I'm about to start....

[DJC62]

I'm about to start my 250 gal reverse flow build. I've used all the calculators and have all the dimensions nailed down I believe. I've been lurking, researching, etc on the various boards a long while now to the point I think I'm ready to go except for one thing. Simple as it is, it's really important I believe. How do I accurately mark my cutout around the domed end of the cooking chamber so it's straight and lined up providing proper fitment for the firebox? I've measured 18.5" from top center of the chamber (which will be bottom center when flipped over) down each side but from that same point down the dome is going to be a little different as there is a short bit that is flat before the curve begins which will throw that measurement off. So how does everyone make accurate cut marks? Has me stumped on how to go about is as I don't want to mess up this cut.

Thanks in advance guys. I'm sure one of the smoker brains on here will have a simple answer that I'm over looking.

 

[radioguy]

Im a big fan of mocking up in cardboard. Make your mistakes in cardboard first. Invest in one of these.

.

RG

 

[DJC62]

That might work, thanks for the suggestion. I can see where this could be useful for other projects so it certainly wouldn't be a 1 time use item. I just got back from my nearest big box store, bought a 8' length of I think it's paneling trim. Going to make a mark down by the dome and the back towards the center of the cook chamber, on both sides and tape it in place. It bends easy around the dome but still has the strength to not sag or anything like that. Should be able to adjust as needed until I've got it like I want it, then mark my line. You know, I've been using the calculators, measuring my tank, reading EVERYTHING I can find then I go out to start marking my cut lines and I'm like, how am I going to make this straight, lined up, etc. Geesh. I hope I don't run into many more of those. Calculator I think Dave posted helped a lot with my segment, arc and such measurements. I used Feldons for fire box size, stack height and so on. I've been flushing my tank, getting ready for my cutting all summer. I'm so anxious to get started on this build and am trying to figure out as much as I can ahead of time as I want it to turn out really nice. Time will tell.

 

[daveomak]

Set the CC level on the ground... Mark the proper height of where you want your cut.... Using a laser level, follow the dot/line around the tank and mark as you go....

Are you using this tutorial to build your smoker....

Standard Reverse Flow Smoker Calculator... by DaveOmak and others... Ready to use.. rev5.. 6/19/15.

Here's to "Alien BBQ" and the folks that first put the calculator together and "1728 Software Systems" for this great "Circle Calculator" and all the folks at "SmokingMeatForums", with a special shout out to Ribwizzard, that contributed their ideas and feedback while this thing was coming...

www.smokingmeatforums.com

..

 

[DJC62]

Hello Dave. Yes I am. I've used the calculator, can't tell you how many times I've gone through it using different measurements as I tweaked the size of vents, stack, firebox, etc. I've also used Feldons for comparison, trying to make sure I'm on track. Any hints or tips as I get going? This is a propane tank build, will be on a trailer once I find a suitable one. Tank size is 30" diameter and about 94" long. I'm planning on a 30" wide, 26" tall, 24" long firebox. 2 doors on the CC. Everything I build will be out of 1/4" new metal. Planning vents on bottom of firebox on both sides and top vent on the firebox door. I'm going with a 7" OD (probably around 6.75" ID stack around 30-32" above the CC and mounted at the top of the CC, extending 4-6" inside the CC but cut at an angle with the angle facing the CC, going to be 2 cooking grates, the bottom grate should be in the neighborhood of 5" above the reverse flow plate, planning on a 1-1.5" dam at the bottom of the cooking chamber to firebox to block grease and so on. Plan on using 7018 DCEP for most welds but will probably MIG where necessary.
I did get the tank cut open yesterday afternoon, went easy and uneventful. My house, shop and barns are still standing!

 

[daveomak]

30-32" above the CC may work OK, from what I have read, to get the optimum draft, 35" "seems" to be the magic number..

 

[DJC62]

I think I'll go a little longer than I planned, can cut it off easier than add to it. Thanks Dave.
Also, my firebox is at the bottom end of the size range, Using the calculator here and Feldons I get a firebox size of 19,050-19,250. My planned size comes out at 18,720. Do you think I should bump that up or is it in the ballpark and not be an issue? I could change the length from 24 to 26 and be about 1,000 over the recommended cubic inches recommended.

 

[daveomak]

Base the FB on the size of the CC... ~22,000 c.i. .... 19,000 is close enough... If your firewood is 24" then I would go with 26"....