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I have two parts of a chimney, one single skinned and the other double skin.

The stove flue size is 5" and the aperture in the roof is 175mm, a little less than 7".

I understand it is typical to have a single skin inside the boat for maximum radiant heat, and to have the double skin through the roof and outside.

Whilst that works for the two parts I have, the flue protrudes too far for my liking and is a recipe for disaster waiting to happen for hitting bridges and the like. In short I would prefer the external flue to be removable whilst I am on the go.

To reduce cost I would like to use what I already have, but I would be grateful for a steer of a way forward.

I have included photos of the parts I have. The dual skinned flue is 1.0m long and the shorter flue is 400mm.IMG_20170519_180310.jpg.cb47ccc092f3f33af243d30af4037518.jpgIMG_20170519_180315.jpg.0ce5349aa4601d9aed8691f99bd0af16.jpgIMG_20170519_180321.jpg.658a6693eb9dc1db5f691645c61f677a.jpg

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Hi Mike

Best way to go is to have a flue made to your exact needs, the stuff from chandlers is crap. There are many people around the system who will build you anything you want. I dont know your location but there is a bloke called Alex here ontoxford who makes by far the best chimlys I have come across in many years of boat ownership, they are so good I have a spare one new and wrapped up for if I ever need another and a long one for when moored and a shorter one for cruising ( bridge clearance etc )

cheers

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1 hour ago, Neil Smith said:

Cut your flue to about an inch below the top of the collar and fill the gap around it with glass rope, then high temp silicone to seal, then get a double skin chimney made to fit.

Neil

Why an inch below the top of the collar? We've just had a damaged flue replaced (or rather the top bit cut off and a new bit welded on) and it sticks above the collar by an inch. The old one was flush.

The old one wasn't concentric with the collar so we used a separate liner and chimney. The new one is concentric so we've treated ourselves to a new stainless steel double skinned one from The Little Chimney Company.

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Many thanks for the replies.

I'm able to cut and if necessary weld to fabricate a flue. Its not obvious from websites how I can join single to double, and double skin to double skin. Are there standard interfaces? Are the ones in my photos standard?

The internal roof has a wooden lining nearby, hence the need to have a short section of a double skinned chimney for a few inches below the ceiling and a couple of inches protruding above the roof; to which I would like to have a demountable double skin chimney to have a reasonable fire draught .

It's important to remove as much of the external chimney as possible for clearance under bridges, trees etc.

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On 21/05/2017 at 23:23, Mikexx said:

Many thanks for the replies.

I'm able to cut and if necessary weld to fabricate a flue. Its not obvious from websites how I can join single to double, and double skin to double skin. Are there standard interfaces? Are the ones in my photos standard?

The internal roof has a wooden lining nearby, hence the need to have a short section of a double skinned chimney for a few inches below the ceiling and a couple of inches protruding above the roof; to which I would like to have a demountable double skin chimney to have a reasonable fire draught .

It's important to remove as much of the external chimney as possible for clearance under bridges, trees etc.

I am not sure that you know about chimney collars.

When I fitted my chimney I cut a hole in the ceiling board, pulled out sufficient foam insulation and repacked the void with rockwool. The single skinned flue then went into and flush with the top of the collar packed as described above. I used a piece of fireboard painted mat black with a wooded trim around the side around the flue to cover the hole I cut in the ceiling board but you can buy ready made ones if required.

I have a removable double skinned chimney that fits over the outer part of the collar with the double skin fitting inside the flue. I have insulated the space between the two chimney linings with spray foam and its shown no signs of heat damage. You can get chimneys in a variety of lengths.

I cant see a collar and have difficulty understanding exactly what you have in the photos.

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The current chimney was a bodge!

I now realise I ought to have a collar but one thing that is bothering me is the current hole I have is 175mm, ie 7". I'm hoping a collar will cover this hole.

I'm confused by the sizes. I'm pretty sure the stove I have has a flue stub of 5" external diameter. I don't know if the flue sizes are governed by internal or external diameter.

I was looking at the multifuel fires fitting kit by:

  https://www.limekilnchandlers.co.uk/multifuel-fires-fitting-kit.html

but I need to check the size of the collar. I also thought I'm not meant to reduce the flue size if mine is really a 5" flue.

I also need the internal trim you mentioned, though was thinking of a brass annular type if they exist. If I understand correctly the internal single skinned flue pipe should go into the collar and end flush with the highest external surface.

Many thanks indeed.

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From what I have seen the "flue stub", what I would call the stove flue collar, has the flue fitted inside it. From memory my  roof collar had a down stand that fitted through the hole in the roof and this was around 1/2 to 3/4 inch wide. That would give an OD for a 5" pipe of between 6 and 6.5 inches so may well cover the hole but the best thing to do is to actually measure one to be sure.

You also need to work out if you need a roof collar that sits at an angle on the roof  so the chimney fits vertically rather than at an angle. This will depend on how vertical the internal flue fits and the slope on the roof box.

The first photo suggests to me that your original flue fitted OVER the stove collar so could never have been packed and made gas tight.

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2 hours ago, Tony Brooks said:

From what I have seen the "flue stub", what I would call the stove flue collar, has the flue fitted inside it. From memory my  roof collar had a down stand that fitted through the hole in the roof and this was around 1/2 to 3/4 inch wide. That would give an OD for a 5" pipe of between 6 and 6.5 inches so may well cover the hole but the best thing to do is to actually measure one to be sure.

You also need to work out if you need a roof collar that sits at an angle on the roof  so the chimney fits vertically rather than at an angle. This will depend on how vertical the internal flue fits and the slope on the roof box.

The first photo suggests to me that your original flue fitted OVER the stove collar so could never have been packed and made gas tight.

The roof curved so the collar will need to be angled. I can measure the angle but not sure if there's much variety and one size fits all?

You are correct, the current flue fits over the stove collar. I need to have another look at the stove collar as I don't recall an internal ledge for a pipe to sit on. I guess this is leaning to a 4.5" tube. with 1/4" of packing (if I'm lucky).

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1 hour ago, Mikexx said:

The roof curved so the collar will need to be angled. I can measure the angle but not sure if there's much variety and one size fits all?

You are correct, the current flue fits over the stove collar. I need to have another look at the stove collar as I don't recall an internal ledge for a pipe to sit on. I guess this is leaning to a 4.5" tube. with 1/4" of packing (if I'm lucky).

On the stoves I have seen the stove collar screws onto the stove top by two set screws inside the collar so the chimney sits on the4se or the lugs they screw into. However there are so many stove variants nothing is certain.

Lest have more experienced input for  MIke

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3 hours ago, Mikexx said:

The roof curved so the collar will need to be angled. I can measure the angle but not sure if there's much variety and one size fits all?

Or you can make a hardwood tapered piece to sit betweeen fhe chimney collar flange and the roof to suit your angle and curvature of the roof.

Edited by David Mack
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On 30/05/2017 at 16:10, David Mack said:

Or you can make a hardwood tapered piece to sit betweeen fhe chimney collar flange and the roof to suit your angle and curvature of the roof.

 

I feel something a little less combustible would be required?

On 30/05/2017 at 16:32, Tony Brooks said:

Limekiln supplied my angled collar. It does not look angled to a cursory glance but is.

 

Thanks, that is interesting. I suppose, depending on its thickness, I could grind or cut some of the material away to match the roof if necessary.

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12 minutes ago, Mikexx said:

 

I feel something a little less combustible would be required?

Others have reported that it works fine. The collar doesn't get that hot. And bolting the collar down to a wooden spacer isn't really any different to bolting it down to a wooden cabin roof, and that is done on many boats.

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  • 3 weeks later...

I purchased one of these:

https://www.limekilnchandlers.co.uk/multifuel-fires-fitting-kit.html

The exististing collar on the stove I have has the dimentions:
Ext 5.033" to 5.080" Int 4.85" to 4.87"

The adapter boss that comes with the kit has upper and lower dimensions:
Ext 5.19" INt 4.79"
and
Ext 4.986" Int 4.66"

Photos below.

I can turn down any of these dimensions to fit externally or internally to the stove collar using fireclay to lubricate fitting and for sealing.

However, I'm wondering if I should make a ledge (ring) inside the stove flue and sit the new 4.5" flue on this and pack with rope and fireclay?

Any ideas?

IMG_20170619_141752-resize.jpg

IMG_20170619_141743-resize.jpg

IMG_20170602_183040-resize.jpg

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I note that you have a flue damper at the top of your stove. You can imagine that when this is closed it will easily trap debris coming down the flue (and it does!), with potentially dangerous results..For this reason I and many others have removed such mechanisms from our stoves and sealed up the pivot holes.   Some here have disagreed with this, but there is plenty of evidence of the dangers.

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49 minutes ago, Mikexx said:

That is something to bear in mind, certainly if the damper becomes difficult to move.

However, with the aid of a torch or using a snake-cam it should be easy to see any obstruction?

What, with the fire burning?  Obstructions can happen at any time, with no warning, when damping down a fire with these dangerous and unnecessary features.

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21 hours ago, BWM said:

Nothing dangerous about a flue damper, being a designed feature of the stove they are fitted to. 

I did say that some may disagree.  But I stick with what I said - they can be dangerous, especially when used by someone not aware of the dangers.

Just because it is a designed feature doesn't mean that it can't get blocked.

  • Greenie 1
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On 6/23/2017 at 15:29, Mac of Cygnet said:

I did say that some may disagree.  But I stick with what I said - they can be dangerous, especially when used by someone not aware of the dangers.

Just because it is a designed feature doesn't mean that it can't get blocked.

Definitely can become blocked, as can a badly maintained flue. A working C.o alarm is essential equipment with any solid fuel stove, along with regular maintenance. The only issue I have with the removal of the damper is the potential for overheating of the range during windy weather in particular. 

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Silly question time (new boat owner),

Why do folk need to remove and re fit the chimney to clear bridges?

Is there a length, from roof to top of chimney, that will clear all bridges?

Tom n Jill.

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1 minute ago, Tom766 said:

Silly question time (new boat owner),

Why do folk need to remove and re fit the chimney to clear bridges?

Is there a length, from roof to top of chimney, that will clear all bridges?

Tom n Jill.

Some chimneys are fitted on the right hand side. Some are too tall. 

 

Some are just right, and pass under the bridge to give greatest clearance (usually those fitted on the left and not too tall) 

Edited by rusty69
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20 minutes ago, rusty69 said:

Some chimneys are fitted on the right hand side. Some are too tall. 

 

Some are just right, and pass under the bridge to give greatest clearance (usually those fitted on the left and not too tall) 

Sorry, I just don't get this right/left thing.  You could say the opposite about boats travelling in the opposite direction!

Actually, the lowest bridges I've come across haven't been arched, so makes no difference.

And the answer to Tom766's question is no.

 

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