# My first RF smoker build, any help would be appreciated

Discussion in 'Reverse Flow' started by jhsdigital, Apr 15, 2013.

1. ### jhsdigitalSmoke Blower

I'm new to this site,  joined today hoping to get some help and feedback on my first RF smoker build. I have been using a 55 gallon drum smoker for a couple of years while looking for an old propane tank for just as long. Last week I had a friend give me a 132 gallon tank from his cabin in the mountains that needed to be replaced. So here we go, I read up on cutting a tank open and after many sleepless nights and internet research I cut it open the other day. I'm glad to say no big explosions, it only took me about 2-3 hours of standing there looking at it to get up enough nerve to climb on and cut away. I should say we filled it up with water and emptied it, then let it sit for a bit before doing so. The other guy in the photos is my good friend who just happens to be an iron worker so the welding part is covered. any input or suggestions would be most appreciated as I don't want to mess this up and hopefully end up with a long lasting great cooking smoker !

Here is a few first day photos

2. ### rasimmoMeat Mopper

Looks like you are off to a good start. If you have not put the numbers in a pit calculator, you should Take some time to look at several builds here before you get too far along. A lot of great information and ideas to steal. Have fun and keep posting the progress.

3. ### jhsdigitalSmoke Blower

Ive punched numbers into Feldons BBQ pit calculator and this is what it spit out,

132 Gallon cooker chamber = 30492 cu in

recommended firebox size = 10164 cu in

my FB dimensions 24x24x24 = 13824 cu in, gives me a size differential of 136%

recommended chimney volume 691.20, using a 4" round pipe @ 55.03"

recommended FB intake air inlet @ 41.47 sq in, Im building 4 @ 3x4" ( recommended 3.5 needed)

FB to Cooker opening (half moon) recommended diameter 16.78"

recommended FB to Cooker opening 110.59"

I understand most of it, except the FB to cooker opening size using a half moon opening. dont understand the 16.78" and the 110.59" parts ??

4. ### daveomakSmoking GuruOTBS MemberSMF Premier Member

jh, morning and welcome to the forum......  The110.59 is the square inches the FB to CC opening should be....  What I would do is measure the diameter/radius of your CC, put the radius into the circle calculator, check the Radius & Segment Height ED box, and adjust the segment height until you get about 110 sq. in....  Below is a drawing I did for another member to help explain what I mean..... Then, keep changing the segment height numbers until you get about 165 sq. in.(110 X 1.5)   that is what I would recommend for the RF plate segment height...  Then chord AB is what the width of the RF plate should be...  The opening at the end of the RF plate should be at least 165 sq. in. for good air flow....   Dave

http://www.1728.org/circsect.htm

http://www.feldoncentral.com/bbqcalculator.html

Last edited: Apr 15, 2013
5. ### rasimmoMeat Mopper

Do what Dave said. Doing it that way will let you have the most available height for the cooking space.

6. ### jhsdigitalSmoke Blower

Dave thanks so much for the info I will keep posting my progress and questions. Going to try and get the doors hinged tomorrow.

7. ### jhsdigitalSmoke Blower

Well, Progress is being made, I wish I had more time to get it done faster though. We got the old fittings cut off the bottom of the tank and the flanges welded on the door. Hopefully next week I can find some time to get it hinged and welded onto the tank.

Should I have it sand blasted after the door is on ????

8. ### jhsdigitalSmoke Blower

Welded on the door hinges last night as well as some door stops. Got some great info from DaveOmak about the FB (Thanks Dave) Does anyone recommend having the tank sandblasted before I move on? Its a little pitted, not much along with some slight rust in spots, but when we grind it in spots for welding, the paint is really nasty to get off.

9. ### jhsdigitalSmoke Blower

Well, I was able to make some time to continue on with the smoker today. So we measured and notched out the FB to CC opening, hopefully we can get it welded up this week.

10. ### daveomakSmoking GuruOTBS MemberSMF Premier Member

Getting there.... Looks good....    Dave

11. ### sqwibSmoking GuruOTBS Member

My build is similar to yours, but If I could change just one thing, I would remove the rounded pice on the right of the tank and weld a flat piece on, this way the top of the firebox will not be inside and create a hot spot.

I had to baffle mine to counteract the radiant heat from the firebox.

12. ### ribwizzardMaster of the Pit

Sqwib,   You dont like the way it looks though, with the rounded end?
• FIXME: needs styling from "post-user-info"
• jhsdigital,   Sqwib is right about the hot spot, I would address that now at this stage, you can do like he said, or another way is install a baffle plate.  Just welding another plate under the top plate of the firebox with about 1/2 inch gap between them will do it. I like the rounded end, so prefer to add the 2nd plate.

13. ### doodleqSmoke Blower

A bit late on this, but see you still have paint on...
I could hardly stand the smell when the area close to where I was grinding got hot...let alone the grinding. Having the cc sandblasted made life a lot less smelly, and work go a lot faster too since you're pretty much ready to weld anywhere.

14. ### daveomakSmoking GuruOTBS MemberSMF Premier Member

Here is a drawing of what SQWIB'S smoker looks like inside.......

15. ### urbotrimmmMeat Mopper

I sandblasted before I even cut tank.  Made fabrication soooooooooooooo much easier.  I did get some rust afterward but a flapper disk on my grinder took care of it in a heartbeat.

16. ### jhsdigitalSmoke Blower

Hi Guys, Sorry Ive been really busy and have not had much time to check the forum,

SQWIB, now that you point it out I could see where that would create a hot spot. I'm going to have to add a baffle plate though, I really like the looks of the round ends.

Dave, Thanks for the drawings, I do much better with visuals. So if I understand this right I'm going to add another plate inside the top of the FB about a 1/2" below the top, all the way across and continue it  into the CC below the RF plate. How far into the CC do I carry it below the RF plate? and is it also about a 1/2' below the RF plate?

SQWIB, could you send me a picture of what yours looks like ? ( [email protected] ) or post one here so I can take a look at it?

17. ### daveomakSmoking GuruOTBS MemberSMF Premier Member

If you have an instant read, non contact therm, you can measure the temp on the RF plate and get a good idea of what it would take to help even out the temps....   It's all "guess and by golly" that will work type thing...  An uneducated guess would be 1/4 of the length of the RF plate..  I really don't have any scientific data to support this guess...

If you do not have a second air inlet, in the firebox, above the fire grate, that could solve the problem also.... by adding air, above the fire, to help move heat into the cook chamber....   Ribwizzard uses that second air inlet.. Folks that have put one in their smokers have written me about how it helps regulate temps and reduces wood consumption in their smokers and cools the firebox without losing heat in the CC.....

Dave

18. ### jhsdigitalSmoke Blower

SQWIB, thanks for the pictures, Dave once again thanks for your input. As far as the baffle plate I ran across this picture on the web, it shows an insulated firebox. If you just insulated the top portion of the box would that solve the hot spot in the CC? And if so, could you use any type of insulation, like regular fiberglass insulation or would it just burn up from the heat inside the FB?

19. ### daveomakSmoking GuruOTBS MemberSMF Premier Member

Insulating the FB will not do anything to reduce the heat, in the CC, on the RF plate...  The heat pouring out of the firebox, is heating the RF plate at the FB end......

20. ### jhsdigitalSmoke Blower

Dave, I thought what SQWIB was talking about was heat being generated from the top edge/corner of the firebox sticking into the CC. So by insulating the top of the FB this could possibly minimize that heat. But I guess you would still have to put a baffle plate in because the FB end would still be hotter.

So here's my next question, will the baffle plate affect the flow since now we are lowering the segment height of the FB to CC size to accomadate the baffle plates?