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Beginning a big RF!

post #1 of 32
Thread Starter 

We cook about 1500 lbs of Q (butts) to raise money for our Scout troop.  Right now we have a gas cooker- about 4'x5' and a Lang  60 RF with a 120 gallon chamber.  I want to build a fatboy RF to increase our capacity and shorten the cook time- right now we run about 36 hours to cook all of our butts, chop and pack.  I am looking to speed things up a bit, as far a volume goes- I know we can't cook bbq in less time on the smoker and have it come out proper.  I have been doing my homework, and have seen some great builds and allot of knowledge shared here. But I still have a few questions.

I have a 500 gallon propane tank lined up ( about 9 ft long and over nearly 3 ft in diameter- this is an oldie but goody). Same source also has a 120 gallon vertical tank( 30" diameter x 54") to throw in. Would the 120 be big enough to make the firebox out of? is the volume there?


 I'm thinking it would be allot less expensive to go that route- using a smaller tank- than build a firebox out of plate.

This will be a trailer rig, see trailer in pic- ignore the oval drum, it might be a chicken cooker or finisher for the butts after about 4 hours smoke on a separate trailer and gas fired, but for this build, I want to mount propane tanks for the RF and firing it with splits on this trailer.

Thanks in advance for your input.


Edited by Fudd - 11/2/15 at 9:18pm
post #2 of 32

Good luck .it is hared work but it is fun .

this is my RF see if you can get some idea for it .

post #3 of 32
Thread Starter 

Thanks African Meat!  hope you are well there.  I appreciate the reply. More pictures to come.

post #4 of 32

  Welcome Fudd. Glad to have you with us!  Check out the Feldons Bbq Calculator to help out on sizes for different things such as firebox size, FB to CC opening, exhaust stack size.  Measure twice, cut once! Good luck with the build and keep us posted!



post #5 of 32
Fudd-what are the dimensions of that 120 gal tank. The problem with just listing the capacity of a tank is that we have no idea what the actual dimensions are- you could have 3-120 gal tanks from different companies and all 3 could have different dimensions. Looking forward to you build.

Thanks for participation with the Scouts. I've been involved with Scouting as an adult leader for close to 30 years now. I'm currently a Scoutmaster for a Special Needs Scout Troop; this is my 5th Scout Troop that I've been associated with.
post #6 of 32

According to Feldon's for a 500 gal. tank you need a 38500.00 .c.i. Fire box  that would be if using pipe (round)  about 38"dia. x 40" long approximately  Since the rule of thumb is to oversize a bit, well you see where I am going?  I am sure Dave will have some great suggestions and input. If that was a picture of the tank, I like it,  build it with the oblong, vertical and you should have a lot of cooking area.



post #7 of 32
Thread Starter 

Thanks for the replies so far.  I'm picking up the trailer this weekend, and plan on looking at the tanks next week.

I ran Feldons BBQ Calculator, that is an awesome tool!  I may revisit the 500 gallon tank since the firebox will need to be so big, but it will definately be on the bigger side of things, 320 gallon +. Allot will be based on what sort of cooking chamber I end up with, obviously... stay tuned.

post #8 of 32
Thread Starter 

Got the tank and the trailer. 

Tank is 39" diameter x approx. 103" long.

Trailer will be getting a 3500 lb axle and some additional cross members.

Couple of questions:

1) any drawbacks as far as using a 120 gallon tank for a cylindrical firebox?


2) RF with fixed baffle plate or Direct flow with movable tuning plates? Advantages to each.


3)As far as the main door, I'm thinking one 60" door that will be counterweighted. 

What do you think?


Also, any way to get the ethyl mercaptan stink out?  Plan on filling the tank with water and degreaser letting it sit then purge with nitrogen or argon prior to cutting it. then should we burn it out?


Edited by Fudd - 5/16/14 at 6:52pm
post #9 of 32
Thread Starter 

Got the new Axle delivered and Hubs assembled.


Thanks to AgriSupply and UPS! remove old axle and new Springs mounted will be the next step.  Nut much on the tank yet, rainy day here.



post #10 of 32
Thread Starter 

New axle installed and tongue shortened. Trailer got some additional bracing to stiffen it too.  Tank getting cut and mounted to supports also. stay tuned... Cutting door shortly.

post #11 of 32
Thread Starter 

Gary- My neighbor, who is helping with my build, has decided to use the oval tank above to make  a RF - in the way you suggested, we'll keep you posted on that build too. He's probably going to have two doors on the flat portion, and casters on that one for a drive way/ patio rig that can be rolled on to his utility trailer if we need to transport it away from home.  

post #12 of 32

Looks great! It looks to be coming along very nicely.



post #13 of 32
Thread Starter 

 Got the tank we're going to use as the firebox- 30" diameter- plan on cutting off both ends and re-using the vented end as the door.  Also plan on installing a deflector plate inside the top of the tank at an slight angle toward the CC and extend it into the CC about 6 inches to deflect the flames away from the baffle, which will be about an inch and a half above the deflector... rebar grate will be welded in on the bottom about 4 inches up to hold welded bar grate for least that's the plan.  

Edited by Fudd - 5/16/14 at 6:58pm
post #14 of 32
Thread Starter 

Been a long hot summer, but progress made!

6 inch SS stack, this sucker is gonna set tall. have about 25 square feet of cooking space once it's done. Stay tuned.

post #15 of 32
In place of the elbow, think about an exhaust plenum to improve air flow....

post #16 of 32
Thread Starter 

Thank you Dave. This is such a great pool of knowledge, and all help is appreciated.   I have seen the plenum diagram recomended to others, and it does make sense- a more fluid flow with less restriction than a 90 deg elbow.  I know that six inch opening is a bottleneck. So we will try to evaluate wether it causes a problem with "stagnant" smoke in the first few firings.  The only way I can think of to gauge that is if we start seeing creosote inside the CC.  Am I right in that line of thinking?


This is our first RF and trying to keep it fairly low budget, we are using what we have on hand.

post #17 of 32
Thread Starter 

Major progress!


Man I am tickled today!!


Mounted the cooker on the trailer- she squatted a couple of inches, but figured she would, that tank is 3/8" thick. It aught to last my lifetime for sure, so I'll be passing this on some day! 


Counterbalance needs tweaking', but we have an Awesome Boy Scout emblem ( Fluer De' Lis)  in SS to mount on the gussets, that'll distract the eye from it.  Function over form all day long! Happy, Happy, Happy! 


Also Pictured:

Fire box to CC opening,

Racks slide out,

and Front door with the vent for FB,


New firepit too- leftover end from FB tank makes a nice backyard pit.


Can't wait for the TBS!

Edited by Fudd - 11/15/14 at 6:20pm
post #18 of 32
Thread Starter 

It's Alive.  got it up to about 500 degrees for a couple of hours, now  off to the blaster.



Question- what has everyone done to seal the CC door? We have a small gap near the bottom.  Thanks.

post #19 of 32

Is the door warped?

post #20 of 32
Pictures of the gap..... Pictures of the hinges and how they were welded...
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