10" Chimney length?

Hi folks, I'm just building a large forge in the Vaughan's style (SFP1 - picture here http://www.anvils.co.uk/forges.htm top right) and it will have a 10"
chimney. Does anyone know what is the minimum chimney length which will draw OK and not smoke out the shop? Thanks The Beagle
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I've been told the chimney should be 4 foot taller than the tallest part of the roof. Rob

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Plus News wrote:

Hey there. In _A Blacksmith Primer_ by Randy McDaniel he gives great details of how the chimney should be.
He says that the size of the chimney should be "one brick square" which is about 8" to 9" square. If you're chimney will be made out of stovepipe, it translates to about 12" in diameter. Run the chimney as straight as possible. For every elbow you add, you reduce the draft by 20%. The opening in the chimney at the forge about 8" or 9" wide and 22" high. This is the same for either brick or stovepipe.
Now, about chimney positioning on the roof he says:
"If using a stovepipe chimney with a rain cap, be sure to raise the cap close to the same distance from the top of the chimney as its diameter. If the pipe is 12" in diameter, then raise the cap 12" to allow proper draft."
"The height of the chimney should be two fee higher than the roof peak if the chimney is within 10' of that peak. If the chimney is more than 10' from the peak then make sure the chimney is 2' higher than the point at which a 10' horizontal line touches the roof. These are standard rules for chimneys that should be followed for forges, fireplaces, or stoves."
He talks more about flashing and stuff and there are a couple of pictures of the chimney concepts mentioned above. I'd be happy to scan the pictures in and email them to you. Or, better yet, I could try and put them in .pdf format and send them to you so you can see and read it for yourself.
Just let me know which you'd prefer.
rvb
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Thanks for the info Rick, but................. Following these rules would mean my chimney was 3m pipe length.....is this enough? The beagle

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The Beagle wrote:

Well, I'm not exactly sure about that. I don't have the luxury of being able to forge indoors. I'm stuck outside for now and have no chimney whatsoever. But, 3m ~= 10 feet. I'm thinking that's long enough for a decent draw.
However, I would direct you to a couple of the other responses to your post for second or third opinions. To be sure, it would be beneficial to call a mason in your area that builds chimneys and ask them.
Sorry I couldn't be of more help,
rvb
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The Beagle wrote:

Everyone answering so far is giving the minimum height above the roof - but in a single-story shed, this may still be a bit short (top to bottom of the chimney) for good draw. 12-15 feet or so is a pretty-good minimum overall length, even if it means the chimney is sticking up 6 feet above a 9 foot roof (or even more, since it's not really starting at the gound level inside the shed). You probably need to brace the chimney if it sticks up that much above the roof.
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Actually depends on how big and hot the fire. For a "normal" home forge at least 10 feet. Since you say large forge, then the diameter might be the problem, but longer is usually better. What direction is the smoke going with normal winds? Other problems might justify more expense.
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I would run a small blower (outside of the chimney) with an outlet centered inside of the chimney tube aiming up. This will create a draft even with a small cooler fire. Jim
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