Ultrasonic Anti-Fouling

[Cheechako]

cant be good for the critters

[Sublime]

The unit available from England "ultrasonic antifouling" is identical to the one available from Boat Sure in Australia - this is just brand engineering in Australia. The price is about 2000 less in England than in Australia for the double transducer unit. Given that ultrasound is used for cleaning purposes by say jewellers, there is no reason why it would not work on boats. Upgrading the English unit will be by chip, for which they will undoubtedly charge, but if the unit works as advertised........ the savings in annual slipping will be huge, and the cost of a diver for anode replacement negligible in comparison.
i am about to trial a combination of Cop r Bote, Propspeed and ultrasound on a boat being constructed at present. Will only be in the water in the new year say March and i will keep users informed here. The suppliers claim the vessel can be "clean skin" - that is NO antifouling with the ultrasound, but I don't have the courage for that. My vessel will be power and kept in the Hawkesbury in Sydney. Cop r Bote needs a 3 monthly wipe down by a diver - that at least should be covered by the ultrasound and not be required, and being metallic copper exposed on the hull should work as well as any copper containing paint, without the ablation effects.

[GordMay]

Originally Posted by Sublime

... Given that ultrasound is used for cleaning purposes by say jewelers, there is no reason why it would not work on boats ...

There may be numerous reasons why the comparison is invalid.

There may be significant, non-linear, effects of scale, wherein small changes can have large impacts. Most boats are significantly larger than most jewels.

There may also be significant differences in the adhesive (& other) qualities between the contaminants usually cleaned from jewels, and those requiring cleaning from boat hulls.

[Cheechako]

I have evaluated Ultrasonic cleaning in an industrial large scale environment. Results were not impressive for anything of size, even for removing oily and other manufacturing residues etc. While the little units work great for cleaning jewelry, I think they are focused in on that particular size/ mass range. I think we would see them used a lot in manufacturing if they worked well due to the need to stop using environmentally harsh chemicals is high. Been in metal trades/manufacturing for 35 years and never seen much use. I dont know, maybe this approach is to "bother the barnacles" to the point they stay away rather than remove them.

[Chief Engineer]

Barnacles have ears?

[lolanreg@smartc]

Gordmay, I reckon that boats usually cost the owner more than jewels!

[Sublime]

His boat comes out tomorrow. Hope he is as good as his word and posts his observations and photos. Nothing like real world rather than theory. If it works, I don't care how it does it, just that it does!!!

[Sublime]

Originally Posted by nmit5903

Well - to all the disbelievers - "critters must have ears" because it works. Its been 6 weeks since fitting the unit and there is already appears to be a noticeable reduction in growth on the undersides. I will be slipping on the 17th and will post photos however at this stage - looking good. My only issue remains whether one unit is adequate for the length of vessel.

There is growth around the waterline but that is easily wiped away with a sponge.

The one added benefit that I hadnt expected is that the fish love it. At any point in time we have upwards of a dozen reasonable sized fish around the area where the ultrasound is fitted - snapper, bream ......which should make for a good bbq on days out. Might turn it off when swimming though - not sure about the sharks!

PLEASE don't delay posting your findings, even without photos. I am going the same route as you!

[lolanreg@smartc]

Sublime, any idea of how it works, through the hull like a depth sounder, or does this make the whole hull structure sort of vibrate microscopicaly ? I've lost the info on it. Be magic if it does what they claim. I'm sure nmit5903 will let us all know.

[Sublime]

I believe it it sets up microbubbles on the hull, which is a disincentive to growth, but also, with certain frequencies of ultrasound , it actually destroys portions of the cell walls or internals of the algae cells. They use a number of different frequencies, which they can do because the unit is digital. Older units were analogue and produced a single frequency, which may be why they failed. I understand different algae need different frequencies. These then die and so lose whatever foothold they may have had, but with a clean hull, it stops them attaching in the first place. As you say, if it works as advertised, then this will really be a great advance for all of us.
However, lets wait for NMIT5903's post - I am biting nails already!!!

[Nordic cat]

I have worked with ultrasonic technology for the last 20 years, and in my opinion, this is in the same category as those magnets that supposedly give you extra mileage.

We supply clamp-on transducers to mount on the outside of pipes, to measure flow, as well as ultrasonic level and sonic velocity analysers.

There are basically two ways to pass sound waves through or into say a boat hull, either you "inject" it like you see on those depth transducers that can be mounted on the inside of a solid hull (no soft cores), or you can get the whole area around the transducer to resonate.

The "injection" method limits the area where the ultrasound penetrates, so no good for this application.

To get a part of boat hull to resonate, you need to find the resonant frequency, which is farly easy given todays technology.

To get the complete hull to resonate is impossible at the energy levels they operate at, and the different frequencies required.

First, hulls have reinforcements, stringers, different layups in different areas, engine mounts, bulkheads. The resonant frequency around all these areas is different, and varies with the distance from the reinforcement.
If the hull doesn´t resonate, it will not move, if the hull doesn't move, the water around it doesn't either, so their claim is not valid.

Our experience with fibre glass pipes shows even small air inclusions in the layup really attenuate the signal and spoil it.

Secondly, we have had transducers, more powerful than these, mounted on big (up to >2 meter diameter) cooling water pipes for power stations, using the lamb wave technology/ resonance system.
These are steel pipes with a rubber lining to cut down algae and barnacle etc. growth. Lots of power is needed to get those thick hard rubber liners resonating!
They need to send divers in there at least once a year, to clean out the area around the transducers, even with the more malleable rubber lining!

Thirdly, if this worked, all the big steel ships would be using it, as new figures show an increase in hull resistance of around 0.1% per week! So if you are burning 100 tons of fuel per day, after a few weeks, the payback time would make this the smartest investment around.

We have used and tested ultrasonic cleaning systems for on-line sensors that need to stay clean to ensure operation. Never had a really good succes, be it soft or hard growth.

Ultrasonic cleaning of gasses on the other hand does work, but that's a completely different story...

So the old adage of "If it's too good to be true, it probably is" still holds true..

Alan

P.S. I noticed that the UK website still reccomends that you use your normal antifouling

[rebel heart]

I'm going to file the magical-electronic-algea-control system right up there with:

- The amazing new solar panel breakthrough that is coming soon and will drop the prices insanely.
- The new product that eliminates varnishing forever and leaves the boat beautiful for all time.
- The new laptop chartplotter that eliminates the need for you to be a competent mariner.


In short, I'll believe it when I see it. And by "see it", I mean when I see it in Practical Sailor, or getting real reviews from people I trust.

[GordMay]

Thanks Alan (Nordic Cat)!

[nmit5903]

Long time in coming but here we go.

I delayed the annual slip to allow some fine tuning of the unit in early Oct. We slipped yesterday and I have provided a link to some photos - will leave it to you to draw your own conclusions.
http://gallery.me.com/nmit5903/100107

Disregard the last few photos of various davit arrangements.

I was dissappointed and have elected to revert to the proven annual antifoul (in fact it is in progress as we speak). I did find the log (speedo) stayed clean throughout however its a lot to spend to spend for that alone. An old toothbrush works well too once a month and is much cheaper.

To be honest neither I or the lads at the slip could see any difference between Girasol and other vessels being slipped yesterday. Perhaps one unit is stretching things too far however I won't find it economic to spend a further $2k ($6k in all) to go that way.

...... anyone heard of that new antifoul that lasts for 5 years (just joking!)

Neil

[Steve Pope]

Thanks for the photo's worth more than a thousand words!