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250 Gallon Reverse Flow FIRST BUILD!!!

post #1 of 77
Thread Starter 

Hey everyone,

   New to the site as of today. Been reading literally all day today. My brother and I just got a 250 gallon propane tank and we're going to start our reverse flow smoker build tomorrow. Figured I'd start a thread now as I will be posting pictures of the progress as we get various things done. I think I've got all my calculations done using various calculators I've looked at posted in these threads. I guess I'll just start today with one question and post others as they arise. I'm going to have a 6" chimney that is 40" long. My question is how close to the cooking grid does this need to be? Also I've seen some with holes drilled in them inside the CC but most I've seen are just cut at an angle. I think cut at an angle with the open side facing into the CC looks best but I've saw several different pictures as far as how far down into the CC the chimney should go. Thanks in advance for all the advice. Can't wait to post progress pictures.

post #2 of 77
Some folks drill holes near the top of the CC, in the exhaust stack, to insure there is no "dead zone" in the CC...
post #3 of 77
Thread Starter 


ok I see. So like I mentioned I didn't see anywhere in the calculators where it said how close to my cooking grates the exhaust needs to be. Is this something that's imperative to flow?

post #4 of 77

Most people put the vent at or very near the top of the cook chamber. That is where the heat stacks up and heat is what generates flow out the chimney. Higher is better for an efficiently flowing reverse flow smoker.

post #5 of 77
Thread Starter 


Ok, I will keep that in mind. Quite a ways from there but I've got a good idea on other aspects of the build. We're going to pick up an old trailer or axle this evening and hopefully start cutting on the doors!!!! Thanks for the info guys. I will post more as more questions arise.

post #6 of 77
Thread Starter 

Ok everyone, another question has come up in the planning phase. In regards to the smoke stack, is it better to come down in from the top of the smoker or better to fabricate a box off the side that the stack gets attached to? Does one promote better/more even heat and air flow? I feel like this would make a difference in the air flow but I've seen several with the attached to a box fabricated off the side of the smoker.

post #7 of 77

I don't think it matters one way or the other as far as how well it draws. Most builders position the stack due to other considerations. such as door clearance, grate space, or just plain how it looks. I have seen each configuration on many different smokers that all worked well.

post #8 of 77
Thread Starter 

Sounds good. Thanks for the reply. I think I'm just gonna come in from the top rather than fabricate a box or the stack on the side. Thanks again for the response.

post #9 of 77
You're welcome.
Take lots of pictures.
We love pictures.
post #10 of 77
Thread Starter 

ok new question has arise regarding smoke stack. Right now my calculations have me using a 6" pipe 40" long. Is it better to use an 8" or 10" shorter pipe or does it matter. I think an 8" would need to be 27" approx. and a 10" needed to be about 18". has anyone experienced any pros or cons of using bigger/shorter pipes? Thanks in advance for any advice.

 

PS. we got our trailer and we're gonna start tearing it apart and getting it ready to mount the tank. Just need some time and good weather. pics will come when we start work.

post #11 of 77

Go with the 8" and 28-30", you need some height to produce draft.

post #12 of 77
Thread Starter 
Quote:
Originally Posted by LenDecaturAL View Post
 

Go with the 8" and 28-30", you need some height to produce draft.


Thanks for the response Len. That's what we'll do

post #13 of 77

Recommended  stack volume for a 250 gal. is 981.8 cu. in.

 

8" stack should be 19.5"

 

7" -  25.5 "

 

6"  -  34.7

post #14 of 77
Thread Starter 
Quote:
Originally Posted by gary s View Post
 

Recommended  stack volume for a 250 gal. is 981.8 cu. in.

 

8" stack should be 19.5"

 

7" -  25.5 "

 

6"  -  34.7


Which calculator is this using? I used Feldon's. I know I've read there are some flaws but the calculator on these forums wont load for me for some reason. According to Feldon's stack should be 5% of firebox. my firebox will be 30x30x30 (planned) and it says stack should be : 6"- 47.77", 8"- 26.87". Like I mentioned Feldon's is the only calculator I can get to work on either of my computers

post #15 of 77

Use the hand calculations Dave put together here: http://www.smokingmeatforums.com/t/172425/standard-reverse-flow-smoker-calculator-by-daveomak-and-others-ready-to-use-rev-4

 

The CC/FB measurement is the problem with Feldons as well as the fact that it is firebox not cook chamber based.  Feldon's also has a note on the chimney section that they should be between 30 and 40 inches tall to promote better draw.

post #16 of 77
Thread Starter 


I promise I'll eventually post some pictures on here just haven't had the time. Plus I'll be out of town all next week so hopefully next weekend we'll make some visible progress. HOWEVER, I hit the jackpot today!!!!! My dad works at a local welding shop that builds flatbeds and bail bed and he is gonna be able to get us a 5x10x1/4" sheet of steel with all our dimensions laser cut for $200. Working somewhere for 25+ years comes in handy sometimes.

post #17 of 77
Thread Starter 

Ok, I'm starting to feel like everyone is going to get tired of me asking all these questions, but my brain hurts trying to get my fb/cc opening figured out. I know what I need for sq in. per the calculator provided by Len. I need 258.02 in sq. Using the circle calculator that is giving me a segment that is 29" W and  12" H. That's simple enough although the ID of my tank is only 29.5" which means the segment is as wide as the ID of my tank meaning I have to mount my FB exactly halfway up on the end of my tank for it to fit. That can't be right. I don't see any others mounted that high. UGH. this probably makes no sense and I'm sure I'm over thinking things here but I just can't wrap my head around it.

post #18 of 77
Not that this is going to be of much help. I have seen Dave mention frequently that the firebox should be as wide as the rf plate. That being said the rest is just process of elimination, is it not?
post #19 of 77
Quote:
Originally Posted by tykenn28 View Post

Ok, I'm starting to feel like everyone is going to get tired of me asking all these questions, but my brain hurts trying to get my fb/cc opening figured out. I know what I need for sq in. per the calculator provided by Len. I need 258.02 in sq. Using the circle calculator that is giving me a segment that is 29" W and  12" H. That's simple enough although the ID of my tank is only 29.5" which means the segment is as wide as the ID of my tank meaning I have to mount my FB exactly halfway up on the end of my tank for it to fit. That can't be right. I don't see any others mounted that high. UGH. this probably makes no sense and I'm sure I'm over thinking things here but I just can't wrap my head around it.


It will work... your tank should be about 80" long.... Plenty of room for food.... Main food rack and an upper removable rack...

I figured a 250 gal. 14.5" radius, 11" seg. hgt., 229 seg. area. and the chord AB 28.14" (RF plate Width)
post #20 of 77
Thread Starter 

Yeah I've been looking at other threads and I think I'm just sitting here at 1140 at night over thinking things. I just need to trust the #'s and get to work. It'll come together. Thanks for the reinforcement on the numbers. What you posted is pretty damn close to what I got +/- a few inches.

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