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Discussion Starter #1 (Edited)
Just returned to my boat after a two week hiatus. My new this season Garmin GMI 20 for some reason was displaying the same reading for both True and Apparent wind. My sense is that it was displaying only apparent wind. This was the case for both wind speed and direction. No previous issues

Tried calling Garmin when I got back to the mooring but they seemed to be having some major systems issues and were not answering any phone calls. Back home did some research and it seems that the wind vane used with the GMI 20 sends only apparent wind info. It then uses info from the GPS / Chartplotter (or a heading sensor) to calculate true wind. The manual for the GMI 20 indicates that there is a system setting for “Heading: sets the reference used in calculating heading information” Won’t be able to see if changing this setting corrects my issue until tomorrow.

Anyone familiar with the GMI 20 think I’m on the right track? Don’t know why this would all of a sudden become and issue or how a setting could change in its own. As these marine electronics become more complex it becomes more of a PITA to diagnose issues and even just figuring out how to configure the settings is a pain.
 

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I don't think this is a Garmin-specific question or issue. No pure wind transducer can send anything except apparent wind data. There are some that incorporate a compass and/or GPS that can do internal calculations, but these are not very common.

True wind needs a heading input, either from a compass or a GPS, and is a calculated value that must be performed by something. The instrument performing the calculation must then put the data on the network.

I don't know much about the GMI 20, but assuming it is the instrument assigned to do the true wind calculations, then the likely issue is 1) a heading source is missing; 2) the heading source has not been assigned, or was forgotten, in the setup menu; 3) the GMI 20 has not been assigned the responsibility to calculate true wind and is looking for the data on the network from another instrument.

You might want to look in the settings and make sure that the GMI 20 has the heading source selected, and is selected to provide the true wind calculations (the source selection is universal to all instruments, but the calculation assignment may not be a specified option for the Garmin - it is for the instruments we have, but I've no experience with the GMI20).

Mark
 

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Is both speed thru water and speed over ground displaying properly? The system needs one or both. If my thru water speed wheel transducer get fouled, same outcome. The brains think the boat isn’t moving, so true would equal apparent.
 

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Discussion Starter #4
Is both speed thru water and speed over ground displaying properly? The system needs one or both. If my thru water speed wheel transducer get fouled, same outcome. The brains think the boat isn’t moving, so true would equal apparent.
Speed is being displayed. Didn’t notice if speed over ground is. Sounds like you both are pointing me in the same direction.
 

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Discussion Starter #5
I don't think this is a Garmin-specific question or issue. No pure wind transducer can send anything except apparent wind data. There are some that incorporate a compass and/or GPS that can do internal calculations, but these are not very common.

True wind needs a heading input, either from a compass or a GPS, and is a calculated value that must be performed by something. The instrument performing the calculation must then put the data on the network.

I don't know much about the GMI 20, but assuming it is the instrument assigned to do the true wind calculations, then the likely issue is 1) a heading source is missing; 2) the heading source has not been assigned, or was forgotten, in the setup menu; 3) the GMI 20 has not been assigned the responsibility to calculate true wind and is looking for the data on the network from another instrument.

You might want to look in the settings and make sure that the GMI 20 has the heading source selected, and is selected to provide the true wind calculations (the source selection is universal to all instruments, but the calculation assignment may not be a specified option for the Garmin - it is for the instruments we have, but I've no experience with the GMI20).

Mark
Mark, thanks it looks like you both have the same idea. My first thought was that an osprey was sitting on the vain and messed something up. Encouraged that it probably is a software setting.

Just as an aside, do you know how pre GPS era wind instruments (Like my old circa 1987 Datamarine ) displayed true wind speed?
 

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True wind is typically calculated using the apparent wind at the masthead and speed thru the water as measured by the sensor for the knotmeter. If apparent wind reads the same as true wind, most of the time it means that the sensor for the knotmeter isn't working or the connection between the wind instrument and knotmeter has become disconnected. If it is the knotmeter sensor, you would not be showing speed through the water, only SOG. If you have a setting that shows a magnetic wind direction, then it is taking data from the fluxgate compass sensor for the autopilot.

But it doesn't sound like you are asking about that.

Jeff
 

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Oops, the others are correct - you need a speed measurement for TWA/TWS. I was thinking of TWD needing a compass/gps.

The troubleshooting is the same. Make sure a speed transducer is selected, make sure it is working, and make sure the instrument is told to calculate true wind.

Mark
 

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Discussion Starter #8
Update: Got to the heading settings on the wind instrument menu. Only settings were true, auto magnetic and manual magnetic. Frustrating that the online manual doesn’t describe what the choices are.

Next looked for settings on the chartplotter. Again cryptic instructions on how to get to the menus. (Rather than touching the “menu“ tab, the wind or compass rose must be touched and held) Ultimately found setting to select heading source. Selected GPS. Not confident that that this will fix the issue. Boat was on a mooring while trying to find settings so without moving GPS heading will not be accurate however true and apparent still seem to be locked on the wind rose and any readings.

Also updated all the software for the devices / network. No effect.

Going through the manual found vessel type must be selected. Next step is to check if sail vs power selected correctly.

Most Garmin systems still down this morning. Must be a major issue.
 

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Update: Got to the heading settings on the wind instrument menu. Only settings were true, auto magnetic and manual magnetic. Frustrating that the online manual doesn’t describe what the choices are.

Next looked for settings on the chartplotter. Again cryptic instructions on how to get to the menus. (Rather than touching the “menu“ tab, the wind or compass rose must be touched and held) Ultimately found setting to select heading source. Selected GPS. Not confident that that this will fix the issue. Boat was on a mooring while trying to find settings so without moving GPS heading will not be accurate however true and apparent still seem to be locked on the wind rose and any readings.

Also updated all the software for the devices / network. No effect.

Going through the manual found vessel type must be selected. Next step is to check if sail vs power selected correctly.

Most Garmin systems still down this morning. Must be a major issue.
The heading settings and the GPS have nothing to do with true wind vs apparent wind. Those are generated from your masthead sensor and the knotmeter. You need to see whether the knotmeter is reading because more likely than not the paddle wheel is fouled.

Jeff
 

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Discussion Starter #11 (Edited)
The heading settings and the GPS have nothing to do with true wind vs apparent wind. Those are generated from your masthead sensor and the knotmeter. You need to see whether the knotmeter is reading because more likely than not the paddle wheel is fouled.

Jeff
Thanks but Garmin's website indicates that it’s wind vane only provides apparent data to the network. Heading information (Either from the GPS or a heading sensor) is then used by the network to compute true wind speed and angle.

I have two knot meters one is electronic and provides the data to the Garmin network. It’s actually a triducer providing speed, depth and water temperature. The second is a paddle wheel type independent of the net work. The speed reading from both are consistent. So I’m getting good speed info. For some reason the Garmin network isn’t using it to compute true wind speed.
 

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So if your system is getting speed thru the water from the sensor for the knotmeter and apparent wind from the masthead, then you should be able to get true wind relative to the centerline of boat. In order to tie true wind to a compass course the system would normally use the fluxgate compass for the magnetic reading.

While GPS generated speed over ground and course over ground can be used instead of the knotmeter sensor and fluxgate compass sensor, if in a current, the results would be less useful than the knotmeter and fluxgate generated true wind.

Jeff
 

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Discussion Starter #13
Garmin has been hacked for ransomware, and they no longer have control of their systems: Will Garmin Pay $10m Ransom To End Two-Day Outage?

Did you make sure a speed source was selected? Check the knotmeter to make sure it is working?

Mark
Sounds like Garmin May be down for a while. Guess I’m on my own for now. As I mentioned to Jeff H both knot meters are working and are consistent.
 

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Discussion Starter #14 (Edited)
So if your system is getting speed thru the water from the sensor for the knotmeter and apparent wind from the masthead, then you should be able to get true wind relative to the centerline of boat. In order to tie true wind to a compass course the system would normally use the fluxgate compass for the magnetic reading.

While GPS generated speed over ground and course over ground can be used instead of the knotmeter sensor and fluxgate compass sensor, if in a current, the results would be less useful than the knotmeter and fluxgate generated true wind.

Jeff
All the sensors and transducers seem to be sending good information so I’m thinking the issue might be with the settings on the GPS/chartplotter. Just saw that there is a setting on the chartplotter to designate the type of vessel. Possibly it was changed from sail to power? Don’t know how that could change unless I did it inadvertently.

Update: Checked the type of vessel selected and it was “sailboat“ not “power boat” so that is not the issue.

Garmin seems to be coming back online partially. A system reset might be the next step but I’d like to talk with support before I do that.
 

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Discussion Starter #15
I have to apologize to all of you who tried to help me solve my problem for sending you on a wild goose chase. Yesterday I discovered that the triducer (Water speed, water temp and depth) sold by Garmin actually does use a paddle wheel for water speed. I incorrectly thought that it somehow measured water speed without the use of a paddle wheel.

My only defense is that the pictures of the tri-ducer on the Garmin website made it appear that the bottom was flat and smooth. It wasn’t until I went to the website of Airmar, the manufacturer of the tri-ducer and saw some clear pictures of it showing that it does in deed use a paddle wheel. Sorry for being a knuckle head.

Now I can dive the bottom and see if something has fouled the wheel. Still haven’t found a setting to to see if there is a way to get the chartplotter or wind instrument to use GPS speed to calculate true wind speed. Garmin support lines are back open (maybe with long wait times) so I should be able to give them a call for some help.

Apologies again.
 

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Often (not always), the speed wheel can be removed, from inside the boat, for cleaning. It would have a screw down collar over it. You’d need a purpose made replacement plug, which often looks the same as the top of the transducer. The first time you do it will get your attention, as you just caused a huge water leak. There should be a flap that slows it down, but still.

tip..... apply silicon grease to each parts o-rings, while you’re at it. They‘ll seal better and last longer.
 

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Discussion Starter #17
Often (not always), the speed wheel can be removed, from inside the boat, for cleaning. It would have a screw down collar over it. You’d need a purpose made replacement plug, which often looks the same as the top of the transducer. The first time you do it will get your attention, as you just caused a huge water leak. There should be a flap that slows it down, but still.

tip..... apply silicon grease to each parts o-rings, while you’re at it. They‘ll seal better and last longer.
Thanks. Just read up on pulling the transducer. The tube does have a flap to slow the water inflow and I have the replacement plug. Need to get some silicone grease and will give it a shot. The installation manual recommends using the plug if you are away from the boat for more than a week in salt water which I am.
 

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Discussion Starter #18
Pulled the transducer last week. Not sure if the flap in the tube worked as more water than expected came in before I got temp plug in. The paddle wheel wasn’t very fouled, nothing hard, just some stringy slime. Was somewhat surprised that so little growth could foul the wheel. After getting the transducer back in true wind reading worked fine.

While talking with Garmin, I was told that only water speed can be used for computing true wind speed. GPS speed can not be selected. It would seem that even if GPS speed was not as accurate as water speed it would be nice to have the option to select GPS speed in a pinch. I’m not typically in areas with large currents, mostly open bays and ocean. The water speed and GPS speed is usually within a half knot or so.
 

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Pulled the transducer last week. Not sure if the flap in the tube worked as more water than expected came in before I got temp plug in.
The flap is probably a bit fouled as well, although, the first few times anyone does this, it gets their attention. No boater can psychologically allow water inside the boat!

The paddle wheel wasn’t very fouled, nothing hard, just some stringy slime.....
I believe these work magnetically. In some form it opens and closes a very low voltage circuit, as the wheel spins past. It does not take much to disturb the reception. If you clean it off and dry it well, some transducer paint a couple of times per year might help.
 
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