Quote:
Originally Posted by lapworth
Thanks for the idea of Solomons, but is 4 Knts the best I can expect ? I know on a fresh breeze with only my main sail I do 3.5 Knts.
The more I see the less I know.
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There are different kinds of speed when navigating a vehicle through a liquid environment. Presumeably since you mentioned not having a GPS, you are talking about your speed through the water read from a knot log.
Speed through the water is the least useful for any kind of navigation time calculation. For it to be of use, you have to also have an accurate knowldge of what the current is doing to you. Speed through the water plus or minus current will give you your speed over the ground.
Speed over the ground (as shown by a GPS) can be used to calculate how long it will take to get somewhere, so long as you can sail directly to that point. If you have to tack to get to your destination, then the distance you cover towards your destintion (Velocity made Good) is needed to determine when you'll get there.
Example:
4.5 Knots through the water
1.0 Knot current against you
3.5 Knots Speed over ground
Now if you have to tack to get to your upwind destination your VMG might be 3 knots or so. Which is what you would have to use to accurately determine how long it would take to reach your waypoint.