How much air flow on a backyard offset

[Lynn Dollar]

BTW, what's helped me the most, is the LSG Fire Basket.


My FB is 20" long. The LSG basket is 12" long. This has enabled me to keep the fire away from the cook chamber, cutting down the direct heat.



That's also when I began smoking with the door closed.

 

[NYC 'Que]

The amount of required airflow is relative to the size of the fire. Don’t care if it’s a 30 gallon smoker or a 30000 gallon smoker. Science is science.


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[NYC 'Que]

People overthink smoking in every way possible and make it harder than it needs to be.

Amen and thank you.


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[NYC 'Que]

BTW, what's helped me the most, is the LSG Fire Basket.


My FB is 20" long. The LSG basket is 12" long. This has enabled me to keep the fire away from the cook chamber, cutting down the direct heat.



That's also when I began smoking with the door closed.

I know I’m going to get crap for this but that fire basket was designed to compensate for a flawed fire box. You’d never need such a grate in a round firebox.


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[Rockinar]

The lesson you learned is not about airflow. The lesson you learned is why people should not buy a 36" offset and everyone recommends 42"+


I agree with SmokeDick. People WAY over think everything.

 

[busmania]

Is this with or without tuning plates?

On a small cooker, running at higher temps can heat the tuning plates up quite a bit, and you end up with radiant heat cooking from underneath.

On my 20" Horizon, with the plates, I can can get the lid thermometers within 5-10 degrees, but the temperature at the grate is 50 to 100 degrees different, due to the radiant heat.

A small gap between the firebox and the edge of the plates helps (how much depends on the cooker). As does moving the fire closer to the door vs the cook chamber, if you have the space.

I built my smoker pretty much specifically to eliminate the burned bottoms I got using my yoder wichita because of the radiant heat. I find slowing the airflow down to where I can still burn a clean fire helps the quality of my food tremendously. In fact, my next build I will work to find the perfect balance of minimal air flow (Which on an offset is still a ton of air flowing over the food) and a clean fire by how wide the fb to cc hole is and how big the exhaust collector hole is on the chimney side. I don’t use tuning plates either, I have almost even temps left to right. In short, I do think too much air flow is as bad as too little. But I have no proof or anything which is why my next build will be built to specifically test these theories.

 

[SmokinAussie]

People overthink smoking in every way possible and make it harder than it needs to be.

Naaah. It's harder than it needs to be which is why people overthink it.

It's why we're here bro! :heh::heh:

Cheers!

Bill

 

[marvda1]

@lynn dollar, how far open did you have the firebox door? pictures that i have seen of people that use the firebox door, have the door open only about 1/4 of an inch or less.

 

[Lynn Dollar]

@lynn dollar, how far open did you have the firebox door? pictures that i have seen of people that use the firebox door, have the door open only about 1/4 of an inch or less.

That was about 1 1/2 years ago and I've slept a few times since, but I believe at that time I'd found 2" open to be my sweet spot.


Although I'm pretty happy with the Brazos, my only interest in this air flow question now, is that I'm looking at possibly upgrading. Trying to figure out how much there's to be gained for money spent.


Ya know, if Franklin's called me right now, asking me if I was ready to buy, IDK what I'd do, I would probably decline because " when in doubt, don't " . For sure, I would ask a lot of questions.



I had ruled out an LSG 24 X 48 because it used tuning plates. Now I'm not so sure tuning plates are a bad thing.


I just have a whole lot of questions to get answered before I drop that kind of money. I'd hoped this post would generate some discussion that would help.

 

[Lynn Dollar]

Something else I need to bring up here about my Old Country Brazos and how it differs.


There's a baffle between the FB and cook chamber. It chokes down the air intake. At its widest point , there may be 3 " of air intake.


This creates the Venturi Effect, the speed of the air flow increases. And highly likely, it shoots into the cook chamber. Opening the door increases air flow through the constriction, and really shoots the heat to the stack end.


So what's happening with my Brazos, being able to move heat end-to-end with the FB door, is probably not applicable to other smokers that do not have that severe air flow constriction.


Your results may vary.



And there's definitely a difference in heat out of the FB. The vids I've posted from Franklin's pit room and the Moberg smokers, back that up. In the Franklin pit room they call the heat " direct heat " . Others may not.



Mad Scientist on YT talks about this here, and if Y'all understand where he goes with this, then fill me in, its over my head. But he's talking about direct heat.


Vid should start at about 44 minute mark.



https://youtu.be/9fb9gEQ5804?t=2509


BTW, the Vortex in your Kettle has a Venturi Effect. It restricts air flow through the Kettle, air flow speed increases and shoots up to the dome, where the curvature of the dome then circulates it through the Kettle, creating extreme convection and improving your wings. Its not the high heat that makes the Vortex work, its the increase in convection that it creates. Though the dome of the Kettle will really get hot from the direct heat shooting up, the air cools quickly as it flows back down.



And the Vortex works even better, if you line the charcoal grate with foil and cut out inside the Vortex, to direct more air flow through the Vortex .......... and keeps your Kettle cleaner from grease drippings.

 

[Lynn Dollar]

I disagree.

Draft (airflow) in an offset is everything.

Baffles or separation between the firebox and the cook chamber is key to even temps, not airflow

You could not have been more wrong.


Baffle was the problem.

 

[Lynn Dollar]

You're the guy over here burning your meat. Perhaps....just perhaps, you don't have it all figured out the way you think you do.

And you were also wrong.

 

[Lynn Dollar]

People overthink smoking in every way possible and make it harder than it needs to be.

Nope. People just want to get better barbecue and are willing to work at it. No such thing as " over thinking" .

 

[CALWLDLIF]

Glad I saw this thread.
Very timely because I just tested a mod to my smoke stack.

I have an Oklahoma Joe longhorn 3 in 1 combo.
To those who don't know about this model, basically a longhorn chamber was walled off 1/2 the length to put a gas grill in.
So basically the smoke chamber is half the length of an average one with a grill occupying the other half.
Seems the fire box is full size though to feed the smoker.

After insulating the smoker because of temp issues I had to really close the exhaust damper to get some heat to the grill. The exhaust stack was very high in the chamber and most of the hot air was leaving the firebox and going straight up to the top and running along the top out the stack.
The built in thermometer in about center of the chamber always read 50-75 deg higher than the grill temp.
The best I could get damping down the stack was 25-35 higher than the grate.

I just used grill temp to cook.

I got the impression after many cooks that all my smoke flavor was going up the stack.
I must say that I could place meat close to the firebox and not burn it.
Bark was balanced top and bottom of meat and no real meat burning that I can remember.

I had the impression the smoker was just an oven.
After reading and watching vids I believe some flow of smoke is crucial to good flavor and tender meat.

Long intro, sorry.

Anyway, I modded the stack to reach grill height and moved it from the back of the chamber to the center.
I guess it took 8-10in's of pipe to do this.

I created extreme flow/draw and could run higher grate temps than the top of the chamber. Never been able to do that.
The built in thermo, center, reads lower than the grate.

Problem, I lost a lot of area close to the firebox because now the heat comes straight out and doesn't rise like it did before, it rises some quite a ways from the firebox.

Also, I think the bottom of the meat will be hotter than the top. not good.
I was able to damper the stack and balance the top of chamber temp and the grill temp.
I let/want the higher thermom to run hotter by 10-12 degs than the grill to I don't burn the bottom.
I am able to adjust and get that to happen steadily.

Draw back? Lost a good amount of cooking area close to the firebox.
Chamber was not that big to start.

I have not done a cook yet I spent time trying to figure out what changes happened.

One Last thing, I have to have a TINY fire, from insulation and keeping smoke from going straight out the top this cooker runs very efficient.

 

[1Gradymaci]

Get your head around the different Heat
Conductive,
Convection,
Radiant. I think Sonny Moberg has it figured out..
But I bet Matt at Mill Scale learned a lot from Franklin, but does not control airflow with FB vents.. JD also uses no vents on his FB, So the mystery is,adapt to what you have if you want to run a offset.. I like small fires in my insulated box personally.

 

[MichPHX721]

275 on a Brazos is really hot. I run my Brazos at 225 to 240 range and that’s with the door open. I just use smaller splits. Burn a small, hot, clean fire and keep your temperature down lower and I believe you will be very happy with the results.

 

[rm41400]

People overthink smoking in every way possible and make it harder than it needs to be.

A lot of truth to this.

Once I learned the basics (much from you brethren) it seems my cooking has gotten better the less I stress and just roll with it. I break a lot of the rules and the end product is still the same when I trust my gut.


I use to cook less because everything had to be perfect according to the “rules”.

The more I cook and don’t stress the little details the better I seem to do.

 

[oldgfbbq]

Enough is Enough Air Flow

How much air flow? Well, how long is a rope? :smile:

Seems to me every cook is different in some way, effected by your fire, ambient temperature, kind and age of wood, charcoal, what one is cooking and how many of them. And in my particular case, having a smoker I made myself while learning to MIG weld. It is in no way as nice or efficient as one professionally made. Would I do things differently the next time? You bet. But, it's mine and I know it like the back of my hand.

I have experienced at one time or another most of the points mentioned in this thread, ie fire too big, too small, not enough air flow, too much air flow, fire to close to cooking chamber, etc. IMO, juggling the adjustments is part of the artform of smoking meat. If your equipment does not give you the adjustment you want, add it to your rig.

In the beginning there was too much variance in temps over the cook chamber, and also wide swings in heat from fire. To address these issues tuning plates were installed (sorry they are dirty in the photo), a variable speed blower was added and so was a charcoal box. It has given me the flexibility to use a charcoal if I wish or burn wood directly on the grate, increase air flow or reduce it. The point of all this is just about anything can produce the Q you want. It's just about figuring out how to use the equipment your cooking on at the moment.

At some point I will move the smokestack.

 

[Chester]

Get your head around the different Heat
Conductive,
Convection,
Radiant. I think Sonny Moberg has it figured out..
But I bet Matt at Mill Scale learned a lot from Franklin, but does not control airflow with FB vents.. JD also uses no vents on his FB, So the mystery is,adapt to what you have if you want to run a offset.. I like small fires in my insulated box personally.

So did you order a Moberg. A few weeks ago you were still deciding among that and the Mil Scale.

 

[Lynn Dollar]

A lot of truth to this.

Once I learned the basics (much from you brethren) it seems my cooking has gotten better the less I stress and just roll with it. I break a lot of the rules and the end product is still the same when I trust my gut.


I use to cook less because everything had to be perfect according to the “rules”.

The more I cook and don’t stress the little details the better I seem to do.

No, that's not what this is about. This is about improving a smoker to get better barbecue.


If Aaron Franklin had not " stressed the details " Texas barbecue would not be what it is today.


If ya don't want to work at it, get a pellet pooper.