woodpecker

Garmin SailAssist

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I just got a new Garmin Plotter with SailAssist. Anyone tried the start line feature or use Laylines? 
Seems like it would need the boat polars to be accurate?
 

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Will need more than just Polars to be accurate, though they are required   

You will need good calibration including leeway, drift and set for the laylines to be useful. That will require good BSP, COG, SOG, heel and heading sensors, properly installed and calibrated, including adjusting your Polars to what your Boat, as loaded and rigged does vs the VPP programs prediction 

Even with excellent sensors & calibration, your start will be a bit wonky as your Polars assume equilibrium, and most of your pre start is maneuvering frequently, below polar speed, and without your downwind sails up.  That typically results in being late, unless you have a long enough close reach to hit full speed, and then your timing will be reasonable.  

 

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On 6/4/2018 at 12:23 AM, LionessRacing said:

Will need more than just Polars to be accurate, though they are required   

You will need good calibration including leeway, drift and set for the laylines to be useful. That will require good BSP, COG, SOG, heel and heading sensors, properly installed and calibrated, including adjusting your Polars to what your Boat, as loaded and rigged does vs the VPP programs prediction 

Even with excellent sensors & calibration, your start will be a bit wonky as your Polars assume equilibrium, and most of your pre start is maneuvering frequently, below polar speed, and without your downwind sails up.  That typically results in being late, unless you have a long enough close reach to hit full speed, and then your timing will be reasonable.  

 

You are making it a lot more complicated than it really is.  Have you ever used a prostart?  It does distance to line based solely on GPS.  Obviously layline is a bit more complicated in light air or with a lot of non-uniform current - but in many situations a GPS based layline calculation is reasonable

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I use B&G Sailsteer and Expedition which Garmin is trying to copy.

Having a fancy display is easy, I’ve had that with IRegatta for years.

Having it make sense and be reliable is harder, and that is where good calibrated sensors come in.

If you want to know when to tack or gybe to hit the favored end line, at speed, within a five second window, you won’t do it on just a GPS. 

If you want to know when to tack to make the mark in oscillating winds and real currents, you need calibration of TWD, set and drift, and good current models for your locale. 

Human intuition can do both pretty well, primitive instruments not so much. 

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