First offset build! Have some questions.

[dacolson]

I’m with you. Half the reason I love the offset.

[thejm]

Hey so my first few smokes have gone well! Im learning a lot about how to manage the fire.

Ive used the smoker 3 times now. I did those chicken thighs about a week ago, did a test butt on Monday and finally, did 3 butts for New Years eve. Each time, I was able to keep my temperatures closer to what I wanted my set point to be. Still a lot to learn but its going along.

Question for you all: What is your procedure to clean up the smoker after a long smoke? Do yall hose out the inside to get any remaining grease out of there? I've never had a smoker like this and don't want anything to go rancid (not sure if thats a concern).

Here are some pics of the cook!

Just before the wrap:

[thejm]

When I was designing the smoker, I suspected that I would need some sort of baffle plate right near the throat to prevent the heat from the firebox from directly entering the CC. It turns out I was right. Without the plate, my temps between the 3 thermometers read 265, 275, ~400 respectively from stack to firebox (left to right). I have no illusions that my temps will be exactly the same all the way across the CC but I'd like to lower the temp of the right most thermometer to the 325 range so that hopefully 3/4 of the smoker would be at 265 and the last 1/4 would be hotter for things like sides (smoke mac and cheese, smoked beans, etc.)

I could use some advice on how big to make the plate and what shape I should make it?

Should I angle it down slightly rather than making it horizontal?

Here are some pictures of the area where it will go. There are some dimensions on the drawings but the front edge of the firebox is 7.5" horizontally from the start of the grate and the top of the throat is 2" vertically below the grate height.

[dacolson]

Here’s a pic of what I did. I spent some time listening to Frank Cox’s podcasts and did some looking at what professional pit builders are doing and decided on a Jambo stile throat baffle. It redirects the heat and smoke directly up to the top of the pit. According to Frank, the standard offset cooks by convection - the air connects down the CC. Redirecting the heat up to the top of the pit as soon as possible protects that end of the pit and accelerated the convection process. This pit has a 50° spread right to left. I had it at 35° during my heat tests but mileage varies I guess. I sold this and confirmed with the new owner it is 50°ish for him too.

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[dacolson]

Btw, your cooks look fantastic. Haven’t done a butt in a while. Might be time to throw a couple on.

[Dirtytires]

For cleanup, I mist the racks/walls with water and close the door to let it steam. (I have a half gal pressurized spray tank I use only for the smoker.) The next day I hit the racks with a wire brush and then scrape out the baffle plate with a wide drywall knife. Lastly, the ash gets cleaned out and I’m done.

Pretty simple and the inside stays pretty clean.

[dacolson]

I don’t have the pressurized spray tank but use a fine mist nozzle on the hose. Might have to get one though now the temps here are well below freezing for the next few months.

[SheffSmoker]

Mine is even easier. I do it the day after a cook so everything cools down first.

Sweep ash out of FB, vacuum small bits out. Bucket under drain valve, open valve, kettle full of boiling water aimed at the fat plug, it melts and all the fat and scraps run into bucket. Then it's a scrub with a kitchen scourer and washing up liquid inside, then rinse and dry with paper towel.

The cook rack I take out and clean with soapy water again with the scourer, rinse and a dry.

All in it take me about 15 minutes to do.

[thejm]

Here’s a pic of what I did. I spent some time listening to Frank Cox’s podcasts and did some looking at what professional pit builders are doing and decided on a Jambo stile throat baffle. It redirects the heat and smoke directly up to the top of the pit. According to Frank, the standard offset cooks by convection - the air connects down the CC. Redirecting the heat up to the top of the pit as soon as possible protects that end of the pit and accelerated the convection process. This pit has a 50° spread right to left. I had it at 35° during my heat tests but mileage varies I guess. I sold this and confirmed with the new owner it is 50°ish for him too.

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Those are some tight looking welds! Great craftsmanship on this piece.

I happened to notice you have the same irrigation controller as I do, the Rachio unit. The magnets on my unit are also covered with metal shavings. Thought that was funny.

I am intrigued by your design to make the smoke go up rather than down but I am concerned that the throat on my smoker isn't as conducive to that since its a football. Ill probably try a few designs and go with one one that produces the best results.

Here is something I quickly mocked up with a piece of cardboard. Anyone else have a throat baffle that looks like this? Any insight into the geometry? Is that too harsh of an angle? Not harsh enough? Too short?

Obviously the actual baffle piece will stretch from one end to the other and I will probably fill in those triangle shaped spots on either side of the throat.

https://youtu.be/fLKGo_aL5lw

[dacolson]

Ya. I wipe that Rachio irrigation controller off every other day it seems. Good magnets on it!

My understanding is that by redirecting the air up immediately, it spirals down the top of the tank, cooking/smoking your meat from the top down. By putting the baffle angled up like that, you block the radiant heat from hitting your grate/meat and get the useful air/smoke heat cycling across the top of your meat which is much more even. I can't argue with the logic, and it worked out great on this build. I'm going a second larger standard offset and will be doing the same baffle. My suggestion here would be to put a plate in the goes from the bottom of the tank at your seam at the bell up 5 or 6 inches above your grates. Like you were going to close off the whole bell with a flat plate, just leave the top 1/3 or so open. To test it out, you could cut the piece and just tack it in. You're basically putting a false wall forcing the air up and over the top of your meat.

Here is the Pitmaster's Secrets podcast Frank Cox recorded on the difference between standard and reverse flow offsets. About halfway through I think he talks about the throat baffle. Jambo does one this way as well.

https://www.youtube.com/watch?v=nQ_R0OBwBqE&t=291s

[thejm]

So after reflecting on my first few cooks and learning how to manage the fire, I'm a little unhappy with how well the smoker draws. Managing the fire was very difficult and it seemed like unless conditions were perfect, the fire seemed to be lacking new oxygen, even with the door open and or cracked. There were times when the fire would rage and others were it would shrink somewhat both without adding any wood. Just seemed like there wasn't enough pull there to strengthen the fire and give it the stability and momentum it needs to have a consistent cook.

Don't misunderstand me, it's not bad, just not what I was hoping for. It's not like a consistent Choo Choo train.

I have been doing some looking around online and reread the section of my Franklin BBQ Manifesto book which deals with smoker design and came up with a few thoughts that I wanted to put into writing for myself but thought I'd share them here too.

1. I have no throat baffle plate in there and I think that will influence the draw. I don't know if it will help or hurt it quite frankly but its something that does need to be installed either way.
2. The top of my firebox is even with the cooking grates but the throat opening is 2" below that since the firebox is insulated. In the book he says that “Try to position the top of the firebox to meet the CC at grate level…Fireboxes that are set too low won’t draw as well.” A couple thoughts about this:
A. When I designed the smoker I did take this into account but failed to consider that my firebox is insulated which puts the top of the throat 2” below the grates. I can’t imagine that 2” would cause that much of an issue but I could be surprised.
B. As I was looking at different smoker designs, I noticed that most of the time there is very little horizontal room between the throat and the start of the grates. In my smoker, I have 7.5”. This is more than enough room for the smoke to rise and make up these 2”. My guess is that if you have your firebox very low (like is typical for a reverse flow) it might cause issues but can’t imagine it its a huge factor in my case.
3. My ultimate guess as to how to improve the draw is to lengthen the stack. I used the calculator when building the smoker which is what led me to the current length of 19” above top of CC but I always felt like it needed to be longer.

I bought some sheet metal and will temporarily attach it to the top of the stack on my next cook to see if it helps. I would also like to hear y’alls thoughts on the top of the throat being 2” lower than the grates. Do any of you who have traditional offsets have your throat below grate level?

[dacolson]

I’m not sure I can comment on the draw. I will say however that whatever you want to try and change, only change 1 thing at a time and test out the effect thoroughly before you change anything else.


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[Big T]

I looked back through your build pictures and I couldn't tell for sure so I figured I'd ask. Do you have a fire grate in the FB or are your coals laying on the floor of the FB? If not I would try laying a piece of expanded metal in the FB and get the coals up about 3''-4'' high. If that doesn't work then I would try extending the stack with a piece of rolled up sheet metal. Like Dave said, be sure to try one thing at a time so that you know whether or not it works. I also agree that I would add a baffle at the throat. If you use a flat plate you'll probably need to add a few more tuning plates to even out the temps.

[Olibinoui]

A out the chminey, is the fat stack box is at the center of CC ? On the pictures et looks like that. Dis you made some calculations for the chimney stack style?

[sandro]

3. My ultimate guess as to how to improve the draw is to lengthen the stack. I used the calculator when building the smoker which is what led me to the current length of 19” above top of CC but I always felt like it needed to be longer

Try 36" and see how it goes; while everything is involved in how well a pit drafts, stack length and section tend to matter more than the rest

[Olibinoui]

Mankussm has a pic in his current build thread: http://www.smokerbuilder.com/forums/vie ... =11&t=7581
Most of the way to the bottom of the first page of the thread. He calls it a ghost plate but it’s the same idea.

These plate can be of different size or you want to keep the convection heatings on the wall of the drum tank?