Originally Posted by rslifkin
I have always wondered why most sailors focus heavily on speed through water
and ignore the GPS
speed over ground readout. Coming from a powerboating background, in my mind, what really matters in the end is "how fast am I moving and in what direction?" So SoG and CoG from the GPS
tell me that. It doesn't really matter if I'm moving a different direction than I'm pointing, or if I'm moving over ground slower or faster than through the water
. That's cool to know occasionally, but is of no use for getting me to my destination
Answer, Part 1.
Do you wonder why?
Sailboat racers led the way on this, beginning to use True Wind
Speed, True Wind
Angle, and Speed Through the Water in the 70's to 80's.
The reason is because to get the most out of your boat
you need to understand how the sails
are working to maximize your boat
speed through the water. If you are fast through the water you will be fast over the ground. We have benchmarks (polar diagrams) and even more important, we are watching our boat speed relative to the true wind, true wind speed and the true wind angle, and the leeway, etc, minute by minute.
We must eliminate as many outside factors as possible, including the effect of current
. When you look only at Sog and Cog, you have combined the effects of many things and it is hard to see what each factor is contributing. We need to separate out the components and optimize each one separately.
is the responsibility of the tactician and navigator.
Boat speed is the responsibility of the helmsman and trimmers.
So the helm
and the trimmers concentrate on boat speed, and for that they need the instrumentation (or a very good seat of the pants feel).
The tactician and navigator watch the competition and where the boat is on the race
course and how we are being affected by currents and land masses, etc, and for that they need GPS and current information.
What does any of the mean to a cruising sailor? Well, for most of us, nothing. We motor
along merrily drinking a beer
with little regard for whether or not we could be doing it faster. Who cares? we're cruising.
But for those who get a thrill out of knowing that they are sailing well, doing the best that they can given the boat and the conditions, we can utilize all of the information available, and strive to do, with just ourselves, what the racer
does with a full crew.
Look, sailing is a sport, it is not just a passenger ride.