Hull side anodes

[Richard Mathews]

Earlier this year we had a survey performed and, as might be expected for a 20 year old craft, some pitting was noted on the sides of the hull. Among the insurance recommendations made was take the hull back to bare metal, blob weld and grind smooth the deeper pits and fit three low profile anodes along each side of the hull.

The boatyard where we intend to do this work has said that they have strong reservations about this as they believe we will not then be able to pass through the very narrow locks to be found on the Llangollen at Hurlestone, due to the increased width of the boat. Our insurers however insist that all recommendations be completed so at the moment we caught between a rock and a hard place!

At the moment I don't know the precise width of our boat, this will be established when she comes out of the water in February. In the meantime does anyone have any experience of these types of anodes being fitted to a narrowboat? Is it common practice to fit these as a solution to corrosion problems and are the locks so narrow that we may suffer such a problem?

Any advice or comments are most welcome.

[Richard Mathews]

Earlier this year we had a survey performed and, as might be expected for a 20 year old craft, some pitting was noted on the sides of the hull. Among the insurance recommendations made was take the hull back to bare metal, blob weld and grind smooth the deeper pits and fit three low profile anodes along each side of the hull.

The boatyard where we intend to do this work has said that they have strong reservations about this as they believe we will not then be able to pass through the very narrow locks to be found on the Llangollen at Hurlestone, due to the increased width of the boat. Our insurers however insist that all recommendations be completed so at the moment we caught between a rock and a hard place!

At the moment I don't know the precise width of our boat, this will be established when she comes out of the water in February. In the meantime does anyone have any experience of these types of anodes being fitted to a narrowboat? Is it common practice to fit these as a solution to corrosion problems and are the locks so narrow that we may suffer such a problem?

Any advice or comments are most welcome.

[DeanS]

On some boats (most?) the anodes are welded onto the curved bits under the bow and on the stern trim.....not on the actual sides...so they shouldnt increase the width of the boat at all. All narrowboats have them...and travel through locks fine. See the images below, and you'll see my point about not increasing the actual boat width.

 

 

 

 

They ARE correct that you WOULDNT put a 3rd anode midway down the length of the boat...as this WOULD be an issue in locks. If the insurance demand 3 anodes...put 2 in the front, and 1 at the back on each side.

Edited December 28, 2013 by DeanS

[DeanS]

Double thread. Perhaps the mods can delete this one.

[station tug]

change insurer and question the qualification/expierience of the servayer..this is probably the worst and possible very dangerous advice....(unless this is a wind up??) if you manage to get the boat into a lock theres a real chance it will get hung up and sink if you are inexpierianced. loss of the boat and life are a real threat....if your boat is a narrow boat it will be 6ft 10 inches the anodes will be 2 inchs each making your boat 7ft 2in...

 

this bits going to get a reaction.....

 

anodes on a fresh water boat are a waste of time and a money making scam thought up by the boat yards.....they protect sod all but a very small area around the anode.........

 

welding up the deepest pits is a great idea (unless youve got spray foam)

 

you could have pockets fabricated into the hull to accomadate the anodes along the hull which will be costly and a fast acting rot spot on the hull...

[mark99]

He means spray foam on the inside (catching fire) not using spray foam on the outside to fill corrosion holes...... just in case you are wondering......

 

And cathodic protection is a well known, understood and legitimate form of metallic protection - used by industry worldwide.

 

Anodes are usually placed either side in the forward and rear "swim" of a boat hence do not add to the width.

Edited December 28, 2013 by mark99

[GUMPY]

On one of my NB I fitted the mid anodes under the baseplate at the edge, boat had a draft of 2ft8 ballasted flat and we never knocked them off.

Present NB has "pockets" for anodes in the sides which have been there since the boat was built (20years ago) with no sign of becoming a rust pocket.

Edited December 28, 2013 by Loddon

[mark99]

Present NB has "pockets" for anodes in the sides which have been there since the boat was built (20years ago) with no sign of becoming a rust pocket.

 

Might have something to do with having a ruddy great localised anode protecting it. lol

Edited December 28, 2013 by mark99

[BEngo]

change insurer and question the qualification/expierience of the servayer..this is probably the worst and possible very dangerous advice....(unless this is a wind up??) if you manage to get the boat into a lock theres a real chance it will get hung up and sink if you are inexpierianced. loss of the boat and life are a real threat....if your boat is a narrow boat it will be 6ft 10 inches the anodes will be 2 inchs each making your boat 7ft 2in...

 

this bits going to get a reaction.....

 

anodes on a fresh water boat are a waste of time and a money making scam thought up by the boat yards.....they protect sod all but a very small area around the anode.........

 

welding up the deepest pits is a great idea (unless youve got spray foam)

 

you could have pockets fabricated into the hull to accomadate the anodes along the hull which will be costly and a fast acting rot spot on the hull...

Most of this is not the case unless you have a very unusual shaped boat. Very few boats are 6' 10" wide at the baseplate- they tend to taper from 6' 10" at the top rubbing strake to 2m (6'6"ish) at the base, because 2m wide plates are popular with boat builders. In this case the anodes can be fitted just above the baseplate without over-widening the hull- the surveyor did specify low profile anodes and you should check the width after they are fitted. If you do have a square hull that's 6'10" wide at the bottom then fit the anodes under the baseplate about 6" in from the edge. Our boat has had both side anodes and some under anodes for years without problems and I do get out and about the system. It goes through the marked narrow locks in the Cheshire flight or on the Caldon and up/down Hurleston OK (though Hurleston was a while back).

 

Anodes do have a limited range. Empirically it seems to be about a radius of 6ft, so one either side at the baseplate covers the bottom and up to the waterline fairly well on most boats.

 

Small welding jobs on the outside with sprayfoam on the inside are not a problem unless the sprayfoam is so thin as to burn through.

 

N

 

Inset anode pockets are OK, but pricey. They don't go rotten any faster than the rest of the hull because the anode prevents this. Again empirically, they may reduce the radius of action of the anode a bit.

[Timleech]

On some boats (most?) the anodes are welded onto the curved bits under the bow and on the stern trim.....not on the actual sides...so they shouldnt increase the width of the boat at all. All narrowboats have them...and travel through locks fine. See the images below, and you'll see my point about not increasing the actual boat width.

 

 

 

 

They ARE correct that you WOULDNT put a 3rd anode midway down the length of the boat...as this WOULD be an issue in locks. If the insurance demand 3 anodes...put 2 in the front, and 1 at the back on each side.

 

Anodes are usually fitted at either end as a compromise, they have a limited range and won't offer much protection to the middle of a long boat. Adding more at one end will do nothing further to protect the middle.

The 'low profile' anodes are made specially for that role, but you need to establish how wide your boat is near the bottom. A lot of hulls are constructed in a way that enables the use of 2m wide plate for the bottom, which would give plenty of scope.

 

Tim

[FadeToScarlet]

I'm probably going to put some in the middle of the boat, because I've got a seam line all the way along between the wrought iron and the steel that could do with a bit of protection, and there was evidence of electrical activity during the survey.

 

Luckily, the hull sides are very corrugated from being bashed about by Severn and Canal and then the DIWE and then Waterways, and I could fit some into the bottom of the dents without them protruding- sort of like anode pockets.

[nb Innisfree]

We had two or three pits exactly midway between the fore and aft anodes, as we our hull sides are set back an inch our two from the baseplate edge we had room for an anode each side and just above the baseplate.

 

When your boat is out of the water hang a plumb bob from the handrails each side of your boat and equal distance fore and aft so that they hang vertically from the rubbing strakes, then underneath the baseplate use a steel tape measure to measure the distance between each one and the sides to work out how much room there is for anodes. (can measure overall width as well)

Edited December 28, 2013 by nb Innisfree

[ditchcrawler]

On one of my NB I fitted the mid anodes under the baseplate at the edge, boat had a draft of 2ft8 ballasted flat and we never knocked them off.

Present NB has "pockets" for anodes in the sides which have been there since the boat was built (20years ago) with no sign of becoming a rust pocket.

I was talked in to having two welded just above the base plate, on most boats this is the narrowest part of the hull, they measured before fitting to ensure they didn't protrude beyond the rubbing strakes. Even so I sometimes knock them on things.

[Richard Mathews]

Firstly - apologies for the double posting, my fault entirely.

 

Secondly, no this isn't a wind-up at all.

 

We already have the conventional anodes fore and aft secured in the swim areas so as not to protrude beyond the width of the boat. This recommendation is to fit these further anodes along both sides. They are one inch deep so would add an extra two inches to the width. I'm hoping that our hull does taper slightly as has been suggested in which case it may not pose a problem. I hadn't considered mounting them on the actual baseplate close to the edge so thanks very much for that suggestion, which may well be acceptable to our insurers particularly if the hull does not taper.

 

Thanks for all your comments and advice, much appreciated.

[RLWP]

 

this bits going to get a reaction.....

 

anodes on a fresh water boat are a waste of time and a money making scam thought up by the boat yards.....they protect sod all but a very small area around the anode.........

 

welding up the deepest pits is a great idea (unless youve got spray foam)

 

you could have pockets fabricated into the hull to accomadate the anodes along the hull which will be costly and a fast acting rot spot on the hull...

So, I took this unprotected bit of metal and hung it in some water for a few years, and it dissolved! So, it must be protecting my hull and keeping away the elephants

 

The surveyors advice is pretty standard for a written report, I suspect that he would say something else on the phone

 

Richard

[Ryeland]

When we had our boat lengthened I fitted a low profile anode in the middle of each side. I thought if they get knocked off I'm no worse off than not fitting any, but in fact three years on they are fine. Not even any scrapes on them. The overall width including the anodes is much less than at the rubbing strips.

 

Richard

[trackman]

We had mid side anodes fitted 18 months ago and have had no problems. Occasionally they catch something but to no ill effect.

I wasn't sure about them but thought it worth a try. So far I'm happy, but we won't know if they have done anything useful until the boat comes out for its next blacking in 6 months or so.

[blackrose]

anodes on a fresh water boat are a waste of time and a money making scam thought up by the boat yards.....they protect sod all but a very small area around the anode.........

 

 

Not in my experience. The pitting on my hull only occured at sites well away from the anodes - midway down the hull sides.

 

If you read any scientific literature on corrosion you will see that although the type of electrolyte has a huge bearing on rates of corrosion, it still occurs between dissimilar metals in fresh water, but at a reduced rate compared to salt water. You can't argue with a voltmeter which measures potential difference. The other thing to bear in mind is that "fresh water" is a bit of a misnomer. Canal and river water can contain enough impurities to render it fairly effective as an electrolyte.

 

These are the sort of thing that the OP wants for midships. I can't understand why they are so expensive? I bought similar anodes a few years ago for about 20 quid each. Has magnesium gone up in price in the last few years?

 

http://www.midlandchandlers.co.uk/Catalogue/ProductDetail/anode-low-profile-mid-mount-2kg-md20lp?productID=b98daf72-5571-4a6c-9972-a079f2ce079c&catalogueLevelItemID=465165f9-ca30-4d4b-b373-61ad06f792d3

 

I had mine welded on just above the baseplate overhang so they don't really increase the width of the hull.

Edited December 30, 2013 by blackrose

[Richard Mathews]

The anodes supplied by Limekiln Chandlers are much less expensive https://www.limekilnchandlers.co.uk/index.php?_a=product&product_id=712

No prizes for guessing which supplier we will be using if we do fit them.

[BlueStringPudding]

I put two extra anodes on my boat midships about 4 or 5 years ago. It was my idea as an extra precaution for a longer boat, by no means essential but neither was it anyone else's money making scam! When she was out of the water for blacking back then I asked the boatyard to check she wouldn't be over wide. They checked the width with a plumb line down from the boat sides to ensure the extra anodes didn't stick out. The chaps at the yard were confident and it cost me about £60 on top of a £800 blacking job so the price wasn't a concern for me. Since then done the Llangollen and all sorts of other scrapey, bumpy narrow locks and tunnels and had no problems at all.

She came out for blacking two months ago (yes, I really did leave it that long between blackings - Norty) and all 6 anodes are still where they should be and no noticeable pitting on the hull.

Edited December 31, 2013 by BlueStringPudding

[mark99]

I put two extra anodes on my boat midships about 4 or 5 years ago. It was my idea as an extra precaution for a longer boat, by no means essential but neither was it anyone else's money making scam! <snipped>

 

As the previous poster Blackrose mentioned above - if you connect an anode to your hull surround it in canal water then connect a voltmeter to

 

1) the anode and

2) your hull

 

and measure the milli-volts produced that is direct proof that metal is being transported from anode to hull. (In other words, your hull is being protected and it's a valid method of hull protection).

 

Granted it may not be perfect when one is slapped on one end and another at far end as it has limited range and canal water may not be a great electroylte - but to deny it is incorrect.

 

NB There are other better systems used by industry (impressed current) that use an external electrical current source to drive the electron flow.

Edited December 31, 2013 by mark99

[Richard Mathews]

I thought you may wish to have some feed back on this issue.

 

Once Sapphire was out of the water, using a plum bob we established that the hull was indeed tapered. Measuring just above the base plate it was found that, on both sides, the width was at least 2.5 inches less than that at the top rubbing strake. It was also noted that the base plate extended approx. 0.75 inch beyond the hull side.

From this we decided to attach three, low profile side anodes equally spaced along both sides of the hull, just above the base plate giving us a total of five anodes in all on each side.

Sapphire has now been in the water for about four weeks. During that time she has done all the Middlewich and Trent and Mersey locks and return journeys without incident. Another owner is now on the Llangollen as I write this.

 

So far, so good. Hopefully these will not turn out to be famous last words!! Should there be any incidents I will post again as others may find the information useful.

[LEO]

I thought you may wish to have some feed back on this issue.

 

Once Sapphire was out of the water, using a plum bob we established that the hull was indeed tapered. Measuring just above the base plate it was found that, on both sides, the width was at least 2.5 inches less than that at the top rubbing strake. It was also noted that the base plate extended approx. 0.75 inch beyond the hull side.

From this we decided to attach three, low profile side anodes equally spaced along both sides of the hull, just above the base plate giving us a total of five anodes in all on each side.

Sapphire has now been in the water for about four weeks. During that time she has done all the Middlewich and Trent and Mersey locks and return journeys without incident. Another owner is now on the Llangollen as I write this.

 

So far, so good. Hopefully these will not turn out to be famous last words!! Should there be any incidents I will post again as others may find the information useful.

 

Hi,

In 2006 a surveyor advised me to fit anodes to the side of my boat, I had 4 fitted (48ft boat) plus those at the front and rear. Had the boat blacked last month, anodes working well and no sign of any pitting.

 

It's a 'slab' sided boat, the only narrow lock I have had slight problems with is the second one up on the Napton flight.

 

L.

Edited April 5, 2014 by LEO