First Smoker... building a small patio RF "Fat Boy"

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thechuck

Smoke Blower
Original poster
Oct 26, 2012
81
10
SouthEast KS
Alright folks... here it is. My plan is to build a small patio RF. Over the weekend I posted in the Roll Call thread a little bit about myself and my idea but here it is in more detail. I work at a steel fab shop and we have plenty of scrap or drop I can use so size and type of material isn't really an issue cause I can find something that'll work. I'm basing my first build off of a 20"x.5" pipe... that's right, a half inch thick piece of pipe. It's what we got so I'm going to use it. Here's a pic of it not cut to size yet, ignore the cut to 5' cause that's what was needed and this piece is basically the drop from that. And as I stated in the roll call thread... YES the bbq calculator and I are great friends!!


I plan on cutting it in half and extending it vertically 9" with steel plate so it's more oval shaped and it'll be 40" long. The diagrams below (which I did quickly in good 'ol microsoft paint after some old sketches, so no comments on my "drawing" skills lol) don't show dimensions but it'll be roughly 40"x20"x29" with the firebox being basically 19" square and using 6" sch 40 pipe for the stack. The drawings are also slightly off, I'll have the firebox even with the baffle plate opening and the doors will actually start to square off from the top of the pipe and not slightly below as it shows.



The baffle plate will start 6" up from the bottom of the pipe at the firebox opening and slope about an inch to the other end (stopping about 3.5" from the end of the smoker for the RF opening with also a lip on top and bottom) and about a 1/4 inch drop from the sides to the center 1 1/2 angle trench. The four racks will be made out of inch square tubing with expanded metal and will slide in and out. I went with different sized doors opening outward so I could accommodate long pans and short pans if necessary but not have to open the whole smoker. They'll be 22"x19" and 12"x19". I'll also have a removable ember box, roughly 18"x18"x10" (with a slightly lower front side) made out of rebar for the base and heavy expanded metal for the sides. The 6" stack will have a rotating damper just after the bend and of course an adjustable cap at the top. I don't have the frame completely drawn out but I figured that would be thrown together with whatever (probably 2" square tube) and have some heavy duty solid wheels on the firebox end and heavy castors on the other end. Plan on moving it in and out of a garage door on flat concrete so I figured that would be do-able.

Now for my main questions that I need help with...

size of material:

My main pipe housing is going to be 1/2" but I was planning on using 3/8" plate to extend it the 9", to frame out for the doors, and for the firebox. I have a good sized sheet of 3/8 tread plate that I was going to use for the firebox and doors if I had enough but I was considering doing the doors themselves in 1/4" since the thickness there wouldn't matter as much. I could use half inch everywhere (price difference is minimal because it's smaller scrap pieces) but that's just overkill, I'm just concerned that for this small size it's going to be a pretty heavy guy.

Which leads me to my next question... the baffle plate. Since price difference in minimal, what size would you use? Like I said, 1/4 to 1/2 isn't a problem getting... so I was thinking 3/8 all around besides the 1/2 pipe and the racks/supports.

Again, I know all of this is probably overkill on size since most decent smokers and components are made out of 1/4 (from what I can tell) but I figured once I got this "little" guy up to temp, which will take awhile granted, he'll be holding steady like a champ from then on with minimal constant babysitting (IF I didn't want to constantly watch it that is).

Sorry for the long post but I'm just looking for some input from the experienced pro's on my sizes and layout... am I crazy for using 1/2 pipe and 3/8 everywhere else (especially the baffle plate)?
 
Good luck and I'll be watching.  I just finished one myself doing that exact same thing.  Piecing and parting what I could find to make work.  :)
 
Just a side note,  hope you've taken into consideration moving that weight.  1/2 seems a bit much,  but if it's what you have I say go for it.  If I had the money I would have made my reverse flow plate a little thicker mainly near the firebox side.  Don't recall what I used but it was thinner.  

My opinion is you will love the thicker metal as it'll take more than just a little wind/rain/ cold temps to bring her down.
 
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Yeah Gent, that's why I'm going for some pretty stout wheels. I was going to just have it stationary on the back patio but there's no good place to put it that would work well (I'll add "expanding patio" to the new house project list... ha). So I figured even with it's weight I should be able to move and position it well enough on the flat concrete of my shop/driveway... a few feet at least.

I liked the idea of the thicker 3/8 RF plate, especially on the firebox end, the only thing is I was going to have 1 1/2 angle as the middle trench part but I think we mainly only have that in 1/4... see any issues with that or do you think I should just slope the two 3/8 plate together and skip the angle altogether?

Thanks guys
 
Personally, 1/2" pipe is a little much, but if thats all you have....

Its just going to be heavy,

As far as your questions, Id use the 3/8 tread plate for the firebox and 1/4" for the doors. For this size smoker, I dont think you would have any problem using 1/4" for the reverse flow, you could always extend the top of the firebox into the cooking chamber with the 3/8", lets say 10" or so, then attach the 1/4" on top of it, so that its double up right where the heat will be hitting it the hardest.

I see by the drawing that you are looking at two seperate doors on the front. I would recomend just doing one frame with two doors. Less fabrication, and it will give you more access to inside your cooking chamber.

And if your going to cut it and add a 9"section, plan on loosing the bottom 10" for the reverse flow, that leaves 19" cooking chamber height. 3 racks will give you roughly 6" between racks. Adding a 12" section gives you roughly 7" between racks. See my point, same labor will be involved welding in the section no matter how much you add, so you might want to go bigger than you originally planed just to get the most out of your labor. Im thinking 14" section added would be just about right for this size cooker.
 
Ribwizzard, I was thinking about one door frame with 2 doors but I wasn't sure how to accomplish that and get a good seal. I'd still want to be able to open both doors independently but the best way I could figure to do it would be to overlap them.

I thought about that on the height also (not sure how I ended up on 9" but it seemed to work). I only ever planned on having 4 sliding racks (2 separate doors) so currently it'd give me 2" (1" each) for the racks themselves and roughly 8" gap between. I've been resisting going bigger all around... wider and taller... because I wanted to keep it within a decent, manageable, "patio" size (laughable I know since I'm using 1/2" pipe). My really close relative that I'd help smoke all the time has a big ol rig so I figured if I was doing any large amounts we'd just do it on his smoker.

Looks like I got some thinkin to do... but I do really like the idea of one frame with two doors... any suggestions on how to do that to get a good seal where they meet?
 
Ok... Here's the new sketches (which should be put into actual shop plans this week). I was trying to refrain from "bigger is better" but Ribwizzard pushed me over the edge and I ended up adding 5" to the vertical plate extension from 9" to 14" (it's only 5" more so why not, right?), made it into one solid door frame instead of two (still two doors), and will now have 3 levels of sliding racks instead of 2... pretty much everything Ribwizzard suggested (thanks again for helping me make up my mind!). Still think I may just do the whole RF plate in 3/8 tho. I've also added in the basic dimensions and lengths so I don't have to explain it all and you guys don't have to guess too much.



I know there are still some small details to figure out... like where the two doors meet (I have a couple ideas and I'm waiting to see what Ribwizzard suggests also), the frame, the stack cap/damper, etc... most of which will probably be figured out and fitted during the build (yes I still plan on taking plenty o' pics).

One thing that concerned me was the placement/height of the stack. According to the calculator, a 6" dia pipe would need to be 15" tall which I depict in the drawings (I used gridlines so everything should be close to scale) but it just looks to be a little short. I just figured I'd add a few more inches to the height to be safe anyways (planned on having a damper after the bend still). Also, is the location I have it ok (starting 11" down from the top and basically centered in the cc)?
 
Working out the drawing details of the door and hinges but I have another question. I have a piece of flat bar drawn in at the end of the RF plate to keep anything from going past the drain hole and off the end of the RF plate. But in my original design I also had some flat bar hanging down at the end... my thinking was it would be a last little heat shield (maybe help keep the radiant heat more even across the RF plate) and also help get the smoke "rolling" around that corner. I'm pretty sure I've seen this on other smokers but don't know if it'll actually be useful or more of a hindrance (mess with the smoke  flow, draft, heat, etc...)

I'm sure I'm way over thinking this but thought it wouldn't hurt to ask people's opinions in case they've had the same thoughts or issues.
 
Looking good now, I like the design changes.  I would not worry about the height of the stack, Just dont go smaller than the 6" dia. I like the placement of the stack. The only thing I see that may be a little off is the reverse flow plate might be a little low., but check the pit calculator and see what it says. I was thinking you would be up around 8 or 9  inches from the bottom.

Should be a really nice smoker when your done.
 
I thought so too Ribwizzard but I've double-checked my math using the bbq calculator and the circle calculator but I found where I made a slight mistake. I pretty much added up a 20" pipe x 40" (12560 cubic in) and then a 14"x20"x40" (11200 cubic in) for the "extension" which equals out to 23760 cubic in. I rounded up to 25000 cubic in. thinking that would make up for squaring out the door frame but once I worked the actual numbers I should be more around 27000 cubic in. (which roughly equals a 117 gallon tank for bbq calculator purposes). That only makes my numbers slightly off but should still work (adding an inch to my firebox making it 22x20x20 would put it at 97.7%, length of 6" dia chimney is now 16" which I was going to do anyways, and firebox opening should be 70 cubic in.). Using the circle calculator for segment height (5.5") and apothem (4.5") gets me my 10" radius and says the segment area is 70.3 which still is right at the new measurements. Even though the RF plate will start at 5.5" and slope down to 4.5" and back up, there will still be more room because that's the bottom point  of the sides sloping down to the middle over another inch.

K... don't know about you guys but I just made my head hurt thinking about all that... follow everything ok? Again, I know small variances won't matter that much but this is also why I like to have it all laid out first and measurements figured out.

I'll show you a rough design later on for what I had in mind for the doors... thanks again everybody (especially Ribwizzard) for the input!
 
Exactly... even with the internet's help (cause you know I didn't remember formulas or details from school... apothem?! come on
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)   I still spent hours working up almost exact numbers. But the best part is... if I'm spending this much time now, just wait til this thing of smoking beauty is done and I spend even that much more time working on my 'Q!
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