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NewCanalBoy

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

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So i'm thinking of fitting a solid fuel stove into my boat and been doing a lot of research on the subject. Been watching a few videos and saw one where a guy had installed his own stove and flue but it just looked odd to me. Why build it so it comes back towards the centre of the boat ? 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 ?

 

 

 

IMG_20200114_100259085__1579045825_2.217.73.164.jpg

Edited by NewCanalBoy

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Why do either. Mine goes up from the stove to the roof àt following the angle of the cabin side.

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The one above is a little extreme but generally it is good to keep some distance between the flue and the cabin side. If you use a straight section of pipe that meets the roof collar at an angle it will eventually leak foul smelling ooze and fail prematurely, it may also prevent you from using a lined chimney. It is best practice for the flue pipe to be central in the roof collar, this also allows for expansion when hot.

The one above is a little extreme but generally it is good to keep some distance between the flue and the cabin side. If you use a straight section of pipe that meets the roof collar at an angle it will eventually leak foul smelling ooze and fail prematurely, it may also prevent you from using a lined chimney. It is best practice for the flue pipe to be central in the roof collar, this also allows for expansion when hot.

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58 minutes ago, BWM said:

. It is best practice for the flue pipe to be central in the roof collar, this also allows for expansion when hot.

But you could still achieve this if the first bit of pipe was say half a meter tall, then put the bend in, then straighten it again ? You're just putting the angled bend in further up nearer the roof - keeping it from protruding into the cabin quite so low.

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My flue is fitted in the stove collar  at an angle to match the tumblehome, with a piece at the top angled so it goes through the roof collar straight and centred.

057Stove fitted.JPG

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Yes, that's what I would like to do, keep it simple looking ! The piece at the top - is it a welded joint you had made or a purchased part you could cement together ?

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Maybe the first guy had an existing hole he wanted to use ?

 

How did you get the angles right ? Must be a simple knack to it ?!

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Just 'cause someone put it on Youtube doesn't mean it is a good idea, or that they know what they are doing! 😁

A straight flue on my boat going vertical from a centrally mounted stove. Central both across the cabin width and length to distribute the heat all over. I then used an angled roof collar as that was the only one I could get at the time, so I didn't know what I was doing either! One day I'll replace it with a straight one.

 

Jen

3 minutes ago, NewCanalBoy said:

How did you get the angles right ? Must be a simple knack to it ?!

By paying attention to the trigonometry lessons in maths class at school. 😁

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I used a metre of flue, two 45 degree bends back to back and a short stub to go through the collar. I think it gives about 120 mm offset.

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Making a flue out of 113 mm steel pipe (aka CHS) is not too hard if you have the kit and can weld.  Draw up the 'Z' shape you want full size on the floor in chalk. Join the two 'corners' across each bend in the pipe and project these bend  lines out. Technically these two lines bisect the angles of the Z.

 

Lay your pipe on top of the long central part. Drop a big angle grinder through the pipe following  the first of the bend lines and keeping it square vertically.   Rotate the bit of pipe you have cut off through 180 deg and tack weld to the other bit. If you have it right the pipe will now be following one half of the 'Z' shape pipe drawing on the floor.  Repeat the cut, turn, tack weld bit at the next bend line.

Check for fit.  Trim to length. Weld the joints up properly.  If you get the cuts wrong it helps to be good at welding up holes!

 

You can also do it by CAD drawing or triggernometry and then  use a bandsaw to cut the pipe.

N

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Looking at YouTube Guy I thought at first he might have done it like that because he had a couple of 30degree couplers, so all he had to do was get the centre section the right length to make it all fit. However, looking closer it doesn’t appear to have couplers - just welded joints. 

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5 hours ago, NewCanalBoy said:

Yes, that's what I would like to do, keep it simple looking ! The piece at the top - is it a welded joint you had made or a purchased part you could cement together ?

Assuming you are referring to my post, yes it is welded.  The pipe is steel about 4mm thick and 4" diameter.  I suspect it is used for drains normally, but is just right for a stove with a 5" collar. (figures are approximate - gap between pipe and collar is a few mm all round)

I had someone make it up for me, so they did the cutting and welding.  Initially, the bottom of the pipe was rested on a small bit of wood to hold it off the top plate.  The top of the flue is flush with the top of the collar.  Stove door rope is pushed down to centre the pipe in the collar, then the gap is filled with high temperature silicone ('Delta" - good for 300C).  The bit of wood at the bottom is then removed and the pipe drops a bit, and has rope and high temperature silicone the same as the top.  I've never had a problem with the 300 degC silicone, but then the top of the stove has never started glowing cherry red ...

Starting with that gap at the bottom and using silicone means the flue pipe can move a little in the collars.  If it is too rigid it can crack the top plate of the stove when it gets hot and expands.  The pipe at the bottom didn't need any modifications to cope with the angle.

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Cut some strips of 4 mm ply as wide as the flue pipe then arrange the pieces to the angles you need to fit your installation, fix the pattern together and from that you can work out the angles required to cut the pipe, remember that you need equal angles on both ends if you want them to marry up neatly. 

 

 

  • Greenie 1

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3 hours ago, CompairHolman said:

Cut some strips of 4 mm ply as wide as the flue pipe then arrange the pieces to the angles you need to fit your installation, fix the pattern together and from that you can work out the angles required to cut the pipe, remember that you need equal angles on both ends if you want them to marry up neatly. 

 

 

This is how i have seen it done by professionals, 100 percent accurate with no fuss.

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8 hours ago, NewCanalBoy said:

That looks smart. I've googled them but can't find anything ?

Ahh yes, little chimney company,  not small, sorry

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23 hours ago, NewCanalBoy said:

Yes, that's what I would like to do, keep it simple looking ! The piece at the top - is it a welded joint you had made or a purchased part you could cement together ?

 

Do what you want with your chimney on the outside, but don't stick parts of the flue together inside the boat. A flue must be one piece so if it's not a straight pipe then the various sections must be welded. If you stick bits together with fire cement or high temp silicone it can fail with vibration or when the boat hist a lock wall. The failure may go unnoticed but you'll have a carbon monoxide entering the boat. Or if the failure means the flue comes apart and falls on the floor while you're moving the boat it could be a fire risk.

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17 minutes ago, Boater Sam said:

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

Which is why I chose to get the stainless one this time, I've previously replaced it twice over 15 yrs in standard steel, although I was burning almost 100% wood for that time

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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. 

Edited by CompairHolman

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