First time Patio RF build from down under

[nikkidee]

Hi All,

I've been trawling the forum for a while now gleaning ideas and inspiration from all these amazing builds. I think a build is a great opportunity to better understand the whole smoking process so I'm embarking on my own patio size build. Tanks with a good diameter have been extremely hard to find here but I finally came across a 19 inch diameter tank at 35 inches long giving me 42 Gal which is small for most but big enough to cut my teeth on for a first attempt. There are a few flanges/fittings to cut off/plug and a bit of rust to sand blast and fix but it's a good size and more importantly the right price.

So far I've plugged in the measurements to the RF calculator and got the following:

9703 cubic inches

39 square inches FB-CC opening, area under plate etc (segment is 15 inches wide by 4 inches high)

10 inches of inlet area

3202 square inches of fire box (I've gone a bit bigger at 15.7 x 15.7 x 15.7 for 3905)

DSC07252.JPG

• nikkidee
• Jun 27, 2017

I work with a switchboard manufacturer who knocked up the fire box for me in 3mm steel.

The stack I'm still working on but I'm thinking 3 inch pipe at roughly 30 inches long will suffice.

My spreadsheet is all over the place with mm-inches, litre-gallon-cubic inches conversions but I think I'm on the right track. Appreciate any feedback if something looks a bit off.

We've marked up the lid and plan to cut in 2 stages, first the two horizontal cuts before welding on the hinges, then cutting the vertical. By doing this at least I can ensure the hinges are in the right place and square, despite the inevitable 'spring' that will occur.

Below is a dummy up with the FB in place. exciting to see it start to take shape.

DSC07261.JPG

• nikkidee
• Jun 27, 2017

 

[kam59]

Looking great nikkidee.

 I would probably increase the exhaust diameter to 4" at 24" tall to help her breathe.

This is just my opinion but it is a lot easier to tweak the door if it is not attached to the cooker. I cut my doors out in increments leaving the top, bottom, corners, and left right center 1". Then let the door cool and finish cutting out. Then I add the door straps and finally tweak the door on my table if need be. As you are adding the straps check the door periodically for fit to see what it is doing.

On your firebox to cooker chamber opening try to adjust for a 1.5" grease bridge to help keep accidental grease from entering the firebox and causing a grease fire. 

I hope this helps. :)

 

[daveomak]

 
Hi All,

I've been trawling the forum for a while now gleaning ideas and inspiration from all these amazing builds. I think a build is a great opportunity to better understand the whole smoking process so I'm embarking on my own patio size build. Tanks with a good diameter have been extremely hard to find here but I finally came across a 19 inch diameter tank at 35 inches long giving me 42 Gal which is small for most but big enough to cut my teeth on for a first attempt. There are a few flanges/fittings to cut off/plug and a bit of rust to sand blast and fix but it's a good size and more importantly the right price.

So far I've plugged in the measurements to the RF calculator and got the following:

9703 cubic inches

39 square inches FB-CC opening, area under plate etc (segment is 15 inches wide by 4 inches high)

10 inches of inlet area

3202 square inches of fire box (I've gone a bit bigger at 15.7 x 15.7 x 15.7 for 3905)

DSC07252.JPG

• nikkidee
• Jun 27, 2017

I work with a switchboard manufacturer who knocked up the fire box for me in 3mm steel.

The stack I'm still working on but I'm thinking 3 inch pipe at roughly 30 inches long will suffice.

My spreadsheet is all over the place with mm-inches, litre-gallon-cubic inches conversions but I think I'm on the right track. Appreciate any feedback if something looks a bit off.

We've marked up the lid and plan to cut in 2 stages, first the two horizontal cuts before welding on the hinges, then cutting the vertical. By doing this at least I can ensure the hinges are in the right place and square, despite the inevitable 'spring' that will occur.

Below is a dummy up with the FB in place. exciting to see it start to take shape.

DSC07261.JPG

• nikkidee
• Jun 27, 2017

Nik, morning...    Good job on the calculations...   FWIW...  The smaller size of the smoker, I would increase the size of the restriction areas... 

5" high on the segment height....   same under the RF plate and increase the area at the end of the RF plate.. 

Exhaust up to 4" and 34" above the CC...

Changing those numbers will overcome the friction from the surface area / volume restrictions a smaller smoker presents....

+++++++++++++   From the tutorial...

The above areas are necessary for great air/heat/smoke flow.... using less may cause an overheated FB.... Narrow / Long CC may require an increase in those numbers due to increased surface area friction to volume... Wide/Fat Short CC may use smaller numbers due to reduced surface area friction to volume... edit 8-16-16... small volume patio type smokers will need some increases in measurements also.. FB/CC, under RF plate, end of RF plate... ~20-30%..

Any questions, I'm here.....   Dave.....

 

[nikkidee]

Thanks Guys,

Due to the width limitation of my FB I've got the FB-CC opening at 15.7in wide with a segment height of 4in. This gives me 44sq In or a shade over 10% more than the calculator recommends. Hopefully this will overcome some of the friction you mentioned.

Noted on the stack size, seems huge compared to the cheap shop bought smoker I've got but I suspect that was built to a price, not a spec.

Given me a bit to think about with the door cut out too.

 

[daveomak]

click on pic to enlarge...

CC door opening height.jpg

• daveomak
• Jun 28, 2017

 

[nikkidee]

Thanks Dave, appreciate your help with this.

Looks like we might want to revisit our door mark up. I was just going to cut at 9 and 12 o'clock.

I've started knocking up the below for the hinges. My rationale is that by stitch welding these with the MIG before finishing the cutout it will provide some strength/rigidity without putting too much heat into it.

DSC07270.JPG

• nikkidee
• Jun 28, 2017

Cheers

 

[kam59]

On a 19" chamber I would make my top cut 12:00 and my bottom cut either at 3:00 or 1" below 3;00. bottom cut depends on where I want the top of my grate to land. On your hinge make sure your pivot point is behind your door flange or the door will hang when you open it.

Here are some pics of mine.

photo109 (1).JPG

• kam59
• Jun 28, 2017

Notice the stop on the hinge this may be something that will work for you,

photo111.JPG

• kam59
• Jun 28, 2017

I hope this helps. :)

 

[daveomak]

If you cut below the 3 o'clock mark, some folks have found it handy to add a drip edge to the inside of the door...  In the event grease splatters on the door, the drip edge will drop the grease inside the smoker body in place of having it run down the outside of the smoker...   Food for thought...  I would tack it in tight to the door...  grease build up should seal it "grease tight" after a few smokes and you will "hopefully" avoid warping the door...

Cutting the top of the door 3" or so below the 12 o'clock position, lightens the door, makes it so you don't have to open it as far to get it to stay in place, and there is plenty of room for food on the top rack, if you install one...  It also make sure there is room above the meat, on the top rack, for heat and smoke to circulate...

These are all modifications from the original smoker builds, that members here have found useful...   Not everyone agrees BUT, the options are there for individuals to design their personal smoker..

The plenum, for the exhaust, also adds to the efficient smoke/heat transfer...  gets the exhaust out of the smoker body for more room on the food racks, in some cases of exhaust installation designs... 

All in all, the members here have come up with some great ideas and solutions to improve on the original design...  I'm happy to catalog their ideas and designs to pass on to others...  All of their ideas and designs have proven noteworthy.... 

Any questions during the build...   I'm listening....     Dave

 

[nikkidee]

Morning/Evening all,

Been a while since I posted though things have been moving along. I thought just in case this is of interest to anyone I'd post some updates.

Taking off from where I left off, we tacked on the lid hinges and cut the door out. It didn't spring as much as I thought it would which was nice.

DSC07277.JPG

• nikkidee
• Aug 24, 2017

Once cut out we framed up with 25mm flat mild strapped the lid in place and tacked the hinges on the CC.

IMG_0509[1].JPG

• nikkidee
• Aug 24, 2017

Firebox door was framed using 25mm flat mild and stitched in place, chipping hammer used for the handle. We made up the hinges to clear the frame and to match the door on the CC.

IMG_0540[1].JPG

• nikkidee
• Aug 24, 2017

Ventilation courtesy of sliding aperture at the bottom below the grate and weber style spinning vent above for cross flow. First cock up was made here when we failed to allow for a dancing holesaw making the holes in the stainless a couple mm bigger on the slide. This resulted in the vents not being able to be closed up completely. Not a massive issue but frustrating none the less, we let it ride and continued on with a frame.

The stack was made up for me by a fabricator we use at work, 4 inch polished stainless pipe and a shade of 35 inches long. We cut at 22.5 deg and TIG welded to create a 45 deg into the side of the CC. Due to the ellipse shape we oxy cut this out and tidied up with a flapper disc on the angle grinder.

IMG_0543[1].JPG

• nikkidee
• Aug 24, 2017

IMG_0546[1].JPG

• nikkidee
• Aug 24, 2017

Some standard BBQ grill plates were butchered to suit and a 90 deg flange tacked in to support them. below photo shows these in place and the stack tacked in place just above the grill height...can also see the RF plate which ended up being 6mm (1/4in) plate.

DSC07491.JPG

• nikkidee
• Aug 24, 2017

Once everything was tacked in place we finished it off with the MIG seam welding where necessary and stitching where we could to avoid putting too much eat into the thing and risking warping. The tank is only 4.5mm thick (about 3/16th)

Using a caustic soda (Sodium Hydroxide) paste I carefully coated and covered the powder coat to 'soften' it for 24 hours. After rinsing off with water then vinegar to neutralise I hit it with the wire wheel on the angle grinder. With all the bits we'd received for free this whole build was running us at about $100AUD ($5USD) so the initial plan of sand blasting and powder coating went out the window and a few cans of pot belly black paint were subbed in.

DSC01241-min.JPG

• nikkidee
• Aug 24, 2017

DSC01245-min.JPG

• nikkidee
• Aug 24, 2017

Still got a few things to do, and a few more coats of paint to put on, but we're nearly ready to season and get smoking.

 

[ahumadora]

Very clean build.Nice work.

Note to pit builders here.   Much easier to cut a hole for square stack with a grinder than round.

post some food pics!