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Talpidae: problems,


Moley

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NB Talpidae went into dry dock yesterday morning for re-blacking and BSS. She has failed BSS on fuel lines not carrying the required numbers, there's a minor gas leak somewhere which we thought we had found and I had nipped up but on the manometer test when the level is supposed to remain constant for 5 minutes it dropped, installation condemned. Dry-dock man is able to rectify both. There were also a few minor niggles which I am able to rectify.

 

However, once the dock was drained and pressure washing commenced, my problems took a quantum leap.

 

I must confess that I have never really bothered with the threads on galvanic isolation and earth bonding because, although they frequently turn into quite amusing arguments (viewed from the outside), that rapidly detracts from any benefit those threads might be. Also, as I have a very minimal 240v installation, I didn't think it applied to me. Well it seems to be having a bloody good go at applying to me!

 

Let me describe my mains installation: Cable from shoreline bollard to plug on boat, from mains inlet to 2-way distribution point, 2 trip switches, 6-amp line to single socket outlet, 10-amp line to 2-gang socket outlet. System is entirely self-contained, nothing is earthed to the steelwork, I may as well bring in an extension lead from the bollard. Besides this, it is almost never connected to shoreline, there's no credit on my meter and no card which BW sell anywhere on the system works in our bollards, a couple of neighbouring boat owners have complained and had the meters taken out of their bollards and are on a constant supply. Very occasionally I might disconnect one of those and plug in for a short while to run a vacuum cleaner around and earlier this week I pinched a connection overnight to plug in a battery charger. That's it, we have no other mains appliances.

 

However, boats on either side of ours (one 3 feet away across a pontoon, the other a couple of fenders away) are permanently connected to their supplies. One of those is a forum member so please be tactful in any replies.

 

On pressure washing there is some long-term pitting and corrosion which would be expected with any boat 25+ years old. However, there is also quite a bit of shiny pitting due to electrolysis, some of it rather deep, and the propeller looks silver, not bronze.

 

If a picture's worth a thousand words, this lot should save me pages:

http://i20.photobucket.com/albums/b204/Mol...ck/09022001.jpg

http://i20.photobucket.com/albums/b204/Mol...ck/09022002.jpg

http://i20.photobucket.com/albums/b204/Mol...ck/09022005.jpg

http://i20.photobucket.com/albums/b204/Mol...ck/09022101.jpg

http://i20.photobucket.com/albums/b204/Mol...ck/09022102.jpg

http://i20.photobucket.com/albums/b204/Mol...ck/09022103.jpg

http://i20.photobucket.com/albums/b204/Mol...ck/09022104.jpg

http://i20.photobucket.com/albums/b204/Mol...ck/09022105.jpg

http://i20.photobucket.com/albums/b204/Mol...ck/09022106.jpg

http://i20.photobucket.com/albums/b204/Mol...ck/09022107.jpg

http://i20.photobucket.com/albums/b204/Mol...ck/09022108.jpg

http://i20.photobucket.com/albums/b204/Mol...ck/09022109.jpg

http://i20.photobucket.com/albums/b204/Mol...ck/09022110.jpg

 

My options would appear to be:

 

Have dry-dock man blow some weld into the deeper pits, black over and try to get rid of ASAP (and caveat emptor).

 

New baseplate and half way up the sides.

 

If we re-plate there is still a question mark over whether or not or for how long we keep the boat but I am certain that, in the present climate, any prospective buyer is going to shy away from any older boat which could potentially require plating.

 

If we re-plate, who (within sensible proximity) could I ask to do it at a reasonable price, what might that price be, and what's to stop it happening again?

 

Alternately, I might be open to offers, as seen.

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Where the hull is pitted, how thick is the remaining steel?

 

I've seen boats that look far worse than that, at least superficially.

 

P.S. sorry that sounded a bit offhand - I know it's a big worry when your 'pride and joy' isn't right - I just hope it isn't as serious as it seems.

Edited by sociable_hermit
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Ade,

 

Very worrying for you, although from the pictures, it doesn't necessarily seem as bad as you are seeing it. I'm guessing you have been told more than the post or pictures bring out ?

 

Some questions,

 

Has the pitting been measured, and if so, how deep are the worst, please ?

 

Is the base as bad, (as you seem to indicate it needs overplating) ?

 

What were the original steel thicknesses ?

 

Some observations,

 

There doesn't seem to be a lot visible in the way of existing anodes, (just some very small ones ??), or am I just not looking close enough ?

 

I can't understand how your 230V electrics enter into anything, if you only rarely connect to a land supply. The lack of a hull bonded earth is a potential danger when you do, and (if we believe the arguments) the lack of a GI is bad news if you stay connected. But in your case, if you stayed connected, it probably wouldn't affect the corrosion situation, as you say no part of the supply is bonded to the boat hull.

 

I'm no expert, (as I'm sure I'll be told :lol: ), but if you have suffered this because of stray mains currents, it can only be because you are sitting between other mains connected boats, and have little to do with your (usually disconnected) 230 volts arrangements.

 

Lets see what others say, but I guess the missing bit of information is "how bad's the damage?". Are you confident it's all recent, since the last blacking ?

 

Alan

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How deep are the worst pits Adrian? My boat is 27 years old and when the hull was surveyed 18 months ago there were a couple of areas of pitting, the worst being several pits about 2cm across and 2.3mm deep at the worst point, leaving a mimnimum of 3.7mm steel thickness at those points.

 

The surveyor was not unduly worried, but suggested that I have the hull shot blasted and coated with a two part epoxy coating. When I spoke to the boatbuilder, he suggested that next time I dock the boat for blacking (later this year) I get him to weld fill the wost pits, which is the approach I shall be taking.

 

Interestingly our boats are about the same age, but mine does not have 240v on board (except a very small inverter, bought about three years ago, which is only connected about 40 hours a year. There is no fixed 240v on my moorings, nor has there been on any of the boat's previous moorings. on this basis the pitting cannot easily be ascribed to the dreaded galvanic action, so it must just be down to natural corrosion over a long period of time in the water. perhaps that is the pricipal cause of your pitting.

 

One thing I do know is that if it got to the point that it needed overplating, I would probably get it done, as the boat wouold be almost worthless wothout it.

Edited by David Schweizer
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How deep are the pits, how thick is the metal ? Are the pits really that bad. In my experience of welding rusty cars, blobbing weld in to a rusty pit will blow a hole right through. Maybe better to leave alone.

 

I didn't see any anodes on your pictures, what do they look like ?

 

When did you last dock and repaint (at least two, pref three coats applied over several days after a full pressure wash and wire brush scrub).

 

Anyway,

Aside from that, most boats over 20+ years, need or have had some overplating. You can't stop the corrosion, only slow it a bit. If you're near salt water, or where there's lots of air in the water (downstream of a lock for example) corrosion increases. The bottom plate is usually better preserved than the water-line beacuse its the air that does the damage, tho' the bottom will get scraped on the mud more than the sides.

 

We had a full side skin up to the waterline done on a 28 y.o. 60 foot boat a few years back for about £8K. This was the last job this yard did before the owner retired so I can't make any recommendations now. This re-plating was forced by the BSS exam where the "examiner" hit the plates with a sledge hammer and he then made his judgment on the basis of the "clang" and the size of dent. Not very scientific IMHO.

 

I'd say that a boat which has had the work done will be more marketable, than one where there's an embarrassed silence or shilly-shallying in answer to the question "has it needed any re-plating".

 

You're choice may of course be limited to boatyards reasonably close to you.

Edited by jake_crew
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This is relayed from Moley. He is at dry dock now ( Stourbridge) and has just phoned. This is the latest.

 

 

The main concern seems to be there is little baseplate showing at the chines.

 

And if she's going to split it will be at corners.

 

 

Hull surveyor coming Monday!!

 

 

Thanks for the posts folks, to say we are worried and feeling rather sick at the moment is slight understatement.

 

Not what we were expecting this weekend. :lol:

No doubt Moley will be back on line once he is back.

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I really cannot imagine that the 240v connections, or the presence/absence of a GI on either your boat or your neighbours, could possibly have any bearing whatsoever on this (the safety impications of unearthed connections are a separate issue altogether). The apparent lack of any sacrifical anodes is more worrying.

 

It is hard to tell about the pitting, no doubt your boatbuilder will be much more help here, it al depends on how much metal is left. If there is still a reasonable depth with maybe just one or two bad pits, maybe a dab of weld in those spots is all it would take for you to continue enjoying Talpidae's delights for many years to come. The chines are often the first thing to go, especially on ex hire-boats, as they get worn away on the shallow edges of the canal (especially the Shroppie); our old "Thistle" had been sunk by that before we had her, but a length of angle welded along each side of the boat cured the problem permanently (ok, 20 years later she had to be re-bottomed, but that's a long long time).

 

We're all rooting for you!

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Thank you Allan.

 

We wait for survey and results, its obvious we have some major problems, we now need to know the extent of them.

 

There were 4 anodes on boat at each corner - which do not really appear on Adrians pics.

They were still not too bad and were going to be probably left on and the 4 new shiny ones we had already bought added also- obviously this was before the hull was pressure washed and revealed our problems!

 

We are also attempting to get quotes for replating so we know where we are possibly aiming costs wise.

Anyyone who has suggestions/recommendations on welders in our area ( Kidderminster) apprieciated.

 

 

I really should not have changed my car yesterday, all very bad timing.

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Snip

 

. . . . its obvious we may have some major problems . . . . .

 

Snip

 

The suggestions in the various posts above are that things may not be as bad as they seem.

 

Although easy for us to say and not so easy for you to do but if the surveyor is coming on Monday please don't grind yourself into the ground unnecessarily before then.

 

If you can't enjoy the boat this weekend, why not take your mind off it a go out in that new car whilst the weather is nice?

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The suggestions in the various posts above are that things may not be as bad as they seem.

 

Although easy for us to say and not so easy for you to do but if the surveyor is coming on Monday please don't grind yourself into the ground unnecessarily before then.

 

If you can't enjoy the boat this weekend, why not take your mind off it a go out in that new car whilst the weather is nice?

 

 

:lol: Thank you xxx

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Hi,

 

Were the pits covered with rust when the boat was slipped?

 

Looks to me like it could be anaerobic pitting, maybe partly triggered/caused by poorly adhering blacking.

 

The silver prop could be magnesium plating from nearby anodes.

 

cheers,

Pete.

Edited by smileypete
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:lol: Thank you xxx

Is the hull being used at all as a 12v "return wire"? Perhaps unknowingly? This would cause pitting.

 

Chris

 

The silver prop could be magnesium plating from nearby anodes.

..............or copper loss due to galvanic action leaving zinc from the original "commercial" bronze (brass).

 

Chris

Edited by chris w
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Long shot, and I'm not an expert so might be barking up the wrong tree entirely.

 

What do your 12V earthing arrangements look like? From the state of the prop, one could almost believe that there's a path from one side of the batteries to the prop (via the engine, gearbox and prop shaft) and a path from the other side of the batteries to the hull, turning the boat into a big electrochemical cell.

 

As you are not shoreline connected very often, that might provide a better explanation for all the plating.

 

Don't panic too much about the sliver plated areas on the hull, they can look quite dramatic without meaning much. Melaleuca had some galvanic corrosion when we bought her, and quite a few bubbles in the blacking, when pressure washed off were silver, but the checked hull thicknesses were fine, and nowhere was down more than 0.8mm from new.

 

The previous owners lived aboard, and had botched the GI installation, which explained the problems we saw.

 

Good luck!

 

MP.

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Thanks for all the comments so far and the good wishes, both public and private.

 

All I have to go on at the moment is guesswork. We are assuming that the original steelwork was 1/4" baseplate (6.35mm) and 3/16" sides (4.7625mm). Would that seem a fair guess? Some of the worst pitting would appear to be around 2mm deep, so 4.7625 - whatever you would expect to lose over 25 years - 2mm = probably not enough.

 

Surveyor is coming on Monday so I will know more then.

 

Existing anodes seem quite reasonable but weren't pictured. The plan was to add new anodes below or in line with the old ones.

 

http://i20.photobucket.com/albums/b204/Mol...ck/09022003.jpg

http://i20.photobucket.com/albums/b204/Mol...ck/09022004.jpg

 

Boat is currently in dry dock by the Bonded Warehouse, end of the Stourbridge Town Arm. Dry dock man, Andy, reckons it's the worst electrolysis he's seen. Andy has only recently taken over that dock and is having quite a bit of work done, new roof over and stop planks being replaced by a winch operated entrance. A liveaboard Sparks has been doing his lectrix today and was also rather impressed by our problem, they've had some electrolysis around those moorings but not on the scale of ours. Sparks reckons there's a major problem at our moorings and would not consider parking there until it was investigated and resolved.

 

I am absolutely certain that my steelwork is not being used as a return path, systems onboard are minimal, all wiring goes out from a positive bus bar (fixed to nylon) through fuse holders to lighting or other services and return to a negative bus bar (fixed to wood with screws which don't go all the way through) and then directly to battery negative. All battery negatives are bridged together. Obviously, there is a connection from battery -ve to engine.

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If it is any comfort, when we had our inspection done when we bought Tawny Owl we had pitting similar to that. Our surveyor pointed it out and recommended we kept an eye on it and filled the pits with blacking. It hasn't recurred.

 

The hull wear sounds like you are going to have a set of shoes, like we did last blacking.

 

It was an awful worry when we found out about our hull wear and lead to a few sleepless nights. Don't despair, put yourself in the hands of your surveyor. I think you will come out OK.

 

Richard

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systems onboard are minimal, all wiring goes out from a positive bus bar (fixed to nylon) through fuse holders to lighting or other services and return to a negative bus bar (fixed to wood with screws which don't go all the way through) and then directly to battery negative. All battery negatives are bridged together. Obviously, there is a connection from battery -ve to engine.

Is there a connection from the negative bus bar to the hull? The prop is connected to battery negative via the engine and gearbox and shaft. Is it possible that the engine isn't connected to the hull (rubber/wooden engine mounts?) and therefore the hull is not connected to battery negative? If so a leakage from battery positive to the hull via damp/dirt/chafed insulation would be enough to pass a current through the water via the prop and hull.

 

Straws, I admit, but worth checking.

 

MP.

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Is there a connection from the negative bus bar to the hull? The prop is connected to battery negative via the engine and gearbox and shaft. Is it possible that the engine isn't connected to the hull (rubber/wooden engine mounts?) and therefore the hull is not connected to battery negative? If so a leakage from battery positive to the hull via damp/dirt/chafed insulation would be enough to pass a current through the water via the prop and hull.

 

Straws, I admit, but worth checking.

 

MP.

If it's like our BMC installation was, then a bond from 12 volt negative to hull was missing, (now sorted).

 

However, even if the engine mounts are isolated, I reasoned the exhaust pipe was probably a pretty good, (though far from ideal!) electrical bond between engine and hull. Mind you, I recall that Talpidae's exhaust fell apart at some stage, so perhaps it wasn't very conducting leading up to that point.

 

I'd still be interested to know the date of the last blacking, and what the verdict on the hull was at the time ? Is it really the case that the majority of this pitting has been whilst it has been on it's current pontoon ? It seems hard to believe, somehow.

 

I also agree that erosion of the edge of the chine will probably be due to a hard life as a hire boat, (I think the boat is belived to have been one of Calcutt's "Wild" fleet ?). It's hard to see that being related to electrolosis. If so it needs "shoeing" but not a major overplate, surely ?

 

I'm no expert, but would have thought by the date of her build 6mm hull sides were pretty common, apart from Springers, and similar. It's easy to measure somewhere like the drain holes to the front deck, or the gas locker drains. Similarly if you can find a bit of baseplate edge that's not lost too much, it should be measurable.

 

Fingers firmly crossed for a good outcome - you deserve it after all the hard graft you have put in to the boat.

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Hi

 

I'm supprised there not more corrosion on the anodes. They dont seem have been doing any thing.

Are they the correct type - material.

After 3 years mine are definetly a lot worse than that and I never moor near shore line connected boats

 

Alex

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I'm supprised there not more corrosion on the anodes. They dont seem have been doing any thing.

I agree.

 

The picture is not that distinct, but the look in "near chandlery" condition not "well used".

 

Ade, do you know when they were fitted, please ?

 

 

The anode I could see in the picture looked like it had been painted over.

 

Are you referring to the original pics, or the two in a later post.

 

In some of the earlier pics there are some small lumps where anodes might be, but they seem to be a kind of extra short rubbing strake.

 

The anodes themselves only show in later pictures, and don't look painted over, I think.

 

But it doesn't look like they have been eroding much, (so far as it's possible to tell from those pics).

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Hi,

 

Do you actually have enough anodes? they only give local protection and will probaly not protect much of the sides of the boat. Perhaps it would give more protection to to add some more - say - 2 more down each side. With 'slab sided' boats this can cause it to catch at times, but better this than steel erosion.

 

Leo.

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If it is any comfort ... we had pitting similar to that .... It hasn't recurred.

 

The hull wear sounds like you are going to have a set of shoes, like we did last blacking.

You mean like this: http://i20.photobucket.com/albums/b204/Mol...ck/09022105.jpg

 

Is there a connection from the negative bus bar to the hull? The prop is connected to battery negative via the engine and gearbox and shaft. Is it possible that the engine isn't connected to the hull (rubber/wooden engine mounts?) and therefore the hull is not connected to battery negative? If so a leakage from battery positive to the hull via damp/dirt/chafed insulation would be enough to pass a current through the water via the prop and hull.

There is no connection from negative bus to hull.

There is no chafed insulation anywhere, new cables throughout, well clear of or protected from anything sharp.

Engine may have rubber mounts but there's a big steel bolt with steel washers through each one and a good electrical connection from engine to engine bearers.

 

I'd still be interested to know the date of the last blacking, and what the verdict on the hull was at the time ? Is it really the case that the majority of this pitting has been whilst it has been on it's current pontoon ? It seems hard to believe, somehow.

 

I also agree that erosion of the edge of the chine will probably be due to a hard life as a hire boat, (I think the boat is believed to have been one of Calcutt's "Wild" fleet ?). It's hard to see that being related to electrolosis. If so it needs "shoeing" but not a major overplate, surely ?

I have to admit that it's been 3.5 years between blackings but I wasn't there last time.

Opinion at dry dock is that pitting is live and recent.

 

Yes, she was Wild Hemlock IV and 4 'corners' are already shod, but I like your idea of angle iron along the sides.

 

I'm surprised there's not more corrosion on the anodes. They don't seem have been doing any thing. Are they the correct type - material?

I'll take some close-ups today.

 

Are you sure it's not a stainless steel prop? The anode I could see in the picture looked like it had been painted over.

I'm sure it's not stainless and that bump isn't an anode.

 

Many thanks to everyone for the comments, I'm off to re-pack stern gland and do some more work myself now, apart from that all we can do is wait and see what the surveyor says tomorrow.

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Hi Aide.

 

The only occasions that I have seen corrosion considerably worse than 'the norm' is were boats have been moored in places which are known to have problems with industrial acids and the like, in my view the rusting of steel boats is 90% a chemical problem the only way to control it is to keep the water away from the steel, in other words 'Paint'..

 

I like you, I have always been highly sceptical of the theories about mains connections, mooring near steel pilling and the like, I'm even a bit sniffy about the effectiveness of sacrificial anodes as my own observations tell me that their presence on a boat is marginal to say the least..

 

The one thing that can be shown to prevent a boat rusting is regular applications of coats of paint, I must say Aide that 3.5 years for a 25 year old ex hire boat is far too long and personally going from your pickies I would be very suspicious of the the quality and quantity of the paint from the past years.. The boat now needs a good blasting (preferably by a steamer), it should really have be done whilst the boat was still wet, it will probably need a fair degree of repair but I doubt a general re-bottoming.. A day with a tricorder contraption will confirm what has to be done, from then on it has to be regular painting, every year is not too often with and older more vulnerable boat..

 

But please don't listen to the soothsayers with their magic black boxes.

Edited by John Orentas
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Engine may have rubber mounts but there's a big steel bolt with steel washers through each one and a good electrical connection from engine to engine bearers.

Ade,

 

Are you absolutely sure about this ?

 

I recall pictures of Talpidae showing a fairly standard flexible engine mount.

 

These usually have a base bolted to the engine bed via 2 large nuts and bolts, and studding projecting upwards from the rubber mount, that passes through the feet of the engine, with a nut and washer on each side.

 

That studding is usually encased in the "rubber", but not electrically connected to the bit that mounts on the engine bed.

 

If there was a bolt passing right through from engine feet to under the engine bed, as it were tightened, it would rather spoil the purpose of the rubber,, (I would have thought).

 

Generally there is no electrical connection through mounts like this, which is why the engine casing should have a strap across bonding it to the frame of the boat. Otherwise you are relying on a connection through something like the exhaust (bad!) or fuel lines or control cables (far worse!).

 

If I've wrongly attributed the type of mounts you have, excuse my ramblings, but usually engines like ours "float" on "rubber" rather than being hard mounted to the engine bed.

 

Alan

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..................in my view the rusting of steel boats is 90% a chemical problem the only way to control it is to keep the water away from the steel, in other words 'Paint'..

Amazing deduction!! Rusting IS a chemical process, corrosion may be a chemical and/or an electrical process.

 

I like you, I have always been highly sceptical of the theories about mains connections, mooring near steel pilling and the like, I'm even a bit sniffy about the effectiveness of sacrificial anodes as my own observations tell me that their presence on a boat is marginal to say the least..

Your previous history of technical posts shows that you're very "sniffy" on basic electrical theory as well so I doubt anyone will be following your advice anytime soon.

 

 

But please don't listen to the soothsayers with their magic black boxes.

Is that because they were invented after 1910? :lol:

 

 

 

Hi

 

I'm supprised there not more corrosion on the anodes. They dont seem have been doing any thing.

Are they the correct type - material.

 

Alex

The anodes must be magnesium for fresh water, not zinc. Zinc will become ineffective after a few weeks due to their gaining a coating of zinc hydroxide in fresh water.

 

Chris

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