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External vs Internal skin tank


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My boat had an external skin tank fitted at some point (probably when the engine was replaced), and the original internal tank is not connected.

 

When I bought it the surveyor didn't like the external tank and said I should go back to the internal one..

 

It seems to me that with both methods the heat would be conducted to the hull then cooled by the passing canal / river water so unless the external skin tank was very thin(!!!!!) the internal tank would cool things just as well.

 

Should I or shouldn't I?

 

Thanks!

 

 

 

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16 minutes ago, nickhindle said:

My boat had an external skin tank fitted at some point (probably when the engine was replaced), and the original internal tank is not connected.

 

When I bought it the surveyor didn't like the external tank and said I should go back to the internal one..

 

It seems to me that with both methods the heat would be conducted to the hull then cooled by the passing canal / river water so unless the external skin tank was very thin(!!!!!) the internal tank would cool things just as well.

 

Should I or shouldn't I?

 

Thanks!

 

 

 

I'd go with the old adage, "if it works, leave it alone".

 

Nobody would have created a new external tank for fun, so either the old one was too small, or it leaked, or it was too thick and therefore inefficient.  There must be a reason for the new tank.

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You could pressure the original tank to satisfy yourself about its condition. 

If the external tank has a larger surface area that could be the reason for its construction otherwise I would suspect the original is defective in some way, leaks or lack of distribution baffles inside is possible.

TD'

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People usually fit an external skin tank in addition to the original internal one because there isn't enough room to fit an extra tank internally, but whichever side of the hull it's fitted on it should perform exactly the same function.

 

It seems odd that your original tank isn't connected. If you take your boat out onto a wide river and rev it hard against the current for an hour or so you may actually find that the engine starts to overheat and requires both tanks to be connected.

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The only argument against an external skin that that hods a little water for me is that it may disturb the water flown around the swim and into the prop. This might affect handling, especially in reverse but in reality it does not seem to.

 

This sort of thing annoys me and I would be pressing the surveyor for a full explanation and justification for his recommendations plus what steps he took to ensure the old skin tank was up to the job.

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6 minutes ago, Tony Brooks said:

The only argument against an external skin that that hods a little water for me is that it may disturb the water flown around the swim and into the prop. This might affect handling, especially in reverse but in reality it does not seem to.

 

 

If you weld a thin protrusion onto the outside of a skip and drag it through the water it won't make any noticeable difference to the way it goes through the water. ?

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We had an external skin tank on Helvetia, intalled apparently because the original internal one developed an irrepairable leak. It worked perfectly well, and having feathered forward and trailinghedges, had no discernable effect on forward or reverse steerage.

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Thanks all.

 

The engine is a Vetus M4.15 and works fine with the external tank. I've never had problems with it overheating, including when I went upstream on the tidal Ouse.

 

It just worries me that the surveyor effectively said I should stop using it ?

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If it ain't broke don't fixit.

Certainly on my boat (with long swims) the room for an internal tank wouldn't work at all - for river use (just as well as I use freshwater cooling) and it mebe trhat's why there's an outside tank.

I wouldn't fuss - unless there's something 'we' don't know...

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13 minutes ago, nickhindle said:

It just worries me that the surveyor effectively said I should stop using it

I can only agree with Tony...

1 hour ago, Tony Brooks said:

This sort of thing annoys me and I would be pressing the surveyor for a full explanation and justification for his recommendations plus what steps he took to ensure the old skin tank was up to the job.

 

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12 hours ago, nickhindle said:

Thanks all.

 

The engine is a Vetus M4.15 and works fine with the external tank. I've never had problems with it overheating, including when I went upstream on the tidal Ouse.

 

It just worries me that the surveyor effectively said I should stop using it ?

he has to justify his existence somehow.

 

boats are so well maintained and designed these days (:rolleyes:) that all surveyors would be out of a job if every survey report identified no (real or imagined) faults.

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44 minutes ago, Murflynn said:

he has to justify his existence somehow.

 

boats are so well maintained and designed these days (:rolleyes:) that all surveyors would be out of a job if every survey report identified no (real or imagined) faults.

 

The problem with that is that on the basis of what we have been told that surveyor could end up costing the OP hundreds of pounds sorting out a non-problem. All because he (the surveyor) apparently did not provide sufficient information about the two tanks and his recommendation for the OP to make an informed decision.

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I had external box section cooling pipes fitted to my narrowboat at Foxes Marina , March as it was prone to overheating when used on the River Nene, fine on canals . The best modification I ever made .My boat is being surveyed later this month if the surveyor suggests I revert back to skin tank cooling I'm afraid I might have to disagree with him . My engine is the old faithful BMC 1.5 

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I guess the best thing about external cooling (typically keel coolers on salty boats) is that if there is corrosion and a leak you still have circulation (if the engine is low enough). 

The worst thing is that you may never know there is a leak and you may be circulating salt water without knowing it.

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15 minutes ago, Murflynn said:

I guess the best thing about external cooling (typically keel coolers on salty boats) is that if there is corrosion and a leak you still have circulation (if the engine is low enough). 

The worst thing is that you may never know there is a leak and you may be circulating salt water without knowing it.

Many 'salty boats' that I know (including mine) have a closed loop of 'fresh water' in the engine and a heat exchanger with 'salty water' flowing thru it.

 

 

 

CAM00314.jpg

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1 hour ago, Tony Brooks said:

 

The problem with that is that on the basis of what we have been told that surveyor could end up costing the OP hundreds of pounds sorting out a non-problem. All because he (the surveyor) apparently did not provide sufficient information about the two tanks and his recommendation for the OP to make an informed decision.

Here is the comment from the survey:

 

"There was an external skin tank fitted on the starboard swim. The reason for this was not determined. The external skin tank was poor and had two protective plates, at the front and the bottom
weld. The bottom protective plate had been ripped off forwards and will not last long.
Recommend: Consider repairing and reverting back to the port internal skin tank."

 

When I had the boat out for blacking the engineer said the tank was sound, and welded the bottom protective plate back in place.

The system is currently drained for a coolant change, and there are no leaks.

 

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17 hours ago, WotEver said:

Nobody would have created a new external tank for fun, so either the old one was too small, or it leaked, or it was too thick and therefore inefficient

That was certainly my case. When I bought my boat, the engine started overheating when going down the Nene, so I did have an external pipe fitted to the swim in Fox Marina. When the two holes for the pipes were drilled, my heart sunk. Still, it was a good decision as engine now happy and the capacity of cooling is 50% up.  Also, I cannot see any problems with steering or reversing. The pipe might not be the most elegant solution, but it works and Foxes fit it to all their boats.

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1 hour ago, Alan de Enfield said:

Many 'salty boats' that I know (including mine) have a closed loop of 'fresh water' in the engine and a heat exchanger with 'salty water' flowing thru it.

 

there's more than one way to skin a cat.

 

 

 

 

IMHO all cats should be skinned

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2 hours ago, nickhindle said:

There was an external skin tank fitted on the starboard swim. The reason for this was not determined...

At this point he should have stopped with his recommendations as he's just admitted that he doesn't know what's wrong with the old tank.

2 hours ago, nickhindle said:

The bottom protective plate had been ripped off forwards and will not last long.

Fine, a good observation, which you have addressed with...

2 hours ago, nickhindle said:

When I had the boat out for blacking the engineer <snip> welded the bottom protective plate back in place.

 

2 hours ago, Alan de Enfield said:

External cooling systems are not unknown on workboats :

 

More efficient keel coolers changing the game | WorkBoat

Why does that anode have an 'up' arrow on it?  Is it to stop the electrons from falling out? 

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