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Boat tracking and skegs


mbabiash
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I’m sure the boat companies have researched this to no end but while watching F1 this morning I was thinking about aerodynamics and my thoughts went to hydrodynamics and boats. It seems that all the research and tuning is in the hull running surface and the skegs and rudders have always been the same. It seems that handling on boats could be improved with a new design of skegs and rudders without affecting wake size. I know nothing about this, I just thought it was interesting.
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More could be done just don’t know how much of an improvement can be achieved and at what cost?

My ‘92 California Skier had a piece of ‘new tech’ called an EP (equal pressure) rudder. It had a sharp front edge and a fat 1” or so trailing edge. It was shaped like an axe head. They claimed it helped tracking because there was equal pressure on both sides of it so the rudder was loaded all the time. Sounded good to me. Didn’t feel any different if I recall.

Don’t see them on any new boats so I guess it wasn’t accepted by builders or boaters as being an improvement.

The Boesch rudder looks like a similar product in design. Anyone drive or ski one of these Boesch boats and could comment on rudder feel or tracking?

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@Dacon62 has it right. 1998 to 2000 on the Prostar 190 were the years with the issue. Note that it did not affect the other models of that era (Prostar 195, SportStar, Skier 19, Prostar 205). Only the 190 had that hull and the problem. Those other models were based on the 1995-1997 hull, which was a very fine hull free from the safety/handling concerns.

 

2001 was the start of the Prostar 197 hull.

The worst slalom equipment I own is between my ears.

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@mbabiash: There is always room for improvement although it does come down to ROI in the case of a consumer product v the outright search for speed with pretty much an unlimited budget for the F1 gang. It is pretty amazing how much time and effort is spent in a wind tunnel for the top F1 teams, the fan spins pretty much 24/7.

 

There are improvements by simply doing some basic blueprinting of your existing skegs, rudder and rudder support. One can improve efficiency and also tune the torque steer with appropriate modifications. One of the product improvements has been the adjustable tab introduced by Malibu, another product is the Acme prop cone, not commonly used but installs at the trailing edge of the prop. As you note, much more effort and time is devoted to hull changes to tune and improve the wake, a lot has to do with which axis the component acts.

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Thread is kind of proving the point @mbabiash proposed - not a whole lot going on.

More maybe in the world of surf boats with things like dockstar. But the reality is that you need fairly robust hardware underwater to put up with the strains, props have seen some big leaps w/ CNC. Maybe if a company saw fit to CNC the rudders and skegs you could get fancier.

 

Rudder tabs are just a solution to hand tuning the rudder.

Rudder winglets were just a solution till they got the hull hooked.

 

I've always felt it wouldn't be horrendous to figure out some form of pylon actuated tracking control. A physical or hydraulic linkage the pylon bolted into with a mechanism such that angle + force would dog track the boat. I figured this would be easier to implement if ski boats used power hydraulic steering like I/O's as you could easily use the deflection to port fluid pressure and influence both the skegs and the rudder. But people like the "feel" of cable steering in these boats.

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The last two comments remind me of one of my college professors who said on day 1 of an engineering design class: "show me something new and I will give you an A for the class". We thought, damn, this should be easy! Well, by class end none of us succeeded in the 'easy A' since every time we brought something up, he could get some old dusty textbook and basically show us it had been introduced long, long ago:)

The rudder tab was merely an example not necessarily meaning it was the first or only.

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@Dacon62 - it pulled the worlds last year but I never heard driver feedback from it.

 

Also in continuation to previous post - I think its more likely to address this now in an accelerometer/servo type apparatus instead of using hydraulics - even cars are moving away from powered hydraulic steering.

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So throughout the years here are the tracking fin/strut/rudder advances/fails. In no particular order and to the best of my recollection from front to back,

 

1) SKEG, Centurion articulating tracking system(CATS)-a front skeg that moves opposite to the rudder to supposedly improve tracking. Introduces in the 90's on the Tru Trac III hull. Not used on their ski boats anymore but the tech has found its way to the wake surf boats.

 

2) STRUT, Mastercrafts strut dongle that protruded out the front of the strut to smooth out water flow to the prop. I don't recall seeing this on MC's or any other brands for some time now.

 

3) RUDDER,

A)Rudder tab to adjust rudder torque. Still used and a great idea.

B)Axe shaped E.P. ((equal Pressure) Rudder. No longer used.

C)MC's winged rudder around 2000. No longer used.

 

So of all the attempts at improvements the only item still being manufactured is the rudder tab.

 

Please add to the list as I would expect that something was missed.

 

@DW could you post a pic of the Acme prop cone?

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