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propane tank smoker technical questions

post #1 of 29
Thread Starter 
Hi everyone, I've been snooping on this forum for a while now doing some research for a build and finally decided to post some questions if you don't mind.

As it stands i have a 120 gallon propane tank that i am using. I am on duty today so i can't measure the tank myself, however, from what googling told me it's roughly 55" long and 30" in diameter. I have looked at the calculator and did the numbers from what yall have posted. My questions are this; how do you determine how deep into the chamber the exhaust stack should be? If it was shorter and flush to the top of the chamber, but had a damper to control flow i would think that the length wouldn't matter at that point. Also, the height of the grate in relation to the rf plate... is it an educated guess? Or is there more science to it than that?

Thanks for any input,
post #2 of 29
Thread Starter 
post #3 of 29

Have you taken a look at Feldons calculator?

I see You just joined the group. When you get a chance will you drop by roll call so everyone can give you a proper SMF welcome?

Happy smoken.


post #4 of 29
Thread Starter 
I did use his calculator, i just didn't notice anything mentioning the exhaust besides the length.

I'll hop on roll call here in a bit... trying to get some sleep before the late watch
post #5 of 29
Thread Starter 
So from what i have on the calculator, here's what i got:
cc: 27720 inches cubed
so the fb should be atleast 9240 inches cubed... i was going to make mine 18hX24wX24d which would make it 10584 inches cubed.
the exhaust says 529.2 inches cubed, so i was thinking of doing a 6" pipe at 18.75"
although i am still a bit confused on how deep into the chamber it needs to be...
Also, 5 x 3" intakes.
For the half moon opening, it says 84.67 inches square... is the recommended diameter very important, because 14.68 inches is what it kicked out for me. Or can i just go with a 20" x 4.25" opening into the tank?
post #6 of 29
Thread Starter 

so my buddy and i are moving along with getting started... and we had decided burning off the paint sounded good. But all we had was wood that was chopped about 3 weeks ago and not split. Needless to say it was still moist.

My neighbors came over to let me know they were concerned my house was on fire, so i should move my car. Haha. I am just glad they didn't call the fire department.
post #7 of 29
Thread Starter 

got the paint off, just took a second and a few stripper pads on the grinder.

i went ahead and picked up some quarter and eighth inch sheets and some other supplies this morning.

Worked on the lid a little bit afterwards.
post #8 of 29


post #9 of 29

Nice    keep those pictures coming 



post #10 of 29
Thread Starter 
So in between watches today i figured I'd do some math, if anyone wants to back me up on it and let me know your thoughts.

If i have the smoker 7" up from the bottom of the smoker i am looking at about 124.1 in sq of fb to cc. (Using radius of circle and height to find segment area...)

As i am looking at it, and maybe i am wrong, so long as my opening of the rf plate is greater than 124.1 i should be pretty set in terms of maintaining good fluid flow...

Am i way off here? Should i be looking at this differently?
post #11 of 29

Yes, the 7" height of cut into the cook chamber will be perfect for your smoker. I double checked it with the post Dave made here: http://www.smokingmeatforums.com/t/172425/standard-reverse-flow-smoker-calculator-by-daveomak-and-others-ready-to-use-rev-4


The only issue I ran into was your first post listed the length at 55 inches and that doesn't work out with the 120 gallons and a 30 inch diameter so I think you were measuring it overall or you are a really tall guy..... :77:


If using Feldon's using gallons as the input, it works out to be the 27720 sq-in you posted and looks about right.


Good luck and keep us posted if you need any help!



post #12 of 29

Can't wait to see it



post #13 of 29
Thread Starter 
Thanks for the input Len, that is correct it was outer dimensions. Haha, i am only six feet tall myself.
post #14 of 29
Thread Starter 
Thanks Gary, i am ready to see it done too :D
post #15 of 29
Thread Starter 
Well i got the valves and the last bit of rough spots grinded off today along with the rest of the tank done with the stripper pad.

and then i started cutting out the firebox, when my circular saw died... so we ran and bought a new one after the grinder with a cutting blade frustrated the crap out of me

only put in a few hours after work... had to watch my bears get beat up by the saints, but i am happy with every bit of progress so far.
post #16 of 29
Thread Starter 
Here's another question for you guys. Mineral wool. I was looking at what is available, is the mineral wool at a local hardware store be able to withstand being used as firebox insulation? It seems like it should, but i was hoping for some more experienced tribal knowledge. I would do ceramic wool, but that stuff gets pricey quick from what I've seen.
post #17 of 29

Getting better and closer all the time



post #18 of 29
Thread Starter 
Well, i got held up because i had to rebuild my sailboat trailer before i could give it to a local charity my friends brother in law runs. But after some work i got the axle and leaf springs replaced.

redid the lid for the smoker so you cant see the welds, i thought would look nicer... so the lid has 1/8 steel skin on it. Which makes it a ton heavier.

made some hinges too

hopefully it will get plopped on the trailer tomorrow and i can get the firebox welded on and start insulating.
post #19 of 29
Thread Starter 

my buddy crawled into it

got the firebox attached going to weld the supports today and hopefully get the trailer painted
Edited by daytonasooner86 - 12/27/14 at 8:15am
post #20 of 29
Thread Starter 

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