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Old 19-07-2015, 17:53   #31
Jd1
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Re: Paddle wheel speed transducer is driving me nuts

Thanks for all the input. I am too lazy to pull the paddle wheel transducer every time I come back from sailing plus it isn't that accurate to begin with. Currently for example it reports less than 4 knots when in fact I am going around 5.5 knots and it's only been about a month since I last cleaned the paddle wheel.
I am still looking for input from anybody that has installed an Airmar CS4500 ultrasonic transducer to find out how accurate it is and how long cleaning interval is. The transducer is about $700 US or so and it would be well worth it to me if it meant accurate speed through the water and only once or twice yearly cleaning.
My boat has to come out for an antifoul job and this would be an ideal time to swap sensors in case the tube thru the hill is different from the current paddle wheel tube.
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Old 19-07-2015, 21:14   #32
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Re: Paddle wheel speed transducer is driving me nuts

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Originally Posted by Jd1 View Post
I am still looking for input from anybody that has installed an Airmar CS4500 ultrasonic transducer to find out... how long cleaning interval is.
Well, you need to talk to somebody who uses one in your neck of the woods. Anybody from elsewhere can only tell you how long between cleanings where their boat lives, and that is pretty useless to you.
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Old 19-07-2015, 21:25   #33
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Re: Paddle wheel speed transducer is driving me nuts

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Originally Posted by fstbttms View Post
Well, you need to talk to somebody who uses one in your neck of the woods. Anybody from elsewhere can only tell you how long between cleanings where their boat lives, and that is pretty useless to you.
While you are of course correct, the vast majority of transducers are of the paddle wheel variety so finding someone that uses an ultrasonic transducer is pretty tough to begin with, never mind someone that sails in the PNW.
I was hooping for a relative benchmark as in "I needed to clean my paddle wheel every two weeks and now I can go 6 months before I need to clean"
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Old 20-07-2015, 08:56   #34
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Re: Paddle wheel speed transducer is driving me nuts

I came up with some old postings from 2013 where Dockhead was contemplating upgrading to an ultrasonic transducer. I sent him a pm to get more info and he asked that I post the questions here ....

Way back in 2013 you were considering installing an ultrasonic speed through the water transducer. Did you ever proceed with that? DId you go with the Airmar unit? What is the result, do you like the switch? Would you do it again ? What is your feeling on accuracy and what kind of cleaning interval do you find is required?
Did the unit fit into the same mounting tube as your previous paddlewheel sensor or did you end up installing the tube that came with the new transducer ?
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Old 20-07-2015, 13:30   #35
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Re: Paddle wheel speed transducer is driving me nuts

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+1, yachts are complex enough without adding more troublesome underwater parts.. I can normally get a good enough feel for boatspeed by eye, and current from the shape of the waves.

Sent from my HTC_0PCV2 using Cruisers Sailing Forum mobile app
For cruisers, this is the answer. If you pay attention, you have a pretty good idea of the speed and direction of the current without the need for a seperate device.

I suspect most racers don't even get that much value out of a paddlewheel but thier racer friends would make fun of them if they didn't have one.
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Old 20-07-2015, 13:40   #36
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Re: Paddle wheel speed transducer is driving me nuts

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Originally Posted by Jd1 View Post
Thanks for all the input. I am too lazy to pull the paddle wheel transducer every time I come back from sailing plus it isn't that accurate to begin with. Currently for example it reports less than 4 knots when in fact I am going around 5.5 knots and it's only been about a month since I last cleaned the paddle wheel.
I am still looking for input from anybody that has installed an Airmar CS4500 ultrasonic transducer to find out how accurate it is and how long cleaning interval is. The transducer is about $700 US or so and it would be well worth it to me if it meant accurate speed through the water and only once or twice yearly cleaning.
My boat has to come out for an antifoul job and this would be an ideal time to swap sensors in case the tube thru the hill is different from the current paddle wheel tube.
Do you understand that paddle wheel units can be calibrated ?
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Old 20-07-2015, 13:54   #37
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Re: Paddle wheel speed transducer is driving me nuts

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Do you understand that paddle wheel units can be calibrated ?
Sure you can calibrate them .... and they might be reasonably accurate for a few days after the calibration too Beyond a few days, all bets are off.
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Old 20-07-2015, 14:00   #38
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Re: Paddle wheel speed transducer is driving me nuts

Oh the cynicism !
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Old 22-07-2015, 00:56   #39
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Re: Paddle wheel speed transducer is driving me nuts

I ran across an interesting tidbit of information in the installation manual of an Airmar paddle wheel transducer :

The water lubricated paddlewheel bearings have a life of up to 5 years on low-speed boats [less than 10kn (11MPH)] and 1 year on high-speed vessels. Paddlewheels can fracture and shafts can bend due to impact with water borne objects and mishandling in boat yards.

A new paddlewheel might make more sense as a first step since the existing unit is well past it's 'best before' date. Who knows, maybe that's the problem I am seeing ....

I would still like feedback on the CS4500 from anyone with first hand experience.
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Old 27-07-2015, 16:23   #40
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Re: Paddle wheel speed transducer is driving me nuts

Sorry, I didn't see this thread earlier.

I too wanted more accurate and lower maintenance speed through water data, and purchased (at considerable expense) and installed the Airmar CS4500.

It's not native N2K or even 0183, so you have to buy a pulse converter box (Actisense is the one I used) which gives you 0183, and feed that into the 0183 listener of your plotter.

It seems to work pretty well most of the time, but is inexplicably wrong some times. It's not a magic bullet and probably not worth the expense compared to a paddlewheel transducer. Hopefully Airmar is still working on this technology and will come up with an improved version. Really accurate STW would be a boon for true wind and other calculations.

By the way, if these transducers would also do DIRECTION, it would be fantastic -- you could then accurately determine leeway. Heading vs COG doesn't give you leeway, because the water may be moving.
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Old 27-07-2015, 16:31   #41
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Re: Paddle wheel speed transducer is driving me nuts

Quote:
Originally Posted by Jd1 View Post
I came up with some old postings from 2013 where Dockhead was contemplating upgrading to an ultrasonic transducer. I sent him a pm to get more info and he asked that I post the questions here ....

Way back in 2013 you were considering installing an ultrasonic speed through the water transducer. Did you ever proceed with that? DId you go with the Airmar unit? What is the result, do you like the switch? Would you do it again ? What is your feeling on accuracy and what kind of cleaning interval do you find is required?
Did the unit fit into the same mounting tube as your previous paddlewheel sensor or did you end up installing the tube that came with the new transducer ?
To answer the other questions:

1. I don't clean it between haulouts (every 2 to 4 months in salt water). This is undoubtedly a big advantage of it compared to paddlewheels.

2. It fit into the tube for the previous paddlewheel sensor (also Airmar, like most of them).
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Old 27-07-2015, 17:43   #42
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Re: Paddle wheel speed transducer is driving me nuts

Thanks for your input Dockhead !
Too bad it turns out that it isn't the magic bullet I was hoping for. For the cost of that transducer I would expect perfect operation.
You haul every 2 - 4 months ???? Wow !!! Around here a haulout and pressure washing sets you back close to $600 (for a 36 ft boat) each time.

I have a bit more information for those that are following this thread.
About a month and a bit ago I decided that my (boat) bottom needed a good cleaning. As it turned out, a quick going over with a sponge did no good and I had to attack things with more vigor. I used a scrub brush over three dives to remove all crud but also noticed that the scrub brush didn't seem to do the ablative bottom paint (which was already very tired and I was hoping for it to hold up until winter) any good. I was suitably impressed with the speed the boat had picked up! Fast forward 4 weeks and you could pretty much see 'stuff' growing on a daily basis. The hull looked worse than before scrubbing and speed was way down again. Add to that the inexplicable poor paddlewheel performance and I was all set to replace the speed sensor on the upcoming haul.
I had one last trip planned before the haul and the paddlewheel had stopped for good again. I decided to pull it and clean it up for the trip. Holy cow, that poor sensor was ALIVE with critters. You could literally see movement everywhere you looked and after a lot of brushing and cleaning I ended up with maybe 20 or more 'things' that moved on the sole. I had NEVER encountered anything like this before - a bit of slime sure but not a heaving mass of critters.
So here is my interpretation of all this .... and there is some guesswork involved ....
I now believe that whatever little bit of anti fouling properties were sill present in my old bottom coat ended up coming off when I scrubbed the bottom. With no protection left at all, the boat bottom became alive with all manner of 'stuff'. Said 'stuff' also took up residency in the paddlewheel. I believe the cloud of antifoul (as it leached out in normal operation) that previously floated by the paddlewheel kept growth in check even though the wheel itself had not been coated.
This morning, in prep for the haul out tomorrow, I pulled the paddle wheel sensor again and although not quite as bad as before, it might have been jammed already from marine life.
I interpret all of this, and my previous reasonable paddle wheel operation when the bottom had a good coat of antifoul, as a clear sign that my issue was the dead antifoul (I am not sure but it might be the third year for the bottom).
I will be painting the sensor with a coat of antifoul when the bottom gets done as well and hope that performance, although far from perfect, will return to acceptable.
If operation still ends up as marginal, I will replace the paddlewheel next.
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