Paddle wheel speed sensor, who needs ‘em!

[Lionshooter]

Interesting post. Some use them; others don't. Personally, every boat I have owned over the past 44 years has had only a compass and depth gauge. Never felt the need to know how fast I was going because I knew what the boat was capable of in every situation.
And if you have the proper screw in dummy plug for your make and model, you don't need to pull the boat to change it out. You'll get a bit of water in the bilge and if you aren't quick enough, you may get a shower to boot.

[EmeraldCoastSailor]

I got tired of cleaning mine so I left plug in about 7 years ago and haven’t regretted it. I am forced to estimate current effects which hasn’t killed me yet.

[noelex 77]

Originally Posted by Galumay

i believe Speed thru Water is required for set & drift calculations in order to correctly compute TWA & TWS.

https://www.bwsailing.com/cc/2017/05...hy-it-matters/

True, but ground wind angle and ground wind speed can be calculated and this is arguably more use to cruising sailors, especially considering it is always accurate even if the paddle wheel is slightly fouled, mis aligned or mis calibrated.

Ground wind is best thought of as “the real true wind” as it is the wind that would be experienced when completely stationary.

[PineyWoodsPete]

Originally Posted by goboatingnow

True wind is best calculated using STW rather then SOG but only to dial out currents , tidal streams etc and essentially provide you with comparable numbers on both tacks

On the open sea the difference is negligible and SOG will essentially be identical to STW.

Maybe I'm not understanding you correctly, but the true wind speed and vector can only be computed with your SOG and COG. Even with no current, there will almost always be COG offset from compass heading - at least in a sailboat...

[goboatingnow]

Originally Posted by PineyWoodsPete

Maybe I'm not understanding you correctly, but the true wind speed and vector can only be computed with your SOG and COG. Even with no current, there will almost always be COG offset from compass heading - at least in a sailboat...

True wind as opposed to “ ground wind “ is the wind you experience if stopped on the water , hence it needs STW and not SOG, true wind is a sailing term and is defined relative to water not the ground.

[Smokeys Kitchen]

Originally Posted by mlydon

A lot of chart plotters refuse to tell you apparent wind info unless you have boat speed info from a paddle wheel.

Always seemed crazy to me - I would think the info would be more accurate with gps sog.....

Matt

This happens to us as well. What also occurs is that our older stand alone auto pilot will not work unless it is receiving speed through the water data. Consequently we pull the wheel and clean it prior to any significant trips

[hjohnson]

Originally Posted by noelex 77

True, but ground wind angle and ground wind speed can be calculated and this is arguably more use to cruising sailors, especially considering it is always accurate even if the paddle wheel is slightly fouled, mis aligned or mis calibrated.

Ground wind is best thought of as “the real true wind” as it is the wind that would be experienced when completely stationary.

Well, except that the forces on the boat (and on the water) aren't related to ground wind, they're related to wind in relation to the water.


The example I always use is First Narrows in Vancouver, BC. During a decent Ebb tide, you can easily have 3 knots+ of current under the Lions Gate. At the same time, if you have a 12 knot westerly, what are the forces acting on your boat? It's much more like being in 15 knots, which makes for a washing machine experience in the shallows there. Conversely, if you have a 12 knot easterly, while on a 3 knot ebb, it's a pleasant sleigh-ride.



But in effect, the speed of the wind w.r.t. the shore is irrelevant. The only thing that matters is the speed of the wind w.r.t. the water.

[roverhi]

I much prefer knowing speed through the water than over the ground. Necessary for evaluating how well you are sailing the boat. Find GPS speed a bit frustrating because it has such a lag. Way more interesting to watch the log zip up to 9K or more surfing in the trades than having your eyes glued to a plotter averaging out your boat speed.

As far as the paddle wheel, it's never been an issue because I pull it as soon as the anchor is down or the dock lines secured. Have sailed many many thousands of ocean miles and have never had a problem with the paddle wheel failing. Have had my GPS and almost all other electronics mess up but the paddle wheel log has been as reliable as the Walker Log.

[PineyWoodsPete]

Originally Posted by goboatingnow

True wind as opposed to “ ground wind “ is the wind you experience if stopped on the water , hence it needs STW and not SOG, true wind is a sailing term and is defined relative to water not the ground.

I've been a sailor for over 60 years, and never heard "True wind" speed and vector being defined as RELATIVE to water. "True wind" - sailing or otherwise can only be defined as relative to the immovable earth SOG/COG. Period.

[noelex 77]

Originally Posted by hjohnson

But in effect, the speed of the wind w.r.t. the shore is irrelevant. The only thing that matters is the speed of the wind w.r.t. the water.

To gain a complete picture of the wind then apparent wind, ground wind and true wind are all relevant. To contend that ground wind is irrelevant is wrong.

For example, if you want to compare the wind the boat is experiencing to the forecast wind or you want to determine the wind that will be felt at anchor, or when you round the headland and current drops out, ground wind rather than true wind will give the accurate information.

The combination of apparent wind and ground wind is particularly powerful. Apparent wind tells the skipper the wind force experienced on the boat and sails, while ground wind shows what the wind is actually doing and if the wind speed is increasing or decreasing and how it compares to the forecast.

For a cruising sailor the big advantage of ground wind is that the information is calculated independently of the paddle wheel, thus errors in the paddle wheel (and these are very common on a cruising boat) will have no effect on ground wind. Information has to accurate to be useful.

Give the ground wind a try, you will be amazed how accurate and stable the information about what is actually happening to wind becomes. If nothing else, if your paddle wheel becomes clogged with weed half way through a trip, you will know how to switch the instrument over so more than just apparent wind information available.

[noelex 77]

Originally Posted by roverhi

Find GPS speed a bit frustrating because it has such a lag. Way more interesting to watch the log zip up to 9K or more surfing in the trades than having your eyes glued to a plotter averaging out your boat speed.

Try reducing the dampening on the SOG display. Modern differentially corrected GPS units, especially the more sophisticated units such as those fitted to GPS compasses, have very rapid updates (up to 10hz) and don’t need the high dampening essential in older units.

[noelex 77]

Originally Posted by PineyWoodsPete

I've been a sailor for over 60 years, and never heard "True wind" speed and vector being defined as RELATIVE to water. "True wind" - sailing or otherwise can only be defined as relative to the immovable earth SOG/COG. Period.

“True wind” is calculated relative to the water.

You are not alone in misunderstanding what the “true wind” display is showing. “True wind” is a rather misleading term. It came about as before GPS there was no possibly of calculating the actual actual true wind on a boat.

“True wind” should have more accurately have been called “water wind”, but we are stuck with terminology. True wind does not eliminate movement of the water. Even if the instruments are 100% accurate it will not display the wind that would be experienced at anchor or the wind that is forecast, or measured by a station on the ground.

[Cheechako]

I didn't actually remove them on a couple of boats but just ignored them and used the GPS speed. Good enough for me. Regardless of any currents, you still know what your course is and make adjustments accordingly. No need to overanalyze it. By the time you've worked out predictions, it's changed!

[sail sfbay]

Originally Posted by JC Reefer

..............Has anyone outright removed the darn thing and regretted it? I’m considering giving it a permanent plug the next time I pull the boat out of the water. Is there any system that depends on that sensor?

I removed my Airmar paddlewheel speed/temperature transducer and replaced it with the supplied plug with the boat in the water. NO REGRETS. I monitor speed over ground on my speed indicator and navigations displays.

[wingssail]

Originally Posted by noelex 77

“True wind” is calculated relative to the water.

You are not alone in misunderstanding what the “true wind” display is showing. “True wind” is a rather misleading term. It came about as before GPS there was no possibly of calculating the actual actual true wind on a boat.

“True wind” should have more accurately have been called “water wind”, but we are stuck with terminology. True wind does not eliminate movement of the water. Even if the instruments are 100% accurate it will not display the wind that would be experienced at anchor or the wind that is forecast, or measured by a station on the ground.

We use the knotmeter (paddle wheel) and we remove it whenever the boat will be stationary for more than a couple of days. When out, we clean it with a soft brush if needed. Frequently we check the hull in the vicinity of the paddle wheel to remove weed which can affect the knotmeter.

While sailing in areas of no known tide or current we check the Boat Speed compared to the SOG and adjust the calibration.

We go to this trouble because our focus has always been on how the boat and ourselves as sailors are performing. We use the knotmeter to allow very accurate calculations of the boat's performance. Our B&G Hercules system relies on Boat Speed from the transducer, (not SOG, although that option is available) to give the best possible evaluation of how well we are sailing.

For example: Our target boat speed upwind in 10 knots of wind is 6.68 knots. If we are using SOG and see that our speed is 5.7 does that mean that we are sailing poorly or is there a current against us?

For navigation purposes, of course, we use SOG and COG to determine arrival times and best course to be sailed.

We refer to the wind relative to the water as TWS not out of misunderstanding because that is the "true" wind that the vessel is actually experiencing and it makes more sense of the boat speed to us than use of SOG.

Sailor with less concern about their sailing performance would understandably be less interested in BSP than SOG.