AC36: The Match (6-15th March. Reserve days to the 21st)


Super Anarchist
I don't believe that onboard wind data is a true reflection of the actual wind direction and speed.  It has to be a calculated figure due to the apparent wind factor.  I realise that there is probably some algorithm that is being used but in my opinion it doesn't accurately reflect the actual conditions.  
True wind direction and velocity are simple vector calculations using boatspeed, COG, apparent wind direction, and apparent wind velocity. Every modern wind instrument system in the last 40 years has been able to do this with reasonable precision.

Because these are calculated values rather directly measured, accuracy depends on the accuracy and calibration of each individual instrument input. The error is the sum of errors of the individual inputs.

One advantage of foiling boats is that you you have generally  near steady-state of pitch and roll, unlike a conventional monohull with a fair amount of vertical acceleration in any kind of sea, which obviously impacts on apparent wind and anything calculated from it. Have you ever watched how your wind instruments oscillate as your boat moves through waves, especially in any kind of sea?

Most instruments have damping functions to remove some of this effect.

It should not be a surprise to discover that a huge amount of effort goes into instrument calibration, constantly. On the old ACC boats, I once asked one of the instrument specialists how often they calibrate instruments. His answer was: "every day."

At the end of the day, it is more accurate than you think, and what matters is the wind direction and velocity that the boat and sails "see". Sailors almost always work in relative figures. 

The instrument systems themselves are humming away in their own little universe of absolutes.

At least on the boats I race, which are pretty conventional.Your experience may vary.



New member
1 hour ago, Priscilla said:

22 knots with 26 peak @ Channel Island outer Hauraki Gulf may push through some puff later.

Channel Island always blows (gets a venturi effect between GBI and the Coromandel), not a good indicator of what is going to happen in the inner gulf.   But of course now I have made this statement I will be proved wrong, and if that means good racing today then I am okay.



New Zealand
Any updated wind and course forecasts ?
Fuck all at the moment and not looking good. Still time but this mornings forecast should have seen some movement by now

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Super Anarchist
Auckland, New Zealand
1 hour ago, 45Roller said:

Well happy birthday mate, hope you have a good one, how is the Guinness there?

for a laugh.. here's an interview with our patron saint from our favourite sailing commentator  :lol:

The one I've had so far was great! NZ usually does St Paddies quite well, but this year everyone appears a little distracted ;-)