Re: Whale Tails
It's the weekly foil, fin, whaletail thread, and again, as always, there are the same misconceptions of what they do how they are supposed to be used.
They are not designed for the same purpose, nor are they used in the same way as tabs (at least when used correctly), so throw those comparisons out the window.
The only thing a foil will do for you is allow you raise the motor higher than without it and help keep the prop from ventilating...that's it.
This may not be possible or helpful on every boat because there are so many different combinations of hull designs, props, motors, HP, how the boat is used, etc. It is also an issue on an I/O because you can't do any of the needed adjustments (raising the outdrive), so if you use one you need to live any of the negative side affects.
The foil should not be dragging in the water at speed, this is where the bolt it on and head for the water crowd makes their first mistake, they do this and find there are odd side affects of having something this large dragging off the lower unit.
Tabs and foils do have some overlap in the final results, but not for the reasons most people assume. Tabs are an adjustable hull extension, that?s it, and are what most people need and want. They also have very few negative affects even if they aren?t needed, but they do help in almost every situation. They work by pushing down on the water.
A foil works by allowing you to raise the motor and not having the prop ventilate, not by dragging in the water and forcing the bow down like tabs do. At low speeds a foil sort of does the same thing, but this is a side affect, not the goal.
If a motor is raised to the best height for performance at top speed it is very often too high for a good hole shot. As you start to take off and give it full throttle (doesn?t need to be full) the prop may be too close to the surface and suck air. The AV plate that is built into the lower unit may not be large enough to prevent the air from being sucked into the low pressure zone in front of the prop in every situation. So increasing the size of the stock AV plate may help?this is all a foil is?an extension of the stock AV plate that is designed into every lower unit.
I also dislike the term foil, because the foil shape is of no value in how it works, it was sort of a marketing gimmick to sell the item, which further confused the issue of how they work and how to use it.
Raising the motor can increase your top speed by reducing the drag on the lower unit, this may also increase your MPG.
There is less bow rise when getting on plane because as you raise the motor it has less leverage on the hull, same with porpoising. There is also less air being sucked in so the prop gets a much better bite.
Sometimes the boat becomes more stable at speed with the prop higher.
It may also allow you to use a different prop for even better performance.
