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Making a flue..........


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7 hours ago, Boater Sam said:

Do it right, do it once and use the best stainless steel pipe you can find.

Yes, it will be done right. I have no experience if welding and have no facilities so somebody else will do that.

 

Just in case anybody wishes to know - the top of a Pot Noodle is 4 inches diameter ?

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Also - does anybody know the dimensions of one of those collars ? I guess they can vary slightly.

 

I know the outside dimensions are 6" for the chimney to sit on. But what about the main body of the thing ? How wide are they in total ? Just trying to work out where it would sit on the roof as I have a grab rail which is annoyingly in the way a little.

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On 15/01/2020 at 00:06, NewCanalBoy said:

Why not keep it going vertical for longer and then make it run parallel to the sloping wall (giving it adequate space) then go vertical again ?

If the stove is set to one side of the boat, as many are, it is likely that due to the tumble home of the cabin sides, you will hit the hand rail if you go straight up.  I fitted my own stove and took a shed load of measurements before doing so, which concluded that I needed an offset flue.  Still cacked my pants when I set to with the jigsaw!

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Right, completed my mock up. The stove is standing on a template showing where the different size hearth could be. There's the correct space behind for air gap/fireproof/tiling. I saw a drain pipe for sale for £2.10 in B&Q (admittedly only 3 inch) so placed it roughly where it will hopefully go. Cut a circular 4 inch piece of cardboard (with the help of a pot noodle) and stuck it on the ceiling where I think it might go.

All in all I'm pleased with how it might look and if somebody does a good job on the flue I'll be happy !!

 

 

IMG_20200116_164858557__1579208143_188.29.164.217.jpg

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But you haven’t cut the angles at the top and bottom. The flue must exit the fire at the top perfectly vertical, and it must enter the collar the same way. Hence forming a Z shape. Nobody could make a flue from that piece of pipe as it’s not currently a template, just an angled pipe. 

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2 minutes ago, NewCanalBoy said:

So what about Dors stove on page 1 - are you saying that's wrong ?

Yup. I’m not saying it doesn’t work, because it obviously does, but it’s poor practise and really doesn’t look right, does it?

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59 minutes ago, NewCanalBoy said:

Right, completed my mock up. The stove is standing on a template showing where the different size hearth could be. There's the correct space behind for air gap/fireproof/tiling. I saw a drain pipe for sale for £2.10 in B&Q (admittedly only 3 inch) so placed it roughly where it will hopefully go. Cut a circular 4 inch piece of cardboard (with the help of a pot noodle) and stuck it on the ceiling where I think it might go.

All in all I'm pleased with how it might look and if somebody does a good job on the flue I'll be happy !!

 

 

IMG_20200116_164858557__1579208143_188.29.164.217.jpg

You need to investigate up behind the ceiling, that there are no steel roof cross beams in the way of the flue pipe, an early morning dew usually shows them up them up outside on the roof, also tapping along the roof, dull thuds means beans. Also screws in the ceiling boards that secure them to noggins on the steel beams, and handrails in the way. You also need to check for any lighting wires up there.  The accurate way to drill the flue hole is to first drill a pilot hole up from the inside with about an 8mm drill bit, hold the drill as vertical and as steady as possible and drill up through ceiling and steel roof in one go. This or these holes will be the pilot for both cutting a big hole in the roof for the collar and for cutting the flue hole in the ceiling, they will match accurately.

 

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9 hours ago, CompairHolman said:

I made my last flue from offcuts of 1 mm thick stainless tube I had lying about, I expected it to just be temporary but in fact there is no corrosion or thinning over the last three or four years and the thin wall radiates heat into the cabin as soon as the fire is lit, there is significantly less heat being lost up the chimney and the draft hasn't suffered,  I personally wouldn't go back to thick wall steel flue. 

 

I've never had a problem will thick walled steel pipe. Never had one corrode through. It doesn't take very long to heat up a thick walled flue and once up to temperature I'm not sure how more heat is lost up the chimney than a thin walled flue?

Edited by blackrose
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1 hour ago, bizzard said:

You need to investigate up behind the ceiling, that there are no steel roof cross beams in the way of the flue pipe, an early morning dew usually shows them up them up outside on the roof, also tapping along the roof, dull thuds means beans. Also screws in the ceiling boards that secure them to noggins on the steel beams, and handrails in the way. You also need to check for any lighting wires up there.  The accurate way to drill the flue hole is to first drill a pilot hole up from the inside with about an 8mm drill bit, hold the drill as vertical and as steady as possible and drill up through ceiling and steel roof in one go. This or these holes will be the pilot for both cutting a big hole in the roof for the collar and for cutting the flue hole in the ceiling, they will match accurately.

 

Then you have to cut out more of the inner lining to get at the nuts holding the collar on the roof...........................................nobody said it was easy.

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Not everyone has scrap lengths of 6mm ply - but if you did, make a template of your flue. Cut strips, about the width of your flue pipe. Arrange rough lengths together to find the bend required. Use small clamps to hold pieces together. When satisfied with the shape, pin and/or glue.  

 

The whole shape can be transferred to paper, lining wallpaper or similar. Or, if the whole shape is not too large, it can be stored, as is, for future reference. It probably will be needed again, but not for a few years. It can be handed to the fabricator for construction of replacements. 

 

I had quite a job to find a welder, the last time I needed to have a flue made, so I had two built. 

 

 

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Not too sure how I have twisted the thread ?!

 

Anyway, back on topic. Might seem like a radical idea but the flue needs to come about 6 inches further inboard because of my handrail. It's a metal rail version welded to the roof at various points.

 

What stops me cutting out a section of say 12-14 inches of it ? Capping the ends of then putting the collar in-between ? Means I could get the flue pipe to run more inline with the sloping wall and kept in out of my way.

 

I mean if there's only a foot of handrail missing you're not exactly going to fall off the boat ?

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4 minutes ago, NewCanalBoy said:

What stops me cutting out a section of say 12-14 inches of it ? Capping the ends of then putting the collar in-between ? Means I could get the flue pipe to run more inline with the sloping wall and kept in out of my way.

That's how mine is.

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4 minutes ago, NewCanalBoy said:

I mean if there's only a foot of handrail missing you're not exactly going to fall off the boat ?

 

Walking along the gunwale, looking the other way, and letting your hand slide lightly along the handrail.   ...   until it isn't there...

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5 hours ago, Higgs said:

 

Not everyone has scrap lengths of 6mm ply - but if you did, make a template of your flue. Cut strips, about the width of your flue pipe. Arrange rough lengths together to find the bend required. Use small clamps to hold pieces together. When satisfied with the shape, pin and/or glue.  

 

The whole shape can be transferred to paper, lining wallpaper or similar. Or, if the whole shape is not too large, it can be stored, as is, for future reference. It probably will be needed again, but not for a few years. It can be handed to the fabricator for construction of replacements. 

 

I had quite a job to find a welder, the last time I needed to have a flue made, so I had two built. 

 

 

That is how I did mine. If you have three lengths of ply the same width as the flue you can fix them together with a single nut and bolt at each joint, That way when the angles right you just tighten it up. From that you can even get the angle of the cut for the pipe ends

 

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4 hours ago, ditchcrawler said:

That is how I did mine. If you have three lengths of ply the same width as the flue you can fix them together with a single nut and bolt at each joint, That way when the angles right you just tighten it up. From that you can even get the angle of the cut for the pipe ends

 

 

Yes, the template makes it very easy to get the angles right for cutting pipe. Luckily, my flue only has a little bend, just before it meets the roof, so the spare doesn't take up much room. This last replacement, one of the two I had made two winters ago, was the second replacement since my ownership of the boat - 18 years. I'm hoping for at least five years use out of the flue. Not sure if that's a short time or not. Seems a reasonable expectation.

 

 

2 hours ago, CompairHolman said:

Go for a welded on collar then you have no potential for future leaks when the sealant on a separate cast iron collar inevitably degrades . 

 

Mine's a welded collar. Original - 1984. Doing ok. I've got a cast iron one waiting in the wings, if it ever needs fitting.

 

 

Edited by Higgs
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I've never understood why boat builders don't fit welded chimney collars, its cheaper, easier and free of potential leaks, the cast iron collar was designed for wooden boats ( which is why it has square holes for coach bolts ) I just think no one has bothered to think about it and its a tradition. My experience of various boats is that the chimney collar is a common source of leaks and repair jobs.

 

If you wanted the traditional look of a cast iron collar then fabricate one from steel plate and tube and weld it on ?

 

 

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15 minutes ago, CompairHolman said:

I've never understood why boat builders don't fit welded chimney collars, its cheaper, easier and free of potential leaks, the cast iron collar was designed for wooden boats ( which is why it has square holes for coach bolts ) I just think no one has bothered to think about it and its a tradition. My experience of various boats is that the chimney collar is a common source of leaks and repair jobs.

 

If you wanted the traditional look of a cast iron collar then fabricate one from steel plate and tube and weld it on ?

 

 

Because boat builders are not necessarily fitting the boats out, have no idea where the stove(if indeed one is to be fitted at all) is going to go or which stove and flue size might be used.

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