# NavList:

## A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

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Re: Course to steer at a given speed.
From: Andrew Seligman
Date: 2012 Nov 28, 11:18 -0500
You need to determine Speed Through the Water to obtain a Course Made Good;  You also have to calculate Leeway and compensate for it.  If the sailboat is on a Starboard Tack, then you Add the Leeway Angle to the boats heading;  Conversely,  if the sailboat is on a Port Tack, you subtract the Leeway Angle from the boats heading.

Andrew F. Seligman
ASA Sailing Instructor
(215)514-6724

On Nov 28, 2012, at 11:01 AM, "Greg Rudzinski" <gregrudzinski@yahoo.com> wrote:

Sean,

Sailboats do not have the luxury of scheduling :( If you have a sloop then you can point 30* off the apparent wind which complicates making a mark, waypoint, or destination. Then there are tidal currents which in some cases will be resulting in a negative headway. To avoid this a sailor needs to time arrival for slack water or have the tidal current directed toward the destination.

Greg Rudzinski

[NavList] Course to steer at a given speed.
From: Sean C
Date: 28 Nov 2012 04:10
A while back, I was reading the chapter in Bowditch dealing with dead reckoning. I was especially interested in the section dealing with course and speed made good. Well, last night on my lunch break (I work nights), I decided to solve a quick problem I made up:

"If I were on a ship which was 10nm due East of port, with a set of 360° and drift of 3 kts., and I needed to arrive in port in exactly one hour, what course and speed should I use?"

I figured the answer to be 253° ---5 kts. But then I started to wonder: That's all well and good for a vessel under engine power, but what about a sailboat? I know the way to figure course to steer at a given speed, but wouldn't turning a sailboat into the current (as in my example) actually slow the speed through the water enough to change the necessary course to steer? Or is this error so small as to be negligible? Or is there some other way to factor that in?

Regards,
Sean C
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