Trouble with stack size need some help!

Jmunson_3 · Post by **Jmunson_3** » April 10th, 2015, 11:01 am

Hi guys I'm new to the forum and reverse flow smokers. I have cooked on several different reverse flows but now I've decided to build my own! I have a 250 gallon propane tank, it has the shallow caps on it, I will have a 30" diameter by 28" firebox to match tank diameter. I have run all my numbers through the feldon calculator a hundred time and have pretty much everything I need. My problem is with my firebox, intakes, CC opening, etc... I will need to run a 5" stack at 50" long from the top of the tank, easy enough but I can't find any 5" to save my life lol. I can decrease diameter but then I'll be longer and this rig is goin on a trailer with roof. Using 4" I'll will be almost 14' tall from the ground to the top and that's a little to tall! Basically I am trying to figure out if I can run dual stacks of say 3" and still have enough length to get past my roof or is dual stacks a big no no on RFS? Any input would be appreciated and don't get offended if I have no idea what you are talking about and ask a million questions lol I'm a newbie!!!

motoridr09 · Post by **motoridr09** » April 10th, 2015, 1:59 pm

You could go with square tubing instead of round pipe. Or make your own rectangular stack to your own dimensions to make it the exact height you want by making it wider or narrower to get the right volume while making it high enough for your roof but not a flagpole sticking out. 4" square tubing will be close to the same volume as 5" pipe, little less but close. Also, dual stacks will work as far as I know. Hope this helps.

Post by **Rodcrafter** » April 10th, 2015, 4:11 pm

The dual stack option will work fine but they will need to be on the same end of the CC for the Rf to work right. Some folks weld them right together. Just use the size pipe you have for the calc and cut it in half to get the right length..

jm2cw

forty_creek · Post by **forty_creek** » April 10th, 2015, 10:58 pm

What RC said! I asked a similar question on my build. Since you are new and I'm barely ahead of you by on a few months maybe this will help.
If you have 4" pipe and the calculator says 40" tall. Make two exhaust 20" tall out of the 4" pipe. Or make your own custom exhaust like motor said. Some of these pros it's like adding 1+1 with us newbies questions. Sometimes we aren't for sure where the 1 came from. As you get in it. Keep asking questions. But we do like pics. Look at me 3-4 month member using "we".
I used Feldons calculator also until I found this site. Look for the site's calculator on the main forum page.

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noXcuse · Post by **noXcuse** » April 11th, 2015, 7:02 am

If you have a Napa Auto close to you, they sell 5" exhaust pipe for like $10/ft. That's what I bought for my smoker. But yes, that is very tall. I'd use 6" pipe and bring it down to somewhere close to 30" tall.

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noXcuse · Post by **noXcuse** » April 11th, 2015, 7:04 am

Any big truck shop should have 6" exhaust pipe laying around. Metal scrap yards, steel yards, etc.

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THEFERMANATOR · Post by **THEFERMANATOR** » April 11th, 2015, 11:00 am

I found a shop that worked with underground water lines, and got a section om EMT tubing from them in painted steel. Took me 5 minutes with a grinder to take the old paint off ,and I was left with a NICE steel pipe that wasn't so thick and heavy I had to worry about bracing it.

SmokinFF · Post by **SmokinFF** » April 11th, 2015, 7:34 pm

How tall is your roof above your smoker? Figure the height of that and get it through the roof. The length of that stack may change your diameter of pipe needed.

Jmunson_3 · Post by **Jmunson_3** » April 11th, 2015, 11:37 pm

Thanks guys I did think about 5" exhaust pipe which is probably what I'm gonna go with just to stick with the whole keep it simple thing lol. But I am kinda basing my diameter off of how high my roof will be and the total finished height of the rig but I really appreciate all the feedback and I will try to get some pictures up as I go just to get some input in case there is something I'm overlooking that y'all's experienced eyes might catch. Thanks again guys!!!

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