Antifouling devices

[senormechanico]

I guess I'm almost nobody, but still happy that I don't need to periodically hire you or any other diver.
I just sail off the dead fuzz now and then.

[Paul L]

Originally Posted by Wood

There is little controlled scientific data about this technology.

Here is a recent article I found:

Acoustic methods for biofouling control: A review

I would use this technology given the correct hull construction AND the manufacturer disclosing all operational specifications.

Otherwise, IMO, it is snake oil

Did you read the full article? What was the conclusion? I was to cheap to buy it for $35.

[Wood]

Try this [direct link to PDF download]:

https://www.google.com/url?sa=t&rct=...s04_LQ&cad=rja

[Paul L]

Originally Posted by Wood

Try this [direct link to PDF download]:

https://www.google.com/url?sa=t&rct=...s04_LQ&cad=rja

From the conclusion

. The relative effectiveness of the acoustic antifouling tri-
als was also often difficult to evaluate. It was often said
that fouling “inhibition” had occurred or that the surfaces
were “relatively free” of fouling. However, without a
baseline such terms become ambiguous. Often no con-
trol was used and generally little quantitative information
was provided on the amount of accumulated biofouling
that occurred. Very little photographic documentation of
the biofouling trials was found.

From the couple of cruisers I've talk to who tried these, I'm skeptical.

[Wood]

Agreed.

But the testing data in that paper shows some efficacy to the technology.

[senormechanico]

Yesterday I put my boat on the grid expecting a mess from sitting at my salt water dock since October without being moved.
To my (not really) surprise, I was able to wash off the bottom with a garden hose and wipe it with my hand.
It was almost like fingerpainting a very thin film of dead slime.
It's hard to gauge from the picture, but the film was about as thick as a sheet of paper.

THIS IS THE FIRST TIME it's been washed in any manner in at least 3 years.

I used no sponge, no pressure washer, just a garden hose.
Best of all, I found not a single barnacle on the hull anywhere.
There were about a dozen medium sized barnacles on the folding prop, along with what looked like a rust colored layer of some kind of coral stuff. I removed the barnacles and scraped the coral (whatever it is) stuff off.
No barnacles on the Isotherm's hull keel cooler either !! Usually that's covered with barnacles.

The knotmeter impeller was free as well which didn't surprise me.
After we installed the UltraSoniTec several years ago, the knotmeter has always been free to move.
Previously, it would be fouled in less than a week.

The UltraSoniTec 4 channel has run 24/7 from my solar panels since it was installed a few years ago, and seems to be doing its job.

I have no financial interest in the company, just a happy owner.

The first pic is an area where I didn't touch the hull at all, just a shot of the garden hose from about 4 feet away.
The second pic is the result of the garden hose to wet it, wiping with a bare hand, and rinsing with the hose.

[0urh]

Senor Mechanico

Looks good and obviously is working well for you

Could you please provide some more details on your ultrasonic installation? Hull construction material, no. of transducers per hull, transducer placement etc?

[RaymondR]

There is an article in the May 2017 Silicon Chip magazine which includes a good discussion on the Jaycar units and details of an updated design which will drive 2 transducers.


The article also has a couple of images which appear to show a definite improvement of a fitted v unfitted boat.


The article explains that the device cycles through a range of frequencies which suggests that ther is a natural frequency phenomenon at work. If so there would appear to be a particular frequency at which the hull material would resonate. If this is the case it might explain why some people have good experiences with the devices and some not.


If a hull resonance phenomenon at a natural frequency exists it suggests that fitting a feedback transducer so that the resonant frequency can be detected and cycling the drive frequency around this frequency might lead to much more effective devices.

[senormechanico]

I have an UltraSoniTec 4 channel unit.
The hull has a foam sandwich above the waterline in the middle of the boat, but not at the bow or engine room.
The foam extends below the waterline to within 8 inches or so of the centerboard trunk.
I had to cut away the foam in a 6 inch circle for the two middle placed transducers so I could epoxy them directly to the outer skin.
The unit draws an average current at 12 volts of around 700 ma. powered by solar.
I leave it on all year long.
I have Micron Extra bottom paint (ablative) and would probably be better off if I had hard paint, as these days the boat doesn't get sailed very often.
My business is at home, but too busy !!
I have no transducers in the amas, so I had a very good A/B test for the ultrasonic protection.
Same paint of course, no barnacles but it took about twice as much effort to wipe off the slime on the amas as on the main hull.

It was easy to see where the transducers were mounted as there were circular areas with absolutely no growth with a 1 inch circle in the middle of those with no bottom paint at all !
Apparently, the ultrasonic vibration kicked the paint right off the hull at the center of the transducer mount.
I have seen no problem with any hull damage of any kind from the installation.

[Markusik]

We use ultrasound extensively in physical therapy. The research shows that, within limits, for certain conditions, it is a real benefit. The "how" of this benefit is less clear. One possibility, supported by science, involves cellular permeability.

Our bodies do their best to provide a beneficial environment for our cells by cleaning and fortifying our lymph, blood, CSF, etc.. Ultrasound has little to do with sound, and much to do with vibration. Vibration can create heat (not a likely scenario on a hull), but also make it easier for substances to cross the cellular barrier. In the benevolent setting of our bodies, improving transport of desirable substances into the cell, and waste products out, is a possibility for the benefit of ultrasound therapy. In essence, it increases the metabolic potential of the cells/tissues in question.

Now suppose you are a hull critter. If you are an algae or other single-celled organism, you must maintain a stable internal environment despite being immersed in unforgiving water. If suddenly all the stuff you are trying to keep in your cell finds it easy to escape, and all the stuff you try to keep out of your cell finds it easy to enter, you must invest much more energy in maintaining your internal environment. Many antibiotics and antifungals work by attacking channels in cell membranes, much to the same effect.

Now if you are a barnacle, or weed, you want (need) a hull surface that is already covered in biofilm. If that biofilm is barely clinging to survival, and sloughing off when the sailing gets rough, then you must settle down elsewhere.

The frequencies in question are high, but not the amplitudes of vibration. While I'm not convinced by manufacturers' claims, I consider the possibility that ultrasound could achieve the desired effects using the low power requirements in question; not by "shaking off" clingers, not by annoying them with noise, but by making the first essential step in fouling (biofilm formation) too costly, metabolically speaking, to establish the conditions that allow latecomers like weeds and barnacles to become established.

I am, however, certain that not all transducers are created equal.

Fair winds!

[senormechanico]

Originally Posted by Markusik

We use ultrasound extensively in physical therapy. The research shows that, within limits, for certain conditions, it is a real benefit. The "how" of this benefit is less clear. One possibility, supported by science, involves cellular permeability.

Our bodies do their best to provide a beneficial environment for our cells by cleaning and fortifying our lymph, blood, CSF, etc.. Ultrasound has little to do with sound, and much to do with vibration. Vibration can create heat (not a likely scenario on a hull), but also make it easier for substances to cross the cellular barrier. In the benevolent setting of our bodies, improving transport of desirable substances into the cell, and waste products out, is a possibility for the benefit of ultrasound therapy. In essence, it increases the metabolic potential of the cells/tissues in question.

Now suppose you are a hull critter. If you are an algae or other single-celled organism, you must maintain a stable internal environment despite being immersed in unforgiving water. If suddenly all the stuff you are trying to keep in your cell finds it easy to escape, and all the stuff you try to keep out of your cell finds it easy to enter, you must invest much more energy in maintaining your internal environment. Many antibiotics and antifungals work by attacking channels in cell membranes, much to the same effect.

Now if you are a barnacle, or weed, you want (need) a hull surface that is already covered in biofilm. If that biofilm is barely clinging to survival, and sloughing off when the sailing gets rough, then you must settle down elsewhere.

The frequencies in question are high, but not the amplitudes of vibration. While I'm not convinced by manufacturers' claims, I consider the possibility that ultrasound could achieve the desired effects using the low power requirements in question; not by "shaking off" clingers, not by annoying them with noise, but by making the first essential step in fouling (biofilm formation) too costly, metabolically speaking, to establish the conditions that allow latecomers like weeds and barnacles to become established.

I am, however, certain that not all transducers are created equal.

Fair winds!

I agree with your theory.
The Jaycar system was described by the Ultrasonitec representative as being "where our product's design was several years ago".

I am just now getting a bit of grass growing around the waterline at the tip of the bow and across the transom of the main hull.
The keel cooler for the refrigerator remains absolutely free of barnacles (a first) as well as the knotmeter and depth sounder (also a first).
The propeller also has remained clean (well, two small barnacles on the aft end of the hub).

The amas have started to grow grass at the waterline in areas exposed to a lot of sun, although they were not protected with this system.

The distance from the transducers is a factor and the amas had no ultrasonic protection, just bottom paint.


My vote is, although not as much as I had hoped for, it's definitely helping.
Just the knotmeter never fouling has made my day, as the transducer is in a difficult to access spot under the V berth.

[slegg]

Originally Posted by fstbttms

So your point is that a single satisfied user in a low-fouling region is proof that the system is effective? Bwhahahaha!

Not a single one. Here in Brasil these transducers were produced by NAUTEC at the time and worked very well. The problem was energy consumption. At that time the system would use 60 Ah per week. That was too much then. Now that wouldn´t be an issue. They were very sensitive of the material of the hull, worked very well with fiberglass, not so well with steel or aluminiun or wood, but apparently it was a matter of correcting the frequency. an attenuation issue.

[Seman]

Originally Posted by Seman

I have just installed the JayCar Sonar transducers on my cat, 48' aluminium, 3 sonar transducers in each hull. Will let you know how it goes. Just now the hulls are dirty, ready to paint next month in Trinidad.

The JayCar Sonar system does not work on my boat, neither does it work on a friends Alu yacht.
Snake oil, as the Yanks say!