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Anenometer and knot meter

redlegmsg66

Shawn Simmons
Purchased an 32-2 this Spring.. Anenometer shows wind direction but not speed.
Mast is down and boat is now in storage. How do I test to determine the cause.
I was thinking I would start with a simple continuity check. Really not certain where to go after that.

Additionally the knot meter worked fine until September when accuracy was off by approximately 2.5kts.

Any ideas greatly aplreciated
 

Jerry VB

E32-3 / M-25XP
Purchased an 32-2 this Spring.. Anenometer shows wind direction but not speed.
Mast is down and boat is now in storage. How do I test to determine the cause.
I was thinking I would start with a simple continuity check. Really not certain where to go after that.
Just guessing, but often the spinner has magnets and the pickup is a reed switch that closes when a magnet spins by. If you do a continuity check, it should be "open" (infinite ohms) or "closed" (0-ish ohms) and should switch between open and closed as you (slowly) turn the spinner.
Additionally the knot meter worked fine until September when accuracy was off by approximately 2.5kts.
Likely "slime" growth on the paddlewheel added friction towards the end of the season.

In the Great Lakes, we also have zebra mussels which like to grow in and around the paddle wheel, but that usually stops the paddle wheel completely. Saltwater has even more critters that like to grow on boats.
 
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Christian Williams

E381 - Los Angeles
Senior Moderator
Blogs Author
We used to pull and clean the paddlewheel before each race (one million years ago). One week in salt water still starts marine growth.
 

redlegmsg66

Shawn Simmons
Just guessing, but often the spinner has magnets and the pickup is a reed switch that closes when a magnet spins by. If you do a continuity check, it should be "open" (infinite ohms) or "closed" (0-ish ohms) and should switch between open and closed as you (slowly) turn the spinner.

Likely "slime" growth on the paddlewheel added friction towards the end of the season.

In the Great Lakes, we also have zebra mussels which like to grow in and around the paddle wheel, but that usually stops the paddle wheel completely. Saltwater has even more critters that like to grow on boats.
Thanks. Im in Wisconsin, sail in the Green Bay area.
 

Roger Janeway

Member II
Following Christian's one-week theory, I now pull out my paddlewheel after every sail unless I'm coming back soon. The more often you switch between the paddlewheel and the dummy plug, the more comfortable you become at opening a hole in the bottom of your boat to allow water to rush in. Practice while out of the water!

On the hard, you can still test whether a signal gets from the sending unit to the knotmeter by manually spinning the paddlewheel and having someone tell you what the knotmeter says. But you'll need to wait until you're back in the water to recalibrate it. That depends on what kind of display you have. If it's a newer electronic Signet unit, calibration is pretty easy. But it's still a pain: You have to motor in flat water, either at a constant speed, or better yet for a known distance, and then motor back the exact same distance (to cancel out the effects of current), compare your unit's knot log to the distance you know you traveled, and then make an adjustment. On my hull, I need to set the calibration at about 125%.
 

Jerry VB

E32-3 / M-25XP
Raymarine ST60 diagnostics: https://forum.raymarine.com/showthread.php?tid=97

The diagnostics indicate the ST60 anemometer uses a reed switch and magnets. The diagnostics (above) are with a powered sensor. To do the same test unpowered, use an ohmmeter between the yellow wire (pin 5) and shield (pin 1) and it should read "open" / "shorted" as you rotate the spinner.

The connector pinout and diagnostics can be found on the Cruisers Forum.

For completeness, you should be able to test the windvane sensing unpowered by putting your ohmmeter between pin 1 (shield) and pin 3 (green). When you rotate the windvane, the resistance should rise and fall smoothly. Likewise, test between pin 1 (shield) and pin 4 (blue). Change to pin 2 (red - power) and verify the resistance varies smoothly between pins 2 and 3 and also between pins 2 and 4.

Other masthead transducers are probably similar... likely you can find the pinouts on the internet.
 
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redlegmsg66

Shawn Simmons
Thank you for all the great info. I will be working on my boat this weekend and will let you know the results of my testing.
 

Roger Janeway

Member II
As others have observed elsewhere on this site, there are many good reasons to permanently plug your knotmeter's paddlewheel thru-hull with the dummy plug, and get your speed data from GPS. The only reasons to keep it are sentimentality or if you really want to distinguish your speed through the water from your speed over the ground.
 

redlegmsg66

Shawn Simmons
As others have observed elsewhere on this site, there are many good reasons to permanently plug your knotmeter's paddlewheel thru-hull with the dummy plug, and get your speed data from GPS. The only reasons to keep it are sentimentality or if you really want to distinguish your speed through the water from your speed over the ground.
help me understand speed over ground verse speed through water.
 

Roger Janeway

Member II
If you are sailing into a 1 knot current, and your boat is moving forward at 6 knots through the water, then the old-fashioned paddlewheel-based knotmeter will read "6 KNOTS" (assuming its is calibrated correctly!). But a GPS device will say that you are moving at 5 knots, because the water is sweeping you backwards at the rate of 1 knot.

If the current is coming right on your side, at right angles to you, then it won't make a difference.

Some of us sail in places with tidal currents (or river currents) well over 1 knot, so there can be a significant difference between speed through the water and speed over the ground ("SOG").
 

Loren Beach

O34 - Portland, OR
Senior Moderator
Blogs Author
It might help to remember that the GPS is a device related to land and air pursuits, where a person's ETA is the most important news. (And where average speeds are always in two or three digits.)

A sailor needs a source of true speed thru the water for assessing sail settings and helm effectiveness.
We average around 6 kts and knowing the effect of tide or current flow or effect of wave action that will make a partial knot of difference is quite important.
The knowledge (eta) of when we might arrive somewhere 40 miles away is also important, but is only one part of the navigation puzzle.

I use my chart plotter routinely for knowing location and seeing when I might be at a waypoint or destination, but also rely on our KM for knowing how to adjust for ambient sea state and sail trim.
 

Christian Williams

E381 - Los Angeles
Senior Moderator
Blogs Author
To my mind, the value of a paddlewheel is in observing speed changes. GPS has a lag, which makes it less accurate for, say, gauging pointing tradeoffs or duration of surfing. It's a racing tool and probably more hope than fact (like the use of polars).

In my cruising world, GPS speed is enough.
 

Dave G.

1984 E30+ Ludington, MI
My Raymarine wind instrument (i50) will not provide a true wind reading without the paddlewheel input so I keep it calibrated & clean. My instinct is that GPS SOG would be a more accurate reference for true wind calculation, but everything I read says it needs to be STW though. Also I don't think the i50 will accept a SOG from the GPS so paddlewheel it is.
 

Jerry VB

E32-3 / M-25XP
Raymarine ST60 diagnostics: https://forum.raymarine.com/showthread.php?tid=97

The diagnostics indicate the ST60 anemometer uses a reed switch and magnets. The diagnostics (above) are with a powered sensor. To do the same test unpowered, use an ohmmeter between the yellow wire (pin 5) and shield (pin 1) and it should read "open" / "shorted" as you rotate the spinner.

The connector pinout and diagnostics can be found on the Cruisers Forum.

For completeness, you should be able to test the windvane sensing unpowered by putting your ohmmeter between pin 1 (shield) and pin 3 (green). When you rotate the windvane, the resistance should rise and fall smoothly. Likewise, test between pin 1 (shield) and pin 4 (blue). Change to pin 2 (red - power) and verify the resistance varies smoothly between pins 2 and 3 and also between pins 2 and 4.

Other masthead transducers are probably similar... likely you can find the pinouts on the internet.
Well, I did some ohmmeter testing on my ST60 masthead transducer and it was a total fail. It apparently has active electronics inside and doesn't "work" unless powered. That's too bad, it would have been nice if it could be tested with just an ohmmeter. :-/
 

Jerry VB

E32-3 / M-25XP
Purchased an 32-2 this Spring.. Anenometer shows wind direction but not speed.
So, the good news is that the complicated part (wind direction) works which means there is a good change the simple part (speed) works too.

Since my personal testing indicates the windspeed indication is "signal conditioned" (it probably is a hall effect sensor rather than a simple reed switch) and your testing indicates wind direction works but wind speed doesn't, it is very likely a bad wire or connection between the masthead and the readout.

Since your mast is down, you should have the masthead sensor removed.
  1. Inspect the masthead sensor pins to make sure they are clean and straight. Also inspect the connector sockets on the masthead as best you can.
  2. With the masthead sensor off, it gives you access to the connector pins which allows you to test continuity from the masthead pins to the (screw terminal?) connector at the base of the mast. If you connect a pin at the masthead connector to the mast you should be able to measure the resistance of the wire in the mast from connector end to connector end. It should be a low resistance value and all five wires should be similar.
    (A helper with a "pigsticker" to gently stick into a connector socket and a wire with alligator clips to connect the "pigsticker" to the mast is helpful here. Alternatively, you can use e.g. pin 1 as you common, then short pin 1 to pin 2..5 at the masthead and measure on the mast base end from the black (or screen) wire to the appropriate other wire. Again, a helper, two pigstickers, and a jumper wire is helpful.)
  3. If the wiring in the mast is OK, check the wiring from the screw terminal to the cockpit instrument readout. For this, I would use the black (or screen) wire as the "common," short it to the successive screw terminals, and use the ohmmeter on the cockpit instrument wiring to verify continuity.
Best case, some place in step two or three you will probably find a bad connection or broken wire.
 

Christian Williams

E381 - Los Angeles
Senior Moderator
Blogs Author
For the record, I am having success with the Raymarine (Tack-tic) wireless anemometer after five years and 10,000 nm.

The masthead unit communicates wireless to the readout in the cockpit, powered by its small solar panel. So, no wires. Also, the readout can be moved around as needed, to provide a view from the helm or from the companionway.

Apparently the device can control an autopilot using Raymarine Micro-talk.
 

Kenneth K

Contributing Partner
Blogs Author
help me understand speed over ground verse speed through water.

If the current is coming right on your side, at right angles to you, then it won't make a difference.

Somewhat true, but sailing/motoring 5 kts due west in a 5kt southerly current (say, at Tacoma Narrows) should give you a 5 K speed-thru-water (westerly vector) and a 7 K SOG (south-westerly vector).

If you are aiming directly to a westerly point, you are drifting south of your point at the same rate you are moving towards it, so you are not making 5K of progress towards your point. I believe this would be reflected in a VMG (velocity made good, towards the point) of about 3.5 K once you turn the boat further north to correct for the southerly drift.
 
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Kenneth K

Contributing Partner
Blogs Author
Actually, I think my math is still off. If you can only make 5K (say motoring), the best you can do in a 5K current is motor at 0K SOG straight into the current and stand still. As soon as you bear off to the west, you will drift south in the current and can never make it to your "due west" point, only to the south of it.

Or, so says the guy who sailed all last season with no speed log, chart plotter, or gps.
 
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