Sailing Logic Blog

Sailing Acronym Jargon Buster!

When learning to sailing, the amount of odd phrases and bizarre acronyms can be overwhelming – and mastering them can be a slow process. No, a sheet isn’t a sail and the heads aren’t somewhere you want to spend a long time, especially when in a lumpy sea. Well today we’re going to dispel the myths and start picking our way through the more commonly used acronyms used in sail training.

SOG - Speed over ground

In sailing, we use two types of speed measurement, Speed through water (or boat speed) and Speed over ground. Speed through water is the speed that water is flowing past the hull, therefore if you’re attached to a mooring bouy – and there’s a tide running – you often see your boat speed dial reading, even though you’re attached to terra firma and not moving. This is where Speed over Ground comes in! Speed over Ground is how fast the vessel is moving in relation to the sea earth, not water. This is usually measured off a GPS signal. Often yachts will have both speeds displayed, as by comparing them, you can see how you’re being affected by tidal flows.

COG – Course over ground

Any self-respecting RYA Day Skipper Theory graduate with have course over ground ingrained into their memory, as it forms a key part of passage planning. Like speed over ground, course over ground is all to do with the tidal effect on your vessel. Course over ground is the course you are travelling in relation to terra firma. Course over ground can be different to your heading for many reasons, but most commonly it’s due to leeway, currents, compass errors or even bad helming!

TWA – True Wind Angle

It’d be unusual to learn about true wind angle early on in your sail training, or even during your Competent Crew course. However, the more helming you do – particularly at speed - the more you’ll become aware of true and apparent wind directions. There are two kinds of wind; true and apparent. True wind direction is what direction the wind would be blowing from if you stopped the vessel moving over the ground. Whereas apparent wind angle is the wind that is generated by our movement in combination with the true wind.

For more hints and tips like this, check out our knowledge centre or browse our courses for a bit of face-to-face learning.

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