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Overplating & Skin Tank - the Kedian way :)


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When my boat had its pre-purchase survey it was pointed out that the base plate had 'a rash of pitting' and the sacrificial chines had been eroded to such an extent that the only economically sensible option was to overplate the base. (surveyor's recommendation), the other sensible option was to walk away and let it be someone elses problem - but I really liked the boat...

I'd read on here (thanks everyone) recommendations for Kedian Engineering so approached Martin for a quote.  Followed an enjoyable conversation and an exact description of the work that would be done (another company had quoted me also but were so vague in the work schedule that I walked away), how long it would take and when he would be able to do the work.  Oh, and a price too...

On the way to Kedian from my home mooring coolant temperature got a bit too high on several occasions  - not quite to overheating properly but worrying nonetheless - so a phone call to Martin asking if a skin tank could be fitted while he was overplating.  "No problem!" from his end.

Martin had posted a couple of pictures in the last overplating thread so I thought I'd add a couple more from the work-in-progress collection.

As can be seen, he has done a great job, explained exactly what he has done and finished off with new blacking (3 coats) not just over his work but the whole hull.  He also added a 'step up' on each side of the hull at the rear - obviously thinking of the inevitable time when someone on the boat decided to take a dip in the canal - to make it easier to climb back on board, or for the Herons / Cranes to have somewhere comfy to stand...

Now looking forward to the trip back to the home moorings without 'worn welds' preying on my mind :)

Thanks to those here that mentioned Martin in high regard for pointing me in that direction (even though at that time I wasn't posting, just haunting here) and permitting me to add an equally enthusiastic recommendation for his work.

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Edited by Athy
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I'll ask one of the moderators to correct my spelling on Martin's name...

@blackrose I took a look at the Beta link, curious, I'd have thought the further the coolant is forced to travel the more efficient the cooling (you should see the baffling on my CPU cooler! ) but as it is another of those 'black arts' who really knows?

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12 minutes ago, Ratkatcher said:

 

@blackrose I took a look at the Beta link, curious, I'd have thought the further the coolant is forced to travel the more efficient the cooling (you should see the baffling on my CPU cooler! ) but as it is another of those 'black arts' who really knows?

Yes, that's true, but what Beta are saying is that complex the baffling requires a more efficient water pump. On most engines what you have is basically an inefficient stirrer which might not be up to the job of getting the coolant around a complex system, so they recommend one simple baffle.

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1 hour ago, blackrose said:

Yes, that's true, but what Beta are saying is that complex the baffling requires a more efficient water pump. On most engines what you have is basically an inefficient stirrer which might not be up to the job of getting the coolant around a complex system, so they recommend one simple baffle.

When I first bought my boat, the twin calorifier coils were, incorrectly, plumbed in series.

This meant the standard Beta 43 water pump had to pump the coolant through the engine, through the calorifier and then through the heating system in a 60 foot boat, including through the WebastoThermptop boiler, before returning to the engine.

Apart from the radiators getting really hot in June,  despite the Webasto being switched off, there was no sign of distress and the coolant temperature remained steady at 80°C, same temperature as when I corrected the plumbing.

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I'm sure that complex baffling will work - as long as the water pump is up to the job - and that's the big proviso. The further the coolant has to travel in a heat exchanger and the more turbulent the flow, the greater the cooling coefficient. But that theory only works up to the point that the additional travel, friction and turbulence can be accommodated by the water pump and the coolant can travel around the system. The moment that the pump cannot cope and the coolant stops flowing is the point at which the engine temperature begins to rise and potentially overheats. So on the subject of baffling there is most definitely a balance to be struck.

My additional skin tank was baffled according to the Beta recommendations using a single baffle. It took the maximum engine temperature down from 100C (yes, I had to be very careful how hard I pushed it on rivers when I only had a single skin tank), down to a maximum of about 85C at max revs on open water for over 2 hours. So on my boat a simple baffle system also worked fine.

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6 hours ago, blackrose said:

According to Beta it's a bit over-baffled. I followed their recommendations when designing my additional skin tank.

http://betamarine.co.uk/keel-cooling-calculations/

Personally I find the whole subject baffling... :unsure:

Surly that is a minimum requirement to stop water short circuiting the cooling surface

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8 hours ago, blackrose said:

According to Beta it's a bit over-baffled. I followed their recommendations when designing my additional skin tank.

http://betamarine.co.uk/keel-cooling-calculations/

Personally I find the whole subject baffling... :unsure:

What martin has done looks pretty well spot on to me.

I can't believe a tank with just one baffle like Beta show would work as well.

Certainly when we had an external tank put on Chalice it was more in the style of Martins, and it worked superbly with no hint that the basic engine water pump couldn't handle it, (BMC 1800)

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2 hours ago, ditchcrawler said:

Surly that is a minimum requirement to stop water short circuiting the cooling surface

That's correct, as shown in the Beta diagram.

51 minutes ago, alan_fincher said:

What martin has done looks pretty well spot on to me.

I can't believe a tank with just one baffle like Beta show would work as well.

Certainly when we had an external tank put on Chalice it was more in the style of Martins, and it worked superbly with no hint that the basic engine water pump couldn't handle it, (BMC 1800)

No it won't work as well - but the point is it only has to work adequately to cool the engine. Mine only has one baffle and it works perfectly.

On the other hand, if a tank is over-baffled and the pump can't handle it, it won't work at all!

Edited by blackrose
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I think Blackrose is out on a bit of a limb here, in any case by what means did Beta become the arbiter of good skin tank design. They have had their own fair share of engineering cockups along the way so who is to say their skin tank diagram is not another apart from experience and Kedian's is just as valid. 

Remember that these days the vehicle water pump is expected to push water through a horizontal radiator with far smaller tubes plus an intercooler, plus a heater matrix. On proper keel cooled boats it has to push coolant through longer internal pipes plus a number of smaller bore external pipes.

In the main I think Kedian's solution is excellent with two caveats:

1. Unless there is a reason in respect of engine/boat layout I would have preferred the cool outlet to be at the bottom to make it easier to drain the tank (unless there is an internal drain plug we can not see).

2. Its hard to tell from the photo but I feel (not know) that it could be slimmer but as Kedian knows it works well as it is so be it.

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1 hour ago, Tony Brooks said:

I think Blackrose is out on a bit of a limb here, in any case by what means did Beta become the arbiter of good skin tank design. They have had their own fair share of engineering cockups along the way so who is to say their skin tank diagram is not another apart from experience and Kedian's is just as valid. 

Why out on a limb? I've provided Beta's recommendations and in my opinion they've provided a more reliable guide and justification than anything else I've seen. If you can show me something else Tony I'd be very interested. I've nothing against Kedian and I know they do some excellent steelwork, but personally I'd certainly rather follow the recommendations of an engine mariniser than those of a  fabricator who most people had never heard of before this forum started. Yes, I'm sure Beta have made some cock-ups but I'm sure Kedian has too.

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I think that I know about about engine water pumps and what they can and can not do. As you have been told by someone else the Beta suggestions are probably the minimum and are not the be all and end all. Your first comment was fine as far as I am concerned when you pointed out that Beta had different ideas but I feel that when you went on to try to justify your comments by talking about the water pump not being powerful enough you went right out on a limb. There are boats with twin cooling tanks, one on each side, there are boats with both skin tanks and keel cooler pipes on the swim. There are boats with very a very long keel cooler pipe running up a central tunnel for about half or more of the boat's length and all would create more friction than Kedian's tank and all work as required. A wide practical experience counts and should not be dismissed on the basis of a single marinisers published advice. I seem to recall that Vetus advise something different. I think I may have found that out via one of your much earlier topics.

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We'll be taking Tichitoro back to her mooring early next week, a pleasant 10 day cruise :clapping:

I'll let you all know how the new cooling system behaves.  I would have thought that as the norm for the engine is in a pressurised coolant system, and that it certainly pumps through the calorifier efficiently that adding a little labyrinth for coolant that replaces a hefty keel cooling system would be likely to present a similar load to the pump.

 

ETA: As the engine is a marinised BMC, its original home would have been in a Leyland van etc. with a radiator cooling system.

Edited by Ratkatcher
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3 hours ago, Tony Brooks said:

I think that I know about about engine water pumps and what they can and can not do. As you have been told by someone else the Beta suggestions are probably the minimum and are not the be all and end all. Your first comment was fine as far as I am concerned when you pointed out that Beta had different ideas but I feel that when you went on to try to justify your comments by talking about the water pump not being powerful enough you went right out on a limb. 

If you had bothered to read the Beta recommendations carefully, you'll have noticed that it was they who talked about water pumps not being powerful enough. That didn't originate from me and I wasn't out on a limb at all - I was merely conveying what Beta said for the benefit of the forum - so please don't shoot the messenger! :)

Also I never said that the Beta guidelines were the be all and end all as you put it - where did you get that idea? However, I do note that neither you nor anyone else has managed to post a link to any other guidelines which contradict what Beta have recommended, so until that happens I will continue to take the Beta recommendations as best practice. I hope that's ok with you? :unsure:

Edited by blackrose
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I think in a well designed system, with an adequately sized tank, gravity alone will do much of the work.  The top of the tank will be at engine thermostat temperature, the bottom at just canal temperature.  That's a huge temperature gradient, and I suspect it would thermosiphon quite nicely, leaving the pump not a lot to do.

It seems to me very odd to suggest any reasonable pump will struggle with a tank with two or three baffles.  As Tony points out it must be far less work than the pump might be expected to do in a non boat installation.

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58 minutes ago, blackrose said:

If you had bothered to read the Beta recommendations carefully, you'll have noticed that it was they who talked about water pumps not being powerful enough. That didn't originate from me and I wasn't out on a limb at all - I was merely conveying what Beta said for the benefit of the forum - so please don't shoot the messenger! :)

Also I never said that the Beta guidelines were the be all and end all as you put it - where did you get that idea? However, I do note that neither you nor anyone else has managed to post a link to any other guidelines which contradict what Beta have recommended, so until that happens I will continue to take the Beta recommendations as best practice. I hope that's ok with you? :unsure:

Perfectly OK with me as long as you do not mislead less technical people.

Here you go - http://www.canaline-engines.co.uk/wp-content/uploads/2014/04/CL02-Canaline-Engines-keel-cooling-tanks.pdf

but note that in the text they advise two baffles, not the one shown on their diagram. Now how many has Kedian fitted?

<sarcasm on>

Must be one hell of a lot of hire and ex hire boats overheating if they were built to the engine supplier's specifications then. :)

<sarcasm off>

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14 hours ago, blackrose said:

Why out on a limb? I've provided Beta's recommendations and in my opinion they've provided a more reliable guide and justification than anything else I've seen. If you can show me something else Tony I'd be very interested. I've nothing against Kedian and I know they do some excellent steelwork, but personally I'd certainly rather follow the recommendations of an engine mariniser than those of a  fabricator who most people had never heard of before this forum started. Yes, I'm sure Beta have made some cock-ups but I'm sure Kedian has too.

But as I said, is the Beta suggestion the minimum standard. A bit like electrics and fridges, maybe you need 4mm cable, but would 6mm be better or worse?

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I feel that basically seem of the more experienced and longer serving members have supported you so there is nothing more to add. I just hope my points did not come across as criticisms but more as constructive comments. I bet if I needed work done on my boat we would both come up with an almost identical solution and any differences would be easy to resolve - unlike the pratt who was too lazy to take a loom securing bolt out of my gas tank when he welded in a new bottom and part sides so I can now only get certain 19kg cylinders into it!

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