Positioning of ultrasonic antifouling transducer

[Ric]

I've been reading the installation instructions for various different makes of ultrasonic antifouling systems. All stipulate that the transducer should be between 200-300 mm from the centre line of the boat.

Does anybody know how this figure is arrived at? And is it really critical? I would imagine that the frequencies would be too high (and wavelengths thus too low) for this to be a resonance issue.

 

[jtwebb]

I fitted mine about 200 mm off centre and further towards the stern than recommended on my 11m boat. I wanted to 'concentrate' on the prop. In practice I find the log impellor does not need regular cleaning now even though it is quite a way from the transducer.

 

[tonytoller]

So does it work?

I fitted mine about 200 mm off centre and further towards the stern than recommended on my 11m boat. I wanted to 'concentrate' on the prop. In practice I find the log impellor does not need regular cleaning now even though it is quite a way from the transducer.

You seem to indicate that your ultrasonic system works - can you confirm? I'm considering fitting one this year, but the reports I've seen are very inconclusive, to the point where some say it has no effect at all.

 

[No Regrets]

Best position is in the bin according to every report so far...

 

[Ric]

I found out from one of the manufacturers that the reason that they recommend fitting it off the centreline is simply because some GRP boats (mostly power boats) are built in two halves in the mould. Most GRP sailing boats are built in one piece, so there is no reason why you cannot fit the transducer on the centreline if your boat is built this way.

 

[Ric]

Best position is in the bin according to every report so far...

There has been ample proof shown in research that ultrasonic sound kills algae. It has been proven that ultrasound is transmitted by GRP and by water. It is therefore a reasonable hypothesis that exciting a GRP hull with ultrasound will have some effect on algae growth.

There have also been controlled experiments done by the MOD which lead them to fit USAF units to their LCVs. There was also a very interesting post here on another thread which showed dramatic difference in fouling between areas of the hull which transmitted ultrasound well (eg stringers) and areas which transmitted it less well.

As with any antifouling, it is very difficult to conclusively prove that a product works well because there are so many variable to control. However, there is plenty of anecdotal and scientific evidence to suggest that these products do have an effect. Given that the Jaycar unit only costs the price of a 5l pot of antifouling paint, it is well worth being open minded and experimenting with one.

 

[Uricanejack]

Maybe this question should be a new thread.

I saw an ultra sound anti fouling system at a recent boat show cost was around the same as having my boat anti foul redone.

I was sceptical but interesred.
Rather than inconcusive sience. What about folk with boats who have tried it.

Does it work.?
Do you have this system?
does your boat get fouled?
Do you keep it in fresh or salt?

My mooring is in Salt and I get a lot of growth between haulouts.

 

[wizard]

I've been reading the installation instructions for various different makes of ultrasonic antifouling systems. All stipulate that the transducer should be between 200-300 mm from the centre line of the boat.

Does anybody know how this figure is arrived at? And is it really critical? I would imagine that the frequencies would be too high (and wavelengths thus too low) for this to be a resonance issue.

I fitted my Jaycar unit approx 65 cms from the centreline just to the side of the engine and saildrive where the the hull was thinner and would transfer the sound vibrations throughout the the hull better.

Results after two seasons are certainly positive -

no barnacles on the saildrive, prop or rudder (still get a few on the bottom (underneath) of the iron keel)
the Kiwi prop blades rotate freely for the whole period from one lift out to the next (due to no barnacles)
general fouling is very much reduced so that now I only use cheap Flag eroding antifouling instead of the fortune I was paying before

So all in all the kit was a good investment, its not perfect but its a definate improvement