Chevetter

I don't have a bilge below the cabin - its very small and (unsurprisingly) is situated underneath the prop at the back of the boat. The entire deck drains into it.

I know I might sound thick but I'm not that thick - note the vent pipe!

I think I want it sealed, so no steam etc. can get into the boat, but it won't actually be pressurised. A check valve (or non-return valve) on top of the overflow pipe should solve the siphon problem.

Hmmm, not a bad point about the siphoning. The valves are there because I may want to restrict the overflow as per a few posts back, but agreed, the whole thing could explode if I shut the top one by mistake..... The return will struggle to run downhill to be honest - the stove is well off the floor as I sain, plus the slope of the boat as well.... but I'll make it go down as far as I can. By the way, does anyone have any ideas as to what I can use for a header tank?

Right, been having a bit of a think, conversing with a workmate who has a lot of experience of installing central heating in houses and we've come up with the following: Should the boiler boil up or produce steam in this design it gets dumped into the bilge. That way no messing about cutting holes above the stove etc. I assume you're all about to tell me that this is a terrible idea though....

Does it have to be literally directly above? That will create a heck of a lot of work for me! A better idea from my point of view would be to take-off directly above the stove but actually vent the steam somewhere else.

Hi chaps, Again comments much appreciated, please see heating system design Mk3. Am I getting there? On the subject of the vent pipe: do I really need this to be down the stove end? Can I not just have a vent out from the header tank into the bilge? It would make the whole thing so much easier. Also, you will notice that my 28mm pipe runs past the top of the rad. Is there any need to do this or can I just stick the feed into one side and hang the header tank off the other side hence saving nearly 1m of 28mm?

My thinking was: Make the feed 28mm all the way down the boat in order for good conductivity of heat. In the return there's no need for this (28mm pipe is expensive)..... although I could be wrong. I figured if its got to go uphill anyway then a bit of 15mm pipe isn't a big deal. Can anyone see a problem withmy design? Anything that I could do better etc? If not I'm actually going to build it Hmm, well it certainly saves me having to buy a towel tail thats for sure plus simplifies the plumbing and ensures a nice flow of hot water up the feed pipe. I suppose it will get rather hot and there's only one of me anyway.... My boat is actually fully spit in terms of air flow (although I do keep the doors open) so thats a bit of an issue, which is the problem that the radiators are meant to solve.

How about this revised design?

Ah right, ok. For some reason I was under the impression that the return from the rads had to be downhill. I'll work out how high the top of the radiator in the kitchen has to be to be uphill from the stove and hence if its feasible.

Thanks for the comments. I'm afraid thermocycling just is not going to happen. Like I said the stove's mounted on a hearth which is a good 300mm higher than the floor, plus the tilt of the boat puts it a long way above any potential radiators in the kitchen. I can't start chopping the physical features of the boat about so I guess by Chris Pink's definition I have already failed Anyways I need a pump, in which case is the Bolin the best one? Re: the header tank: how big do they typically need to be? Is it actually possible to buy one? Like I said, I was just going to use one from a car. I'm also not 100% sure what you mean by a 'gravity fed rad'? How would that fit into my system? Things that I can move: radiators, pipes, pump, header tank. Things that I can't move: walls, the stove.

Hi Chaps and chapesses, Long time since I've been on the forum I know, but I've come back to ask for your advice+opinions. Basically I've been doing a liveaboard while re-fitting type thing for just over a year now (which is somewhat of a challenge, if you've ever tried it) and with winter coming I've saved my last week of time off from work for building my central heating system. My boat is 40ft with a 25.5ft cabin containg 3 rooms - a 9ft lounge/bedroom, a 4ft bathroom and a 12.5ft kitchen/diner. I already have a Boatman stove with backboiler installed and it's 'just' a matter of installing the central heating system. Here's a pic of my design - comments, suggestions, criticism etc welcomed (apologies for the shoddy drawing) So far I have the following questions: Reading other topics on the forum, I think that a Bolin pump will be the best choice as it needs to be quiet and be able to go at the lowest point of the system. Is that sensible? Do I need to care about matching the number of BTUs of the rads to the number of BTUs of the back boiler? Is there much benefit to fitting a thermostat to control the pump? I was thinking of just having a switch. Header tank: where do I get one? Presumably it needs some kind of pressure release valve and dump pipe out of the side of the boat? I was thinking of going to the local automotive scrapyard and hunting under the bonnets of various cars until I found something appropriate? None of this is bought or built yet apart from the boatman so the whole design can be changed if necessary. Thanks in advance

WD40 is ok but it isn't the best 'dismantling lubicant'. I use something called PlusGas - works much better.

Can't say that I have no. I'm at work at the moment so I haven't got the time to do it but this evening, or maybe tomorrow evening I will sit down and work out the rate of corrosion in grammes of steel per month based on a set of nominal conditions. When you say chemical corrosion, which chemicals are you referring to? I've noticed that everyone's washing up scum seems to accumulate around my bows

I don't think you're seeing what I mean: 3 Boats: | B---path to earth--------------(||||||||||Boat A||||||||||> a n.......isolated......................(|||||||||mine|||||||||||||> k | --resistive path to earth----(||||||||Boat B||||||||||||> | Boat A and boat B are not properly isolated and are both earthed to the bank. Boat B has a high resistance in its path to earth. Therefore they are 2 electrodes floating in a weak acid with a resistive path inbetween them. So what have we got (assuming the boats don't manage to sit at exactly the same potential to ground - extremely unlikely)? The path of least reistance between the boats (i.e. from the positive to negative terminals of the battery) passes through my boat as it is easier for electrons to pass through my steel than around it in the water. The direction of travel depends on the potential that the two boats A and B sit at but the result is that my metal is pulled from my boat and sticks to either A or B. This could be an explanation for the blacking coming off - as the metal ions move they have to get past the blacking to get to the other boat. Resolution: hang some more reactive metal anodes over the side and provide a good conductive path to the hull, therefore the anode metal is removed instead of the hull metal.