Wind Without Movement

Sailing instruments and WSO100 report.

Thought is the wind, knowledge the sail, and mankind the vessel.

August Hare

Ok, I lied; said I wouldn’t write for a while. Sorry. This post I had started and had left simmering in that draft folder since we were last moored here in the Merrimack back in September (2019). A couple sailor friends had asked about how we liked (or disliked) some of our new gadgets. So, this is our response. Better late than never, but still fresh!

You guessed it: another pseudo- technical post about doo-dads we’ve added to Fayaway. We keep occupied by making “home improvements”, and we hope perhaps readers will also find some of these interesting, as these instrument installs are instrumental to our journey as well. Take how we read the weather…

About to get hit with lightning!?

Land dwellers take for-granted daily weather reports readily available from various internet and cable media sources. So easy to pull out a smartphone and check the internet, television or maybe on your car radio and listen to the weather person interpret your weather forecast. You take this for granted. This information is held in the back of your mind, perhaps useful for later selecting clothing, or possibly weekend activities.

For Fayaway, weather has an immediate, direct and possibly critical impact to our life aboard, as well as to all travel decisions. For example, yesterday the wind was a steady 20-25 knots, with gusts to 30 knots. So, we decided to stay aboard, keep hatches closed and not dinghy over to the nearest dock. Why get salty and wet as we bounce into oncoming waves? No attached garage with a warm dry car to climb in and out of!

We use alternative means for determining weather. Let’s start with a few of the radio receivers aboard with which we use to gather weather details.

  • Maretron WSO100 is a solid state wind speed/direction, temperature, humidity and barometric pressure transmitter, sitting mast-top. It feeds the weather information into a special network of devices using the NMEA2000 protocol.
  • iCom M506 VHF radio. Nothing special here as all VHF radios have weather bands. We listen frequently to NOAA regional weather forecast broadcasts.
  • Iridium Go! Satellite receiver, connected to an external antenna. Far out into the blue, Predictwind sends GRIB files via this system. We also receive email weather reports through this ingenious little system.

When we’re preparing for a passage offshore or simply going up the coast, we use all this technology for identifying approaching weather. Of course if in range, we’ll use the ol’ smartphone and iPad too!

But what’s the big deal about the WSO100? For starters, it has no moving parts to wear out, bend or break, such as wind cups, bearings, rods, etc. Birds can’t break the wind vane by sitting on it, because there isn’t one. The WSO is completely bird-proof! Regular wind indicators use a mechanical, spinning set of cups, as well as a vane, both with electronic transducers.

Birds love to roost on lightweight sailboat instruments. Note the bent-over wind cups on the wind sensor!

WSO speed and direction is measured by ultrasonic vibrations. It measures how long sound takes to travel between three points. Sound will travel faster in the direction of the wind, and at a rate proportional to its speed and direction. Sensors are arranged specifically with respect to which way the boat points (see graphic below). A little onboard computer makes calculations for the velocity difference between each point very quickly and transmits the result to onboard displays at the helm and navigation station. All this magic happens using very little electricity.

Borrowed from internet, possibly originating from Practical Sailor Magazine.

A stubborn lot we are, even though monetary cost is now comparable, most boat owners still use the old-fashion mechanical indicators. But consider that all NOAA and virtually all professional and otherwise scientific weather stations have switched to this method. While not typically an issue aboard, these sensors are also resistant to freezing ice. Try sleet and freezing rain with your little wind cups!

Apparent wind data is transmitted to several displays around Fayaway. This one is at companionway.

So now that we’ve had this new fangled gadget aboard for two years, and in continuous use now for almost a year, what’s been our experience? I had researched and found quite a bit of Internet chatter regarding this particular brand (Maretron), as well as that for other manufacturers (eg Airmar). As usual, you need to filter out senseless and unfounded detail, but opinions do sometimes open up concerns for further research. I recall some self-proclaimed “expert” sailor/racers claiming slower response times, which could presumably affect their tacking or sail trim decision timing. Come on! It doesn’t take me being an engineer to understand this excuse is ridiculous and easily debunked. Ironically, while still insignificant, traditional cup-style sensors actually do have incrementally slower response, as it takes additional time for the swinging mass to change velocity. Otherwise it’s just something new that stubborn traditional sailors are slow to accept.

Ultrasonic wind sensor install on Fayaway’s mast. No moving parts here!

Our experience? Nobody can discern any difference when looking at the displays. Speed and direction still look the same, no matter what device is feeding the data. We have noticed some weird behavior in very heavy rain, such as sailing through a squall, which doesn’t last very long. But twice we’ve had to reboot (cycle power) to the unit when it’s obviously erratic readings make no sense. By obvious, I mean the wind is obviously not blowing 35 knots. Taking about 15 seconds, cycling the power seems to shake out its confusion and return all indications to normal.

Thanks for reading, and… No matter which way the wind blows around you, do make a wonderful day. Do take the opportunity to hug your kids, whenever you have it!

2 thoughts on “Wind Without Movement

  1. INVIA (captain)

    Interesting read! Especially after I have installed my 3rd traditional cup-style sensors in 3 years as it continuesly has started to fail. Had been sailing in 800kn of wind and more according to my 1st sensor….

    Liked by 1 person

    1. Thanks for your comments. I have (since writing this post) learned that Maretron lost the contract and no longer offers the WSO. However, Airmar offers a comparable wind unit. Airmar also has recently come out with an ultrasonic water speed sensor! Very cool!

      Liked by 1 person

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