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Moguluk...
Moguluk...

Posted: Fri Dec 28, 2012 3:03pm

Post Subject: Roof collar for the stove on my narrow boat

When the weather gets a bit warmer, I want to re-seal the roof collar that supports the flue pipe from my Morso Squirrel stove on my narrow boat. Is there a neoprene rubber seal available? Or does one have to be cut out from a piece of neoprene rubber? Or does the collar have to be bedded down with a heat resistant sealant? Anyone no the answer please?

Tony-B...
Tony-B...

Posted: Fri Dec 28, 2012 3:44pm

Post Subject: Roof collar for the stove on my narrow boat

I am sorry but this sounds very much like a question from a less experienced boater who has diagnosed their own problem and come to the wrong conclusion. To be much real help I need to know why you want to seal it, what is leaking into the boat and when. I also need to clarify what you want to seal because leaks between the collar and roof are rare, leaks between the stove pipe and collar are very common. Whilst I would be unwilling to put neoprene any where near a flue collar it would probably be OK between collar and roof but far from OK between the pipe and collar. I may need to send you some picture so please answer by email to Tony@tb-training.co.uk and I will send you an answer and also post a similar one here. Tony Brooks

Tony-B...
Tony-B...

Posted: Fri Dec 28, 2012 7:42pm

Post Subject: Roof collar for the stove on my narrow boat

Thew answer below plus two diagram sent direct to teh questioner. Dear Tim Many thanks for getting back to me with the info I asked for. The most frequent cause of leakage from the flue area is using an un insulated chimney so combustion products condense on the inside, trickle down and then spill down the side of the boat, or leak between flue and collar - especially when the flue - collar joint has been sealed with fire cement that has cracked/broken away. However this usually results in black tary liquid when the stove is running hard in frosty weather. I suppose the temperature drop when rain comes could cause it but I do not think it is likely, especially if the leak is fairly clean water. We have to decide if this is a rain water leak between collar and roof or collar and flue. I think that you will have to remove the fire board on the underside of the roof to gain access to the bolts/nuts that hold the collar on so at that point you should be able to see where the leak is. I agree high temperature silicon is probably the best you can do for the seal between flue and collar. I always leave a small upstand of flue above the collar by a mm or two to allow a fillet of the sealer. At this point I must point out, although I am sure that you are aware of it, that a stove running away can produce temperatures above that specified for the sealer but I have yet to see any fail. Sealing the collar to the roof is a different matter because roof collars come with straight or angled flanges so the chimney can sit upright. Unfortunately the angel does not always fit the roof profile or people insist on using a straight flange on many angled roof. All too often this is solved by a wooden wedge packing piece. If yours has one of these it could be rotting and collapsing. If this is the case my best advice is to see if you can obtain an angled flange that is a fair fit to your roof so no packing is required. I am a little concerned that any form of rubber sea that fits close to the flue could catch fire if the stove runs away. I am also not sure how it would react to having just two fixing bolts so the flue or chimney could rock the collar on the roof through the compliance of the "rubber". If you do decide to go down this route I would advise that your centre hole is about an inch all round larger than the flue and this gap be packed with the high temperature sealer before fitting the chimney. I am not aware of any suppliers of ready made seals so you will have to cut your own. I think you can obtain the sheet material from Seals+direct (01425 280415) or Hills Rubber of Reading. I think if you give them your collar they would make the gasket. (0118 958 0535). You could also consider one of the rubberised "cork" gasket materials. On my boat the flange angle was a good fit for the roof so I used the high temperature sealer around the centre inch or so and "paintable" silicon for the rest and 8 years on - touch wood - no leaks. You obviously know that single skin chimneys can cause this sort of problem but so can double skin ones unless you fill the void between both skins with something (see attached diagrams). Some use lightly crumpled kitchen foil while I and others use aerosol foam to fill and insulate the gap. If you use expanding foam just take care it does not push the chimney off and into the canal. I stretched cling film over the collar, filled the chimney with foam and then pushed it hard onto the collar so the whole thing made a good fit. The Clingfilm acts as a release agent and is just cut away or torn off when the foam has hardened. I hope this answers your question and explains why I did not want to give a direct answer on the forum. Tony Brooks

Tony-B...
Tony-B...

Posted: Fri Dec 28, 2012 7:43pm

Post Subject: Roof collar for the stove on my narrow boat

Thew answer below plus two diagram sent direct to teh questioner. Dear Tim Many thanks for getting back to me with the info I asked for. The most frequent cause of leakage from the flue area is using an un insulated chimney so combustion products condense on the inside, trickle down and then spill down the side of the boat, or leak between flue and collar - especially when the flue - collar joint has been sealed with fire cement that has cracked/broken away. However this usually results in black tary liquid when the stove is running hard in frosty weather. I suppose the temperature drop when rain comes could cause it but I do not think it is likely, especially if the leak is fairly clean water. We have to decide if this is a rain water leak between collar and roof or collar and flue. I think that you will have to remove the fire board on the underside of the roof to gain access to the bolts/nuts that hold the collar on so at that point you should be able to see where the leak is. I agree high temperature silicon is probably the best you can do for the seal between flue and collar. I always leave a small upstand of flue above the collar by a mm or two to allow a fillet of the sealer. At this point I must point out, although I am sure that you are aware of it, that a stove running away can produce temperatures above that specified for the sealer but I have yet to see any fail. Sealing the collar to the roof is a different matter because roof collars come with straight or angled flanges so the chimney can sit upright. Unfortunately the angel does not always fit the roof profile or people insist on using a straight flange on many angled roof. All too often this is solved by a wooden wedge packing piece. If yours has one of these it could be rotting and collapsing. If this is the case my best advice is to see if you can obtain an angled flange that is a fair fit to your roof so no packing is required. I am a little concerned that any form of rubber sea that fits close to the flue could catch fire if the stove runs away. I am also not sure how it would react to having just two fixing bolts so the flue or chimney could rock the collar on the roof through the compliance of the "rubber". If you do decide to go down this route I would advise that your centre hole is about an inch all round larger than the flue and this gap be packed with the high temperature sealer before fitting the chimney. I am not aware of any suppliers of ready made seals so you will have to cut your own. I think you can obtain the sheet material from Seals+direct (01425 280415) or Hills Rubber of Reading. I think if you give them your collar they would make the gasket. (0118 958 0535). You could also consider one of the rubberised "cork" gasket materials. On my boat the flange angle was a good fit for the roof so I used the high temperature sealer around the centre inch or so and "paintable" silicon for the rest and 8 years on - touch wood - no leaks. You obviously know that single skin chimneys can cause this sort of problem but so can double skin ones unless you fill the void between both skins with something (see attached diagrams). Some use lightly crumpled kitchen foil while I and others use aerosol foam to fill and insulate the gap. If you use expanding foam just take care it does not push the chimney off and into the canal. I stretched cling film over the collar, filled the chimney with foam and then pushed it hard onto the collar so the whole thing made a good fit. The Clingfilm acts as a release agent and is just cut away or torn off when the foam has hardened. I hope this answers your question and explains why I did not want to give a direct answer on the forum. Tony Brooks

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