Jump to content
Strawberry Orange Banana Lime Leaf Slate Sky Blueberry Grape Watermelon Chocolate Marble
Strawberry Orange Banana Lime Leaf Slate Sky Blueberry Grape Watermelon Chocolate Marble
Gabby&Jack

Installing woodburner - collar?!

Featured Posts

We've ordered all our bits to install the woodburner - including a collar of 6" outside diameter (5" inside diameter) and it said it was suitable for a 4" - 4 3/4" outside diameter flue. 

 

But on looking at it, the gap seems huge between the flue and the collar. It's 15mm gap all around. Is that normal? When we put our fire rope in to stuff it out, there's still quite a lot of wiggle room. 

 

Do we put stove rope in and then seal it on inside with fire cement and outside silicone and then it will be fine - or do we need a smaller collar? 

 

Thank you canal forum knowledge!! 

 

Gabby 

121273182_337325347497424_7679228104411036195_n.jpg

Share this post


Link to post
Share on other sites

15mm all around is too much. You only need 5mm all around as an expansion gap.

 

If the collar fits the stove then haven't you got the wrong diameter flue or can you get different diameter collars for your stove? Otherwise you might be able to get a short section of bigger diameter thick wall pipe welded onto the bottom of your flue to make it fit the collar and reduce the gap.

 

Anyway, once you've solved that, pack the gap with some glass rope and then seal the top with Envirograf high temp silicone sealant which goes up to 1200C. Don't bother with cement, it's crap and just goes brittle and falls out after a while. You can use cheaper Plumba flue high temp silicone to seal around the top of the roof collar/flue but use Envirograf for the stove collar as it's hotter down there. Once you've bought Envirograf you may as well use it for both.

Edited by blackrose

Share this post


Link to post
Share on other sites

You can use what you've got  if need be Minimising the number of joints is more important and if the flue fits the stove, then it makes sense to use that, rather than introduce an extra joint that can leak with a size change collar. It will just cost you more in extra glass fibre rope and high temperature silicone. As @blackrose said, don't use fire cement at the top. The flue expands when it gets hot and if it is held rigid at both ends it can put a lot of stress on the stove top that can lead to it cracking. Silicone flexes as the flue expands and reduces the stress. I've not used Envirograf, so can't comment. Fire cement at the stove end cracks up after a while and needs digging out and replacing, so a better alternative is a good idea.

Jen

Share this post


Link to post
Share on other sites

But at the moment the flue doesn't fit? A 15mm gap sounds a bit dangerous if it's already been packed with rope and the flue is still moving in the collar as the OP said.

 

If an expansion joint is properly welded onto the bottom end of the flue it's not going to leak. There's nothing wrong with welded joints in flues, it's overly wide rope/silicone joints that you want to avoid. 

Edited by blackrose

Share this post


Link to post
Share on other sites

How is it dangerous? The important thing is that the gap doesn't let water, tar and smoke get in to the boat. Water and tar are unsightly, only smoke is dangerous. As long as the material used to seal the gap is impervious to all three, then the important bit is the adhesion of the silicone to the collar and pipe. A larger gap actually reduces the shear stress on these interfaces as the pipe expands with heat. Once it is filled with silicone gunge, the existing movement will disappear.

Edited by Jen-in-Wellies

Share this post


Link to post
Share on other sites

We'll just have to agree to disagree Jen.

 

An expansion gap that's too large will be more difficult to seal properly. I think that's a statement of the obvious. Leaks may start to appear as it expands and contracts. Silicone by its nature is flexible, so it's not going to make the movement between the OP's collar and flue magically "disappear"

 

Gabby & jack - try what Jen suggests - if you can still move the base of the flue in the collar by hand it's not safe.

Edited by blackrose

Share this post


Link to post
Share on other sites

The half inch gap will be ok, just pack it with the thick inch thick fire rope, first ring smother with heat proof silicone and poke down, this first ring will stick, then a couple more rings on top, finishing with more silicone. To be honest I just use cheap silicone, it's all fire proof, but I of course must recomend the expensive fire proof type. :) My collar and flue pipe have a half inch gap too because I fitted a smaller stove, don't like it too hot, and kept the same collar, no problem at all, no leaks.

  • Greenie 1

Share this post


Link to post
Share on other sites
19 minutes ago, Jen-in-Wellies said:

How is it dangerous? The important thing is that the gap doesn't let water, tar and smoke get in to the boat. Water and tar are unsightly, only smoke is dangerous. As long as the material used to seal the gap is impervious to all three, then the important bit is the adhesion of the silicone to the collar and pipe. A larger gap actually reduces the shear stress on these interfaces as the pipe expands with heat. Once it is filled with silicone gunge, the existing movement will disappear.

You may be labouring under a misapprehension. This is the lower stove end of the flue.

Share this post


Link to post
Share on other sites
3 minutes ago, Sir Nibble said:

You may be labouring under a misapprehension. This is the lower stove end of the flue.

Nope it is  the upper end, just upside down. What you can see is the underside of the flue collar. It just hasn't been fitted to the roof yet.

Edited by Jen-in-Wellies

Share this post


Link to post
Share on other sites
Just now, Jen-in-Wellies said:

Nope it is  the upper end, just upside down. What you can see is the underside of the flue collar.

That's what I thought, the picture is a roof collar upside down with a flue pipe in it. I would pack it out and put some great proof sealant to stop rain getting in.

Share this post


Link to post
Share on other sites
1 minute ago, Jen-in-Wellies said:

Nope it is  the upper end, just upside down. What you can see is the underside of the flue collar. It just hasn't been fitted to the roof yet.

Yes you're right. It's me labouring under a misapprehension.😄

  • Greenie 2

Share this post


Link to post
Share on other sites

 

I think it will be ok. Pack the rope in really well and seal the outer last few millimetres with black silicone. I usually do that on the underside, too, inside the boat, The assembly needs to be firm, to help keep the flue stable in its fitting on the top of the stove, but with some give for expansion, so the flue doesn't stress the stove top. 

 

 

Edited by Higgs

Share this post


Link to post
Share on other sites
1 hour ago, bizzard said:

My collar and flue pipe have a half inch gap too because I fitted a smaller stove, don't like it too hot, and kept the same collar, no problem at all, no leaks.

Same here, we fitted a smaller stove some 7 years ago.

Bottom end of the flue is very tight in the stove and sealed with fire cement, there is no movement at all. We have just had the top collar off as the boats been painted, when refitting  we filled the gap with rope and sealed above and below with Envirograf 1200deg sealant, used the whole tube ;)

 

Edited by Loddon

Share this post


Link to post
Share on other sites

If you can find some intumescent tape its great for stuffing collars, expands a bit as it gets hot. You can buy intumescent paste in a gun tube, must try it one day.

Share this post


Link to post
Share on other sites

Thank you for all of this!! Yes it is the roof collar upside down 

 

Having round a few marinas and chandlers it seems the 6" is the correct size and we just need to correctly fill the gap. We're going for thick fire rope ladding - and lots of sealant. So we'll avoid the cement - thanks for the tips.

 

Wealth of knowledge, as per!

Share this post


Link to post
Share on other sites
2 hours ago, Tracy D'arth said:

If you can find some intumescent tape its great for stuffing collars, expands a bit as it gets hot. You can buy intumescent paste in a gun tube, must try it one day.

 

When I was building data centres in London, the local authority fire officer would inspect each data hall to ensure all holes had been filled with vermiculite and intumescent sealant.

 

Without his sign off the data hall couldnt be used.

  • Happy 1

Share this post


Link to post
Share on other sites
8 hours ago, blackrose said:

But at the moment the flue doesn't fit? A 15mm gap sounds a bit dangerous if it's already been packed with rope and the flue is still moving in the collar as the OP said.

 

If an expansion joint is properly welded onto the bottom end of the flue it's not going to leak. There's nothing wrong with welded joints in flues, it's overly wide rope/silicone joints that you want to avoid. 

I thought he was talking about the roof end of the flue not the stove end. Do I have it wrong again?

Share this post


Link to post
Share on other sites
2 minutes ago, ditchcrawler said:

I thought he was talking about the roof end of the flue not the stove end. Do I have it wrong again?

No you understood correctly as pointed out by Jen and myself in earlier posts.

Share this post


Link to post
Share on other sites
9 minutes ago, Rob-M said:

No you understood correctly as pointed out by Jen and myself in earlier posts.

Thats because I reply when I read something, not several pages later.

  • Greenie 1
  • Happy 1

Share this post


Link to post
Share on other sites
On 10/10/2020 at 09:32, bizzard said:

The half inch gap will be ok, just pack it with the thick inch thick fire rope, first ring smother with heat proof silicone and poke down, this first ring will stick, then a couple more rings on top, finishing with more silicone. To be honest I just use cheap silicone, it's all fire proof, but I of course must recomend the expensive fire proof type. :) My collar and flue pipe have a half inch gap too because I fitted a smaller stove, don't like it too hot, and kept the same collar, no problem at all, no leaks.

In the distant past I built some turbocharged performance engines for a car being raced at Le Mans. This used Wills rings, a sort metal sort of "O" ring as head gasket between liner and head, which required a groove machining in the cylinder head face. 

We used to locate these with a dab of clear silicone sealant purely for assembly purposes. Nothing special, just basic clear silicone sealant. 

Upon stripping the engines where any sealant had squeezed into the combustion chamber space there was no sign of any degradation of the sealant. It certainly didn't seem to suffer as a result of the heat. (On the whole we didn't want any sealant in there!) Combustion temps in engines are high. Very high.

I would be more than happy with ordinary silicone, once cured, being able to take the heat. Though there may be other reasons as to why one that is recommended is more suitable.

  • Greenie 1

Share this post


Link to post
Share on other sites
1 hour ago, RS_Pete said:

In the distant past I built some turbocharged performance engines for a car being raced at Le Mans. This used Wills rings, a sort metal sort of "O" ring as head gasket between liner and head, which required a groove machining in the cylinder head face. 

We used to locate these with a dab of clear silicone sealant purely for assembly purposes. Nothing special, just basic clear silicone sealant. 

Upon stripping the engines where any sealant had squeezed into the combustion chamber space there was no sign of any degradation of the sealant. It certainly didn't seem to suffer as a result of the heat. (On the whole we didn't want any sealant in there!) Combustion temps in engines are high. Very high.

I would be more than happy with ordinary silicone, once cured, being able to take the heat. Though there may be other reasons as to why one that is recommended is more suitable.

Exactly. I've mentioned the silicone heat thing on here a few times, I get no response. I presume folk carry on buying the expensive rip off special? heat proof stuff.

 When I'm in a scientific mood I carry out simple experiments, The silicone one I think is in this thread, no need for loads of googling like most seem to do on here.   Just think scientifically. :):(

Edited by bizzard
  • Greenie 1

Share this post


Link to post
Share on other sites
5 hours ago, bizzard said:

Exactly. I've mentioned the silicone heat thing on here a few times, I get no response. I presume folk carry on buying the expensive rip off special? heat proof stuff.

 When I'm in a scientific mood I carry out simple experiments, The silicone one I think is in this thread, no need for loads of googling like most seem to do on here.   Just think scientifically. :):(

There needs to be a like button on these forums🙂

Now, how do I get a 5" flue through a wooden roof...? (Or should I start a separate thread..?)

Share this post


Link to post
Share on other sites
5 hours ago, RS_Pete said:

There needs to be a like button on these forums🙂

Now, how do I get a 5" flue through a wooden roof...? (Or should I start a separate thread..?)

Is this the wooden deckhead (ceiling) or does the boat have a wooden roof?

PS the greinies and their accolites are 'like' button equivalents.

Edited by LadyG
  • Love 1

Share this post


Link to post
Share on other sites
8 hours ago, RS_Pete said:

There needs to be a like button on these forums🙂

 

If you look at @bizzard post you quoted, you'll see a little green arrow has appeared at the bottom over to the right. This is a "greenie", basically a "like", which I have just placed there on your behalf - and also because he comes out with good stuff and surreal stuff in roughly equal measure, so he deserves them sometimes! :D

  

At the extreme bottom right of this post, you'll see a grey disc with a white arrow. Clicking on that will bring up a menu to choose a response from - I clicked the greenie for you, but you can chose just one from that list.  Hope that helps! 

  • Love 1

Share this post


Link to post
Share on other sites
37 minutes ago, Sea Dog said:

If you look at @bizzard post you quoted, you'll see a little green arrow has appeared at the bottom over to the right. This is a "greenie", basically a "like", which I have just placed there on your behalf - and also because he comes out with good stuff and surreal stuff in roughly equal measure, so he deserves them sometimes! :D

  

At the extreme bottom right of this post, you'll see a grey disc with a white arrow. Clicking on that will bring up a menu to choose a response from - I clicked the greenie for you, but you can chose just one from that list.  Hope that helps! 

 

 

Thanks, still learning my way !

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

  • Recently Browsing   0 members

    No registered users viewing this page.

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.