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Cooling


MrsM

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3 hours ago, Onewheeler said:

The question must be asked whether 40 hp is useable. How big is the boat? I've got 38 hp in my 15.5m nb and have never gone over 2200 rpm for more than a minute or two out of a max rpm of 3000 (and I've been on plenty of rivers in conditions which were marginal). At some point the hull just pulls down and the wash goes up. The advantage of an oversized engine is that it can run with less stress if the prop is matched. So, how big is the boat and how big is the current skin tank?

It's 58ft. Not sure of the exact size of the tank (will measure tomorrow) but it is a lot less than 10 sq/ft. The surveyor noted it was small when the boat was last sold in 2018. It has been in a marina since then.

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11 minutes ago, MrsM said:

It's 58ft. Not sure of the exact size of the tank (will measure tomorrow) but it is a lot less than 10 sq/ft. The surveyor noted it was small when the boat was last sold in 2018. It has been in a marina since then.

Remember that surveyor was acting for the then purchaser and also covering his own back. Saying that gave the purchaser a reason to get the price reduced and ensured they had no comeback on the surveyor if it did overheat.  By all means measure it but I could never advise that you spent money on cooling alterations until you actually try the boat at high speed/power on the river for half an hour or more.

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3 hours ago, Tony Brooks said:

There is a lot of truth in that. personally I would do a prolonged high speed trial to see if it really does overheat. My own 35HP engine in a 54ft narrowboat ran at over 2000 RPM from Keadby to West Stockwith without overheating. I never measured it but I suspect the skin tank was a little undersized according to the Beta figures.

 

Mrs M should learn when the boat reaches its hull design speed on the Trent so she never tries to exceed that speed. That seed will be less or a lot less on canals. If she has a satnav she could use that to find the throttle position after which the boat speed refuses to rise although the engaging  speed does.After that point  you just waste fuel in making waves and trying to lift the boat out of the water.

Great advice thank you.

3 hours ago, Tony Brooks said:

 

Only until the calorifier has heated up then it adds no extra cooling unless you run domestic hot water off. That action gives the Mrs M a safety procedure to use if the skin tank turns out to be too small and the engine overheats.

Thanks Tony. I saw the Foxes Afloat use that technique with their boat on a river. Good to know it's an option if things get a bit heated.

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3 hours ago, Bee said:

As a long term solution a bigger skin tank is the answer but I have seen car / van engines installed pretty much straight out of the vehicle complete with fans and rads and they worked sort of OK. Nowadays most car rads are complete with electric fans and shrouds so I reckon a bit of basic plumbing and bodged wiring would assist the cooling just fine. Might make the engine compartment a bit warm though.

I'm very reluctant to bodge anything until I've tried and learnt the boat. Was thinking that perhaps the warm air could be vented into the cabin to provide a small drying area for wet garments? Just a thought at this stage, from what I'm hearing most if you seem to manage just fine with tanks that are theoretically a bit wee.

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2 hours ago, The Happy Nomad said:

The prime method of cooling a car radiator is air flow surely? The fan is just for assistance, usually when stationary. The fan would be running permanently and the heat would not dissipate.

You're right about the airflow, a radiator is just a heat exchanger, back in the good old days of motoring before electric fans it was quite common to turn the heater and fan on full to dump heat while the car was stop start in a traffic jam on a blistering hot day somewhere near Blackpool. So, yes, its not really a permanent solution but I have seen water cooled Ruston engines from small plant and old fashioned fixed fans working quite happily with rads in narrowboats, lots of air cooled listers and particularly Armstrong diesels seem to work even if they singe the hairs on your legs if you stand too close so air is quite good at carrying heat away.

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I wouldn't let it put you off the purchase.

 

Several steps:

 

1 do nothing

2 check the engine specs for max speed unloaded and full power. I don't know that engine, but unloaded is probably a bit over 3000 rpm and loaded about 90% of that.

3 See what engine speeds you can get to with prop disengaged and in gear on open deep water. You'll get a quick indication from that of whether you are overpropped, underpropped or about right.

4 Do some speed trials in open, deep water. You'll soon find the point at which the front end tries to go up, the back goes down and you could surf on the wake. That depends on the hull shape.

5 See how long it takes for the engine to overheat, if at all, at near that speed. Depending on hull shape you might be happy with max speed before overheating, or decide to do something about it.

6 There are phone apps which will report your speed to a precision of 0.1 km/h. I've got gps speedometer, distance meter from Smart Mobile Tools. There are many others.

7 if you can do 9 or 10 km/h in a narrowboat without overheating you're doing better than many. My boat is comfortable at 9 km/h, and slowly overheats at 10 (more when the water is cold).

 

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25 minutes ago, Onewheeler said:

I wouldn't let it put you off the purchase.

 

Several steps:

 

1 do nothing

2 check the engine specs for max speed unloaded and full power. I don't know that engine, but unloaded is probably a bit over 3000 rpm and loaded about 90% of that.

3 See what engine speeds you can get to with prop disengaged and in gear on open deep water. You'll get a quick indication from that of whether you are overpropped, underpropped or about right.

4 Do some speed trials in open, deep water. You'll soon find the point at which the front end tries to go up, the back goes down and you could surf on the wake. That depends on the hull shape.

5 See how long it takes for the engine to overheat, if at all, at near that speed. Depending on hull shape you might be happy with max speed before overheating, or decide to do something about it.

6 There are phone apps which will report your speed to a precision of 0.1 km/h. I've got gps speedometer, distance meter from Smart Mobile Tools. There are many others.

7 if you can do 9 or 10 km/h in a narrowboat without overheating you're doing better than many. My boat is comfortable at 9 km/h, and slowly overheats at 10 (more when the water is cold).

 

That sounds very sensible and I shall follow these steps. Thank you so much. 

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I should point out that narrowboats are displacement boats and unless the underwater shape is designed to be 'slippery' - most are not. Accordingly its not surprising that some boats overheat when pushed to 6-7 mph.

I ordered mine with extra long swims front and back (the builder grizzled a bit) and the engine - 50HP works hard to get going at that speed...

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Interesting bit in this video about engine over heating and the cooling tank being on the base plate and fitting a new skin tank in the normal swim position to solve the problem. Starts at 4:50, if you don’t want to watch the whole thing.

 

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On 16/07/2020 at 08:38, Onewheeler said:

The question must be asked whether 40 hp is useable. How big is the boat? I've got 38 hp in my 15.5m nb and have never gone over 2200 rpm for more than a minute or two out of a max rpm of 3000 (and I've been on plenty of rivers in conditions which were marginal). At some point the hull just pulls down and the wash goes up. The advantage of an oversized engine is that it can run with less stress if the prop is matched. So, how big is the boat and how big is the current skin tank?

It's 58ft. Not sure of the exact size of the tank (will measure tomorrow) but it is a lot less than 10 sq/ft. The surveyor noted it was small when the boat was last sold in 2018. It has been in a marina since then.

Thanks chaps. Feeling a bit more confident after all this help. Measured skin tank this morning and it is 7sq/ft. Just bought the boat so will see how she handles rivers for a season and review. 

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45 minutes ago, MrsM said:

It's 58ft. Not sure of the exact size of the tank (will measure tomorrow) but it is a lot less than 10 sq/ft. The surveyor noted it was small when the boat was last sold in 2018. It has been in a marina since then.

Thanks chaps. Feeling a bit more confident after all this help. Measured skin tank this morning and it is 7sq/ft. Just bought the boat so will see how she handles rivers for a season and review. 

Thats two thirds, you may be OK

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7 hours ago, Tony Brooks said:

As the video above is about blacking remember that if too many coats of blacking build up on the skin tank it can cause overheating but probably more in cases of marginal tank size.

 How many boats do you know of that have overheated from too much blackening? 
  I would say that there are a lot more overheating issues caused be other defects then those caused by too much blackening.

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4 minutes ago, PD1964 said:

 How many boats do you know of that have overheated from too much blackening? 
  I would say that there are a lot more overheating issues caused be other defects then those caused by too much blackening.

Only a hand full but I never said it was a major cause, just another cause that needs to be bourn in mind, especially if the skin tank size is marginal or once everything else has been checked.

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4 hours ago, MrsM said:

It's 58ft. Not sure of the exact size of the tank (will measure tomorrow) but it is a lot less than 10 sq/ft. The surveyor noted it was small when the boat was last sold in 2018. It has been in a marina since then.

Thanks chaps. Feeling a bit more confident after all this help. Measured skin tank this morning and it is 7sq/ft. Just bought the boat so will see how she handles rivers for a season and review. 

That is considered absolutely adequate for 28 HP then. So its at best 75% enough for 38 HP. The chances of you overheating is minute, maybe if you flogged at maximum revs for an hour against a flood stream when you should not be boating anyway.

Stop worrying about it, there are loads of boats with less cooling area than that.

 

Tanks on the base plate are known to be pretty hopeless, impossible to bleed all the air out, no chance of any thermosyphon cooling or distribution fins and on shallow canals they are in the mud anyway. There was a shell builder who had an affair with them, was it Piper at sometime?

TD'

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41 minutes ago, Tracy D'arth said:

 maybe if you flogged at maximum revs for an hour against a flood stream when you should not be boating anyway.

 

 

TD'

That has always been my view, If I need the engine flat out for an hour I dont want to be there

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1 hour ago, Tracy D'arth said:

Tanks on the base plate are known to be pretty hopeless, impossible to bleed all the air out, no chance of any thermosyphon cooling or distribution fins and on shallow canals they are in the mud anyway.

If you're in a shallow canal you won't need full power...

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On our previous narrowboat, a cruiser stern, if you looked at the skin tank in the engine compartment you would say that it was undersized. However, it actually extended forward into the cabin about 3ft and it was mostly sheeted over so hidden from view, and provided some heat into the wet locker.

 

I am not saying yours is like this, I have no idea how common this is or if it was looked for. 

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13 minutes ago, PeterF said:

On our previous narrowboat, a cruiser stern, if you looked at the skin tank in the engine compartment you would say that it was undersized. However, it actually extended forward into the cabin about 3ft and it was mostly sheeted over so hidden from view, and provided some heat into the wet locker.

 

I am not saying yours is like this, I have no idea how common this is or if it was looked for. 

That sounds like a good setup. I could see all the way round ours but it sounds like it shouldn't be much of a problem. Great idea to have a heated wet locker on your old boat.

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On 16/07/2020 at 09:28, Bee said:

As a long term solution a bigger skin tank is the answer but I have seen car / van engines installed pretty much straight out of the vehicle complete with fans and rads and they worked sort of OK. Nowadays most car rads are complete with electric fans and shrouds so I reckon a bit of basic plumbing and bodged wiring would assist the cooling just fine. Might make the engine compartment a bit warm though.

 

Unless you can get that hot air out of the engine compartment you'll be wasting your time with car radiators. You could install bilge blowers I suppose but you might struggle to shift all the warm air out fast enough.

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On 16/07/2020 at 09:43, Tracy D'arth said:

Most boats with skin tank are under cooled when you measure the area. Very few boats can use the full power of the engine before the hull and water interaction limit the speed.

Most owners don't worry about it and just enjoy their boating without ever realising it.

 

Consider adding a plate heat exchanger to the calorimeter circuit to heat the radiators in the boat, you can dump a lot of heat that way without dumping your hot water overboard. And in winter you have a toasty boat even with the doors open.

TD'

 

Once the calorifer and radiators get hot you'll be in exactly the same situation as you were. The rads just won't dump the heat quickly enough and as you say in summer when you really need the additional engine cooling it would be like an oven in the boat. 

 

Since I installed an additional skin tank all my engine cooling problems were solved. If most owners don't realise their engines are undercooled it's probably because they're just plodding around on canals and they aren't really using their engines properly. But if you're on rivers regularly you'll need it properly cooled either with adequately sized keel cooling or some sort of raw water cooling. Anything else is just a bodge.

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On 16/07/2020 at 18:43, Tracy D'arth said:

 

 

Consider adding a plate heat exchanger to the calorimeter circuit to heat the radiators in the boat, you can dump a lot of heat that way without dumping your hot water overboard. And in winter you have a toasty boat even with the doors open.

TD'

Can you explain this setup a little more please? I'm having trouble envisaging it (and the engineer in me likes to understand these things even if I have no intention of implementing them). Many thanks

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6 hours ago, Awayonmyboat said:

Can you explain this setup a little more please? I'm having trouble envisaging it (and the engineer in me likes to understand these things even if I have no intention of implementing them). Many thanks

The heat exchanger has two pairs of connections. The return from the calorifier to engine goes through one pair and the other pair is inserted into a wet central heating system. Heat from engine coolant is thus transferee to the central heating allowing the central heating pump to circulate it. On a gravity system positioning of the heat exchanger is important so the hot water it produces can rise in the pipework.

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