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czolgosz

what is the difference between VMG and VB VMG?

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Hello all,

I know the english forum is pretty slow around here, but I'm trying to figure out what the difference is between the vmg and vb vmg pilot modes. I didn't really get a good understanding of this from the faq. Could anyone please explain it to me?

Thanks!

- Czo

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Basically the VMG mode is the best result of cos(orthoHeading-Heading)*boatSpeed. Say your WP is at 0, and wind is coming from 0, obviously the orthoHeading is 0, but problem is that your speed is 0 too. If you start changing heading by let's say 10degres, speed will come. Of course there is a best angle where speed and heading is optimal. This is the Best VMG and this is when cos(orthoHeading-Heading)*boatSpeed is best.

VBVMG does something similar, but tries to optimize the next tack. In fact more or less it makes the same computation but based on 2 tacks. In most of the case in fact it will follow the ortho, except if the angle is not within the best wind angle upwind (or downwind).

I hope this helps.

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hi,

VMG is the course that will give you the fastest approach rate on 1 tack, while VBVMG will give you the best approach rate on 2 tacks. In end effect the VBVMG give a route that is closer to the orthodromic route than VMG.

You can find a illustration of the VMG vs VBVMG course at the following page (should you have not found it already):http://wiki.virtual-loup-de-mer.org/index.php/Comportement_du_bateau_selon_le_mode_de_pilotage

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I know the english forum is pretty slow around here ...

Pretty slow!? You asked your question at 20h17 CET and got an answer at 20h41 CET ... is this pretty slow? ;)

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Nope, that's awesome! Thanks SBS and Phille! Every time I've posted I've received great help. I just noticed I was the first person to post in a month. :) Oh well, living so close to Quebec I should really just learn to speak French!

Thanks again!

- Czo

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