Hydrofoil worthwhile for me?

[Chamelion]

Hello all,

Recently purchase my first boat and I've found myself curious about hydrofoils.

My boat is a 4.4m fibreglass runabout with a 50hp yamaha 2 stroke on the rear. I tend to carry 3-4 people most of the time plus esky with food, battery, 30L fuel, fishing gear etc. I'm not unhappy with the performance, the speedo reads 53ish km/h flat out and she seems to get onto the plane without much trouble. But having said that I'm not against lowering fuel consumption, getting onto the plane easier and staying there at lower revs.

Is a hydrofoil of some sort (which one?) going to be of benefit to me?

Cheers :)

Matt.

[trueblue]

Foils can create drag, and can reduce your fuel economy.

That said, some boats don't perform very well without them, but they have to be set up exactly right and suit the motor and boat.

But beware that if incorrectly set up they can be downright dangerous.

Can be beneficial, can be dangerous....

[finga]

They're mainly used as an aid to get on the plane a bit better.
This is usually in boats with outboards set up incorrectly.
They're designed to just skim on top or just out of the water of the water after your planing.
You might have problems with prop selection and/or outboard setup.
Some more details of the prop and pictures of the outboard positioning might give you a better answer.
As mentioned above they are beneficial to some and a pain in the posteria for others.
How's the steering?? Heavy or light.

It could also be the best performance your boat can get with the combination of motor and hull.
It sounds like a pretty good setup to me performance wise seeing she's a 4.4m boat with a 50 on the back with 3 blokes and their gear inside.

[Mindi]

When I moved to Qld from Vic 6 years ago I was amazed at how many hydrofoils I saw (still see) they were never popular in Vic at all and as far as I know they still are not. Very much more common here... I have never really understood the whole hydrofoil thing as a result. On first principles I would have thought if the motor was better with a big ventilation plate then it would have been made that way..?

[PADDLES]

i reckon they are handy to get up on the plane when your rig is on the edge of being underpowered. for instance my 6.2m boat has got a 140 suzuki motor on it, realistically a 150 or 175 would be more appropriate. i tried a foil and have found that if i take off with the motor trimmed in, the back of the hull pushes up onto the plane way quicker than without the foil. as the back is coming out of the water i am trimming the motor out at the same time to get a good ride. using this method gets me up on the plane quicker and with a lot less stress on the motor and obviously the fuel savings that go with it.

[reidy]

ran one on my old 12' tinnie/8hp evi.Had trouble getting her out of the hole in the wind with the 8.Put a fin on her and no problems she'd jump straight out and away.
Cheers
Reidy

[Chimo]

The 2 sets on 115s on the Vag do just what you want Matt and the one on a tinny with 9.9 does it too. On a 10ft tinny going flat out with one up and a 9.9 with foil the thing turns like an MG TC, TD, MGA and and MGB. Sits as flat as can be whereas prior to fitting if you moved the tiller the thing felt like it was going to flip you out.

I've used them on many boats for years in Vic and Qld and I'm still waiting for the dangerous, its going to kill you thing to happen. I think its a bit like the Yetti!


Cheers
Chimo

[Dirtysanchez]

I had similar set up on my old half cab, 4.4mt with a 60hp (DT60) Suzuki smoker on the back.. One mechanic said the compression was down, and conned me into a foil.. it was OK.. Finally threw a piston and had a rebuild. The improved performance of the motor + the foil was scary. it just got too far out of the water and one day one of the guys on board with me decided to dive into the cabin to grab a beer. Boat went completely onto the port side, and the motor was out of the water.
LOTS of water came in over the gunnels, and we all shat.
Water police were not far away so they came over to check us and the guy at the helm commented the whole hull was out of the water!

If you are contemplating one, get some advice from a decent mechanic. If your motor is solid and has heaps of compression, you are probably better off as you are.

[Horse]

I have fitted one to my 17' Oceaneer. It made it a significantly better riding boat as it allows a lot more nose down trim. I could have played with motor wedges but this was a quick fix that worked wonders

[trueblue]

Can be beneficial, can be dangerous....

It all comes down to set up and the individual boat.

You really need to be understanding what effects are being caused by what before thinking about a foil.

Learn about trimming in, trimming out, and how that gives you bow up and bow down conditions, and how this is beneficial or hazardous in various sea conditions. Learn about porpoising, and how to stop it.

Go for a ride in other boats and get the driver to experiment with trimming in and out and note the ride difference in other boats compared to your own.

Understand how motor installation height affects different boats.

Understand what propeller differences can be and what is right and wrong.

Then you will be able to properly judge if you need a foil or not.

You can easily go and spend your $100 to $150 on a foil and install it and experiment with it - no problems, but if you don't understand the general dynamics of the boat without it, you won't really know what the foil is really doing because there are so many other variables.

cheers

Mick