First run on new reverse flow

[daveomak]

Also, looking at the FB and air inlet, see if you can raise the wood grate up about 2-3" and check the cooking results...

If you do the mods suggested, and are happy, then we can discuss the air inlet mods to the FB....

Dave

 

[hickorybutt]

Dave,

If I raise the height of the stack, would that help suck heat through the CC?  Ideally, would it be better to have a larger diameter? 

I can easily order some 3" truck exhaust pipe and connect it to my current stack to raise it up to 30".  That seems really tall, but I guess the stacks on the other smokers I've seen (i.e. Lang) are much taller and wider.

Also do you think that the 90 degree bend on the stack is causing issues?  I looked at several other smokers with decent reputation that have the same design - Oklahoma Joe, Horizon, Brinkmann Trailmaster LE.

As for the firebox, I can raise the grate up a couple of inches to give some airflow under the fire.  Would your next suggestion be to add an inlet further up the FB above the fire?

Thanks for your help, and thanks to all as well.

 

[daveomak]

Dave,

If I raise the height of the stack, would that help suck heat through the CC? ++ Yes

  Ideally, would it be better to have a larger diameter? ++ No, 3" is what the calc calls for... 27 1/2" so I would go 30" above the CC...

I can easily order some 3" truck exhaust pipe and connect it to my current stack to raise it up to 30".  That seems really tall, but I guess the stacks on the other smokers I've seen (i.e. Lang) are much taller and wider.

Also do you think that the 90 degree bend on the stack is causing issues? ++ It can.... It can cause friction... reducing exhaust flow...

As for the firebox, I can raise the grate up a couple of inches to give some airflow under the fire.  Would your next suggestion be to add an inlet further up the FB above the fire? ++ With the type of air inlet you have, you "may not" need an upper air inlet... test the smoker first.

Thanks for your help, and thanks to all as well.

 

[gary s]

Looks like you got a lot of questions answered, One thought is if you look at the plenum design that Dave has as well as quite a few other members that would allow you to go with a larger ID pipe and a shorter stack, just a thought.

Gary

 

[daveomak]

This is an excerpt from Feldon's Calculator, that I think is an important criteria for a smoker that properly breathes..... Take it for what it's worth and adjust your smoker accordingly...

Chimney Size
Enter the diameter of your chimney pipe to find out how long it should be.
• A chimney that is too short may produce insufficient draft (drawing of air). A chimney that is too long may cause the air to cool before it exits, reducing effective draft and worse, dripping of exhaust materials onto food!
• Many horizontal smokers have an exhaust between 30-40 inches in length, but there is no hard and fast formula.
• If you are building a horizontal smoker with a vertical cooking cabinet, realize that the cabinet partly acts as an exhaust, thus you may greatly shorten the chimney.

 

[gary s]

Smoke Stack Question for Dave;

I see what Feldon's says about size  But if you increase the pipe diameter would that not allow a little shorter stack? I thought it was based on Cubic inches, What is your opinion, Does your calculator figure the stack size?

This is a good topic I have seen a lot of different answers and builds with long and short stacks, I know you spend a lot of time on calculations and helping lots of new smoker builders (and some old ones)

Your input and thoughts would be greatly appreciated

Gary

 

[daveomak]

Gary..... A chimney works because of pressure differential.... A chimney on a home forces a draft because the air pressure 20' above the ground is less than the air pressure at the ground... The higher pressure seeks the low pressure area.... In a stack on the smoker... the additional height is needed to help create the pressure difference between the FB and the top of the stack... Hot air is less dense than cold air.. as the smoker warms up, the outside cold air tries to displace the lighter hot air....
That principle can be seen on this forum with MES owners... adding a tin can to the exhaust stack to improve flow..
If you read the Feldon's note again, they mention the warmer replaces the excess stack height ... as the warmer becomes part of the stack...

If you want to do a test, cut the stack off of your smoker and see how it works, or add an additional 5' section (temporary) to the stack.... As soon as you add the additional 5' the air entering the FB will increase dramatically..... cut it off.... ain't got much draft....

 

[hickorybutt]

Guys,

Thanks for all of the great suggestions.  Really appreciate everyone's help.

I ordered 3" diameter truck exhaust pipe with a connector and clamps to add on to my stack, I'll raise it up to around 27"-30" tall.  I'll also probably roll-on some high temp paint.

I'll also do the other two suggestions from Dave - removing CC/FB damper if possible, and raising FB grate 2"-3".

Since I am waiting on the truck exhaust pipe to ship, it may be a week or two before I can make the adjustments.  At that point, I'll likely smoke something next weekend (maybe MLK day vacation!) after adjustments are made and will report back to everyone on any progress made with temps.

Thanks again!  This is the reason why I joined the forum.  I've been smoking for a couple of years now, but I still consider myself a newbie. And it is great to get some tips from guys who have been doing this for decades.

Take care.

 

[buda q]

Hey Hickory, you might want to share this website and Feldon's also with that custom pit builder. Just sayin.....haha

 

[hickorybutt]

Yeah, as with a probably lot of custom built pits found on Craigslist, there are bound to be a couple of design flaws.  Hopefully with these easy and cheap modifications it will improve performance.  I was really pleased with how it performed last weekend, getting an even temperature and holding temperature.  It sure beats the cheaper offsets found at big box stores.  It just took a while to get up to temp and I had to leave the damper half way open to hold 240.  Maybe a taller stack and removing the CC/FB damper will create a better draw and suck heat on through.  We'll see!

 

[ribwizzard]

I can't see where you went wrong at all for that price.

Almost every pit has a learning curve, and may need a few adjustments to make it cook right. I wouldn't down the builder too bad, it's a nice looking unit.

Something else you might try while waiting to make you modifications......play around with your fire! Different kinds of wood will produce different temperatures, and so will the size of the pieces of wood , and where your center of fire is located. If you look at everyone's pit fires in all the posts on this site, they are all different, because they have learned their pit and build the fire based on what works for that pit. I build my pits the way I like to burn my fire, and this builder may have as well. call and ask him more about how he builds his fire.

 

[hickorybutt]

Thanks Ribwizzard, great suggestion.

I think the builder could have most definitely made the smoke stack taller, but it's still a solid unit. He had 10-12 other smokers there for sale so he has spent a lot of time into building pits. Calling to get more info on the ins/outs of his pits is a great idea.

 

[gary s]

You ever get your mods done? if so how did she cook?

Gary

 

[hickorybutt]

Gary,

I ordered the truck exhaust pipe, it came earlier in the week, and I cut it to length last night.  This evening I am going to put the pipe on the stack, try removing the CC/FB damper, and I'll be doing a brisket and butt smoke for Saturday's supper.

Q-view to come, and results of mods will also be shared out.

Thanks again - more to come soon.

 

[hickorybutt]

So I added the truck exhaust to the stack, which now makes the stack 28" total height.

image.jpg

• hickorybutt
• Jan 20, 2014

I 'attempted' to smoke a brisket and butt Friday evening / Saturday morning. Sad to say that I miserably failed at this attempt. The first time I used my smoker a couple weeks ago, I started out with lit coals from a chimney in a big charcoal basket and then added sticks throughout the cook. This past weekend I tried using just sticks, and never got a hot bed of embers/coals started for some reason. The logs would just stay lit but never burned down. I had the dampers wide open and even tried with the FB door completely open, and never got a bed of embers. So my temps were wildly inconsistent. The brisket was ruined, because after messing with the fire for 4 hours and not having any luck, I gave up at 4:30 a.m. and just said screw it, I'm going to bed.

Saturday evening I went back to the charcoal basket, started with a full chimney of mixed KFD Blue and Royal Oak. Once the coals were lit, I started adding sticks. Smoker got right up to 300 degrees after 45 minutes. I then smoked sausage balls and Mac n Cheese at 300 for around an hour and a half. The smoker held 300 just fine with the dampers 75% open and a steady fire.

So in summary, the increased stack length seemed to work. My smoker was able to hold 300 when I needed it to.
But I think I just have some practicing to do on fire management. And I'm sure that will come with time as I use the smoker more.
Any suggestions?

Thanks!

 

[buda q]

Howdy! I think that people are going to tell you to practice, practice, practice. Sounds like you got some things figured out. I just cooked on my reverse flow for the first time this weekend and it's different from what I'm used to. I think the practice will be fun and delicious though. Good luck!

 

[ribwizzard]

That's usually how I start my fire, get a chimney full of white coals going good, scatter it out on the grate and lay two logs on it , one they start burning good, I'll lay one more across them, then just add one at a time as it needs it. To me, those size logs in you pic look a nice size for that pit, so it should run real nice. It's hard to get a wood fire going with out charcoal inside a box.

Still would like to see that pit with a lil bit larger exhaust stack, diameter wise...

 

[gary s]

I too start with charcoal in a chimney, a little charcoal in my basket,then start adding splits. sometimes,    I usually dump some charcoal in my basket, fire up my weed burner, charcoal is ready to start adding splits in about 5 min. I then take my weed burner an go over my racks and inside the cook chamber, helps speed up the warming up process. I have started with just wood used weed burner to get it going. Also make sure your wood has been seasoned, green wood is hard to start and imparts a bitter taste to me.

Gary

 

[hickorybutt]

Thanks guys.

Makes me wanna get out there and smoke again to continue practicing. Single digits here in Cincinnati this week... I'm not brave enough to man the pit in this weather.

 

[abaralnek]

Fair weather smoker huh? Lol