# RF offset 275 gal smoker

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#### hoosier_j

##### Newbie
Original poster
Getting started on my build. Dimensions are 59”X44”X27” firebox will be 30”x30”x24” (1/4” thick), FB/CC opening 21” diameter half moon, 52.5” long RF plate (1/4” thick) 5” above FB/CC opening. I plan to sandblast exterior and burn interior to clean up. Planning for two cooking grates. Looking for advice on lid size, chimney size/placement, proper way to finish exterior/interior (paint?) and best handles for lid

Welcome from ND.
May find some useful information here;

hoosier_j
Welcome from ND.
May find some useful information here;
I appreciate the link, was looking for the answers to my specific questions on previous forums, didn’t see any on lid opening/size. Any guidance is appreciated!

Post up a profile pic of the tank. May help out.

Jim

hoosier_j
That looks like a fuel oil drum. If so and it is not round, but oblong, how do you plan to orient it?

hoosier_j
Hello Hoosier_j and welcome aboard!

So your tank being oval - or oblong - makes these calculations a little more challenging but still not to complicated. So first off, it's important to calculate the volume of your cook chamber tank. All other calculations can be made from that number. Using the dimensions you gave above, I calculate the volume of your tank to be about 238 gallons. Is that what you get?

Next, a good practice is to run your numbers through a pit calculator - there are several good ones online. Here's the one I like to use:

Using 238 gallons for the CC tank, the calculator says your fire box should have a volume of 18,326 cubic inches. The dimensions you gave above put the actual volume of your FB at about 118% of that target...which might be a little too big. If possible, you might think about reducing the size of the FB until your actual number is between 100 and 110% of the recommended volume. A professional pitbuilder whose advice I trust told me that's the "sweet spot" for FB to CC volume ratios.

Then next is the stack/chimney. Are you planning a round or a square stack? The calculator says that if you went with a 6" round stack, it should be 38" tall. The calculator won't advise you on where to place it. My best advice would be to locate the opening from CC to the stack at or just above the level of your upper cooking rack. I built a RF smoker last year. Here's a couple pics that show where I placed that opening on mine. My CC was round instead of oval, but you can still get an idea of where to place yours.

I you want to browse through it, the link to that build is here:

Your throat opening - the FB/CC opening - can be calculated too. According to all the other numbers, the area of your throat opening should be about 173 sq. inches.

The only other important number to calculate is the area of your intake vent on the FB. That calculator says yours should be about 65 sq. inches.

I hope any of that helps, and I apologize if I'm sharing information you already know. One of the first and most important things to do when designing a new build is to get those dimensional numbers close. It's the best way to be sure your new smoker will draw properly. Air flow is the key to a pit that performs as it should.

Good luck with the build! I'm looking forward to following!

Red

hoosier_j
Post up a profile pic of the tank. May help out.

Jim
Thanks Jim, posting a pic in main thread.

Thanks Jim, posting a pic in main thread.
That looks like a fuel oil drum. If so and it is not round, but oblong, how do you plan to orient it?

That’s exactly what it is, good eye! Planning on adding firebox to the side pictured above.

JLeonard
Hello Hoosier_j and welcome aboard!

So your tank being oval - or oblong - makes these calculations a little more challenging but still not to complicated. So first off, it's important to calculate the volume of your cook chamber tank. All other calculations can be made from that number. Using the dimensions you gave above, I calculate the volume of your tank to be about 238 gallons. Is that what you get?

Next, a good practice is to run your numbers through a pit calculator - there are several good ones online. Here's the one I like to use:

Using 238 gallons for the CC tank, the calculator says your fire box should have a volume of 18,326 cubic inches. The dimensions you gave above put the actual volume of your FB at about 118% of that target...which might be a little too big. If possible, you might think about reducing the size of the FB until your actual number is between 100 and 110% of the recommended volume. A professional pitbuilder whose advice I trust told me that's the "sweet spot" for FB to CC volume ratios.

Then next is the stack/chimney. Are you planning a round or a square stack? The calculator says that if you went with a 6" round stack, it should be 38" tall. The calculator won't advise you on where to place it. My best advice would be to locate the opening from CC to the stack at or just above the level of your upper cooking rack. I built a RF smoker last year. Here's a couple pics that show where I placed that opening on mine. My CC was round instead of oval, but you can still get an idea of where to place yours.

View attachment 698449

View attachment 698450

I you want to browse through it, the link to that build is here:

Your throat opening - the FB/CC opening - can be calculated too. According to all the other numbers, the area of your throat opening should be about 173 sq. inches.

The only other important number to calculate is the area of your intake vent on the FB. That calculator says yours should be about 65 sq. inches.

I hope any of that helps, and I apologize if I'm sharing information you already know. One of the first and most important things to do when designing a new build is to get those dimensional numbers close. It's the best way to be sure your new smoker will draw properly. Air flow is the key to a pit that performs as it should.

Good luck with the build! I'm looking forward to following!

Red
My initial search came up with 275gal, I will try to confirm the actual volume, appreciate your input and photos!

JLeonard
View attachment 698459
That’s exactly what it is, good eye! Planning on adding firebox to the side pictured above.
Depends on a few things...But, I could almost 3 racks running in that thing.

Jim

hoosier_j
lordy Y'all are good at cypherin' stuff.... makes me feel silly when I ask charcoal questions..

My understanding is the FB should be 1/3 the vulume of the cook chamber...

Me & my cousins just picked this up the other day, Was a hog roaster and now we want to make offset smoker. Where all the angle iron is, that is the cut for door.

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Me & my cousins just picked this up the other day, Was a hog roaster and now we want to make offset smoker. Where all the angle iron is, that is the cut for door.

Cool.. looks to be about the same thing as the OP's ...

Cool.. looks to be about the same thing as the OP's ...

ty...sir will do

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