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Transition from seawater to freshwater 25 Nov 2022 11:03 #133053

  • Duncan Gilmour
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Thank you for that, Peter. It did seem a reasonable idea to me, too. However, Balliol suggested, in an earlier post, that in this case, the anodes with the highest potency will prevail:

Zinc anodes additional to MG or Al will do nothing. The most potent anode (Mg>Al>Zn) will prevail. The zincs will just be idle.

So, I suppose hanging anodes would work in the case of needing the extra that Mg would give you but not the other way round.  I'm sure Balliol will correct me if I have misunderstood.

Thanks again


Duncan

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Transition from seawater to freshwater 25 Nov 2022 10:52 #133052

  • Peter White
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Hello, I keep my steel motor cruiser in Port Ariane off the River Lez just south of Montpellier. The water is fresh, but we spend several months per year in the salt water of the Etang de Thau or the Sete, Rhone canal. I am now using Aluminium anodes on the hull and hanging anodes depending on where we are. Magnesium in Port Ariane and Zinc in salt. So far they seem to be working well. Hanging anodes sound like an added complication but I find them simple to use by dropping them over the side when moored and pulling them up when shortening ropes etc. I have always assumed the Midi is fresh water once past the first locks as it is fed from fresh water lakes as far as I know.

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Transition from seawater to freshwater 31 Oct 2022 16:19 #132639

  • Duncan Gilmour
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Thank you Balliol. I did read a very interesting contribution from you during a search of the forum. And I thank you for this one. I have had some advice from an anode supplier (anode outlet in Kent) who tell me that they would suggest aluminium given the salinity of the canal water and that aluminium is fast becoming a very common anode for multiple situations. Another company (allanodes) prefer to fit aluminium for all but a few water types.

My hull is well coated, generally, and I will look at the anodes when the boat comes out of the water this winter. I guess the amount of wear will indicate the amount of potential corrosion there is.

Thank you for your input. I think you have saved me a lift out!


Duncan

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Transition from seawater to freshwater 31 Oct 2022 13:52 #132638

  • Balliol Fowden
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As I have often said before galvanic corrosion prevention is a bit of a black art and the degree of corrosive potential that may exist depends upon various factors. For example, how well painted is your hull? Do you have any corrosion problem at the moment? How long are the zincs lasting in Puerto whatever?

Opinions are dangerous, but if your hull is well painted methinks you worry too much about the Med passage aspect if you will only be on salt for a week or so.

I have no idea what the salinity of the Midi is but it is reputed to be very polluted with poo, which might tend to increase the potency of the electrolyte, hence aluminium anodes may be a better choice than magnesium.

I also have minimal experience of just how corrosive the supposedly very saline Med water is, but suspect that it will not significantly deplete aluminium anodes in a few days. Magnesium might fizz a bit.

Presuming that you can’t access your bolt-on anodes in the water (in which case change them in the water when you get to the MIDI) then the compromise might be to fit aluminium anodes and then observe over time (by feel if necessary) once you get to the Midi. Perhaps plan a lift within the first year to see how they are doing.

Balliol.
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Transition from seawater to freshwater 31 Oct 2022 12:22 #132634

  • Duncan Gilmour
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Following on to this (and I'd like to invite Balliol Fowden to jump in if he wishes), if the water in the Canal du Midi is salty/ brackish, would aluminium anodes be a better bet than magnesium? If I then move up the canal to Toulouse and beyond, towards Bordeaux, will the aluminium work just as well, particularly as I will be returning through the same salty/ brackish water on my way to the Rhone later in the year. Finally, I have been advised by the boatyard here in Spain that I should lift out the boat on arrival in France because the fresh water anodes will deteriorate in only a few days at sea. They haven't specified the metal but I am imagining, from Balliol's description, that they are talking about magnesium. If I were to fit aluminium in Spain, would a week to 10 days be acceptable as a salt water transit into the Canal du Midi? It seems quite an expensive undertaking to lift the boat out simply to replace a few bolt on anodes but not as expensive, I grant you, as losing galvanic protection by having the wrong types.

So, in brief, may I ask Marty, Balliol and others in the know, how salty is the water in the lower reaches of the Canal du Midi, what would be the best material type to choose for French Inland waterway cruising and could I reasonably do it prior to a salt water sea transit lasting up to 10 days?

Many, many thanks


Duncan

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Transition from seawater to freshwater 01 Oct 2022 00:09 #132205

  • Paul Hayes
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I second Peters remarks about shade, most important. This year in July we were in Narbonne 43⁰ shade, and there was no shade, goodness knows what the direct in sun temperature was, but I couldn't stand being in it after about 13.00 until after 18.00, brutally hot.

Paul Hayes

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Transition from seawater to freshwater 30 Sep 2022 18:56 #132204

  • Peter Cawson
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I think you'll find that in summer the rain won't be much of a problem without a canopy but the intense sun will be. You'll need something to offer shade - I had a small bimini made that is fixed to the radar arch and the whole lot can be lowered or raised in less than 10 seconds in advance of bridges or other obstacles. My boat was rather similar to yours and I could perhaps offer suggestions for making cruising in French summers much more comfortable. Feel free to PM me.

Peter


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Transition from seawater to freshwater 30 Sep 2022 17:56 #132203

  • Duncan Gilmour
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Thanks Paul

That's the sort of info I was looking for. I'll be summer month cruising so it shouldn't be too much of an ordeal, particularly if I stow most of the canopy away below decks.

Many thanks

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Transition from seawater to freshwater 30 Sep 2022 16:03 #132200

  • Paul Hayes
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Hi Duncan
At 5m you might as well take it down on entry into "The System" and leave it down. If not the 3 bridges at Narbonne, especially the Roman one will do it with a nasty noise.

Raise the canopy at night if you want, but as Peter says all canals have 3.5m headroom or less specified.

You could come up the Rhone and Saône as far as Saint Jean de Losne with it up.

Paul Hayes
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Transition from seawater to freshwater 30 Sep 2022 11:57 #132196

  • Peter Cawson
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You'll have to get used to lowering your canopy in France, not just in the deep south.
The main north south through routes have numerous bridges with height of 3.5.m, but many smaller canals have bridges where air draft needs to be around 3.2-3.3m.

If interested I could send details of how I modified my motor cruiser with 5m canvas canopy and radar arch into a useful vessel in France

Peter


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Transition from seawater to freshwater 30 Sep 2022 11:26 #132195

  • Duncan Gilmour
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Thank you Paul, that is really good of you! What a kind and generous forum this is!

I would much appreciate further info regarding increasing the draft on the Robine but I would hope the VNF would trumpet the news (if they trumpet anything?)

Regarding the Midi bridges, yes, Capestang is the most tricky but "should" just fit and, in answer to another poster's question, I do have a profile for my boat in various configurations. Being a cruiser rather than a barge I do have removable height in the form of a canopy and radar arch. Whilst not difficult to lower it does take a few minutes to unpop the Tenax clips. It would be useful to me to know if I am going to have a series of bridges of airdraft less than 5.5m, in which case I shall have to pick a day with good weather (or dress up) and run with the canopy down. Cruising the Garonne & Midi, I am getting the impression this might be quite often, the Rhone less so!

Very many thanks, once again


Duncan

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Transition from seawater to freshwater 29 Sep 2022 22:46 #132186

  • Paul Hayes
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Hi Duncan

News in form Narbonne.

"The lower part of the Robbine is closed for maintenance all winter until next March (2023), the program is supposed to include returning the canal navigable though the last lock to full depth . Let's hope that they do, I'll let you know in the new year.
At 1.15 draft a boat cannot pass through at the moment.
I hope this helps."

As far as Midi bridges are concerned Caperstange is the most awkward due to the"ears" in the arch. If your profile fits it, which it should, then all the others, while being tight for space will be passable.
If in doubt come to a stop and hand the boat through.
A few years ago we took a 28m x 5.05m barge through Capestange on route to Narbonne, to clear the "ears" by about 6cms, we had to add 6 tonnes of water ballast to inflatable swimming pools on the decks.

Paul Hayes
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Transition from seawater to freshwater 29 Sep 2022 13:33 #132179

  • Balliol Fowden
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Duncan,

I don't think anybody could give you an absolutely definitive answer. The DBA Knowledgebase offerings are the best I have seen. Quite apart from the difficulty of accurately mapping the precise profile of each bridge (and do you have a precise profile drawing of your boat?) the situation will always be variable subject to canal water levels, wind (which can elevate levels at the downwind end of a bief measurably) and whether somebody has just drawn off or filled a lock just down the bief. You have to assess each bridge as you get to it and also have enough margin in hand for any short term water surges caused by lock operation.

Many vertically challenged barges carry a simple tell-tale on the bow, in our case a fibreglass whip aerial set to a couple of inches above mean wheelhouse level, but that doesn't help with the Midi bridges.

Balliol.

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Transition from seawater to freshwater 28 Sep 2022 21:49 #132174

  • Duncan Gilmour
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Thank you Pete

As I said, I have seen the documents you refer to.

Thank you

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Transition from seawater to freshwater 28 Sep 2022 21:19 #132173

  • Pete Milne
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Duncan Gilmour wrote: Thanks Pete

I have seen those and they are useful. However, VNF must have a database of the height of every single bridge on their network. I don’t think they publish it.

What would be useful to me would be to know if I need to keep my canopy and arch down all day, or if only one or two bridges will require it. I don’t think the DBA knowledge base is able to do that.

As so many bridges are curved (and some are even bent) , it's not a simple matter of height. The Library has VNF's quite detailed published description of the Midi bridges, HERE
Pete Milne, Quo Vadis , Gent.

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Transition from seawater to freshwater 28 Sep 2022 20:03 #132170

  • Duncan Gilmour
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Thanks Pete

I have seen those and they are useful. However, VNF must have a database of the height of every single bridge on their network. I don’t think they publish it.

What would be useful to me would be to know if I need to keep my canopy and arch down all day, or if only one or two bridges will require it. I don’t think the DBA knowledge base is able to do that.

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Transition from seawater to freshwater 28 Sep 2022 09:57 #132162

  • Pete Milne
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There are several documents about Midi bridges in the DBA Library HERE . They don't necessarily all agree!
Pete Milne, Quo Vadis , Gent.

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Transition from seawater to freshwater 28 Sep 2022 09:49 #132160

  • Duncan Gilmour
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Thank you Paul

Our draft is 1.15m but, obviously I would like a bit of a buffer in that. I’ve been working on 1.5m minimum. I had heard that the approach and the Cabal Dudu Robine was shallow but was hoping it would be sufficient. I am still in the planning stage but am hoping to travel NW up to Bordeaux. Low bridges are also a concern. Theoretically, I should get through Capestang bridge but there doesn’t seem to be any info on the height of many other bridges, only that they are higher than Capestang.

Thanks for the offer to ask your friend. That would be much appreciated!

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Transition from seawater to freshwater 27 Sep 2022 17:15 #132147

  • Paul Hayes
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Hi Duncan

What is the draft of your boat?

Knowing Narbonne, and some of the boats that go "the long way round" to get to the Med I'm wondering if you will get though the lowest lock on Le Robine, Ecluse de Mandriac.

Almost no traffic goes through it now, and they are all very shallow drafted.

If you let me know your draft I'll ask a friend who lives down there and is an expert on the canal.

Personally I think that entering at Le Grau-de-Roi would be your best bet. Sete is good also.

Paul Hayes
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Transition from seawater to freshwater 27 Sep 2022 12:55 #132142

  • Duncan Gilmour
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That is very useful to know, thank you. I may have to reconsider because my draft is 1.15m minimum and I would like at least 1.5 m to be comfortable. I could, as Marty suggests, enter around Agde and transit fairly rapidly (before the summer tourist season) into the western reaches of the Midi.

I might take a drive to Narbonne and knock on a few hatches. Do you have any liveabord contacts there who might appreciate a chat and Pastis?

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Transition from seawater to freshwater 27 Sep 2022 12:50 #132141

  • Duncan Gilmour
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Thank you very much for that. Yes, the plan is to enter at Port La Nouvelle and transition to the Canal du Midi via the Canal du Robine and then move Westwards towards Toulouse. We will, eventually have to transit the Etangs to get to the Rhone for our Northern journey.

Any further tips much appreciated!

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Transition from seawater to freshwater 27 Sep 2022 07:55 #132136

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Hi
The first lock from Med going up to Narbonne has limited depth, I'm told by people living on boats there that it's limited to under 1 metre draft.

There is pressure on VNF to dredge the channel, but when and if it happens is anyone's guess.

The port at Narbonne has a good management team, and a small livaboard community who are very friendly and knowledgeable.

As Marty suggests Naval Allemand have a decent reputation and a boat hoist.

Or go a bit further east to Sete or Le Grau-de- Roi and you are spoiled for choice for yards which can lift you.

As Balliol has commented Dutch steel cruisers generally have a far different paint system than the "black bitumen" used on narrowboats and barges. Your antifouling will almost certainly be painted on top of a perfectly good paint finish, not bare steel as it is on most narrowboats, as is The Blacking.

Paul Hayes
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Transition from seawater to freshwater 27 Sep 2022 03:56 #132135

  • Marty Latham
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If you are going to go to Narbonne, I'm assuming you are planning on entering the canal system at Port la Nouvelle. There may be an issue with heavy weed between Port la Nouvelle and Narbonne. An alternative to consider is the Herault River at Grau d'Agde. Also there is a very experienced yard there, "Chantier Naval Allemand". Once in the midi region and if you plan to cruise the Etang or the lower Rhone de Sete you will travel through a considerable amount of salty water.
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Transition from seawater to freshwater 26 Sep 2022 21:37 #132134

  • Balliol Fowden
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I don’t know what they do in Turkey but round my neck of the woods and in modern times most steel boats are painted with a full epoxy anti-corrosion treatment first. Anti-foul can then be added if desired, but it is primarily an anti-fouling coating, not an anti-corrosion coating.

Balliol.
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Transition from seawater to freshwater 26 Sep 2022 19:13 #132133

  • Duncan Gilmour
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Thanks very much for this contribution.

I was talking to a narrowboater friend of mine who also owns a yard in Turkey and he suggested that the marine antfoul would wear off quickly leaving me with no protection and the boat would rust. He said that the fresh water antifoul was more of a bitumen base and lasts around three years but shouldn't be put on top of the marine coating as it would shed, as it is designed to do, leaving me with no protection. Would you suggest getting the boat marine antifouled again this winter and only switching to fresh water antifoul the following year (2024)? Regarding the anodes, I confess I don't know much about the subject but was led to believe that Magnesium would not work in salt water and zinc would not work in fresh water. I guess you are saying it is a trade off between the rate of decay of the anodes and the protection they offer the steel hull. Either way it seems that if I fit any of the three metals you suggest, there will be very little in the way of degradation in the short term. If I fit fresh water anodes and they are not needed, I guess there is no harm done and they will just sit there?

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Transition from seawater to freshwater 26 Sep 2022 17:50 #132132

  • Balliol Fowden
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Firstly, I am not sure why you would want to remove the present anti-foul. Unless local regulations prohibit it (which I doubt they will) an anti-foul coating is becoming more and more necessary inland (except as everywhere on ecological grounds!) given the spread of fresh water zebra mussels etc. Your "seagoing" anti-foul should work just as well inland until spent.

Magnesium anodes are the most potent for inland use but can give excessive protection locally which can cause the paint to bubble off around the anodes. Many suggest that aluminium anodes are the best compromise.

Irrespective, if you fit magnesium or aluminium anodes and leave the boat in salt water for too long they will be excessively active, and the Med is very saline. However I doubt that any harm will occur for a limited period of only a few weeks. Any "harm" will be excessive anode depletion and perhaps some paint bubbling local to the anodes, but the anodes will protect any affected areas.

Zinc anodes additional to MG or Al will do nothing. The most potent anode (Mg>Al>Zn) will prevail. The zincs will just be idle.

It would probably be best to leave it until you are in fresh water in case you are delayed in the Med, but I wouldn't lose sleep over it.

Personally I do not believe that fresh water anodes do that much good anyway in relatively clean fresh water, except where components such as bronze propellers are very close to steel. The fresh water electrolyte is too weak. I don't have anodes on my own ship, except where the bronze bow propeller can rest very close to the steel, but with a relatively thin Dutch steel cruiser hull I would not counsel against the practice.

Balliol.
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Transition from seawater to freshwater 26 Sep 2022 15:50 #132131

  • Duncan Gilmour
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I'm going to be moving my Dutch steel cruiser boat from the Costa Brava into the French canal system next year. The boat has been in salt water since 2010 and was fully anti-fouled last year. I understand that I will need to pressure wash the anti-foul off and apply fresh water blacking. As well as that, I believe the anodes need to change from zinc to magnesium.

I would like to ask you guys for advice. Ideally, I would like to get this work done this winter in the Costa Brava. The transit to Narbonne and the Canal du Midi is about a 9 hours and we would, ideally, like to take a week or so to make the journey. My question is how critical is it to get the boat into fresh water as soon as the boat has the blacking applied? Similarly, if I were to swap the anodes out to magnesium, could I trail a couple of zinc anodes on wire clipped to the inox handrail for the salt water transit before removing them once in fresh water?

Failing that, does anyone have a boatyard they would recommend in the Narbonne area? I could get it done there. I am planning to use a boatyard/ marina in that area in order to apply for a 6 month visa, in any event.

Many thanks for the thoughts

Duncan

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