Double-skinned chimneys

[nicknorman]

Last year we got lots of toxic sludge running down the side of the boat from the chimney. Over the summer we bought a double-skinned chimney. 1st use last night with pretty dry wood, but disappointed to find goo on the roof this morning. What's to be done about it?

[bizzard]

Last year we got lots of toxic sludge running down the side of the boat from the chimney. Over the summer we bought a double-skinned chimney. 1st use last night with pretty dry wood, but disappointed to find goo on the roof this morning. What's to be done about it?

I've found that by doing away with any chimney that overlaps the collar flange does the trick.

I stopped it years ago by siliconing in lightly a chimney tube ''INSIDE' the collar,lightly in case it strikes something and so will knock out without causing damage.You can also try winding string tightly around chimney base and collar to soak up the goo and change the string often.

[Guest Quo Vadis]

Last year we got lots of toxic sludge running down the side of the boat from the chimney. Over the summer we bought a double-skinned chimney. 1st use last night with pretty dry wood, but disappointed to find goo on the roof this morning. What's to be done about it?

 

Snap!

I'm all ears

[n.b.Goldie]

Last year we got lots of toxic sludge running down the side of the boat from the chimney. Over the summer we bought a double-skinned chimney. 1st use last night with pretty dry wood, but disappointed to find goo on the roof this morning. What's to be done about it?

 

I find that a double skinned chimney, where the inner skin sits inside the collar, prevents goo from running down the outside of the chimney. BUT if you are using a rain hat (chinaman's hat) then any moisture will condense onto its underside and then drip onto the roof.

 

Unless it is raining fairly hard I remove the rain hat when the fire is lit and put it on only to keep the rain out when the fire is out. When the fire is lit any rain entering the chimney will just turn to steam and 'float away'.

 

Regards

Ditchdabbler

[churchward]

Last year we got lots of toxic sludge running down the side of the boat from the chimney. Over the summer we bought a double-skinned chimney. 1st use last night with pretty dry wood, but disappointed to find goo on the roof this morning. What's to be done about it?

 

 

The fix for this passed to me on and used on our double skin chimney is as follows.

 

Use baking aluminium baking foil and make a sealing ring to push into the void between the inner and outer skin. Don't fill teh void (you still want the air gap) just enough to make a stable ring around the bottom that will sit on the roof chimney collar. Fit the chimney to the collar so that the aluminium ring sits nicely and seals over the collar. I then used some high temp sealant to cover the foil (may not be necessary) let dry and that was that.

 

There have been no leaks since. Roof is clean.

[Pretty Funked Up]

You need to get a seal between the inner chimney lining and the flu pipe itself. If the flu protudes out the roof a couple of inches it will likely seal anyway without any 'doctoring'.

If not the aluminium foil suggesion above should do the trick nicely.

GL

[nicknorman]

I find that a double skinned chimney, where the inner skin sits inside the collar, prevents goo from running down the outside of the chimney. BUT if you are using a rain hat (chinaman's hat) then any moisture will condense onto its underside and then drip onto the roof.

 

Unless it is raining fairly hard I remove the rain hat when the fire is lit and put it on only to keep the rain out when the fire is out. When the fire is lit any rain entering the chimney will just turn to steam and 'float away'.

 

Regards

Ditchdabbler

Thanks. I lied slightly in that last night was the second night -1st night we left the rain hat on and got drips from its edge. I hoped that by not fittng it last night that would fix the problem but alas not.

[Joshua]

Last year we got lots of toxic sludge running down the side of the boat from the chimney. Over the summer we bought a double-skinned chimney. 1st use last night with pretty dry wood, but disappointed to find goo on the roof this morning. What's to be done about it?

 

The best solution is to avoid producing tar in the first place.

 

I don’t blame anyone for misunderstanding the difference between properly seasoned wood and a bit of ‘dry’ wood that you pick up from the canal side.

 

I heat my house with 6 woodstoves and I feed them with wood from my own woodland, which I cut and season myself.

 

I have been doing this for 12 years but it took me many years to really understand how important the preparation of the wood is.

 

The practice in my area of France is to use wood from certain trees only and to season it for a minimum of 3 years before use. Seasoning means 2 years exposed to sun, wind and rain but properly stacked with a good free air current around it, then 12 months under cover.

 

Properly seasoned wood gives fantastic heat, burns easily, slowly and steadily and gives no tar.

 

If not properly seasoned it burns with difficulty but once going burns fiercely, quickly and without much heat and produces plenty of tar which itself then becomes a major fire hazard.

 

I haven’t heard of any chimney fires on a boat but until I learnt the difference between good and bad wood I suffered 3 chimney fires in my home one of which nearly burnt my house down and kept burning for 3 days even after the fire brigade had been to put it out!

 

Joshua

 

 

[nicknorman]

The fix for this passed to me on and used on our double skin chimney is as follows.

 

Use baking aluminium baking foil and make a sealing ring to push into the void between the inner and outer skin. Don't fill teh void (you still want the air gap) just enough to make a stable ring around the bottom that will sit on the roof chimney collar. Fit the chimney to the collar so that the aluminium ring sits nicely and seals over the collar. I then used some high temp sealant to cover the foil (may not be necessary) let dry and that was that.

 

There have been no leaks since. Roof is clean.

Thanks, that sounds like a plan and I will try it.

 

The best solution is to avoid producing tar in the first place.

 

I don’t blame anyone for misunderstanding the difference between properly seasoned wood and a bit of ‘dry’ wood that you pick up from the canal side.

 

I heat my house with 6 woodstoves and I feed them with wood from my own woodland, which I cut and season myself.

 

I have been doing this for 12 years but it took me many years to really understand how important the preparation of the wood is.

 

The practice in my area of France is to use wood from certain trees only and to season it for a minimum of 3 years before use. Seasoning means 2 years exposed to sun, wind and rain but properly stacked with a good free air current around it, then 12 months under cover.

 

Properly seasoned wood gives fantastic heat, burns easily, slowly and steadily and gives no tar.

 

If not properly seasoned it burns with difficulty but once going burns fiercely, quickly and without much heat and produces plenty of tar which itself then becomes a major fire hazard.

 

I haven’t heard of any chimney fires on a boat but until I learnt the difference between good and bad wood I suffered 3 chimney fires in my home one of which nearly burnt my house down and kept burning for 3 days even after the fire brigade had been to put it out!

 

Joshua

Yes I agree with all that, although complying with it on a boat is not easy! The wood in question was bought in a string bag a few weeks ago but seemed dry because of its weight -pretty light- but I agree that the moisture content was probably still fairly high. I will perhaps try fossil fuel tonight, it having had plenty of time to season"

[bottle]

I filled the 'air gap' between the two skins with asbestos rope.

 

Keeps inner pipe/chimney warm and reduces condensation, was also recommended insulation foam.

[richardf]

I filled the 'air gap' between the two skins with asbestos rope.

 

Keeps inner pipe/chimney warm and reduces condensation, was also recommended insulation foam.

 

Yep, similar idea to mine - the gap between the two chimneys filled with fire retardant rockwool. Means the inner chimney stays hot and the products don't condense.

[nicknorman]

I filled the 'air gap' between the two skins with asbestos rope.

 

Keeps inner pipe/chimney warm and reduces condensation, was also recommended insulation foam.

Thanks Keith, I'll try that if he foil ( which we have on the boat) doesn't fully fix the problem. Was that you moored at Tamworth / Ventura yesterday? We foolishly tied up to visit the new John Lewis and inevitably spent a fortune!

[bottle]

Yes, it was, we needed Sainsburys, not quite a fortune spent but almost.

[Ray T]

Variation on a theme: I've wrapped exhaust wrap round the inner skin then secured it with fire resistant expanding foam from a spray can. The foam came from Wickes.

 

The inner skin fits inside the chimney collar on C F.

 

Quote from: The Solid Fuel Technology Institute, Stoves in boats.

 

"INSULATED CHIMNEY

Insulated pipe outside and inside the

cabin, for safety and to keep the smoke

HOT so it rises. Uninsulated pipe cools

the smoke down and drastically spoils

stove performance. (8.2)"

STOVES IN BOATS

Some of the basics about fitting and using solid

fuel stoves on boats in the UK and Ireland.

The numbers in (brackets) are sections in

British Standard BS 8511:2010 Code of

practice for the installation of solid fuel

heating and cooking appliances in small

craft where much more detailed information

can be found. The code isn't compulsory, but

will always be referred to if an accident occurs.

 

Edited October 21, 2011 by Ray T

[ditchcrawler]

The best solution is to avoid producing tar in the first place.

 

I don’t blame anyone for misunderstanding the difference between properly seasoned wood and a bit of ‘dry’ wood that you pick up from the canal side.

 

I heat my house with 6 woodstoves and I feed them with wood from my own woodland, which I cut and season myself.

 

I have been doing this for 12 years but it took me many years to really understand how important the preparation of the wood is.

 

The practice in my area of France is to use wood from certain trees only and to season it for a minimum of 3 years before use. Seasoning means 2 years exposed to sun, wind and rain but properly stacked with a good free air current around it, then 12 months under cover.

 

Properly seasoned wood gives fantastic heat, burns easily, slowly and steadily and gives no tar.

 

If not properly seasoned it burns with difficulty but once going burns fiercely, quickly and without much heat and produces plenty of tar which itself then becomes a major fire hazard.

 

I haven’t heard of any chimney fires on a boat but until I learnt the difference between good and bad wood I suffered 3 chimney fires in my home one of which nearly burnt my house down and kept burning for 3 days even after the fire brigade had been to put it out!

 

Joshua

I bet your chimney is more than 6 foot long.

[nicknorman]

I can report that following the baking foil treatment, there is no goo on the roof this morning! Thanks all for the tips.

[Joshua]

I bet your chimney is more than 6 foot long.

 

 

Considerably, which of course will affect the likelihood and intensity of any chimney fire but does not change the amount of heat and tar a given piece of wood will produce.

 

Until you have experienced just how much difference there is between a bit of ‘dry’ wood and properly seasoned firewood you couldn’t possibly imagine it.

 

Watching good firewood slowly purr away in a well designed wood burner and feeling the incredible heat it gives off, is a wonderful experience.

 

Working with wood that roars away in a frenzy of flames once you finally coax it into life but which paradoxically gives off very little heat and covers your wood burners glass in a haze of tar, is not.

 

Joshua

[County4x4]

Joshua - I dream about customers like you!!

 

Andy

[Pretty Funked Up]

Joshua - I dream about customers like you!!

 

Andy

 

we dream about having an endless supply of that kinda wood.

oops forgot to mention FREE endless supply

[nipper]

I can report that following the baking foil treatment, there is no goo on the roof this morning! Thanks all for the tips.

Same with mine! Problem sorted!

Edited October 27, 2011 by nipper

[Tony Ross]

Glad to see it's not just me having these issues with double skinned chimneys! I thought it was the seal between the liner and the flue pipe so thought of getting some asbestos rope wrapped around the outside of the liner so as to form a tight seal. Am struggling to visualise how the aluminium baking foil is working from the description given. Is the foil being made into some form of gasket or is the whole gap between the inner and outer skins being filled. Can anyone post a line drawing to explain?

 

regards,

 

Tony

Edited October 31, 2011 by Tony Ross

[nicknorman]

Glad to see it's not just me having these issues with double skinned chimneys! I thought it was the seal between the liner and the flue pipe so thought of getting some asbestos rope wrapped around the outside of the liner so as to form a tight seal. Am struggling to visualise how the aluminium baking foil is working from the description given. Is the foil being made into some form of gasket or is the whole gap between the inner and outer skins being filled. Can anyone post a line drawing to explain?

 

regards,

 

Tony

Hi Tony

 

I just rolled up some foil and stuffed it into the gap between the inner and outer skin. I didn't try to fill the entire void with foil, just the gap between inner and outer skin at the bottom.

 

The problem arises because there is no seal between the chimney inner pipe and the roof outlet, so hot and moist gases can get into the intervening space, contact the cold steel outer skin, condense and run down the inner surface of the outer skin. Gases are probably encouraged to circulate by the cooling against the skin causing the gases to fall, whilst new hotter gases are encouraged to rise.

 

I think adding the rolled up foil into the gap, whilst not creating an airtight seal, helps a lot to stop the gases circulating into the space. Because the foil has a very low heat capacity, it will quickly reach the temperature of the flue gases, and once the temperature is the same, there can be no condensation on the foil surface.

 

Whatever, it does seem to work well!