John Martin

Sidedraft or Hood

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Which draws better???

Which removes more smoke???

Is one or the other suited for different kind of work???

Does a fan placed inside either chimney help with drafting and removal of smoke???

I am wondering because I think that when I make my next forge, I want to do a hood because you can heat any part of the piece you are working on without the side draft getting in the way. But I also think this is a good topic for discussion.

Edited by m_brothers

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A sidedraft doesnt need electricity to draw but i think almost any hood would require a blower to get the same effect.

I think the most important thing is to have your flue size smaller than the actual size of your chimney, In square inches.

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Hoods don't draw well at all, even with a blower in them. It has to do with the size of the opening compared to the volume of the blower or stack.

So, how about this, make a hybrid. Build a side draft that you can remove the bottom part and attach a hood to the now open ended stack for when you need a hood.

Frosty

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shop01.jpg
So something like this wouldn't draw well at all???

Non working links removed

What if I did one like bruces where I could have the three sides, and they could be unhinged to allow for larger items to be worked with, like a gate or something. But yeah, I am very interested in this. Edited by m_brothers

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The site wouldn't let me jump directly to the pictures you linked but there is a pretty good summary on the site here. Forge Chimneys

A brief read of the section seems to say what most of the guys here have been saying. A hood draws too much ambient air to make a strong draft for pulling smoke. They recommend placing a hood close to the fire to limit the ambient air flow. They're recommending oversized stacks for them too.

I made a hood some years ago and unless the thing was almost on the forge table, about 10" it hardly drew at all. As an experiment one time I wired a piece of 6" pipe inside the hood so it extended to about 6" from the fire and behind it. Drew like a champ but smoke that got past it still curled out around the hood.

The one large hood I've seen that worked well was brick masonry and the chimney had to be at least 20" sq. It still leaked smoke but not terribly as long as the main door was open.

Frosty

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So if I have the forge hood like 12-20" above the forge table then I need like 14" chimney diameter??? Or will that still not work, and I'll have smoke everywhere??? And then end up wasting a lot of time, money, and material, and end up making a side draft one?

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I just don't know. I think there's info and maybe a formula here on IFI somewhere for figuring flue size, length, etc. but I don't know where it is off hand. The hood I made has a 12" stack and doesn't draw worth spit. The pics don't look it but the hood is only about 20" above the table.

What my experience has been is hoods don't work nearly as well as a side draft do. If I needed to be able to expand my forge table around the firepot where the side draft rests I'd think about designing one that can be removed or tipped up or changed out with into a low laying hood.

Maybe use charcoal or coke or pre-make a load of breeze for those occasions to reduce smoke as well.

The one pic you linked that opened for me showed a hood as large as the forge table and laying maybe two feet above it. When I lowered my hood that low it was always in the way and still didn't draw well.

As a side note the fellow in the pic looks kind of like me. Poor guy.

Frosty

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11271.attach

Edited by Frosty

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Most likely, But It also depends what you plan on heating. the link that frosty provided all the information as far as i can see, EX, if you heat armor then you might need a large totally enclosed hood. Maybe removable sides or if you could somehow control the hight of your hood?

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John:

Check this one out, about half way down the page, "Log Village." This might be more to your liking.

Steam Show Smith

There is also more info about side draft hoods and how they work on this page.

I have a couple ideas though, I'll kick them around and maybe make a couple sketches if I think they're worth looking at.

Frosty

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Hi, its been a while since I've posted on here but for what it's worth I built a over-head hood type forge and still use it. My set-up is a little different - I used an old furnace blower to create a forced draw.

Second_Fire_004.jpg
There are pics in my gallery showing most of the detail. The hood unit is adjustable up and down - I have it about 16" off of the forge most of the time; it's really only up higher when I'm cleaning out the firepot. Having said that the next forge I build will be a sidedraft. Irnsrgn had a blueprint on here a while back that showed how effective even an 8" stove pipe sidedraft was. Maybe Glenn or Andrew can direct you to it. Hope this helps.

Jason

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i use the side draft with the 12 in di pipe ,it draws pretty well if it whern't for my super power blower( getting a speed contol switch) wich sometimes overpowers the draft but othere than that i find it works very well compaired to my old cone hood i was using befor, where a slight breez upset the smoke

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I would definitely recommend a side-draft setup. The Hofi version posted is good if you want to go out thru a wall rather than the roof; I have a modified version of this which just uses 12” round pipe going out thru the wall. The “Super Sucker” side draft looks good, too.

http://www.iforgeiron.com/forum/f7/pics-my-forge-setup-9718/

You don’t need a smoke shelf like the “beautiful iron” guy says.
IMHO

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m_brothers,
I posed the same question to a group of smiths last Tuesday. The shop that we were in has a side draft hood. It works very well without any assistance. He went to this after the hood that he first installed would not work, even with a fan to assist. He did say that when constructing the side draft hood the design of the smoke shelf inside was very important in it's operation. My plan is a side draft hood. Jerry W.

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I built a forge a couple of years ago with a hood, prior to that I'd always used forges with side draughts, and found it useless for extracting fumes. I'm now collecting the bits together to convert it to a side draught.
The only advantage that I've noticed with a hood is that it catches flying debris from the fire (sparks, the occasional stone etc.). Most commercially built hearths have hoods and top draught extraction.
Does any one know how much difference insulated pipe makes?

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Yep, Besides being very expensive, Its hard to get in 10 inch let alone 12. Besides the chimney dont get very hot, I can put my hand on the hood itself and not get burnt.

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I have just built a charcoal forge, andam buildinga hood, more to protect the roof of the shed and catch sparks than to extract smoke, i find the forge does not smoke much if the fire is right. The side draught would remove smoke better, but not protect the roof.

I intend to put a whirlybird extraction fan on the top of the chimney to help draw any smoke away, but doubt that it will help much as there will not be the suction to pull the smoke into the hood, only clear any smoke that drifts into it.

I think it depends on what your main objective is.

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Actually, Side draft hoods, pull a lot of smoke as soon as there is a temperature differential between in side and out side. They are constructed like a regular fire place only in miniture. Correctly built both create a draft up the stack.
A straight up hood without the smoke shelf and throat restriction pulls less well than a side draft. I've seen this demonstrated on 95 deg F. days with every window and door open.
I don't remember every seeing sparks from a coal forge going out of the stack but maybe charcoal is so light that it is a problem

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