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Old 04 May 2004, 17:21   #1
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Hydrofoils

Is there any real benefits of having these fitted to outboards, and what if any ar the disadvantages?
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Old 04 May 2004, 17:37   #2
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I've got them on my Yamaha 90hp and I find that it lifts the stern and gives a better ride. I can't say that it makes us go any faster or whether it is any more economical, but it has changed the way our boat handles the rougher stuff.
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Old 04 May 2004, 17:54   #3
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It certainly made a big difference to my boat, the weight distribution is very aft heavy, and the lift produced off them makes the boat plane a lot quicker, which is a big help when pulling skiers. It also increased the effect of trimming the engine in or out. I found the planing speed was noticably reduced,and also a reasonable saving in fuel (although how much exactly i don't know). If your boat is slow to get on the plane or you want to lower the planing speed to make it easier to tow kneeboards or other 'slower' items then give them a go
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Old 04 May 2004, 18:00   #4
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As for disadvantages - when i fitted them, i caught part of the leg with the drill chuck and took a small chunk out which peeeed me off

Other than that it took a while to adjust them so the boat tracked straight (i got the ones with 'wing tips' on). Once they were set up though, no problems at all
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Old 05 May 2004, 07:15   #5
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Got to ask the noobie question.

Why dont engine manufacters fit them as standard? I too see lots of claims about them and wonder if the hype is true. If it is I would get some.


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Old 05 May 2004, 09:41   #6
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Quote:
Originally Posted by steedthrust
Got to ask the noobie question.

Why dont engine manufacters fit them as standard? I too see lots of claims about them and wonder if the hype is true. If it is I would get some.


Steve B

A few reasons I suspect:
1) Not needed on a well set up and correctly balanced boat
2) Of no use for lower speed applications such as semi-displacement boats
3) If used on semi-displacement boat it could have the effect of making them run "nose down" slightly.
4) Then can cause handling problems if fitted to a well balanced boat, making the stern high caused by the lift - if they were built in by the manufacturer, they would need to be removable.

Also, I personally feel they are only of use with power trim, so you can control the amount of lift/trim effects.

They are of most use to stern heavy boats, or boats that struggle getting on the plane (ie towing my best mate on water skis- he's not the slimmest of people shall we say )
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Old 05 May 2004, 09:57   #7
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To add to the points above they must also increase friction and therefore increase consumption and reduce speed. Race boats try to have as little metal in the water as possible hence things like surface drives. Des
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Old 05 May 2004, 10:06   #8
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Hmmm,
These could be of use for our dive boat!
With the bottle rack behind the console we have to sit 2 people in the bow, & another 2 by the console just to get it on the plane.
Then if we stop quickly it does a good impression of a submarine.
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Old 05 May 2004, 11:44   #9
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Originally Posted by Scary Des
To add to the points above they must also increase friction and therefore increase consumption and reduce speed. Race boats try to have as little metal in the water as possible hence things like surface drives. Des

The foils themselves do have a frictional component, but where you benefit is the fact they lift the hull if you use the power trim, reducing the wetted area and consequently the amount of friction. My avon will plane at about 9 knots with these on. If you imagine the wetted area when you are running at full speed, engine trimmed out, then imagine it even if it just lifted by 1", the wetted area is a lot smaller, consequently less friction, increased fuel economy and theoretical top speed.

God, I must sound like I'm selling them!!!!
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Old 05 May 2004, 12:04   #10
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Quote:
Originally Posted by ribnwheels
1) Not needed on a well set up and correctly balanced boat

4) Then can cause handling problems if fitted to a well balanced boat, making the stern high caused by the lift - if they were built in by the manufacturer, they would need to be removable.

Also, I personally feel they are only of use with power trim, so you can control the amount of lift/trim effects.

They are of most use to stern heavy boats, or boats that struggle getting on the plane (ie towing my best mate on water skis- he's not the slimmest of people shall we say )
You state this as fact. Are you sure?

I personally found them most use for giving longitudinal stability on a single engine boat and both longitudinal and transverse stability on a twin engined boat.
They didn't reduce top speed nor did the boat plane at noticeably lower speed.
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