Paddlewheel Simulator, Boat Speed vs SOG, Ground Wind, Log

[mattnj]

Always had Raymarine / Airmar paddlewheels which have never worked reliably, unless I clean them each week, which never happens, more often than not I end up with totally nonsense LOG/Speed/App Wind info...

So i've built a standalone GPS > Paddlewheel simulator (its been done before on this site) which interfaces directly to the back of an ST60 (although should work with anything similar?)
It is a small standalone unit that just has the5 wires to connect to back of instrument and away you go, includes its own GPS module for ease of wiring and a resistor for the Temp sensor... accurate SOG sent to device giving you ground wind and the LOG now logs accurate distance over ground.....fit and forget!

I am sure everyone will shoot me down in flames but surely this is better than false paddlewheel info.... I cant get my head around why boat speed with a wheel would be so important over something simple....Is it just because when these were all installed (20+ years ago) GPS wasn't so cheap/easy..... do people use paddlewheel and find it reliable, maybe it's just me!

I know it wont show tide etc, but modern electronics show me that info...anyway, its done and works well. PM if you want one for yourself and I can knock a few up.

 

[RichardS]

Mine is not reliable because I don't have one.

I have a SOG1 which feeds simulated paddlewheel inputs into the ST60 from my GPS so it's always 100% accurate SOG.

You can also buy a SOG2 which includes the GPS receiver as well .... and outputs NMEA GPS data if you want to use that elsewhere.

Of course, it's great in the Med where SOG = STW* but if you're in a tidal area and want STW you will still need a paddlewheel or similar.

CruzPro SOG1 GPS NMEA 0183 to Paddlewheel Speed Pulse Converter.

CruzPro SOG2 GPS NMEA 0183 to Paddlewheel Speed Pulse Converter.

Of course, building your own is another option.

Richard

* Yeah, yeah, yeah ..... we all know.

 

[flaming]

Depends what you're using the info for. If you're using it for navigation, then sure if you know the limitations of SOG vs STW, then it's no great loss. If however you're trying to find performance then SOG is no good at all.

For example we were out this last weekend, for the 1st time since October 2019, and trying to get the boat up to speed. For us in the weekend's conditions that meant trying different setups to get the difference between 6.9kts and 7.3 kts upwind. And then the speedo is the crucial instrument to me (the helm) as we sail upwind. I'm glancing at it probably every 5 seconds or less to see if I'm still at speed or if I need to put the bow down a few degrees and build speed. There's no way you could do that with SOG in a tidal venue. You'd have different targets on each tack, and different targets as you sailed across the course into different tide, and then different targets as the tide built or slackened.

Naturally we remove the paddlewheel at the end of each day's racing and fit it again the following morning. It's just a thing we do.

 

[Refueler]

mmmm interesting concept and kudos for making it.

But I am interested in BOTH SOG and STW .. which then gives me a true indicator of the boats performance .. current etc.

Oh and my paddle wheel ... Echopilot Duo is lazy when first starting out .. but a burst of throttle and it soon wakes up ! Then sail / engine no prob.

 

[mattnj]

I'm glancing at it probably every 5 seconds or less...... There's no way you could do that with SOG in a tidal venue. You'd have different targets on each tack, and different targets as you sailed across the course into different tide, and then different targets as the tide built or slackened.

if racing at that level then that's very different to most people out cruising.....although I am not 100% sure on your reasoning, the GPS SOG would still show the difference between 6.9kts and 7.3kts wouldn't it?? There new modules are super accurate position and 10hz update rate.....

I think a race boat needs both showing and a whole load of other electronics showing race lay lines and all sorts of fancy calculated stuff!
Wasn't really aiming at that part of boating, just lazy cruising (although we all like to sail fast when we can!)

 

[RichardS]

if racing at that level then that's very different to most people out cruising.....although I am not 100% sure on your reasoning, the GPS SOG would still show the difference between 6.9kts and 7.3kts wouldn't it?? There new modules are super accurate position and 10hz update rate.....

See post #2. It's not about GPS accuracy or precision. It's about what you're actually measuring.

Richard

 

[mattnj]

See post #2. It's not about GPS accuracy or precision. It's about what you're actually measuring.

Richard

I understand it's measuring different things...

Obviously both is ideal.....my view point is.....for me....STW is unnecessary agro to maintain a reliable wind reading.

 

[Boathook]

I like both as it does show where the back eddies are and how well my sail trim is working or not as normally the case. Its also been interesting when on holiday comparing the distance traveled through water compared with over land. One holiday the land was nearly 30 miles longer so it meant that I had 'played' the tides correctly.

 

[RichardS]

I understand it's measuring different things...

Obviously both is ideal.....my view point is.....for me....STW is unnecessary agro to maintain a reliable wind reading.

I doubt whether anyone is going to argue with you. On a cruising boat it's apparent wind that really matters and you don't need a paddlewheel for that.

Richard

 

[flaming]

if racing at that level then that's very different to most people out cruising.....although I am not 100% sure on your reasoning, the GPS SOG would still show the difference between 6.9kts and 7.3kts wouldn't it?? There new modules are super accurate position and 10hz update rate.....

Yes. But my target for a given wind speed is 7.3 kts boat speed. How do I know when I first put the sails up what my adjusted GPS target should be? Especially considering that unless my course and the tide line up perfectly I can't just sum them. And of course the target would then be different on each tack... And when I slow down is that because I'm driving badly, or have we just crossed a tide line?
And that's before you start the perennial forum favourite topic of Ground wind vs True wind, and why ground wind does not work for assessing performance relative to targets.

 

[flaming]

I doubt whether anyone is going to argue with you. On a cruising boat it's apparent wind that really matters and you don't need a paddlewheel for that.

Richard

STW is interesting to anyone who is bothered about the performance of their boat, and making it sail well. Plenty of people for whom racing is a total anathema still care about and get satisfaction from making their boat sail well.
If you sail in a tidal location that does mean a paddlewheel. If you're luck enough to keep your boat in the med then GPS would probably be good enough for anything short of high end racing.

 

[mattnj]

STW is interesting to anyone who is bothered about the performance of their boat, and making it sail well.

Er no.... you may be getting a bit too preachy now .....because I am bothered very much so.... Just don't look at the STW "every 5 seconds" but more of a feel the wind on your face approach and trim sails continuously.....on my own often....

Each to their own...

 

[GHA]

So i've built a standalone GPS > Paddlewheel simulator

Link to the design? Can't be that hard with an arduino/esp, I need to do the same at some point to view the nmea output from a hopefully doesn't clog up nasa electromagnetic log on a st60 display .

edit, found some - 22.000 pulses per Nm, what voltage are the pulses going into the display?

 

[mattnj]

Link to the design? Can't be that hard with an arduino/esp, I need to do the same at some point to view the nmea output from a hopefully doesn't clog up nasa electromagnetic log on a st60 display .

edit, found some - 22.000 pulses per Nm, what voltage are the pulses going into the display?

It's actually 19500 per nm on my Raymarine at 1 calibration factor....5v works for signal (original spec is 10v) yeah easy enough in Arduino/ESP

 

[GHA]

It's actually 19500 per nm on my Raymarine at 1 calibration factor....5v works for signal (original spec is 10v) yeah easy enough in Arduino/ESP

Another one to add to the list, ta
Hopefully 3.3v will work, then esp standalone, all the data is on wifi anyway
Can you remember the wiring? Actually a ST40 bidata I have.

edit, think this is it>>

 

[Stemar]

Pretty much everyone who has a log has GPS on board, which gives SOG, but mine can take a second or so to respond. The advantage of a paddlewheel is that it's an instant response to that change in sail trim, not to the change in wind speed that happened a few moments later. In a Snapdragon, I need all the help I can get...

There is, of course, a solution to dodgy paddlewheels, but it's a bit out of my budget.

Airmar UDST800 P617V Ultrasonic Sensor with NMEA2000

• Brand: Airmar
• MPN: 44-218-1-01
• Model: UDST NMEA2000
• Availability: In Stock
• Lead Time: 5-7 days
• £1,165.00

How's about some of you clever electronics guys come up with a home brew that will fit my ineffective NASA log?

 

[GHA]

It's actually 19500 per nm on my Raymarine at 1 calibration factor....5v works for signal (original spec is 10v) yeah easy enough in Arduino/ESP

Up and running, 3.3v 50mS pulse from an esp8266 gives 2.2Kt on the bidata.

Edit - oh no it isn't! Sketch tuns pin on and off each loop, 110mS delay or pulse every 220Ms gives 1Kt on bidata so just over 16,000 pulses per Nm? Just so happened I picked the serial in pin to output so when a new sketch is getting uploaded the boat does about 70Kts

 

[RichardS]

STW is interesting to anyone who is bothered about the performance of their boat, and making it sail well.

I'm more concerned about whether the beers in the fridge are cold enough.

Richard

 

[GHA]

The advantage of a paddlewheel is that it's an instant response to that change in sail trim, not to the change in wind speed that happened a few moments later.

Not with a raymarine st40 bidata, playing around just now there seems to be a fair bit of averaging going on inside the display, takes a good few seconds to settle down with a change in input.

 

[mattnj]

Not with a raymarine st40 bidata, playing around just now there seems to be a fair bit of averaging going on inside the display, takes a good few seconds to settle down with a change in input.

Yes, anyone that thinks a paddlewheel is fast is dreaming, takes over 5 seconds to show correct reading......i was surprised too....Nothing instant about it.....