True Wind on B&G Zeus 3: missing something obvious?

[DougMc]

What are we missing?

Our Zeus 3 (and Triton) displays know about the apparent wind speed and direction from our masthead WS310, and they know about our boat speed and direction from GPS.

It seems we are missing some (probably obvious) setting to tell the display(s) to properly implement the True Wind calculation. They do give a true wind reading, but it is obviously wrong and essentially mimics the apparent wind.

So, we've spend a good long time poking around in Network -> Sources to try to make sure that True Wind has access to the info it needs. The options include the windsensor and the autopilot or "this device". I presumed either the autopilot or "this device" would know about gps derived SOG, but none of the options has given us valid True wind.

I feel there must be some setting we are missing. Any ideas????

Thanks
doug

[Rucksta]

There is a setting for true wind to use SOG.
Under devices?? Might be data sources.
Its a checkbox that defaults to boat speed even without a log detected.

[DougMc]

Thanks, I had already found that setting under Advanced -> Instruments and “use SOG” is checked for both True Wind speed and direction.

Surely it doesn’t have to be done in two places? That would be perverse…

[Rucksta]

Originally Posted by DougMc

Thanks, I had already found that setting under Advanced -> Instruments and “use SOG” is checked for both True Wind speed and direction.

Surely it doesn’t have to be done in two places? That would be perverseB&G…

Pretty sure it's data sources (as well?) but not looking at a Zeus screen atm.

[DougMc]

Originally Posted by Rucksta

Pretty sure it's data sources (as well?) but not looking at a Zeus screen atm.

I did find "boat speed" under data sources to be pointing to the depth transducer... I don't believe this model of depth transducer gives boat speed so I unchecked it. With no other option to check, hopefully it will default to GPS.

It will be another few days until we will be moving again and I can test this. I'll post a followup one way, or another.
thx

[hjohnson]

Ideally, though, you want "true wind" to actually be based on STW, rather than SOG. Sea state, and the forces applied to your boat are all relative to the water, rather than a hypothetical fixed point on the earth.

Picture riding a 4 knot current through First Narrows in Vancouver, BC (not an uncommon tide change), and making 5 knots through the water, so 9 knots SOG. Coming the other way is a 12 knot breeze (as measured by an anemometer on shore).

Your apparent wind is going to be 21 knots, and the sea state (and the forces on your boat) are going to be the same as though you were in a 16 knot breeze, rather than 12 knots.

I know that my Garmin instrument pack (distant descendent of Silva Nexus system) calculates true wind speed using data from the knotlog, and true wind direction based on data from our heading sensor. GPS doesn't really factor into it at all.

[stevead]

It's under Settings->System->Advanced Settings->Instruments.

Here's some piccies.

[noelex 77]

Originally Posted by stevead

It's under Settings->System->Advanced Settings->Instruments.

Here's some piccies.

This is correct, but as Doug does not have a heading sensor he will also need to select both:

"Controls whether SOG is used as Boat Speed when calculating true wind"

And:

“Controls whether COG is used as Heading when calculating true wind”

It should be noted that while called "true wind" by B&G, it is more correctly termed ground wind when the speed reference is SOG.

Even if you have a paddle wheel it is worth trying the switch to ground wind. If you are a typical cruising boat, ground wind results will be more accurate and reproducible than true wind results. If there is any current true wind and ground wind are telling you different things, both are useful, although the information has to accurate to be of any value. On a cruising boat true wind is often not accurate enough to be of much use unless you work hard to keep the hull and paddle wheel clean, mount the paddlewheel in an ideal location and have some sophisticated calibration adjustment.

Ground wind remains very accurate. The SOG information used to derive ground wind does not suffer any calibration errors, and it is not affected by fouling. Nor does it alter from one tack to another or vary with different angles of heel.

[DougMc]

Originally Posted by stevead

It's under Settings->System->Advanced Settings->Instruments.

Here's some piccies.

Yup, thx. Already did that but it still wasn't working. Now remains to be seen if my last change (boat speed sensor) will fix it after we start moving again in a few days.

[DougMc]

Originally Posted by hjohnson

Ideally, though, you want "true wind" to actually be based on STW, rather than SOG. Sea state, and the forces applied to your boat are all relative to the water, rather than a hypothetical fixed point on the earth.

Indeed, but we don't have a STW sensor. The whole kerfuffle is because of some misconfiguration that's preventing even SOG calculation of True wind.

[stevead]

I did find "boat speed" under data sources to be pointing to the depth transducer

Unless your depth sensor is a triducer, this just seems wrong.

Maybe worthwhile to turn everything on and get the Zeus to refresh its sources.
Settings->Network->Sources->Auto Select.

Perhaps the NMEA 2000 network has reconfigured itself and the CAN bus addresses of different devices has changed,

[DougMc]

Following up with a confirmation of the solution.

As suspected, it wasn't enough to tell the Zeus to use "SOG" for True wind speed and direction I also had do deselect the DSTXXX sensor under the Boat Speed source.

(Refresh Sources didn't change anything.)

Thx
Doug

[stevead]

Glad you've got it sorted.

I also had do deselect the DSTXXX sensor under the Boat Speed source.

It seems suspiciously that you do have a Triducer (depth speed & temperature) installed. To the best of my knowledge Airmar transducers use the "DST" prefix to indicate a triducer.

What does the B&G Zeus display in the Device List? If it is indeed a Triducer perhaps the speed sensor is faulty or the paddlewheel fouled?

[Dr. D]

Related, though not totally on topic, is this thread I started:

https://www.cruisersforum.com/forums...ce-277980.html

In my SW version in the Zeus3 and Triton2, I can select to use SOG as STW. However, when calculating true wind direction it appears STW is still used. As my triducer was fouled and giving zero as STW, the calculations of current and TWD were both inaccurate.

[DougMc]

Originally Posted by stevead

Glad you've got it sorted.

It seems suspiciously that you do have a Triducer (depth speed & temperature) installed. To the best of my knowledge Airmar transducers use the "DST" prefix to indicate a triducer.

What does the B&G Zeus display in the Device List? If it is indeed a Triducer perhaps the speed sensor is faulty or the paddlewheel fouled?

We're no longer at the boat, so further investigation will have to wait. The sensor is hard to access internally, but careful snorkeling shows no sign of a paddlewheel, fouled or otherwise...

If I recall correctly, the device list just showed something like DSTXXX.

It is a bit of a puzzle.