Building an Offset Barbecue Smoker – Part Two
If you’re just now jumping on board my “building an offset smoker” wagon, you should probably go and read part one first. This post will make a lot more sense!
Once we get to this part of the build, it’s important to note how much support I needed – physically – but also with strategy. Propane tanks are big, and heavy, and kind of dangerous. I wouldn’t have been able to do it without Monte coaching me through it all. He is a jack of all trades, the kinda guy who – rather than going out and buying a part, is more likely to fabricate and build the part instead. And build it better. He’s known for being able to build just about anything – from restoring and modifying classic cars to houseboats and Swiss family Robinson styled camps on the river with everything in between.
Without his use of the forklift and tractor, moving this hunk of steel would’ve been practically impossible. I’m also positive I wouldn’t be as happy with the results as I am because of his guidance and “suggestive” direction. It wouldn’t have come together like it did without him. Bottom line.
Joining the Tanks
This was the most difficult and annoying part of the entire process. Joining two round tanks in a way that looked acceptable while still being functional was a test of patience. Monte made most of these cuts with the torch as it would’ve taken me years with the grinder. I found a calculator relating to thermodynamics including input and output and came up with a size estimating the volume of the tank against the draw of the smokestack. I also calculated the size of the hole on the firebox to be big enough to pull hot air from the fire into the cook chamber – and then ultimately out the smoke stack. The is pretty complicated, as you want hot air to enter the cooking chamber quickly, but then you don’t want it to exit too quickly – or inefficiently. I suggest doing some basic research and spend some time on the math here – it’s pretty important. Lastly, began the process of welding these two giant hunks of steel together.
I took an afternoon to do some of the easy stuff and built the sliding grill grates, as well as the rails inside the cooker. Once they were in place, took a little off the lower ledge and they slid in and out really easily
Luckily, I received a piece of salvage pipe for free and used that for the smokestack. The entire smokestack design is hard to explain, but it’s pretty easy to see how it was built from the pictures. Basically, we boxed out a section of the tank, built a support system for the pipe, and enclosed the whole thing in plate. I’m really happy with how it turned out.. The idea is that you get as much of that stale smoke out of the tank at grate level, while keeping as much of the heat as possible inside.
If you read part one, you know that this beauty is a 1969 boat trailer (repurposed, of course). The trailer had to be modified to support the weight of what would ultimately be two tanks. Some things I replaced: the axle with a new 2000-pound axle, wheels, and tires. We cut out the old tongue and replaced it with a heavy duty piece of pipe to lengthen the trailer a few feet and beefed up the whole thing with some heavy-duty cross supports that were salvaged from an old hog pen gate (oh, the treasures you find in Springfield, Louisiana).
Firebox Door and Insulation
I wanted to insulate the firebox from the start. I’ve read and I truly believe that an uninsulated firebox will use at least twice the amount of heat that a insulated firebox would. With the leftover second tank I purchased, I essentially cut a section to act as a sleeve to slide inside the outer piece that was already welded to the tank. This would allow far less heat to leak through the steel and keep it warm and toasty inside. Welded a few pieces of angle iron in the bottom as rails for the sleeve to slide in. This was a pain but worked well after a few adjustments. Then, welded a piece of flat bar in the back to prevent ash from going between the two layers. Marked a door on a piece of plate and cut it out. Finally, I welded the entire flat plate (complete with already-cut hole) to the end of the firebox and cut the corners off with a torch. Cleaned up all those edges and added hinges like the main firebox doors.
Burning out the Tank and Sandblasting
After all of this, the tank will still stink. There is a chemical in propane called Ethyl Mercaptan that is put in the gas to make it stink so you don’t blow yourself with the odorless propane. The best way to get rid of it is to build a big fire in the cooker and it’ll be gone for good.
Work Surfaces and Final Touches
Now, we are seeing an end in sight! From here, it was the small details to cover. The last thing to do was to install the work surfaces and something to cover and dampen the smokestack in case of rain or for storage. Made an eclectic “A”- shaped piece that Cait calls “The Bird” and welded it up top with a couple of fins for support when it’s wide open. One of my favorite touches is the slide in water pan that is above grate level which makes it super easy to fill and keeps it out of the way of everything else.
We painted everything in about 2 hours. Used a Rustoleum gloss black paint primer combo for the trailer, and used a Rustoleum high temp paint for everything else. I helped with the trailer and Caitlyn used an electric Wagner sprayer to do the body. She’s far better at making things look good than I am.
The last step is to season it. Caitlyn, bless her sweet heart, helped me rub a half gallon of lard all over the inside of the cook chamber before we burned a hot fire for about 3 hours. This process is very similar to seasoning a cast iron pan and just as important to protect against rust. The outside is protected by the paint and primer, the inside is not.
I was happy with how the dynamics of the cooker worked, although knew I was going to need to make a few modifications. I opened up the throat (the area between the firebox and the cook chamber) about fifty percent. I needed more heat passing into the cook chamber, and I installed another seal at the top of the cook chamber doors as I had some smoke leaking around the doors.
It’s kind of weird and a little bit sad for me being finished with the build. I’m sure there are more tweaks that will need to be made in the future, but for now it’s ready to cook. Last year at this time, I would’ve never been able to finish a project like this because of my lifestyle, let alone in four months. Crazy how much things can change in such a short amount of time…
We’re already planning some BBQ’s and look forward to having y’all over. In the meantime, if anyone is interested in sitting by the smoker and chatting about BBQ – you know right where to find me.