Hydrofoil Stabilizers

[lunker99]

What has been your experience with these? Do they help get boats on plane quicker/easier and save fuel as advertised or just a gimmick? Thanks in advance.

Paul

[stinkycat]

Only had experience with a flat bottom 16' Lund Rebel from the early 90's. The hydrofoil that we had was a "whale-tail" brand I think. The boat has a 40hp Merc. The hydrofoil helped significantly getting on plan when we had a heavy load. It also helped with porpoising which was the main reason we put it on.

[REW]

Lunker,
It depends.
It depends on the boat, it depends on the foil used, and it depends on the motor.

Generally speaking, the foils do help to get the boat on plane. However, this help is quite dependent on the angle of the motor at the time of use. i.e. if it is trimmed too far in, the foil may actually cause more drag than lift.
If it is trimmed too far out, the motor will cavitate as usual.

If you have a boat - where you can't keep it on plane at a specific speed, the foils will generally help to plane the boat at a speed that is 2-4 mph slower than without the foil.

Also, generally speaking, the foils will take some speed of the top end of the boat, than if the foil wasn't installed. How much, is quite dependent on the type of foil, the specific boat motor rig, and finally the height of the motor. i.e. for a given configuration, if the motor is higher there will be less drag from the fully trimmed out motor and foil, than if the motor were lower.

Summary:
If you have an underpowered rig and need more lift on the bottom end, and if you want to keep the boat on plane at a slower speed, but are willing to give up some top end speed - go for it.

If you are concerned about absolute top end speed - with the boat motor combination that you have - then don't add a foil.
I really know of no foil that isn't going to cost the rig at least a little top speed. It only makes sense. The foil is going to be in the water. If anything is in the water at any angle other than 0 degrees, it will be causing drag which causes the speed to be slower.
Sometimes this change in speed, is virtually negligible, i.e. less than 1 mph. In other cases, it may be as much as 5 mph - for certain boat, motor and motor height combinations.

Take care
REW

P.S.
If you need the low speed lift that is provided by a foil, but don't want to give up any top speed, and or if you want the ability to compensate for a boat lean due to loading imbalance, consider the use of fully adjustable electric or hydraulic trim tabs. Fully adjustable trim tabs work to be able to be fully deployed or tilted down on a need by need basis. i.e. they can be tilted down a lot to help with planing out a boat. They can be tilted part way down to help keep the boat on plane at a slower speed, or when working rough water. Then, they can be fully tilted up out of the way, when the captain wants to run full speed with no drag in the water from the trim tabs. They are more costly, but they do give the ultimate in overall boat control.

Another option that is only about 1/4 the cost of fully adjustable tabs, is the use of the Nauticus auto tabs. These trim tabs use tabs that are virtually identical to the fully adjustable tabs. The difference is in the actuating mechanism. The Nauticus don't have the ability to be user adjustable. They are actuated by gas struts, similar to the struts used to hold up the hood of an automobile or the rear hatch cover of a van. The gas struts provide a downward pressure to keep the tabs fully extended for starting conditions. Then, as the boat speed increases, the water pressure against the tabs cause them to lift and rotate back up out of the way. Since they are virtually retracted at full speed, they generally provide 0 - 1 mph speed reduction at top speed.

Also, since the tabs are working all the time, they work as shock absorbers crossing waves. i.e. as a boat bounces when crossing a wave, the tabs work in conjunction with the gas struts to quickly dampen out the boats bounce. I have found that with out tabs, a boat might bounce 3-4 times on a high speed wake crossing. However, with the gas strut activated trim tabs, there is virtually - 0 bow bounce. i.e. the bow comes up and down as it crosses a wave and that is the end of the story.

Take care
REW

[Phil T]

I've been using them for years. 17 1/2' boat with a 90hp OB(3/4 of the hull's rating), and lots of weight at the stern. I've had various brands, and haven't noticed a lot of difference between them. My current foil is a DoleFin that I found at K-Mart years ago. It's a cheap way to learn if one will help.
A foil will make the trim angle of your engine "touchy." It will also hold the bow down and "stick" the boat to the water in heavy waves, providing more control. I like them, you may not. Buy an inexpensive one and learn for yourself.