Calculate right opening amount for smoke distribution plate OK Joe Highland?

[Tallbald]

I made flat plate style smoke baffle plates for my new Highland smoker. I had the steel on hand ( from the old rusted out smoker) and the time. Does the total amount of open space between the spaced out plates need to equal the total area of opening between firebox and cook chamber? I know the spacing gets wider as the plates progress toward the end opposite the firebox. I just kinda eyeballed things, but wonder if I should reduce the total number of plates altogether at the exhaust end. Is there a calculation I can make? Thanks, Don.

 

[daveomak]

Generally.... the plates are spaced to get a uniform heat distribution to the cooking surface.. If you have plates, the first is tight against the FB end.. then the spacing would be something like 1/4", 3/8", 1/2", etc... Some folks have used a non-contact therm to measure the plate temps... others have used cardboard tube biscuits, on the food grate, to see how even the temps are when they cook.. chicken thighs are a good tool to see how even the temps are...
Adjust the plates the way you want your smoker to cook...
For a 24" long CC, a good start would be.. 5 each 4" plates.. that would leave you with 4" of total gap to work with having 5 gaps to adjust... cooking surface temp being the final criteria... the end gap will be what it is...

 

[Tallbald]

Thank you! That is exactly the information I was hoping someone could offer. I had just sort of spaced them increasingly and hoped for good results. My plates are about 5 inches wide and there are 6. May remove one though as the last in line butts up against the left end, which I see might not be good. My Highland is I seem to remember 35 inches inside length. I will use what you've said as an experienced start point. and do the canned biscuit test to see where to adjust if at all.
When I do find the best spacing I will make a notched "story stick" to duplicate the spacing smoke to smoke.
Thank you again. So much to learn, and so much wise experience to benefit from ( I just have to process it all). Don.

 

[Rings Я Us]

I have seen plates with holes in them and the farthest plates have more or larger holes. Kinda the same principle.
You can mix and match gaps in hot or cold spots. Should be ok after a few tests

 

[Tallbald]

Mixing and matching I think is part of the fun in learning the art. Thank you! Don.

 

[jim2]

Mixing and matching I think is part of the fun in learning the art. Thank you! Don.

While jumping around on several BBQ sites I ran across something I had never heard.
One member said he had both a modified smoke stack and baffles on his smoker. The problem he said is that he cannot get the smoker up to a reasonable temperature.
The reply from the baffle manufacturer said you should have one modification or the other but not both.
Any one know anything about this?
Thanks,

 

[daveomak]

You want a car that goes 0-200 in 1/8 mile or a car that get 40 MPG...

A side fire box smoker is not a finely tuned machine....

A reverse flow smoker IS finely tuned to get the smoke and heat to travel twice as far, around a 180 degree turn, with over twice the friction and still maintain a fairly close temperature gradient across the cooking surface that is easily controllable...

 

[Heart of Dixie]

Generally.... the plates are spaced to get a uniform heat distribution to the cooking surface.. If you have plates, the first is tight against the FB end.. then the spacing would be something like 1/4", 3/8", 1/2", etc... Some folks have used a non-contact therm to measure the plate temps... others have used cardboard tube biscuits, on the food grate, to see how even the temps are when they cook.. chicken thighs are a good tool to see how even the temps are...
Adjust the plates the way you want your smoker to cook...
For a 24" long CC, a good start would be.. 5 each 4" plates.. that would leave you with 4" of total gap to work with having 5 gaps to adjust... cooking surface temp being the final criteria... the end gap will be what it is...

I spent a Saturday morning with a blank spreadsheet, big bag of lump and three Igrill 2 digital probes. It was really interesting to see the difference little moves made. I kept having a 60 to 80 degree difference from firebox to the cook chamber end until I tried 1" spacers on the two bolts holding the first angled plate attached to the firebox bulkhead. Then, voila! With first lay in plate butted up to the angled one, then slight 1/4 to 1/2" gaps between the next two the difference became about 10 to 20 degrees, something I could live with.

 

[bl0wingsm0ke]

This is a very informative thread. Does anyone change their plates based on the cook? Maybe have “presets” of where the plates go based on the cook?

 

[Heart of Dixie]

This is a very informative thread. Does anyone change their plates based on the cook? Maybe have “presets” of where the plates go based on the cook?

Once I figured out where I got a good temperature across the CC, I have not changed them. I recently went from the stock 3” smokestack to a 4” one and now it averages about 2 degrees side to side, best mod I have done on my 2004 Oklahoma Joe since I bought it 14 years ago.

 

[bl0wingsm0ke]

Once I figured out where I got a good temperature across the CC, I have not changed them. I recently went from the stock 3” smokestack to a 4” one and now it averages about 2 degrees side to side, best mod I have done on my 2004 Oklahoma Joe since I bought it 14 years ago.

Interesting. That will have to be something that I consider doing. That just gives the smoker more draw? Sorry not well versed in aerodynamics haha.

 

[Heart of Dixie]

Blowing Smoke - I had some draw issues that were especially more pronounced on humid and or low wind days. I decided the added tuning plates restricted flow too much for they were not included in the initial design of the smoker. The first thing was to use Feldon's BBQ calculator (its online) to find out that my stock stack was too short in the first place . I added an extension and it worked somewhat better but still not great. A little more research led to an article on stack width/flow and it said that 4" was the minimum suggested width for an offset. Back to Feldon's calculator inputting a 4" stack width to get my answer on correct length. Since my unit already had a 3.5" exit port, going to 4" was easy using vent pipe from Home Depot. The draw improved significantly. Now its easier to start a good hot fire, the smoker comes up to temperture quicker, and maintaining a small hot fire is much easier. I burn 10"- 12" sticks and keep my firebox door open.

 

[bl0wingsm0ke]

Blowing Smoke - I had some draw issues that were especially more pronounced on humid and or low wind days. I decided the added tuning plates restricted flow too much for they were not included in the initial design of the smoker. The first thing was to use Feldon's BBQ calculator (its online) to find out that my stock stack was too short in the first place . I added an extension and it worked somewhat better but still not great. A little more research led to an article on stack width/flow and it said that 4" was the minimum suggested width for an offset. Back to Feldon's calculator inputting a 4" stack width to get my answer on correct length. Since my unit already had a 3.5" exit port, going to 4" was easy using vent pipe from Home Depot. The draw improved significantly. Now its easier to start a good hot fire, the smoker comes up to temperture quicker, and maintaining a small hot fire is much easier. I burn 10"- 12" sticks and keep my firebox door open.

Awesome information. That is great to know about the efficiency of the firebox. I will need to check that calculator out myself. Getting up to temp quick is very appealing. Thank you for the help.

 

[daveomak]

https://www.smokingmeatforums.com/t...eady-to-use-rev5-6-19-15.172425/#post_1264161