sailing efficiency meter

[tspeer]

Originally Posted by Fanie

Probably the easiest of them all to do judging by what you wrote there.

Angles are measured with a Clinometer.

...

No, an inclinometer measures the angle of heel (actually, it measures lateral acceleration). Leeway angle is the hydrodynamic equivalent of apparent wind angle. It is the difference between the boat's heading and it's velocity through the water.

Although speed through the water is measured, the direction of travel relative to the water is typically ignored, assumed, or estimated. The estimate comes from the difference between heading and course over ground, taking into account any current. But you have to know what the current is.

What exactly are you looking at measuring ? I was under the impression just speed vs wind angle / aparent wind angle would be it.

Using a wind vein should have your chart almost dead on all the time if it works properly.

I want to sail for data to build and validate a VPP that will be the basis for engineering future changes to the boat. The fundamental sailing performance equation for steady conditions is
Vb/Vt = sin(gamma - beta)/sin(beta)
where Vb is the boat speed, Vt is the true wind speed, gamma is the point of sail (0=head to wind) and beta is the apparent wind angle, measured between the apparent wind vector and the boat's course through the water. Beta is the sum of the apparent wind measured to the boat's centerline, and the leeway angle. So leeway angle is needed to complement the apparent wind measured by the wind vane.

Beta is also the sum of the hydrodynamic drag angle (atan(Drag/Lift)) and the aerodynamic drag angle. Leeway angle is essential to being able to estimate the lift and drag of the hull as opposed to the rig and topsides.

In essence, I'm turning this boat into a sailing technology testbed, so I need a different set of measurements than a typical sailboat. And I need to be able to digitally record all the dynamic measurements, not just observe them on an indicator.

[Fanie]

Seems to me a gps module can get you most of the information, direction and speed, aparent wind you can get from aboard, true wind and current speed you could measure from bouys transmitting over the area you are going to test, it would probably change with the tide. To get current direction you may have to add a fixed point and a loose one so the loose one can rotate around the fixed.

Add a logger and you can let rip.

[Landlubber]

Fanie, Fanie, Fanie,.......you are a sick man mate......remind me as I help you out of your inverted cat one day in the middle of no where, that a good mono is a joy to behold. The worse it gets the louder you turn up the stereo and sleep on...cats need someone at the helm so that they purr!

[Fanie]

Oh hello Lubby, cough cough

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