Re: hydrofoil (whales tail)
I can only speak to my personal experience in putting foils on my own boat. Here is what I found.<br /><br />Whether the foil is in the water or not when the boat is planing depends on the position of the mounting point (the anti-cav plate) relative to the bottom of the hull and the design of the foil. <br /><br />If the ACP is inline with or slightly above the bottom, the foil will be surfaced fully or partly at speed and have less drag but also it won't be doing much good in leveling the boat. Obviously, the farther out of the water it is, the less effect on running angle but also less drag. <br /><br />I tried two different foil types, the first one was designed to be out of the water at speed (it is in the form of a Vee). It helped with the holeshot but once up on plane the boat still ran a bit nose high. Speed loss with this foil was minimal. <br /><br />The second foil is known as the "Stingray". It is designed to work best while fully submerged. It has a pronounced airfoil shape which needs water flowing over it to produce max lift. I tried moving the motor to put this even with the hull bottom and got poorer results than when it was positioned lower where the foil was under water when planing. If you have power trim or a jackplate on the outboard, this may be easy to try. For me, it meant remounting the engine but the results were informative.<br /><br />When it was down in the most effective position, drag was enough to reduce top speed by a little over 1 mph but the improvements on control were dramatic. The most noticable factor was the ability to plane with a normal load at 13mph while without it minimum planing speed was 17mph. I thought the overall benefits were worth a little off the top so that's the one I kept. <br /> <br />Like they say, your results may vary.<br /><br />-xsb
