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Author Topic: New Stingray Hydrofoils  (Read 7032 times)

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New Stingray Hydrofoils
« on: July 26, 2011, 09:55:13 PM »
There are some new design hydrofoils that will soon be available in Australia that may be of interest to boaties. These should be available from your local chandler or boating accessories store.

Product blurb below.



XRIII
The revolutionary StingRay™ XRIII was the world’s first hydrofoil to feature a no-drill method of
attachment meaning no more cavitation plate holes. This enhanced design effectively captures
and focuses the prop’s thrust cone to create an incredibly fast hole shot while improving stability
and fuel efficiency.

See top picture.

**************

Stealth
The latest release from StingRay™ is the innovative Stealth design, featuring dual angle of attack
wings. The first angle gets you on plane faster than ever before while the second angle reduces top
end drag while providing stability.

See 2nd picture

*************
Classic StingRay
The StingRay™ Classic foil was born based on the need to simply improve a boats performance
and handling characteristics. The StingRay™ Classic hydrofoil stabiliser provides the extra
performance every boat needs due to their aerodynamic design created to produce higher water
pressure on the underside of the hydrofoils surface, creating lift to bring the stern up and force
the bow down.

See bottom picture




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Re: New Stingray Hydrofoils
« Reply #1 on: July 26, 2011, 10:15:59 PM »
For anyone who doesn't know what a hdrofoil is / does, I quickly knocked this up based on personal experience. I'd be interested in other people's thoughts on this.......



What do hydrofoils do?
Engine mounted hydrofoils can significantly improve hole shot speed, stabilise a boats ride, can keep a boat on the plane at slower speeds and can reduce fuel consumption. On some occasions a properly suited & fitted foil will improve cornering and reduce propellor airation (often called cavitation)

How do hydrofoils work?
Essentially an engine mounted foil adds drag to the rear of the boat when power is applied causing the bow to rise higher in the water. This rear end drag gets more of the boat out of the water, moving from displacement to planing sooner. As the engine is trimmed in and the boat levels out, the foil also levels out and reduces the drag again. Some foils are flat, others are hydrodynamically designed to also add lift while at level ride; similar to the aerofoil affect of a plane's wing.
Foils really come into their own when a planing hull is over loaded or the propellor selected is too highly pitched or cupped (to gain higher top end speed) for the weight, layout and load of the boat in a given situation. Example; a boat with two people may jump out of the water perfectly but with four people the boat may struggle to get up and onto the plane.
Another scenario when foils help is when  boat is under powered.

Many foils still retain some drag at all speeds, even if it is only a barely noticeable percentage at top speed. Often the pros outweight the cons of having a foil fitted.

When to fit a foil
I recon anything under a 25 horsepower engine may not get much benefit from a foil.
Before fitting I recommend you check that your engine is revving to it's recommended RPM; you could be barking up the wrong tree. You may not have the correct size/pitch propellor, or for that matter you might not have the right motor for the boat...
Also, make sure you check the leg length of the motor to your boats tramsom is suitably matched. If these not matched properly, you could probably improve the boats performance without a foil simply by raising or lowering the motor on the transom.

Foils Vs Trim Tabs
Trim Tabs and foils at first appearance achieve the same thing; faster hole shot, slower planing speeds, more stable ride.
Trim tabs have one advantage in that they can be independantly used to control a boat's roll AND pitch.
Example; a boat with 2 people is often balanced, a third person or even a full live-well can throw the port to starboard balance out; the boat might be heavier on one side. Trim tabs can counter act this where an engine mounted foil cannot. In saying that, an engine mounted foil is significantly cheeper than both hyraulic or electric worm drive trim tab systems.

Cheers,


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Re: New Stingray Hydrofoils
« Reply #2 on: July 27, 2011, 06:53:28 AM »
Having tested quite a few foils I have to agree with most of what Fitz says.  They can, however be useful on boats with less than 15hp as well.  A couple of things Fitz didn't mention are, 1. That annoying wake that catches up and comes over the back of the boat when you back off, a foil reduces, and in some cases stops this happening.  2.  Stability at rest.  Grap a piece of ply about the same size as a foil, and holding it flat, try to move it up and down through the water.  It's bloody hard.  When the foil is mounted on the outboard it has the same effect and stops the rear of the boat moving up and down at rest.
A couple of scenarios where I wouldn't recommend a foil.  1. if you do a lot of off shore work.  A following wave can create a lot more downforce on a boat with a foil, and that's something you don't want.  2.  The fitting of a foil with a pronounced downturn at the rear onto a small Alluminium hull.  I have experienced on  both a Savage Jabiru and a 3.9 Horizon that the downturn can cause too much of a bow down stance to be safe.  The hulls tend to bite into a wave and sheer off course.  Having power trim can reduce this problem.  It's very difficult on some hulls to have the foil clear of the water at full speed, and that is where it should be.  Unfortunately, the original Stingray does have a pronounced downturn, and I would recommend a flat foil for these boats.  The Horizon was cured by cutting 50mm from the rear of the Stingray eliminating the foil.

 

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