AlastairW
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Posts posted by AlastairW
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10 minutes ago, Psyche said:
I need a big steel boat😅
Nah, whole point of me using my big steel boat to find as many uncharted rocks as possible was so that you don't need one. Less scratches on the keel than I thought there might have been too !!
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There is a new, updated cruising guide to Stewart Island / Rakiura now available. A bit more comprehensive than the older guide, 85 pages, chartlets and satellite illustrations, and, best of all, free download as a pdf.
Download is hosted by the Otago Yacht Club on their web site at https://otagoyachtclub.org.nz/wp/stewart-island-sailors-guide/
Feel free to share it around
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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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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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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, 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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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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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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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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15 hours ago, Dave said:
Does it actually self clean? I've got MacGlide on my boat which is supposed to self clean, but it builds up a layer of slime which doesn't come off, even with a decent amount of speed. I also find that the slime dries at the waterline which allows barnacles and such to get a foothold, it is very easy to clean though.
Dave, the stuff we have (Seaspeed V10x) self cleans reasonably well as long as you are using the boat a lot, and don't give the slime a chance to get a hold. But once any fouling gets a hold, it gets more difficult. With the slime, we find that if we get out in a decent wind and a bit of a seaway, when we come back in again, we can see where it has started to wash off. We have dirty slime down here....... Leave the boat sitting on the berth for longer than a few weeks though, and it gets harder. Washes off really easily though when I get physical with it.
I took the boat out of the water in February and cleaned it thoroughly. Went off down to Stewart Island till the end of March. When I got back to Dunedin, the bottom was still spotless. I wasn't moving her every day while there. but often enough to keep her clean. Back on the berth in Otago Harbour, and within 3 weeks of not moving, and the slime built up. Otago Harbour has become a lot more weedy/fouly in the past couple of years.
I know exactly what you mean about the barnacles, and it will be the same for long weeds etc too. We haven't had an issue with those for a couple of years now, we use an ultrasound unit to manage those.
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8 minutes ago, CarpeDiem said:
What do mean by that? I guess I do not understand the difference between foul-release and anti-foul...
Antifoul has nasties in it that deters or kills the offending biology, silicone foul release doesn't. It operates like a non-stick frying pan, so the greeblies are washed off by the motion of the boat through the water.
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I've been using silicone foul release for over 5 years now, started with soft coating since it was all that was available, now using a hard coating.
The soft coating was a nightmare to apply, and failed to live up to the durability claims. We were told we would get 5 years out of it minimum. It did it's job as a foul release, but wore so rapidly that we had to start considering replacing it after just over 2 years. Thankfully, that product is no longer available.
We've been using a hard coating now for about 2.5 years. It performs better all round. When clean, at cruising speed under power, we have about an extra knot over what we got with a clean hull and conventional antifoul. We have about an extra 0.5 knot over the clean soft silicone foul release. With one caveat, the product we are using seems pretty durable. We poke around in a lot of interesting corners that you really probably ought not take a 40ft yacht, so we "bump" the keel a bit, but never at speed. We don't seem to be losing much of the coating through this.
The one caveat I mentioned is that when we had this product applied, we deliberately raised our waterline, so that out bottom coating now extends about 150mm above the actual surface level. We've found this year, in our 3rd summer with this coating, that the product above the waterline is deteriorating and breaking down. I think it is UV damage, and we're talking to the manufacturer about it. They have been very helpful. Below the actual waterline, no issues at all with deterioration.
Cost to have our boat done professionally and properly (sandblast back to bare metal, 1 coat expoy primer, 2 coats expoy immersion coat, 1 coat silicone), just under $8000 two and a bit years ago.
And then of course, since it's a foul release and not an antifoul, you need to completely rethink how you manage keeping the bottom of your boat clean......... And you need to have that clear in your head before you start down the foul release path.
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5kg bottle - 4 weeks give or take a wee bit. 2 people, hearty meals cooked from scratch, using the oven for baking etc about every other day, sparing use of the Califont. Use a wee bit less when it's warm, a wee bit more when the temperature drops.
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1 Dunedin to Havelock and back over the December to February period, immediately followed by a run down to Stewart Island which was cut short by lockdown. Pity it had to come to a halt.
2 Back down to Stewart Island in one of the good weather Winter spells (we have a good cabin heater.....)
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Thanks IT, we have a Waypoint Ocean 4 person, also in a soft bag, vacuum sealed, and kept out of the sun. We got that one, even though it wasn't the cheapest, but the manufacturer gave a 3 year service period, and it worked out better value over the longer term. I am bothered though, that the problems seem to happen after service, and it would be good to get a feel for how common it is for issues to be found when the raft comes up for it's second (or subsequent) service.
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I know it's kind of beside the point of there being emergency survival gear in the raft, but knowing that the gear in the raft is probably inadequate just hammers home to me why we carry a grab bag with water, food, torch, plb, first aid kit, etc. As for the deflation etc, how old are these rafts and what is their service history? Genuinely interested as I have a raft coming up to time for it's first service, and the cost of it makes me question if it's worth having it done until we actually need the certification for heading offshore.
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Before our time, Wild Bird had a keel cooled system for the engine (60hp Nissan). Had a 500 litre tank of fresh water low in the bilge. The previous owners had issues with the cooling being inadequate to let them develop more than about 40hp. This is a steel boat, so good thermal conductivity. They could get better in Winter when the sea water was a bit cooler. Boat was based North of Auckland. I suppose that a larger keel tank would help there, but say you had a 1000 litre cooling tank - you'd be lugging an additional 1000kg of water around all the time.
What we have now - which the previous owner installed - is a dry exhaust, fresh water engine cooling, a Savage heat exchanger with raw sea water supplied via a belt driven pump. Certainly works, and we can maintain cruising revs on the diesel for days at a time, going into adverse weather, with no abnormal temperatures.
From my point of view - this being my first boat with a dry exhaust system - there are a few drawbacks. The exhaust runs hotter, not a major issue for us. The exhaust system isn't muffled as effectively as it is with a wet exhaust. Depending on the position of the exhaust through hull and the direction of the breeze, the fumes can get quite unpleasant in the cockpit, not a problem when you are sailing, but you inevitably need to run the donk for a while at some point. Whether you have a system like ours, or a keel cooled system, they are all things which will need to be considered.
For us, and it may well just be to do with the exhaust through hull location, the issue with fumes is enough to have us toying with changing over to a wet exhaust.
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Just checked the Environment Southland website. Seems very straightforward, and not really anything you wouldn't be doing to make sure you aren't losing boat speed anyway. The pass lasts for a year, is free of charge, sounds a bit as if it is as much of an exercise in ensuring that folk going into the area are aware and have thought about pests etc as it is about enforcement.
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I sailed down there 2 years ago it's well worth the effort,I read somewhere you now need some sort of certificate to say your antifouling is up to date or something now cant remember where I saw it.Bollocks really when you see how many cruise ships pass through.Put the trip on your bucket list though only saw 2 other yachts while we were down there.
You need to make a declaration (I think you do it on-line) that your hull is clean before you get into the fiords, and are liable to be inspected - don't ask me where or how. It's probably on the Environment Southland web site somewhere. As you say though, look at the number of cruise ships and fishing boats around down there.
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We're looking to do this from early December, and taking a leisurely 6 months over it, but going up the East and down the West coasts. Starting from Dunedin, and aiming to be back down in Fiordland/Stewart Island for the more settled period of March - April. Paths could cross......
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There are enough different models of integrated lifejackets/harnesses about to give a good choice. I find that having an integrated unit means I have all bases covered when it's needed. And the L/J's are so compact now you don't even notice it is there. For me, it's the only way to go.
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Have had a Rocna and now on an Excel. I find the Excel a better anchor for a wider range of situations, but, as SM has said, you do need to use good technique/practise when deploying it. But then, ought we not be doing that all the time anyway?
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+1 Why bother about all that minutae. There are far better things to be spending time on.For most, the easy answer is just buy from a nz dealer. Vhfs are not expensive, and it will have the right standards, certification etc.
No k
Need to know all this stuff.
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iPads
in MarineTalk
Looks a bit on the expensive side to me. Have been running Oziexplorer on a couple of Android tablets for years now, Suitable tablet costs a couple of hundred at worst, the program costs about $40, and the charts are freely available from LINZ.
Heading out on Wednesday...
in MarineTalk
Posted
Positively tropical in Lords River and Paterson Inlet too