Design 3

Design
Page 3

Design Rationale - Accuracy

Accuracy is the bottom line

The most important mission of your instrument system is correctly reporting wind direction (see Wind direction).

Everybody can see and act on the 20º wind shift. The ability to discern the 5º shift, and having the confidence to believe it is key.

A 1º error in heading throws off wind direction by the same amount.
A 1º error in apparent wind angle can throw wind direction off as much as 3º.

This is why proper math, accurate sensors and diligent calibration are so important for a true wind instrument system.

Of course, none of these things can be determined directly. However, there is a reliable overall way to gauge how good an instrument system is at doing true wind – the change in wind direction when you tack or jibe (the “wiggle”).

Wiggle = (Wind Direction before tack) – (Wind Direction after tack)
There are about ½ dozen instrument systems that claim to calculate wind direction. Finding out how much wiggle they produce is a good way to determine which ones to consider.

Your trophy collection and peace of mind depend on it.

Using GPS in place of paddle and compass

Why go to the bother and expense of installing speed and heading sensors on your sailboats when a GPS provides the same information at a tenth the price and hundredth the effort? A GPS is already needed for position (which trumps speed and heading), so why even consider a paddle and compass? For sailboats, if navigation were the only consideration, COG and SOG from a GPS would fill the bill. However, when it comes to using speed and heading to monitor and improve sailing performance, there are several things to consider before you dismiss the idea of using a paddle and compass.

For more information, read our white paper on the subject.

Calibration

All instrument systems require calibration to make displayed information correct and useful. Calibration adjusts for sensor inaccuracies, installation misalignment and environmental issues (e.g. boundary layer and sail upwash).

Conventional calibration methods are covered in your instrument's manual. You can read about Ockam's conventional calibration starting at Calibration Overview and in our Manual. The big problem with conventional calibration is that there never seems to be time to do it, even if it were not so intimidating.

Ockam also offers a unique calibration procedure that automates the calibration process. Called DeWiggler, this application allows you to concentrate on crew training and race preparation instead of twiddling your instruments. Read more about it.

More information:
How Ockam Calculates things (PDF)
Calibration Theory & Practice (PDF)