Fouling resistant log transducer

[jbees]

Years ago we had a B&G Harrier log which had a turbine on a retractable stalk for the water speed transducer. it was very accurate throughout the season. When it died we changed to a series of waterwheel types and a laser type which were all fairly useless as fouling rapidly produces variability with course and speed regardless of where they are mounted.
Does anyone know of a manufacturer of a retractable turbine type transducer (or have an old B&G transducer). I like to keep a DR plot going just in case.

 

[pvb]

Why don't you simply antifoul the transducer?

 

[William_H]

I have seen one example of a B&G ultrasonic log. 2 transducers are set up some distance apart on the hull. The sound wave is transmitted from one to the other. Dopler effect frequency change is translated to water speed. No concerns about fouling. However any mechanical turbine or paddle wheel will suffer from fouling. good luck olewill

 

[pvb]

However any mechanical turbine or paddle wheel will suffer from fouling.

Not if it's antifouled.

 

[michael_w]

Remove the impeller when you're not using the boat. Don't worry about sinking, the most water you'll let in is a pint or so.

 

[reeac]

Not if it's antifouled.

My Airmar transducer instructs me to anti foul it but I've found that it still gets clogged up just as much - that's using International boot topping.. Now I don't bother and just clean it when it stops working.

 

[FulmarJeddo]

Not if it's antifouled.

I have always avoided antifouling my log paddle wheel, especially since getting a splash on one once that jammed it up. This year I replaced my old Autohelm ST50 as the display was playing up and replaced the paddlewheel at the same time. The instructions advised painting the transducer with water based antifoul. After a bit of a hunt I found Echo antifoul. A few online chandleries list it, some as ECO. I found that my local chandlery, Pirates Cave had just got some in for the first time. It comes in a very small pot for about £15. My boat has been in the water since Easter and the log is working a treat. Normally by now I would be getting fouling problems.

 

[ex-Gladys]

Remove the impeller when you're not using the boat. Don't worry about sinking, the most water you'll let in is a pint or so.

+1 for me, particularly with the modern Airmar fittings with the flap to reduce water ingress. I have to clear up no more than a couple of spoonfuls of water

 

[theoldsalt]

I have always avoided antifouling my log paddle wheel, especially since getting a splash on one once that jammed it up. This year I replaced my old Autohelm ST50 as the display was playing up and replaced the paddlewheel at the same time. The instructions advised painting the transducer with water based antifoul. After a bit of a hunt I found Echo antifoul. A few online chandleries list it, some as ECO. I found that my local chandlery, Pirates Cave had just got some in for the first time. It comes in a very small pot for about £15. My boat has been in the water since Easter and the log is working a treat. Normally by now I would be getting fouling problems.

Force4 seem to stock your recommendation but it is for transducers. No mention of using it on a log. Is this what you use on your log impellor?

http://www.force4.co.uk/marlin-echo...gclid=CLGghY2ulsYCFQYewwodfmwACw#.VYE2glKYZdg

 

[prv]

I've just started using this stuff: http://www.ebay.co.uk/itm/AIRMAR-WA...710?pt=LH_DefaultDomain_3&hash=item418339873e on my log sensor. We launched at the end of March, I've pulled the transducer a couple of times since then expecting to need to clean it, but not a speck. I'm impressed. The last couple of years it was regularly jammed up with tubeworm and home to a family of tiny shrimp-like beasts; I often left it stuck and only pulled it out to get it working for longer trips.

The paint is quite runny, so you get a thin coat that won't gum up the works. I applied two coats, as recommended. It doesn't take much - I expect the small bottle will last for many years. The only slight problem is that it's black, the same as the transducer, so you need to careful not to miss any bits!

Pete

 

[FulmarJeddo]

Yes, that's the stuff. The pot I bought was labelled ECHO but with the same graphics. I applied it with an art type paint brush. Make sure the paddle wheel spins freely when its dry.

And as Pete says, you only use a small amount so it should last for years. I guess if the pot thickens up over time, being water based a drop of water should thin it down.

 

[PaulMcC]

I have seen one example of a B&G ultrasonic log. 2 transducers are set up some distance apart on the hull. The sound wave is transmitted from one to the other. Dopler effect frequency change is translated to water speed. No concerns about fouling. However any mechanical turbine or paddle wheel will suffer from fouling. good luck olewill

If you want to go the whole way then you need an ADCP. Oceanographers use then to measure current profiles. Similar to the B&G setup but with 4 transducers. This allows measuing the current profile from the surface to the seabed and the vessel speed relative to both the seabed and the water. I'm not sure how much they go for currently (I bought them for work 15 years ago any they cost most of £100k each). Wouldn't be suprised if they are still almost that expensive as it's a very niche market but sooner or later someone will come up with a more mass market product, well useful for yachts rather than just oceanographers, and the price will come down.