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Building a Hofi style chimney, question...

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Posted · Report post

Finally hit the scrap yard at the right time to get some square ducting. Grabbed a 5 foot section, rectangular rather than the 13 inch square in Hofi's example. The plan is to use this duct to make my own Hofi style forge chimney, and eliminate the right-over-the-firepot version I'm running now, which would eliminate the rain drips and get me started and plugging all the holes in the leaky patio roof.

I'm thinking the orientation of the duct should be with the long side vertical, so the opening for the smoke is taller than it is wide. This is roughly the same height above the forge table as the current hood and chimney.

Any input would be appreciated. I want to cut the hole in the patio wall (and get a good section to fill in the overhead chimney hole) just once and get it right.

thanks.

post-182-0-23157500-1330721163_thumb.jpg

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Posted · Report post

I agree with the vertical rather than hortizontal of the ductings, but is that galvinised?

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Posted · Report post

good point, didn't notice that when it was covered with baked on grease inside and out. Maybe I should have left it that way.
Oh well, 4 bucks and some good scrubbing exercise down the tubes.

Next project.

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Posted · Report post

I'm guessing the chimney will get too hot and produce galvi fumes? Is that why this piece is a no go?

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Posted · Report post

The Hofi chimney tends to run cold, but that is not a good reason to risk poisoning yourself. If zinc or galvanized metal is heated to as low as 700F it is giving off toxic fumes that can cause serious health problems. There are worse things than zinc fumes, but zinc fumes are pretty bad and can kill you. Metal fume fever is something I never want to experience.

Now it is good coated sheet metal and suitable for a cold forming process, and many other applications...just not a chimney, and especially not the indoor part of a chimney.

Phil

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Posted · Report post

I had a Hofi hood for over a year, it was made out of mild steel, 4 feet long, and I had galvanized pipe on it, but I WOULD NOT make the hood it's self out of galvanized. Now the pipe I used was galvanized, And if it gets hot and makes fumes, the draft will pull it up the flue with the smoke.

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