# Vertical offset new build - looking for opinions



## clyde79 (Dec 29, 2011)

I'm new here and I'm building a tow behind vertical offset smoker... I'm using a blasting cabinet made of 1/4" steel with a 40"x40" footprint and roughly 67" tall... I'm using a 28" diameter by 48" length oil tank for the fire box... Would it be better to cut the opening from the firebox to the cooking chamber in the side OR the bottom of the cooking chamber?? Can do either because of the way I am joining the two pieces...


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## pops6927 (Dec 30, 2011)

Massive door on that offset - great workmanship!  The offset folks will be along soon with your answer, just admiring here!


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## SmokinAl (Dec 31, 2011)

Holy cow that thing is going to weigh a ton. 

Being that thick it should hold the heat really well.

Can't wait to see it all done & smoking!


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## bubbonehead (Dec 31, 2011)

That's going to be very tough looking. My first observation would be that your air inlet is too small. I would suggest adding two more if you can, maybe one on each side of the one you already made. You can always damper them closed when needed. Secondly I'm trying to visualize how air flow will be managed between fire and smoke chamber. There should be some form of dampener or deviding/tuning plate set up. I'm thinking that on vertical smokers that usualy is down on the bottom, however if I'm looking at what you have so far correctly your explosives shed will set quite a ways down into your oil tank. Drawing from the bottom would create a dead spot in the fire box in terms of air flow (volume above the bottom edge of smoke box). Can you raise that point by building up from your cut-out with some 1/4" plate? If not I would suggest using both side and bottom making sure to engineer dampeners that you can easily adjust. Just my 2 cents worth.


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## clyde79 (Jan 1, 2012)

that air inlet extends under the rack for the fire and has 10 1" holes, 5 on each side i wanted to keep an air source under the fire, to make up for the volume needed i'm gonna put a slide vent in the door. for the opening into the cooking chamber i'm kicking around the idea of two opening one on the side and one on the bottom each measuring 5" x 24" with a baffle plate over them.i posted to get some ideas on that. i cant raise the cabinet any more overall height would be to great thanks in advance for any ideas


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## bubbonehead (Jan 2, 2012)

OK, remember that this isn't an attack, I'm just trying to help brother. According to the rough dementions you noted in the beginning, your cook chamber is in the neighborhood of 100,000 ci. Your fire box is 29,555 ci. so you're already under the recommended size ration on the fire box but not to a point that can't still work if you engineer it right. OK, now for the size of fire box that you do have you need at least 88 or 89 ci of air inlet area. If that pipe is say 3" in diameter, you would need 12.55 of them to feed enough fresh air to support a good fire. By extending the pipe into the box as you have you have created drag reducing air flow. That's a good design for something like a gas burner were the gas is under pressure and you want to deliver it to a specific location. Airflow is similar to water flow. Think in terms of the path of least resistance. That's why the exhaust pipes on a Harley work better the longer they are. All that length creates more back pressure. But you're not pushing air in, you're drawing it in. 

Here'a a link to the calculator. Spend some time working with this to keep yourself from building something that looks really cool but doesn't work a good as it could.

http://www.feldoncentral.com/bbqcalculator.html


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## clyde79 (Jan 2, 2012)

i cant type fast wasnt taken it as an attack sometimes my typing skills screw up how i want it to sound .i used that calculator my cooking chamber came out to 80000 inches and left me with 110% on the firebox sinking the cabinet in the tank is a must because of height issues i would like it to still fit through a garage door . i really like the way your smoker came together "bubbonehead" i was just fishing for some input from and help on polishing my ideas im trying not to rush and get it right the first time


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## bubbonehead (Jan 3, 2012)

I know exactly what you mean. That's why I wanted to make sure you understood my intent. I tend to be a bit blunt in person, I'm sure I can sound worse by typing.

Anyway, I can't wait to watch your smoker come together. I'm sure it will killer unique.


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## clyde79 (Jan 3, 2012)

anybody watching this post have any ideas or opinions on adding air intake? thinking of doing a slide baffle in the door. or should i keep the intakes as low as possible


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## sprky (Jan 3, 2012)

Well first off I'm no builder, I follow the builds as I like them. I sat and looked at your fire box for a bit, and think I may have a couple Ideas that may work. If my ideas are out in left field the PRO builders here will correct me.

Option 1; Add 2 more intakes like you have 1 on each side of existing. Then also add a sliding intake in the door. use the lower intakes first then if needed the door.

Option 2; Remove the existing intake and make a sliding or pivoting intake using most of the area. Beef up the inside around intake with channel, and cover the opening with expanded metal.

Option 3; combine option 2 along with intake in door

These are just thoughts so take them for what they are worth. They may spark other ideas as well.


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## ribcooker (Jan 7, 2012)

Are you building your fire right on the expanded metal surface shown? I assume so; therefore you will collect ash around your inlet pipe. What about a couple levered vent/clean out baffles on the underside? We have a rotisserie with a round fire box and that is our only air intake and it works pretty well


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## clyde79 (Jan 8, 2012)

yes the fire will sit on the expanded steel. i left enough height to allow for plenty of ash but as of now the ash will be a pain in the neck to clean out. not quite grasping the levered vent/clean baffles do you have any pics?


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## ribcooker (Jan 8, 2012)

I could get some pics later in the week but I'm headed out of town in the am and I'm about an hour away from the cooker I'm talking about. From the looks of your work so far I'm sure you could improve on the design. Basically I'm thinking a series of vents along the bottom of your firebox following your existing air pipe. attach the vent covers to a lever handle below your air vent now. As ash builds up we work our handle back and forth to let out ash and clear air flow in, We keep an ash pan under the box to catch the ash. Does require every hour or so to maintain your temps but hey you can't just sit there and watch the thing....


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## clyde79 (Jan 8, 2012)

i got what you're saying this way it vents and cleans at the same time i like that got a way of doing it wont be able to mess with it til next week ill post pics when im done


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