Re: Hydrofoils
From last weeks thread on the same subject.
There needs to be a sticky on foils and tabs indicating what each will and won't do.
The two are NOT designed to do the same thing, at least not in the same way, although the marketing makes you think they may. There is some overlap in the results though.
Tabs become a tunable (in some cases) extension of the hull, depending on how they are adjusted they can help get on plane faster, allow you to plane at a lower speed, stop porpoising, improve ride at speed, improve rough water ride, level the hull on plane, plus other things. They do this by pushing down on the water behind the transom where they can get better leverage.
A foil does one thing when used correctly, it allows you to raise the motor higher than you could without it by preventing the prop from sucking air…..that’s it. People often say they are of no value, because if they were they would come stock on motors…..well they do come stock, virtually every motor comes with an anti ventilation plate, the foil is just an extension of the stock one, similar to the tabs being an extension of the hull.
The term foil is also misleading, the foil shape has little to do with how it works, a flat sheet of aluminum will do the same thing (just like the stock AV plate).
To be used correctly a foil should not be dragging in the water at speed, this is where all the negative comments and results come from. With the foil dragging in the water on plane it may lower the top speed, cause odd cornering, and on some hulls create a scary situation. On an outboard you can raise the motor and possibly improve performance with a foil. By raising the motor the motor has less leverage on the hull so it reduces bow rise, being higher the drag from the lower unit is also reduced, this may increase top speed plus increase mileage. The reduced leverage on the hull can also reduce poroising at speed. These improvements aren’t guaranteed, they are only possibilities if you do the work of raising and lowering the motor to fine tune it, in the end you may also need to change the prop for best results.
On an I/O you can’t raise the motor, so there is a good chance you will experience one or more of the negative issues I talked about earlier when the foil drags in the water. So if you like it fine, if it does funning things and you don’t like it, don’t use it. It may also be a trade off of good and bad.
On an outboard a foil may not be the best way to achieve these results, and it may not help at all, it is very dependent on the exact hull, motor, prop, loading of the boat and how it is used. Tabs can typically make improvements on just about any hull, some hulls may need them to perform well at all, and others may do quite well without them, but still improvements may be seen with them.
Now back to the OP’s question. Leave it off and try it, some aspects of the performance may improve and some may decrease, you decide if it works for your situation or not. Tabs will probably make noticeable improvements in several areas with no negative effects.
