My first 80Gal RF build... This is going to be a blast!

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alaska

Meat Mopper
Original poster
Sep 2, 2013
176
14
Big Lake Alaska
Its time to give this a whirl and I hope everyone shares their opinion, preferably prior to my squeezing the trigger or sparking the torch. My plan is to build an 80 gallon RF using this air tank as the CC. I also want to make the fire box in a square fashion as opposed to cutting an end off this tank.


The tank says champion oil less on the side and it is a verticle model. What I plan to do is make the firebox square and have it attach on the left hand side. What thickness of metal should I make the FB out of? Why do some people make a frame out of square stock then skin it, is that necessary? Could someone assist me with a drawing of some type so I can really ask question by referencing the drawing?

Measurments

Circumference of tank 77.5 inches

Length not including ends 35 inches
 
Alaska, evening....  some folks build the FB....  add 1x2 on edge.... stuff 2" rock wool in for insulation... skin the outside...  stuff rockwool into the tube also... 1/4" for inside FB.. 1/8 for outside....  you could fill the space with sand also...  don't plan on moving it when done.... 
 
Alaska... look in my signature... there's a few links to my build.
Hopefully a few photos can help
There's also a pit calculator link.
 
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Alaska, evening....  some folks build the FB....  add 1x2 on edge.... stuff 2" rock wool in for insulation... skin the outside...  stuff rockwool into the tube also... 1/4" for inside FB.. 1/8 for outside....  you could fill the space with sand also...  don't plan on moving it when done.... 
I may need to do that if the weather causes problems like some are describing.
 

Here is the tank that I plan to use. I loaded a few numbers in these two calculators and .....? 

SQWIBs Calculator

CC - 165021.72 Cu. In

FB - 38.03 inches

Daves Calculator

CC - 18480 Cu. In

FB - 6160.00 Cu. In

I plan on swinging by the local Steel Shop to price out the metal for the FB so could someone give me an idea on what size you come up with along with the recommended thickness of the metal? 

Thanks 
 
Alaska,morning,for the firebox my preference would be at least 1/4" thickness,and a grate for the fire,so you wont burn it out on the bottom,my calculations from the size you gave were

cc- 165021.72 cu in

fb- 55007.24 cu in

for a square firebox these were my measurements,you will have to deceide what size you want the firebox

a 50"h x 50"w x 24" length will give you almost the same size firebox at 109.1%

An undersized firebox will require frequent fueling and may not adequately heat the cook chamber. A slightly oversized firebox is preferable.

Firebox Dimensiare)

Firebox Dimensions (Round)

Calculations

Height

40

inches

Width

35

inches

Length

40

inches

Diameter

inches

Length

inches

Specified
Firebox Size

56000.00

cubic in.

Recommended
Firebox Size

(1/3 of cook chamber)

55007.24

cubic in.

Size Differential

101.8%
 
I based those numbers on a cylinder-type cook chamber,dave omak helped me with a lot of questions,and a few of the other guys as well,there is a lot of good info to help you along the way,im no expert by any means,but will try to help,thanks danny
 
I was looking at another build and the person is using a 115 gallon tank and his FB is 25 X 24 X 18 In saying this why would my FB need to be 50 X 50 X 24. this seems like a big difference in size.
 
SQWIBs Calculator

CC - 165021.72 Cu. In

FB - 38.03 inches

Daves Calculator

CC - 18480 Cu. In

FB - 6160.00 Cu. In

( 80 gallon / 7.48 )  X  1728 =  18,480 cubic inches.....   

How did the other calculator come up with  165,022 cubic inches..  

6160 cu. in. for the FB is correct....  20 x 20 x 16 = 6,400 cu. in.     

Something is amiss.....   recheck stuff.....   If you need someone to help, I'm here....    
 
Dave.... Thanks for taking a look at the numbers! I was reading some other post and saw many opinions regarding making your firebox larger to keep from having to load it more often. As you know I'm here in Alaska and the temperatures will be extremely cold. I intend to use this RF every time I get a chance regardless of the weather.
  1. What are your thoughts on increasing the size of the FB to provide for a longer burn?
  2. By having the tank that I have for this build, insulating it would be a problem. If I were to insulate the FB would that assist me in any way?
  3. I pulled up the Circle Calculator and came up with the following numbers with the tank I'm using. Did I do this correctly? 
Radius 12.32

Segment Height ED 4.73

Chord AB 19.409

Apothem OE 7.59

Central Angle 103.94

Arc AB 22.35

Circumference 77.409

Segment Area 64.018

Triangle Area 73.656

Sector Area 137.67

Total Circle Area 476.84

Can I get some input on a 2 door vs 1 door Cooking Chamber.      Is it dependent on what I plan to cook/smoke?

Thanks everyone in advance for your feedback.... Alaska AKA Jerome      
 
 
Dave.... Thanks for taking a look at the numbers! I was reading some other post and saw many opinions regarding making your firebox larger to keep from having to load it more often.  

Build the fire box bigger.... 25-50%or even 100% larger....   You don't have to change any of the other dimensions/numbers...  Leave everything else as if you built your smoke exactly as the calculator says for your size Cook Chamber....
  1. What are your thoughts on increasing the size of the FB to provide for a longer burn?  Good idea....

  1. By having the tank that I have for this build, insulating it would be a problem. If I were to insulate the FB would that assist me in any way?  Probably a little....  considering the amount of wood your have, is it worth it ??   You can insulate it later if  you wish...  at least on the sides you can get to......
  2. I pulled up the Circle Calculator and came up with the following numbers with the tank I'm using. Did I do this correctly? 
Radius 12.32

Segment Height ED 4.73

Chord AB 19.409

Segment Area 64.018

The highlighted numbers above are all adjustable....   If they are what the calculator recommends for it's "standard design", I would increase the ED until the Segment area was about 90 sq. in..   then use that new ED for the FB to CC opening, and also the new AB for the width of the RF plate.....  double and triple check the diameter of the tank and rerun the calcs with any different diameter you come up with BEFORE you cut the RF plate...

Can I get some input on a 2 door vs 1 door Cooking Chamber.      Is it dependent on what I plan to cook/smoke?  Yes, make the door(s) large enough for a moose hind quarter...

Thanks everyone in advance for your feedback.... Alaska AKA Jerome      
 
Last edited:
 
SQWIBs Calculator

CC - 165021.72 Cu. In

FB - 38.03 inches

Daves Calculator

CC - 18480 Cu. In

FB - 6160.00 Cu. In

( 80 gallon / 7.48 )  X  1728 =  18,480 cubic inches.....   

How did the other calculator come up with  165,022 cubic inches..  

6160 cu. in. for the FB is correct....  20 x 20 x 16 = 6,400 cu. in.     

Something is amiss.....   recheck stuff.....   If you need someone to help, I'm here....    
Dave can you check the calculator I have in my signature and see whats up. If it's inaccurate or out of date let me know and I'll update

Thanks
 
 
SQWIBs Calculator

CC - 165021.72 Cu. In

FB - 38.03 inches

Daves Calculator

CC - 18480 Cu. In

FB - 6160.00 Cu. In

( 80 gallon / 7.48 )  X  1728 =  18,480 cubic inches.....   

How did the other calculator come up with  165,022 cubic inches..  

6160 cu. in. for the FB is correct....  20 x 20 x 16 = 6,400 cu. in.     

Something is amiss.....   recheck stuff.....   If you need someone to help, I'm here....    
thats what I got on the Pit Calc 20x20x16=6,400

 
 
 
SQWIBs Calculator

CC - 165021.72 Cu. In

FB - 38.03 inches

Daves Calculator

CC - 18480 Cu. In

FB - 6160.00 Cu. In

( 80 gallon / 7.48 )  X  1728 =  18,480 cubic inches.....   

How did the other calculator come up with  165,022 cubic inches..  

6160 cu. in. for the FB is correct....  20 x 20 x 16 = 6,400 cu. in.     

Something is amiss.....   recheck stuff.....   If you need someone to help, I'm here....    
Dave can you check the calculator I have in my signature and see whats up. If it's inaccurate or out of date let me know and I'll update

Thanks
My computer doesn't have the software to open it or get it to work.....   I tried.....     Dave
 
 

did you dowmload it first then try?


My puter says I need the original installation source...  Software came with this machine....  I don't have the orig. source...   



Just checked software updates..... AOK....
 
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Good morning everyone..... Dave, SQWIB and Black, I appreciate your taking a look at my numbers. I got my hands on some metal a few days ago, it was an old sluice box! Here are the measurements 1/4 in thick, 18 in sides, 38 in bottom and 18 ft long.....Think it was worth $25??

Q -- What parts do you guys recommend I use this for?

Q -- Dave... You mentioned I could make the FB even larger so the 20 X 20 X 16 that you came up with should only be the smallest I should make it, is this correct?

Q -- Cutting the CC Door.... There was post dealing with warping the metal. Some recommend using a grinder, plasma cutter, torch, sawzaw..... I would not use a torch but would a plasma cutter not provide the best cut?

Q -- How do you determine the size of your air vents on the FB door. 

 
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