than anyone for pioneering the design for use on amphibious planes… long before use on surfboards. Earlier canoe style rounded “hull” designs created so much “downward lift” (suck) that they couldn’t get out of the water. By 1912 they had it pretty well worked out. Many of the plane floats I’ve checked have dual concaves and slight reverse rocker behind the step to enhance lift.
Meanwhile, development of the flying boat hull continued. It was soon realized that rudimentary hulls like the Canoe suffered from a great deal of drag in the water and often produced a downward “lift” that was impossible for the airplane’s wings to overcome. Among various corrective measures tried were:
a small aerodynamic surface installed ahead of the float to help raise its bow out of the water;
vertical standpipes in the float, that equalized pressure from top to bottom,spoiling downward “lift”;
small hydrofoil surfaces installed on either side of the float to help raise the airplane in the water;
variable angle of incidence wing to produce more lift for takeoff.
Eventually the right configuration was found–a stepped, hydrofoil hull. The hull was designed to produce lift as it moved through the water. When it raised itself sufficiently to expose the step, drag abruptly decreased, and the hull quickly rose further to plane on a small area of the step. The pilot easily sensed these actions. The quick rise and increase in speed told him that his craft was planing and ready for takeoff.
This design became so well understood that some experimental hulls were made to plane at very low speeds (20 mph), too slow for the aerodynamic controls to be effective.
Now, a flying boat could very handily out-lift a land plane using the same engine. Curtiss’ flying boats became well-known for their heavy lifting ability at takeoff Hulls were further modified to spread their bow waves laterally, to keep spray out of cockpit and engine. By 1912 Curtiss flying boat hulls became the standard of the world and were flagrantly copied.
Here are pics of an older “OWL” Surfboard of mine with a similar, but less abrupt step hull design. Note offset fin…
Ben Aipa was showing me a 9’0 board he had shaped some 15 years ago, that had that tail. The current owner told us both it was the best board he’d ever had, that’s why he kept it. Ben explained the concept that at low paddling speeds, the board didn’t plane yet so the extra area in the tail gave extra planning and paddling ease, until soon after dropping in. Then the board lifts enough to start to plane, and the faster water flowed more cleanly around the pintail. Ben said the concept really worked, the rider can feel a cleaner ride. But he told us his glassers and sanders hated doing them, and there were too many sand-throughs, so he abandoned the design but that he still believes in it.
