Opinions on hydrofoils

[Disschord]

Hi guys what's peoples views on hydrofoils these days
What are the pros and cons

Thanks

[rodbolt17]

works well on some hulls, not so good on others.
what makes you think you may need one?

[Disschord]

I was asking because I have a shetland 535 an old 17.5ft heavy plaining hull boat with a yamaha f40 fitted. It gets on the plane but sometimes struggles when heavy loaded and wondered if the hydrofoils might help lift her out the water and in doing so increase a little speed and fuel efficiency

[boscoe99]

Seems to be lots of opinions as to the pros and cons of hydrofoils.

In my case I used one and it worked very well. Lots of bang for the buck. Got the boat on plane easier, let me run at a lower boat speed before the boat would fall off plane, and reduced propeller ventilation in sharp turns.

Now for some reason they don't work for others. Those others seem to be very vocal about hydrofoils being useless. Just because they did not work on a certain boat and motor configuration does not mean they will not work on other boat and motor configurations.

Hydrofoils are like propellers. It has to be tried to see if it works for the operator or not.

I changed mine so that it clamped on so that I did not have to drill holes in the anti ventilation plate. Did this because I was not sure the hydrofoil would be beneficial and if removed I did not want open holes left. The clamp on configuration worked so well I just left it as is.

You won't know if it has benefits until you try it.

[boscoe99]

I was asking because I have a shetland 535 an old 17.5ft heavy plaining hull boat with a yamaha f40 fitted. It gets on the plane but sometimes struggles when heavy loaded and wondered if the hydrofoils might help lift her out the water and in doing so increase a little speed and fuel efficiency

Make sure you have the optimum propeller size and engine mounting height first. Then try a hydrofoil to see if it offers an additional improvement.

That motor needs to be able to turn at or near 6000 RPM when at wide open throttle, with the boat loaded, with the engine trimmed to the most efficient trim angle. 90% of motors seem to be over propped. Makes the motor seem sluggish and it is not good for the health of the motor.

[robert graham]

But you know that a 17.5 ft. Boat with a 40HP outboard could be considered a bit underpowered...but the hydrofoil may help it achieve and maintain plane speed....I have used a 50lb. sandbag way up in the bow and it can help some...

[Disschord]

I am aware a 40hp is considered to be about as low as you can go for a boat this size for sea use but It's all I have and I am trying to make the best of what I have

Thanks

[SHAWND43]

In your case hydrofoil is the trick, it will make the best use of an underpowered motor setup.