[TheForge] Stack Cover

[David E. Smucker]

What Darrell describes is what I call a "Shot Gun" stack cover.  Not really 
a cover at all but a way to limit rain coming down your stack and present 
zero back pressure so you get maximum draft.  This is now a common 
industrial stack cover or top.  It works because, very little rain falls 
straight down -- when it rains the wind is blowing so rain is falling at an 
angle.  The stronger the rain, the high the wind in most cases.  The stack 
top consists of a larger diameter section of stack that fits over the normal 
size and is shimmed out so that there is space for water to drain out and 
flow to the roof and not down your stack to the forge.  The rain traveling 
at an angle strikes the side of this larger extension and run down the 
inside and out the annular space and on to the roof.  Rule of thumb is to 
make this stack extension 4 times the diameter.

Why go to this trouble -- because a common hat type stack cover creates so 
much back pressure that it typically cuts the effective draft in half.

My stack is 15 inch diameter and my "shot gun" extension (100 percent open 
at the top) is 16 inch diameter.  It extends 60 inches above the 15 inch 
stack and overlaps by 12 inches so it total length is 72 inches.  It works 
very well.  It doesn't suck your hat off, but I don't have smoke in the shop 
either. (This on a hood type forge not a side draft.)  With light rain I get 
a little water down the stack, with heavy rain I get almost none.

Look for a future article on this in the AACB Newsletter.

Dave Smucker

----- Original Message ----- 
From: "Riverbend Blacksmiths" <riverbendblacksmiths at mac.com>
To: "Sponsored by ABANA" <theforge at mailman.qth.net>
Sent: Wednesday, November 22, 2006 4:35 PM
Subject: Re: [TheForge] Stack Cover


>I too just finished installing a stack (an 8" black stove pipe)  through 
>the steel roof of my shop. It connects down to a thick sheet  metal chimney 
>that I built and welded up in the shop. It draws very  nicely from the side 
>(side draft). I bought an off-the-shelf cap that  fit the diameter of my 8" 
>pipe, but would like some input from others  in the forum to see what's 
>best. We had a lot of rain and driving  winds, so there was a nice puddle 
>in my coal ash bucket after the  rains that drained on through.
>
> I'm sorry, but I can't understand or picture Darrell's directions  that he 
> provided here. Am I the only one?
>
> Marsha.
> Ontario, Canada
> -----
> On Nov 22, 2006, at 11:59 AM, Darrell wrote:
>
>> A 4' section of 14" diameter pipe over the top of your stack would  work 
>> the best. Attach the section overlapping the top of your stack  a couple 
>> of inches using three one inch channels spaced around the  stack. Rain 
>> that enters the top of the 14" piece will hit the side  and fall out the 
>> gap at the bottom of the 14" piece onto the roof.
>>
>> Darrell
>>
>> ----- Original Message ----- From: "Lynn and Susan Lang" 
>> <langfarm at together.net>
>> To: <theforge at mailman.qth.net>
>> Sent: Wednesday, November 22, 2006 5:38 AM
>> Subject: [TheForge] Stack Cover
>>
>>
>>> Hello
>>>
>>> What turns out to be the best cover for the forge stack?
>>>
>>> Want to keep rain and snow out but allow smoke out...
>>>
>>> I put up a 12" pipe, told that anything smaller will not be  adequate...
>>>
>>> Thank you
>>>
>>> lynn
>>>
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>
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