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VMG relative to wind - with a rotating mast

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This is a bit of the thought experiment, as I probablly have better things to spend a load of cash on, than try to get a reliable VMG to windward on my insruments, but we can all dream


Current setup - 8.5 Multihull, with rotating mast.

No mast head gear, no paddle wheel, just raymarine A60 charplotter on NEMA 2000


What I am thinking is using something like calypso cups (or the vavuud) as masthead gear, then their bluetooth to NEMA0183 gateway, then a 0183 to 2000 converter.

I like the look of these as they incorporate a compass into the mast gear, so the rotation of the mast is irelevent. (sailtimer did something similar, but I've not heard great things about them)

However, bluetooth to 0183 to 200 seems like a lot of interfaces and sounds like a recipe for multiple places for problems to hide.


The alternative is to go with a more traditional masthead gear, then add something onto the mast to measure rotation, but even the cheap gear out there for this seems madly expensive, and is going to need some very careful calibration.


Any other suggestions on how to get decent wind information on a rotating mast?



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their ultrasonic model (though a little pricey) has a built in GPS and so you wouldn't even need it to tallk to your chartplotter - just have a couple of cheap tablets to connect to.

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Nope, only one bluetooth connection allowed. And their app doesn't know which way the boat is pointing, there is a calibration mark on the sensor for pointing of towards the bow.

Hence why I want the NMEA sentences so my daylight viewable chart plotter can actually use the information properly

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Use one of these, it has all the gauges you need and can give you great coffee to boot! 

It will need attaching to the top of the mast for accurate readings.

Takes a while to calibrate.



windy Windup.jpg

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yeh - except I suspect its not particularly waterproof.  The Ultrasonic is IPX8 to 10m - oh wait that wouldn't be any good for you either!


Oh well back to the drawing board!

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The only way I know is conventional instruments, and a control pot - like a rudder angle sensor, but for the mast. Navico used to do one, but it's no longer available.

I can likely come up with something when I'm back in September if your interested.


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