First time RF Build Super Noob

Discussion about Reverse Flow Smokers
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JollyMeyer
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First time RF Build Super Noob

Post by JollyMeyer » June 19th, 2019, 9:25 am

Hi Folks!
Just some background: I am a Canadian interested in firing up some smoky goodness and have been lurking about on the topics of building and smoking meats for the last few months now. I am by no means an expert welder, fabricator of the sort, but enjoy using my hands building things in efforts to grow my experience and save money. Here I am in my first build ever, in the final stages of design to build a reverse flow offset smoker. I am looking for recommendations, and opinions on what I have for my smoker build. Below are my design dimensions, and calculations.

What I am working with:
Cooking chamber and fire box will be constructed with 1/2” thick 24” (outside diameter) steel.

Dimensions: Diameter shown is inside diameter.
Cooking chamber (CC): 23”(dia.) x 40”; Vol= 16619.03 cubic inches
Firebox (FB): 23”(dia.) x 15” Vol= 6232.134; 12.5% larger than recommended.
Firebox to Cooking Chamber opening: 53.78 square inches; 10% larger than recommended.
FB to CC opening is a ‘football’ shape that is 6 3/8” in height and as a consequence FB will extend 17 5/8” below the CC.
Baffle plate: 20 1/16” x 37 15/16” x 0.25” (Opening of baffle plate is equal to area of FB to CC area).
Chimney: 3” (dia.) x 44”; Vol=311.6 cubic inches equal to recommended size.

I have used Feldon and Smoker build calculators to determine the required volumes/areas of the smoker. Moreover, I am well aware of the consequence in regards to the 1/2” thick steel unfortunately beggers can’t be choosers, it was free. I am open to any criticism of the design!

The questions I have are components I am not 100% certain of, and are below.

1.0 Firebox:
(1.1) Should I place two doors or one door? If I have, one door, is it more optimal to have the door on the side of the firebox or the at the top?

(1.2) How high is the charcoal grate placed from the bottom of the Firebox?

(1.3) Should I have an inlet opening placed below the charcoal grate and one at mid fire basket height?

2.0 Baffle Plate:
(2.1) Should I make the plate removable, or just fix it to the cooking chamber? I feel as if this is a very uneducated question. The reason I ask this is because I was thinking I could place a charcoal grate and turn the cooking chamber into a BBQ. I have 0 experience with an offset smoker and I really can’t help to play around with it and experiment; I have heard some people say a good offset smoker could grill steaks like a bbq. If you have opinions and sources on this please share!

(2.2) Is it recommended for me to have the baffle plate on a slope?

(2.3) Should I bother placing a ‘fall’ for the baffle plate at the firebox to cooking chamber opening?

3.0 Cooking Chamber:
(3.1) How far should I place the cooking grate from the baffle plate? I’ve seen some numbers varying from 4” above the baffle plate to 9”?

(3.2) How large should I cut out the door, or rather how far back on the smoker? I am still undecided if I should stick with 1 door or have two doors. Reason for two doors would primarily be to reduce the weight of the door given it is ½” thick steel.

(3.3) What is a comfortable height to have the smoker at? This will probably take some playing around with hope to have some ball park numbers to play around with.

4.0 Chimney:
(4.1) I intend to put the chimney at the same level of the cooking grate, is this acceptable?

(4.2) Does a horizontal portion of the chimney count towards the chimney volume? Some smokers I’ve seen have the chimney approximately 4-6” horizontally away from the CC and then go upwards, does that horizontal section count towards my required volume?

(4.3) Should I consider larger diameter and smaller length or small diameter and larger length? If I use 4” pipe I only need 24” in length, but if I use 3” pipe I need 44”, does this matter? These were determined by the recommended volume 311.6 cubic inches.

(4.4) How do I size a plenum and is it worth doing?

Thanks, and look I look forward to your feedback and advice.

Jolly!



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Re: First time RF Build Super Noob

Post by towtruck » June 19th, 2019, 12:52 pm

JollyMeyer wrote:
June 19th, 2019, 9:25 am
Hi Folks!
Just some background: I am a Canadian interested in firing up some smoky goodness and have been lurking about on the topics of building and smoking meats for the last few months now. I am by no means an expert welder, fabricator of the sort, but enjoy using my hands building things in efforts to grow my experience and save money. Here I am in my first build ever, in the final stages of design to build a reverse flow offset smoker. I am looking for recommendations, and opinions on what I have for my smoker build. Below are my design dimensions, and calculations.

What I am working with:
Cooking chamber and fire box will be constructed with 1/2” thick 24” (outside diameter) steel.

Dimensions: Diameter shown is inside diameter.
Cooking chamber (CC): 23”(dia.) x 40”; Vol= 16619.03 cubic inches
Firebox (FB): 23”(dia.) x 15” Vol= 6232.134; 12.5% larger than recommended.
Firebox to Cooking Chamber opening: 53.78 square inches; 10% larger than recommended.
FB to CC opening is a ‘football’ shape that is 6 3/8” in height and as a consequence FB will extend 17 5/8” below the CC.
Baffle plate: 20 1/16” x 37 15/16” x 0.25” (Opening of baffle plate is equal to area of FB to CC area).
Chimney: 3” (dia.) x 44”; Vol=311.6 cubic inches equal to recommended size.

I have used Feldon and Smoker build calculators to determine the required volumes/areas of the smoker. Moreover, I am well aware of the consequence in regards to the 1/2” thick steel unfortunately beggers can’t be choosers, it was free. I am open to any criticism of the design!

The questions I have are components I am not 100% certain of, and are below.

1.0 Firebox:
(1.1) Should I place two doors or one door? If I have, one door, is it more optimal to have the door on the side of the firebox or the at the top?
If you make one door make it on the side so you can get ashes out easier.
(1.2) How high is the charcoal grate placed from the bottom of the Firebox?
Three to four inches is enough
(1.3) Should I have an inlet opening placed below the charcoal grate and one at mid fire basket height?
Just below is all that is needed
2.0 Baffle Plate:
(2.1) Should I make the plate removable, or just fix it to the cooking chamber? I feel as if this is a very uneducated question. The reason I ask this is because I was thinking I could place a charcoal grate and turn the cooking chamber into a BBQ. I have 0 experience with an offset smoker and I really can’t help to play around with it and experiment; I have heard some people say a good offset smoker could grill steaks like a bbq. If you have opinions and sources on this please share!
Plate needs to be fully welded in and have a dam at the far end
(2.2) Is it recommended for me to have the baffle plate on a slope?
No
(2.3) Should I bother placing a ‘fall’ for the baffle plate at the firebox to cooking chamber opening?
No
3.0 Cooking Chamber:
(3.1) How far should I place the cooking grate from the baffle plate? I’ve seen some numbers varying from 4” above the baffle plate to 9”?
4" is good
(3.2) How large should I cut out the door, or rather how far back on the smoker? I am still undecided if I should stick with 1 door or have two doors. Reason for two doors would primarily be to reduce the weight of the door given it is ½” thick steel.
Most go 1" behind top center and 1" below widest part in front. The top cut keeps water out and the bottom cut lets the bottom grate be at the widest part.
(3.3) What is a comfortable height to have the smoker at? This will probably take some playing around with hope to have some ball park numbers to play around with.
Counter top height works for me
4.0 Chimney:
(4.1) I intend to put the chimney at the same level of the cooking grate, is this acceptable?
I have no input there
(4.2) Does a horizontal portion of the chimney count towards the chimney volume? Some smokers I’ve seen have the chimney approximately 4-6” horizontally away from the CC and then go upwards, does that horizontal section count towards my required volume?
No
(4.3) Should I consider larger diameter and smaller length or small diameter and larger length? If I use 4” pipe I only need 24” in length, but if I use 3” pipe I need 44”, does this matter? These were determined by the recommended volume 311.6 cubic inches.
It all matters where you want the smoke to come out...most want it out of their face
(4.4) How do I size a plenum and is it worth doing?
I'd poke that exhaust in at the top and not worry about it...but that is me
Thanks, and look I look forward to your feedback and advice.

Jolly!
Welcome. I bolded my answers in your post....take note I am no where near an expert but I do have a 1/2" thick smoker. It takes a solid hour or more to get it up to temp.

You also want a dam or lip from the bottom of the cc at the fb opening so any drippings that may get under the plate don't get into the fire box.



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Re: First time RF Build Super Noob

Post by Big T » June 19th, 2019, 5:51 pm

Welcome aboard!


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Re: First time RF Build Super Noob

Post by JollyMeyer » June 19th, 2019, 10:32 pm

Thank you for the welcome!

Thanks Towtruck for the time to answer my questions. I will add the adjustments to my drawing, once I have a bit more time I'd be more than happy to post it. I did cut the plates for the throat that are welded to the CC and FB. Hope to weld them onto the pipes this coming weekend.

I do find the FB a bit of a weird geometry given the dia. will be 24" (outer dia.) x15". I may just end up making two doors, or else I'll have to bend down at at the side door to feed the fire.



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Re: First time RF Build Super Noob

Post by Dirtytires » June 19th, 2019, 11:11 pm

Welcome to the crew.

Just my experience but you will get more opinions if you cover only only a few points in a post. A lot of members do this on their phones and won’t respond to a long post.

Interested to see what you design.



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Re: First time RF Build Super Noob

Post by Pete Mazz » June 20th, 2019, 4:22 am

I"ll add that you make a charcoal basket "V" shaped and add an ash pan, or simply a curved plate for cleanup.


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Re: First time RF Build Super Noob

Post by JollyMeyer » June 20th, 2019, 10:12 am

Thanks for the tip, I'll make a shorter posts next time.

In regards to the v-shape basket, should design it running parallel to the direction of the firebox or perpendicular? I'll have to pick up some grate material soon.



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Re: First time RF Build Super Noob

Post by Pete Mazz » June 21st, 2019, 3:43 am

Image


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Re: First time RF Build Super Noob

Post by mp4 » June 21st, 2019, 7:04 am

I originally made mine too low and the ash would pile up to the grate. I raised the grate high enough that I could place wood under it to pre-heat. It works great now...ImageImageImage



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Re: First time RF Build Super Noob

Post by JollyMeyer » June 27th, 2019, 11:47 am

Wow those look great! I'll definitely consider this, I assume your air intake on the FB is towards the bottom?



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Re: First time RF Build Super Noob

Post by mp4 » June 27th, 2019, 7:04 pm

JollyMeyer wrote:Wow those look great! I'll definitely consider this, I assume your air intake on the FB is towards the bottom?
Absolutely - as low as you can reasonably get it.



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Re: First time RF Build Super Noob

Post by Dirtytires » June 27th, 2019, 9:06 pm

Make sure you leave room for an ash pan....



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Re: First time RF Build Super Noob

Post by JollyMeyer » June 28th, 2019, 10:17 am

I have some extra plate I can make an ash pan with! Has anyone had issues with ash covering up the intake; I assume that what the ash pan is for too.



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Re: First time RF Build Super Noob

Post by Dirtytires » June 28th, 2019, 10:33 am

You have to mount the intakes a bit up off the bottom. Most people don’t want hot ash dropping out the vent during a cook. And no, don’t cover or block any part of it with the ashpan.



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Re: First time RF Build Super Noob

Post by mp4 » June 28th, 2019, 8:18 pm


JollyMeyer wrote:Has anyone had issues with ash covering up the intake; I assume that what the ash pan is for too.
Not that I know of. My problem originally was that the ash piled up beneath the fire so it didn't get good air flow.



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