October 31, 2009 08:35
One of the longstanding seafaring dilemmas is how close to the wind to sail, when tacking upwind. Whether in a nutshell pram or a big cruising catamaran, there is always the question of whether it would be faster to (a) minimize the distance by sailing close to the wind, or (b) head off the wind for more speed but a greater distance to cover.
Maybe you have tried to answer this question by using the ETA on your GPS chartplotter. But when you have been on a tack for awhile, the ETA on many brands will suddenly go blank right when you need it most.
And did you know that Velocity Made Good (VMG) decreases all by itself, the further you get off the rhumb line (the straight line to the destination)? If your speed is constant, even if you are on a correct tacking angle, VMG erroneously shows slower and slower speeds the longer your tack continues.
SailTimer solves these problems. It quickly tells you (1) how long is it going to take to tack to my destination, and (2) what are the optimal sailing angles to get there?
Even on an $800 GPS chartplotter, your normal sailing on tacks is viewed as "cross-track error". But now, if you have an iPhone or iPod Touch running SailTimer, you can plot a waypoint on an aerial photo and calculate the time to get there with tacking correctly accounted for. As you can see from the graphics below, you can also calculate the distances on each tack, and much more. SailTimer Lite is a FREE download from iTunes, and the full version is US $13.99.
The link to SailTimer in the App Store is at: IndepthNavigation.com
[image]http://www.motionparallax.com/TCDVDs/4versions/AppStoreGraphics/Map.jpg[/image] .. [image]http://www.motionparallax.com/TCDVDs/4versions/AppStoreGraphics/Options.jpg[/image] .. [image]http://www.motionparallax.com/TCDVDs/4versions/AppStoreGraphics/NameWaypoint.jpg[/image]
..
[image]http://www.motionparallax.com/TCDVDs/4versions/AppStoreGraphics/Results.jpg[/image] .. [image]http://www.motionparallax.com/TCDVDs/4versions/AppStoreGraphics/Waypoints.jpg[/image]
Maybe you have tried to answer this question by using the ETA on your GPS chartplotter. But when you have been on a tack for awhile, the ETA on many brands will suddenly go blank right when you need it most.
And did you know that Velocity Made Good (VMG) decreases all by itself, the further you get off the rhumb line (the straight line to the destination)? If your speed is constant, even if you are on a correct tacking angle, VMG erroneously shows slower and slower speeds the longer your tack continues.
SailTimer solves these problems. It quickly tells you (1) how long is it going to take to tack to my destination, and (2) what are the optimal sailing angles to get there?
Even on an $800 GPS chartplotter, your normal sailing on tacks is viewed as "cross-track error". But now, if you have an iPhone or iPod Touch running SailTimer, you can plot a waypoint on an aerial photo and calculate the time to get there with tacking correctly accounted for. As you can see from the graphics below, you can also calculate the distances on each tack, and much more. SailTimer Lite is a FREE download from iTunes, and the full version is US $13.99.
The link to SailTimer in the App Store is at: IndepthNavigation.com
[image]http://www.motionparallax.com/TCDVDs/4versions/AppStoreGraphics/Map.jpg[/image] .. [image]http://www.motionparallax.com/TCDVDs/4versions/AppStoreGraphics/Options.jpg[/image] .. [image]http://www.motionparallax.com/TCDVDs/4versions/AppStoreGraphics/NameWaypoint.jpg[/image]
..
[image]http://www.motionparallax.com/TCDVDs/4versions/AppStoreGraphics/Results.jpg[/image] .. [image]http://www.motionparallax.com/TCDVDs/4versions/AppStoreGraphics/Waypoints.jpg[/image]