Rotisserie smoker modification, need advice

[redwood smoke shack]

Hello all, I bought a BBQ trailer 5 months ago and just finally got all my permits and business license to vend. I have a "Cadillac smoker" style cooker mounted on the front. The person that constructed the trailer fabricated every last inch so it's completely custom. I'm having a draw issue with the smoker, it's a 565 gallon tank (72"x48"), (2) stacks (22.5" tall, 3"diameter, 9.5" circumference) and a firebox that runs almost the entire length of the cooker (60"x17"x12") with an 8"damper on one end. I'm thinking the stacks are too small, I can't get it to draw a nice thin blue smoker like I can on my Lang 84. I've search on this forum for smoker build calculators and all I can find are ones for offsets. It has 10 racks inside also. I've used it a few times for small cooks and the final product tastes good but looking at the color smoke I'm paranoid that I'll bite into meat with a bitter flavor. I'm attaching some photos, I want to get vending but need to get this smoker dialed in. Thanks for all the help in advance, if there is any place that I'll get the answer it's here.

 

[redwood smoke shack]

There is also a slide damper on the inside of the firebox where it meets the tank. About (6) 8" squares that can be opened or closed. Never really messed with this, would this help my problem? If so how would I use it?

 

[ebijack]

Without seeing the smoker inside and out. I'd have to guess you need at least (2) 6" exhausts, maybe 8". All those bends in the stacks hinder/slow down the flow also. Are there any plates directing/controlling the flow from fireboxes into the cook chamber? Or just the sliders you mention. Exhaust placement will affect flow also. Your firebox is a bit offset.

 

[IamMadMan]

I can't get it to draw a nice thin blue smoker like I can on my Lang 84. I've search on this forum for smoker build calculators and all I can find are ones for offsets. It has 10 racks inside also. I've used it a few times for small cooks and the final product tastes good but looking at the color smoke I'm paranoid that I'll bite into meat with a bitter flavor.

I haven't used a wood burner if over 20 years......

But I'm sure you know that wood burners will give off more visible smoke than non wood burners. Also relative temperature and humidity will also effect the amount of visible smoke from the cooker.

I can't answer your question about stack calculations, but maybe Paul from Shirley might chime-in with his experience.

Start with a hot bed of coals and try adding splits rather than larger logs.
At the point when the whole cooker begins to come up to temperature and the fire is stabilized, this will become the blue smoke state. You don't need a big piece of wood to get a good smoke, in fact, when it comes to making "thin blue smoke", bigger is NOT necessarily better. The key is to have small amounts of wood burn efficiently, so you get the sweet smoke flavor, and not a bitter, over-smoked flavor.

Dampened wood or cold wood on a fire can give off white smoke until the wood is heated and dry. This type of smoke is mostly moisture escaping from the wood and may not be from poor combustion.

White smoke from poor combustion or from poor airflow in the smoker is heavy, smells overpowering, and it can cause that bitter acrid taste that everyone fears.

Rule of thumb is to follow your sense of smell. Bad smoke is overpowering and smells bad. Follow your nose rather than your eyes.

.

 

[dwfisk]

Without knowing all the dimensions it is a little speculative on my part but your exhausts "look" to small, maybe 2 @4 inches? I'm planning the build of a +600 gallon traditional offset and will go with at least 8 inch, maybe 10 inch to get the volume I need. I would run your actual dimensions through Feldon and compare the air inlet area between your firebox and cook chamber, I'm betting it is larger than Feldon suggests. As a general rule, as the connection area increases, you need to increase exhaust volume so even the Feldon recommendation for exhaust might be to small. Just my $0.02. Best of luck!

 

[Fwismoker]

Start by stepping up the exhaust incrementally until you get the draw you need. It does look to be on the small side for that size cooker.

 

[Pitmaster T]

Notice mine has slightly bigger "Dodge 5 Inch stacks" Simply add another stack is what I would do.