Polars: max speed
Post by iconPost by lotsemann | 2014-11-25 | 00:19:56

Dear Cvetan,


Is it possible to add information about the maximum speed to the data about optimum upwind and downwind angles?

Thanks for your attention!

commenticon 5 Comments
Post by iconPost by redcobra | 2014-11-25 | 10:27:17
Hello,

I would also add a question to this: the sailing simulator is recommending me a constant TWA of 50° (port) for the next 9 hours and gives a heading of 70° (in this moment). On the other side the Polar chart tells me that the optimal TWA for my actual boat speed is TWA=49°. How to deal with this delta of one degree?

Thanks
Post by iconPost by zezo | 2014-11-25 | 14:20:42
It would be better to sail the perfect TWA if possible, but for your position that would mean switching from 51 to 49 at some point. You can see in the polar chart exactly how much speed you lose with one fixed twa.

You can also use the green track line to see approximately which twa gives best progress compared to the blue isochrone lines.

Please note that when there is a wind gradient the dots on the track tool lines don't always match the isochrones _exactly_ because the longer-period isochrones are generated with more than 10-minute step and that changes the result slightly.
Post by iconPost by lotsemann | 2014-11-25 | 17:50:26
Another thing to consider:

Depending on the circumstances, the VMG for one degree less or more than the optimum is very close or equal to the optimum.This may also lead to such deltas.
Post by iconPost by zezo | 2014-11-25 | 18:44:14
Yes, indeed. VMG for the example above with wind speed 8.8 are like 5.95, 5.97 and 5.98 for 49-51°
Post by iconPost by redcobra | 2014-11-25 | 17:07:46
Many thanks for your feedback!
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