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Careful with that Silicone AntiFoul


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3 hours ago, wheels said:

I have discussed the Hemples silicon based AF in the past, but a bit too early for most, as it was once only available for Commercial applications here in NZ. As in, it was only imported in 44Gal drums and went direct to shipyards. It's great to see that has changed and is now available to the average boater.
As said above, it does not have Biocides in it. But the development came about for two reasons. Firstly for commercial, TBT was being phased out. Secondly, the Copper based AF's have had many of their ingrediants phased out from use and the performance of Copper Based is becoming poor. Thirdly, People are becoming much more aware of what we are putting into our environment these days. So for any Company that advertises they have a safer alternative, then they obviously will gain an edge in market share with their product.
As also said above, the slippery coatings DO NOT stop growth. But then, non of the Copper based Coating were doing that anyway. The only product that ever maintained a completely clean surface was the very expensive self eroding coatings that contain Hydrogen Peroxide. But they only last 12months.
The only down side of the Silicon coatings is that they do need a resonably fast hull for self cleaning. I think minimum was 12kts. That's is far above most Hulls. But they are easy to brush down.
The coating should last 5yrs because that is what they were designed for on Commerical Vessels. Commercial Vessels have to go through Survey every 5yrs. A Commerical owner does not want to have to haul out any sooner due to cost. On a Sailing Hull, there should be no reason what you cannot get 5yrs. If you were one that used the very first kind of non commercial products on the market, then you might not get 5yrs. Don't let that put you off on what is now available. The performance is improving all the time. After all, they are a very new and still developing product.
These products work in a similar way to Prop speed etc. They are still only available for commercial application due to 2 reasons. The product is sprayed on with a commercial pressure sprayer. Because it is silicon, that pressure applicator needs to be used for that product only. Anyone that uses these silicon products and then tries to spray a normal Paint coating on a Boat is going to be in for a big surprise. No matter how well they cleaned the equipment. The same goes for keeping any possible overspray from floating arund in the air. A microscopic spec of silicon on another surface is a nightmare when it comes to painting. Even the materials and equipment used on preparation of the Hull before recoat needs to be kept separate from normal paint handling areas. Or at least, it is wise to anyway.
The only downside I see to it is the cost. It might be OK when viewed over 5yrs, but it's a big chunk to have to find every 5yrs.

Most of that is pretty accurate Wheels, we're looking to get somewhere around 10 years out of the product we use, at least that's what the US manufacturer quotes in their literature, and I expect they would get their backsides sued off over there if it wasn't the case, and they've been in business with this product for some time. Minimum speeds are now lower too, thankfully. There's not a hope that we could ever get our boat up to 12 knots. Some products will now start stripping at about 6 knots. When we were looking at what to use to replace the original soft coating, I came across one product (from International I think), that started stripping at less than 5 knots. As you say though, trouble is that you can't get most of the really good stuff in yacht sized quantities, even if you can get it in the NZ marketplace. Can't say what the requirements are for other products, but all of the prep work and coatings for Seaspeed are just what you would do for any underwater surface, nothing special used. Only the silicone coating needs dedicated equipment - no special sprayer or anything, normal diaphragm sprayer works well, but it IS silicone.....

 

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50 minutes ago, zug said:

1 it seems like a very round number

2 for most of us, who trundle around near hull speed, where hull speed is in the region of 7 knots, an extra knot feels like it's going to require some magic wave drag supression

3 has it become completely impossible to compete in racing without silicone af as this suggests? News to me.

 

Still interesting though.

You'll notice I said ABOUT a knot.........      If you have your doubts, that's fine. 

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The idea of not needing to haul out for 5 years is extremly enticing... but I am wondering about the prop/saildrive...

What about damage from strops when getting hauled out?

Does it go on the prop/shaft/saildrive as well or does that still need to be propspeed'd every 18mths?

Even half a knot would be a significant advantage....

So I wonder how this tech fits within the racing rules, specifically Rule 53... - would this silicone qualify as a "specially textured surface"?

RRS 53. SKIN FRICTION  A boat shall not eject or release a substance, such as a polymer, or have specially textured surfaces that could improve the character of the flow of water inside the boundary layer.
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29 minutes ago, CarpeDiem said:

The idea of not needing to haul out for 5 years is extremly enticing... but I am wondering about the prop/saildrive...

What about damage from strops when getting hauled out?

Does it go on the prop/shaft/saildrive as well or does that still need to be propspeed'd every 18mths?

Even half a knot would be a significant advantage....

So I wonder how this tech fits within the racing rules, specifically Rule 53... - would this silicone qualify as a "specially textured surface"?

RRS 53. SKIN FRICTION  A boat shall not eject or release a substance, such as a polymer, or have specially textured surfaces that could improve the character of the flow of water inside the boundary layer.

Can't say what other hard products would be like, but the stuff we use is HARD. Very resistant to abrasion. We haul on a cradle, but I don't see how soft strops will cause damage.

We still use Propspeed, though I am considering trying some Seaspeed on it this year. It may or may not take to the prop, I don't know, my feeling is that it won't last for any longer that Propspeed, but I have some on hand, so nothing lost by trying.

I gave up racing 30 years ago so wouldn't even try to interpret the rules, but, the co-efficient of friction of a non stick silicone is surely less than conventional antifoul. IS that a specially textured surface? Someone else can decide that.

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20 hours ago, AlastairW said:

We haven't had an issue with those for a couple of years now, we use an ultrasound unit to manage those.

It's likely the coating keeping you clear of Barnacles. The Ultra sound devices are a total waste of time. They don't work and well tested and proven that they don't work.

So who makes Seaspeed? Sounds interesting. I think over the next few years, these release type AF products are going to be like new Battery technology. Rapid intro's on to the market and each with a new idea in their coatings technology and for us, very difficult to keep up with developments.

The reason why Hemples did not have a consumer Silicon product was due to the guy (a good friend of mine) originally importing Hemples. He is also a keen and highly experienced Boat owner. He was only interested in the Hemples product for commercial reasons, due to the difficulty in "Pleasing" the Consumer boat world in relation to AF's. He told me the most common arguments in the Boat coatings world was in relation to AF's and he just wasn't interested in going there with such a new technology and so radically different to anything else around. Hemples was the first to come up with Silicon based AF by the way.
His view was to keep to the usual tried and true products that they could easily argue with tried and true, "You must have done something wrong" replies.
Hemples approached him and said they wanted to buy him out and expand the business in NZ.

When we used to haul out in Havelock, we would only have a slime on the Hull die to the frsh water running through the Marina. Yet the difference in speed between dirty and newly coated Hull was 1.5Kts at same cruising Revs. We normally cruised at 6.5kts which meant around 8-10ltrs per hr with the big 6.
The worst we ever had was when the boat was moored over the Picto side and both Hull and Prop was filty with weed and shell fish growth. We could only get 3kts from her and I had to have two attempts at getting around the Top, as the Tide turned before rounding into Pelorus and we started gong backwards. We had to run back to Port Gore for the night and have another shot the next morning.

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Very interesting discussion. I am currently at this stage:

bottenskrap.thumb.jpg.18506dc5663536faad0f31ced6645424.jpg

This is just testing to see how hard it is to remove the old stuff. Sooner or later I will have to re-do the antifouling from the ground up. Probably not this time as I am running out of time and would like to do this thoroughly including some filling and long-boarding.

I gather from what I read here that a silicone-based system may be a good fit for me but there is no easy going back.

/Martin

https://www.reflectometrist.eu/

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1 hour ago, wheels said:

It's likely the coating keeping you clear of Barnacles. The Ultra sound devices are a total waste of time. They don't work and well tested and proven that they don't work.

So who makes Seaspeed? Sounds interesting. I think over the next few years, these release type AF products are going to be like new Battery technology. Rapid intro's on to the market and each with a new idea in their coatings technology and for us, very difficult to keep up with developments.

The reason why Hemples did not have a consumer Silicon product was due to the guy (a good friend of mine) originally importing Hemples. He is also a keen and highly experienced Boat owner. He was only interested in the Hemples product for commercial reasons, due to the difficulty in "Pleasing" the Consumer boat world in relation to AF's. He told me the most common arguments in the Boat coatings world was in relation to AF's and he just wasn't interested in going there with such a new technology and so radically different to anything else around. Hemples was the first to come up with Silicon based AF by the way.
His view was to keep to the usual tried and true products that they could easily argue with tried and true, "You must have done something wrong" replies.
Hemples approached him and said they wanted to buy him out and expand the business in NZ.

When we used to haul out in Havelock, we would only have a slime on the Hull die to the frsh water running through the Marina. Yet the difference in speed between dirty and newly coated Hull was 1.5Kts at same cruising Revs. We normally cruised at 6.5kts which meant around 8-10ltrs per hr with the big 6.
The worst we ever had was when the boat was moored over the Picto side and both Hull and Prop was filty with weed and shell fish growth. We could only get 3kts from her and I had to have two attempts at getting around the Top, as the Tide turned before rounding into Pelorus and we started gong backwards. We had to run back to Port Gore for the night and have another shot the next morning.

The product isn't keeping us clear of barnacles, we'll have to agree to disagree about the ultrasound. I KNOW that the unit we use, with correctly positioned transducers, is very effective on our steel yacht. It would be a bit less so on a GRP yacht, and totally ineffective on a wooden or ferro one. I'm no expert, but do have a background in relevant underwater acoustics research, I understand the underlying theory, and also the constraints on the practical application. Anyway, as I said, I'm happy to agree to disagree, I'm not pushing a product, each to use the tools they find works for them.

Seaspeed is manufactured in the US by Seacoat SCT. And I agree, as the effectiveness of antifoul products is limited by the range of permitted active biocides, foul release will become more common. 

 

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3 hours ago, wheels said:

The Ultra sound devices are a total waste of time. They don't work and well tested and proven that they don't work.

That's a bold statement. 

NZ has some pretty strict laws that make selling products that have been 'well tested and proven not to work" to be very illegal.

There's literally dozens of independent test reports, diy comparisons and diy tests that support the ultrasound manufacturers claims. 

I suggest that you start with reviewing https://nordkyndesign.com/category/marine-engineering/electronics/ultrasonic-antifouling Eric Bretscher is a well respected NZ engineer who has, amongst other things, developed and tested his own ultrasonic AF system. 

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All up, the system eradicated the barnacle problem and it is immensely valuable to me for this reason. In the absence of hard growth, the surface is easy to clean, stays smooth and it can be recoated with minimal effort each time. It extends the intervals between haul-outs for me provided I dive and scrape off the soft growth from time to time once the antifouling is a year old or so.

 

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59 minutes ago, CarpeDiem said:

That's a bold statement. 

NZ has some pretty strict laws that make selling products that have been 'well tested and proven not to work" to be very illegal.

There's literally dozens of independent test reports, diy comparisons and diy tests that support the ultrasound manufacturers claims. 

I suggest that you start with reviewing https://nordkyndesign.com/category/marine-engineering/electronics/ultrasonic-antifouling Eric Bretscher is a well respected NZ engineer who has, amongst other things, developed and tested his own ultrasonic AF system. 

 

I can second that

 

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1 hour ago, CarpeDiem said:

NZ has some pretty strict laws that make selling products that have been 'well tested and proven not to work" to be very illegal.

You obviously don't watch the Infomercials on TV in the late night and early mornings then. Wow there are some wild claims in those shows.

I have a major background in Sound, mostly audible sound, but also Ultra Sound. When this idea first hit the market, I had mentioned my concerns here on Crew and we had a big discuss about it.
Fullers Ferries tried large units on the Ferrys a few years back now. They failed to do anything measurable in keeping the Hulls clean and they had them removed. We discussed the subject again then.

The idea of using Ultra sound was first developed for large water containment tanks for industrial cooling units. It was supposed to stop Algae forming. These units were large powerful devices and to a point, did work. However, they were extremely directional as far as the area's kept clean. Which is how Ultra sound works. It is very directional. Any shading by any object in the water would then coincide with algae growth on the other side of the object. So it was obvious it has some kind of ability.
However, these Units were producing Kilowatts of ultrasound energy to do the job. You would not want to get into the water with them on. That is why we don't see them in Swimming pools. To privide that kind of energy takes a lot of Electrical power. No problem when you have a Buildings electrical system to couple to. But the things found on Boats are teeny tiny things, simply because they would flatten the Battery far too fast otherwise. They are far too small to do anything. This power problem was the very first thing that got my attention. I knew it simply was not possible to do as claimed.

The other concern I had, it means the Hull is blasting high frequency sound into the Water where animals that actually use ultra sound live. Think of Dolphins and Whales etc. Plus we have no understanding of just what affect it may have on any kind if fish life that has the ability to sense Sound. Many fish do sense sound.
As far as Plant growth goes, it won't care how loud the sound is, till the point where it is powerful enough to actually be damaged. For shellfish, I have no idea if they can sense sound and I doubt anyone has tested that. Anyway, from the info originaly pushed to promote these devices, the idea is that the Ultrasound is supposed to disrupt the Plant in such a way as it cannot grow and dies. That takes a serious amount of sound power to do. For Shelfish, the High frequency vibration might perhaps annoy them, perhaps but I doubt it. High frequency as far as ultra sound goes, cannot be felt untill the energy is at scary levels and it disrupts life via pain, heat and eventually if powerful enough, being pulled apart via cavitation. So the idea a Shellfish is kept up late at night from the loud party sound of the ugly gang in the apartment above and eventually leaves the neighborhood is about as far fetched as me just describing the shellfish being kept up late at night by the ugly gang in the apartment above and eventualy leaving the neighborhood.
 

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While you raise some interesting further discussion points. Your post has produced no evidence at all to back up your claim. 

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They don't work and well tested and proven that they don't work.

Where is this well tested proof that these units don't work?

Or is this just your opinion based on personal or anecdotal experience?

The evidence available seems to be quite the opposite to your assertion that the technology doesn't work.

Here is a third piece of evidence. 

https://www.researchgate.net/publication/304251445_An_acoustic_antifouling_study_in_sea_environment_for_ship_hulls_using_ultrasonic_guided_waves

 

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3 hours ago, wheels said:

You obviously don't watch the Infomercials on TV in the late night and early mornings then. Wow there are some wild claims in those shows.

I have a major background in Sound, mostly audible sound, but also Ultra Sound. When this idea first hit the market, I had mentioned my concerns here on Crew and we had a big discuss about it.
Fullers Ferries tried large units on the Ferrys a few years back now. They failed to do anything measurable in keeping the Hulls clean and they had them removed. We discussed the subject again then.

The idea of using Ultra sound was first developed for large water containment tanks for industrial cooling units. It was supposed to stop Algae forming. These units were large powerful devices and to a point, did work. However, they were extremely directional as far as the area's kept clean. Which is how Ultra sound works. It is very directional. Any shading by any object in the water would then coincide with algae growth on the other side of the object. So it was obvious it has some kind of ability.
However, these Units were producing Kilowatts of ultrasound energy to do the job. You would not want to get into the water with them on. That is why we don't see them in Swimming pools. To privide that kind of energy takes a lot of Electrical power. No problem when you have a Buildings electrical system to couple to. But the things found on Boats are teeny tiny things, simply because they would flatten the Battery far too fast otherwise. They are far too small to do anything. This power problem was the very first thing that got my attention. I knew it simply was not possible to do as claimed.

The other concern I had, it means the Hull is blasting high frequency sound into the Water where animals that actually use ultra sound live. Think of Dolphins and Whales etc. Plus we have no understanding of just what affect it may have on any kind if fish life that has the ability to sense Sound. Many fish do sense sound.
As far as Plant growth goes, it won't care how loud the sound is, till the point where it is powerful enough to actually be damaged. For shellfish, I have no idea if they can sense sound and I doubt anyone has tested that. Anyway, from the info originaly pushed to promote these devices, the idea is that the Ultrasound is supposed to disrupt the Plant in such a way as it cannot grow and dies. That takes a serious amount of sound power to do. For Shelfish, the High frequency vibration might perhaps annoy them, perhaps but I doubt it. High frequency as far as ultra sound goes, cannot be felt untill the energy is at scary levels and it disrupts life via pain, heat and eventually if powerful enough, being pulled apart via cavitation. So the idea a Shellfish is kept up late at night from the loud party sound of the ugly gang in the apartment above and eventually leaves the neighborhood is about as far fetched as me just describing the shellfish being kept up late at night by the ugly gang in the apartment above and eventualy leaving the neighborhood.
 

With all due respect, I'd suggest reading Eric's articles that were referred to earlier. The rationale behind utrasound as used on small boats isn't to try to kill existing organisms with high power sound (which you can do - I know a fair bit about that), instead, the aim is to stop the establishment of organisms on the hull while they are still at the immature stage. That can be done quite successfully using a low powered unit. Different organisms are susceptible to different frequencies, so you need to deliver a swept frequency pulse. You also need to have an adequate number of transducers, strategically positioned. Organisms won't establish on a surface which is uncomfortable to them.

Two weeks ago, coming back down the coast from Oamaru, we had pods of dolphins playing around under the boat having what looked like a great time. Not being driven off by uncomfortable pain at all. We've found the same with seals. My previous work in the field showed us that larger fish were actually attracted to sounds (even high power) at certain frequencies.

The technique we're talking about here isn't the same as the more common ultrasonic cleaning techniques, which is what you seem to be referring to. 

Anyway, I know it works, I was confident before I installed the system, and I wouldn't still be using it if it wasn't effective. 

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18 hours ago, CarpeDiem said:

Where is this well tested proof that these units don't work?

Or is this just your opinion based on personal or anecdotal experience?

The evidence available seems to be quite the opposite to your assertion that the technology doesn't work.

Here is a third piece of evidence. 

https://www.researchgate.net/publication/304251445_An_acoustic_antifouling_study_in_sea_environment_for_ship_hulls_using_ultrasonic_guided_waves

So either you did not read that paper, or you do not understand it (sorry I don't intend that to come across harshly).  If you read it again, and you will see that it is exactly as I stated above and will go over again here.
You will also see that this is not about an product fitted to a Hull somewhere and how well it works. This was nothing more than a lab test carried out by some Uni guys. Also they were using a range of frequencies and a very small test area. Basically no more than the surface of the transducer. I would expect that surface of the transducer.likely coupled to a plate, would be kept clean.
At frequencies as low as 17Khz to 19Khz, the power they used woudl be easily audible to most people. If these were fitted on multiple hulls in a marina, the sond would be very noticible. Young Children would likely be screaming and have their hands over their ears. It would be one way of getting rid of that Seal from the Marina.

Which brings me to a great example as proof ultrasound does not work. Ever seen how dirty the transducer face on the Sounder gets?? If this worked, the face would remain clean as a wistle. Those things are punching down in the vacinity of 600W for a small one and 1.5Kw for the larger ones and the commercial things are in the 10's of Kw's and the commerical transducers don't keep clean either. Now mind you, we are talking about extremely high frequencies here. But the surface of the transducer is subject to harmonics that create clicks that are in fact audible. They are also capable of cracking the tranducer face if operated out of the Water. You should NEVER operate a sounder transducer out of water by the way, because of that.

Another great test is that for any Hull using these things, if it were working, then every point on the Hull where a transducer was fitted (I am assuming it's firing through the Hull) there would be a localised patch of extremely clean hull progressively getting dirtier as you move out and away from the Transducers mounting position. Yet that does not occur.

So as shown in that article you need extremely high power and specialized equipment and that is waaaay outside what these little consumer devices are capable of. I did not say ultra sound does not work. I did say those little consumer devices sold for our Boats do not.
 As I also said, they are used commercially in Cooling plants. The power required is huge. So huge, it would be dangerous to get into a tank with one operating. Even though frequencies above 20Khz are above our hearing range, you can still have hearing damage from these intense sound energies. Early on in my carreer, I made a very silly mistake of putting a transducer up to my ear. It was 30Khz. Waaaay above our hearing range. Yet I was suddenly hit with intense ear pain, deafness and ringing in that ear. Thankfully the deafness was short term. But I also only held it up to my ear for a fraction of a second.

As I said, I have a lot of professional experience in this field. I know how it works, I know it's limitations, I have studied it in great depth. I have used it in many applications. I would consider myself well trained, but not to the extent of a degree in it, as my main carreer was in audible sound. Of which I am highly qualified.

As I also said, Fullers are just one that tried a proper commercial Marine unit and it did not work for them and they had it removed again. There are many instances of people trying them and finding they do not work. Just ask yourselves why they are not found everywhere. If they worked as well as AF coatings, they would be reccomended by everyone. They have been available for, at a guess, some 30+ years.  

 

16 hours ago, AlastairW said:

With all due respect, I'd suggest reading Eric's articles that were referred to earlier. The rationale behind utrasound as used on small boats isn't to try to kill existing organisms with high power sound (which you can do - I know a fair bit about that), instead, the aim is to stop the establishment of organisms on the hull while they are still at the immature stage. That can be done quite successfully using a low powered unit. Different organisms are susceptible to different frequencies, so you need to deliver a swept frequency pulse. You also need to have an adequate number of transducers, strategically positioned. Organisms won't establish on a surface which is uncomfortable to them.

And also with all due respect, there has been no actual testing to find if that is true or not. There is no evidence as to whether an organism is affected by these ultrasound frequencies. It has always been suggested, but no one has any scientific proof, apart from situaions like that paper above states. You can also include those devices you fit in the wall socket at home to scare away Mice and some even suggest Cockroaches. They do not work. Some even claim they Ultrasound transmits back through the House wiring and radiates out everywhere. Also tested and proven false. Yet they still sell the things. But that is aside from the discussion here.
As I said above, the ultimate test is that the Hull would be clean at the mounting point of each transducer and would slowly get dirty as you move away from the area. So you would have these circular patches everywhere. Ultrasound does well at transmitting directionaly. It has poor ability at transmitting along and then radiating out. So the Hull itself does not resonate at that high frequency. It attentuates quickly in the material. By how much depends on the Tensile strength of the steel. Higher tensiles will tend to "ring" easier.

I've said enough. If you think it works for you, then that's awesome. More power to you as they say :-)

 

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8 minutes ago, wheels said:

So either you did not read that paper, or you do not understand it (sorry I don't intend that to come across harshly).  If you read it again, and you will see that it is exactly as I stated above and will go over again here.
You will also see that this is not about an product fitted to a Hull somewhere and how well it works. This was nothing more than a lab test carried out by some Uni guys. Also they were using a range of frequencies and a very small test area. Basically no more than the surface of the transducer. I would expect that surface of the transducer.likely coupled to a plate, would be kept clean.
At frequencies as low as 17Khz to 19Khz, the power they used woudl be easily audible to most people. If these were fitted on multiple hulls in a marina, the sond would be very noticible. Young Children would likely be screaming and have their hands over their ears. It would be one way of getting rid of that Seal from the Marina.

Which brings me to a great example as proof ultrasound does not work. Ever seen how dirty the transducer face on the Sounder gets?? If this worked, the face would remain clean as a wistle. Those things are punching down in the vacinity of 600W for a small one and 1.5Kw for the larger ones and the commercial things are in the 10's of Kw's and the commerical transducers don't keep clean either. Now mind you, we are talking about extremely high frequencies here. But the surface of the transducer is subject to harmonics that create clicks that are in fact audible. They are also capable of cracking the tranducer face if operated out of the Water. You should NEVER operate a sounder transducer out of water by the way, because of that.

Another great test is that for any Hull using these things, if it were working, then every point on the Hull where a transducer was fitted (I am assuming it's firing through the Hull) there would be a localised patch of extremely clean hull progressively getting dirtier as you move out and away from the Transducers mounting position. Yet that does not occur.

So as shown in that article you need extremely high power and specialized equipment and that is waaaay outside what these little consumer devices are capable of. I did not say ultra sound does not work. I did say those little consumer devices sold for our Boats do not.
 As I also said, they are used commercially in Cooling plants. The power required is huge. So huge, it would be dangerous to get into a tank with one operating. Even though frequencies above 20Khz are above our hearing range, you can still have hearing damage from these intense sound energies. Early on in my carreer, I made a very silly mistake of putting a transducer up to my ear. It was 30Khz. Waaaay above our hearing range. Yet I was suddenly hit with intense ear pain, deafness and ringing in that ear. Thankfully the deafness was short term. But I also only held it up to my ear for a fraction of a second.

As I said, I have a lot of professional experience in this field. I know how it works, I know it's limitations, I have studied it in great depth. I have used it in many applications. I would consider myself well trained, but not to the extent of a degree in it, as my main carreer was in audible sound. Of which I am highly qualified.

As I also said, Fullers are just one that tried a proper commercial Marine unit and it did not work for them and they had it removed again. There are many instances of people trying them and finding they do not work. Just ask yourselves why they are not found everywhere. If they worked as well as AF coatings, they would be reccomended by everyone. They have been available for, at a guess, some 30+ years.  

 

And also with all due respect, there has been no actual testing to find if that is true or not. There is no evidence as to whether an organism is affected by these ultrasound frequencies. It has always been suggested, but no one has any scientific proof, apart from situaions like that paper above states. You can also include those devices you fit in the wall socket at home to scare away Mice and some even suggest Cockroaches. They do not work. Some even claim they Ultrasound transmits back through the House wiring and radiates out everywhere. Also tested and proven false. Yet they still sell the things. But that is aside from the discussion here.
As I said above, the ultimate test is that the Hull would be clean at the mounting point of each transducer and would slowly get dirty as you move away from the area. So you would have these circular patches everywhere. Ultrasound does well at transmitting directionaly. It has poor ability at transmitting along and then radiating out. So the Hull itself does not resonate at that high frequency. It attentuates quickly in the material. By how much depends on the Tensile strength of the steel. Higher tensiles will tend to "ring" easier.

I've said enough. If you think it works for you, then that's awesome. More power to you as they say :-)

 

No problem, matter closed. As I said, we can just agree to disagree.

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Sea-speed and Hempel SilicOne mentioned so far. Sea-speed is not available where I live as far as I know and SilicOne seems to be fased out and replaced by Hempaspeed TF. Anyone with experience of Hempaspeed TF? It is said to be less complex to apply and hard rather than soft.

/Martin

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Hmm have to agree with Wheels on this one -I am yet to see an electronic system actually work-and yes I am constantly around hard stands for work.

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5 hours ago, Black Panther said:

 

 

That was a good start of the day and week. Now I have to bicycle to work.

/Martin

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If sound waves were to or did work. We could resurrect the Navy degaussing buoys in the tiri channel??

Only knew of one vessel that was in the panmure river that tried the sound wave thing. It all it did was those in close proximity chew thru zincs,could never prove t was the wires hanging overboard but once it dissapeared so did the chewing of zincs.The average time was 4 months on a block.

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