Tank #1 of 3- 12 gallon RF

Discussion in 'Reverse Flow' started by smellslikesmok, Aug 13, 2013.

1. smellslikesmokNewbie

. As i mentioned in roll call ive got 3 tanks i need to convert to cookers or the mrs is gonna cook me! So i want to start with the smallest build and get some meat smoked and on the table ASAP to let her know there is hope.  This was given to me by a friend. He cut the top off of two propane grill tanks and welded them together. Looks like it'll hold, worse case i can run a bead around the inside once i cut out the door opening.

The calculators i could find online indicate this would be about a 11.75 gallon tank, but i plan to bump out the front so the door sits vertically and opens up the chamber for a little more room for meat.

With the tank and the bump-out im guesstimating 2984 cu.in. (2714.25 for the tank and 270 for the bump-out). So a 10x10x10 firebox would give me a 101.5% size differential.

This drawing is not to scale!!!!

https://statich.smokingmeatforums.com/5/5c/5ca3ed2a_SmokerBuild.pdf
My questions right now are how much space do i need under the RF plate? Calculator says a half moon with a 4.51" diameter for the FB to CC opening.  So is that to say i could get away with 2.25" from the bottom of the tank to the underside of the RF plate?   Can you guys check me on this.  Last thing i want to do is start cutting without some confirmation.

Then how much space do i need for airflow opposite of the firebox coming from under the RF plate and into the CC.  Right now ive got +3.5" to spare.  This may change the dimensions of the door cutout and send me back to the calculator

Thanx in advance for everyones help!!!!!

carl

2. daveomakSmoking GuruOTBS MemberSMF Premier Member

My questions right now are how much space do i need under the RF plate? Calculator says a half moon with a 4.51" diameter for the FB to CC opening.  So is that to say i could get away with 2.25" from the bottom of the tank to the underside of the RF plate?   Can you guys check me on this.  Last thing i want to do is start cutting without some confirmation.

SLS, morning and welcome to the forum....    The opening between the FB/CC in the calculator, makes an unnecessarily high hole that elevates the RF plate......     In my signature line are 2 calculators that use the diameter of the tank for that opening size.....  That lowers the top dimension of the opening and allows for a lower RF plate thus allowing for more cooking space.....   When you have calculated the opening size, I suggest increasing the area under the RF plate by 1.5....  thus reducing the friction loss while the heat/smoke/air travel it's length and take a 180 deg turn to the exhaust....   the opening on the end of the RF plate should be the same or greater area that is under the RF plate.... In my opinion....

Dave

Last edited: Aug 16, 2013
3. smellslikesmokNewbie

Thanx Dave, That makes a world of sense  Now where did i put my pocket protector and slide rule???.

So the area of the segment is 7.95 so your recommending bumping that to 9.45.  Man if we wouldve had these online calculators back when i was in school i might have actually enjoyed math! So now we're talking about being 1.66" off the bottom of the tank, and a chord length of 8.29"  That answers my  questions perfectly and fills in the two missing dimension from my drawing Thanx Again!!!!!

Looks like ill end up with about 10 inches height in the CC.   Whats the going wisdom on how high above the RF plate a rack should be in a smallish RF cooker like this?? Then i can see about splitting the difference of whats left for a second rack.

SmellsLikeSmoke

4. daveomakSmoking GuruOTBS MemberSMF Premier Member

SLS, evening.... I see I made an error.....  In the one calculator it uses the radius for calculating the segment area...  forgot what the other uses...   I hope you caught the "fill in the blanks" correct dimensions......

You could put in rack supports at different heights.... start at 3" above the RF plat and adjust until you run out of angle iron...    Absolutely no point in not making the smoker fit anything you want to smoke.....   There \$0.02 ......

Speaking of school.....   I had a slide rule......  That made math real easy....

Dave

5. smellslikesmokNewbie

Evening Dave,

Honestly those calculators werent clicking in my mind,,,,I googled another and it started making sense. I didnt notice your mis-speak, but im sure i used radius in the calculator.

Ill be determining number of racks later but i will consider your suggestion.  Right now i needed to know the height of the first rack so i can finish designing the bump out for the door.  Ill keep planning this evening but i should be makin' sparks in the morning!!!

So does it make sense to increase the size of the firebox, opening to the chamber, and stack size,,, assuming i can throttle it all down with dampers?  Or should i just try to dial this thing in as accurately and by the numbers as possible?  First build so i dont know what to expect exactly.

SmellsLikeSmoke

7. smellslikesmokNewbie

No thoughts on oversizing components?

8. daveomakSmoking GuruOTBS MemberSMF Premier Member

Oversized is fine....   make sure it's all air tight so you can control the temps....    control mainly with the air inlets to the FB....    and a choke plate on top of the stack to "slow" the exhaust in the event of air leaks in the smoker..

9. smellslikesmokNewbie

Thank you sir!  You've been a huge help in getting me started on this build.

SmellsLikeSmoke

SLS,

Welcome to SMF!  This is the place to get great advice and many opinions.  You are off to a good start, it is much easier to change on paper than more cutting and welding.

There is so much information here, sit back, search and read.  The calculators give good info on the sizes (area)  of various smoker openings.

Ask questions & post pictures....most important have fun!

RG

11. smellslikesmokNewbie

Layed out my openings and sparked up the grinder Saturday morning.  I'm gonna scrounge around the shorts bin at work tomorrow and see if i can find what i need for the door and stand.

SmellsLikeSmoke

12. smellslikesmokNewbie

Hello all!  I found some cut-offs in 1/4" plate at work that will work fine for the FB.  Looking at Feldon's calculator and wondering how it takes into account all the different configurations for FB's that ive seen on the many builds in this forum.  Things like whether there is an ash tray, or how many inches there is below the fire grate.  Is the "Recommended Firebox Size"  based on cu.in. above the grate?

13. smokejumperSmoking Fanatic

The "Recommended Firebox Size" is based on the total volume to include the area both above and below the grate.

14. smellslikesmokNewbie

Thankyou Sir, just wanted to confirm that before i moved forward

SmellsLikeSmoke

15. phat ricoNewbie

Hey SLM, you make any progress on your build? I just picked up a tank close to the size of yours and I am interested to see how yours turned out.