Hybrid Smoker. Can it be done? How to calculate?

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Sleeman
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Hybrid Smoker. Can it be done? How to calculate?

Post by Sleeman » June 12th, 2019, 1:36 am

This is my first post on this site. It seems like if you look back through all the posts in this forum you can find answers to most of your questions but it does take time to look so If this has already been discussed, please send me to the right thread.

This will be my second build. Although my first smoker was good in concept and I was able to produce some good product with it, I eventually learned from sites like this that it was not well designed. I built it before there were online calculators (even before Feldon's) to help with sizing and one of the biggest mistakes I made was making the FB too small. It worked but took a lot of effort. What I am hoping to achieve with my new design is a hybrid smoker. As someone said in another post, most of us are trying to design a smoker that can do all the things we need it to so we only have to build one good one. So here is my idea:

I want to build a horizontal reverse flow (rectangular chamber) with offset FB (square) and a VC (rectangular) above the FB. I would like to be able to isolate the horizontal RF from the VC and use the VC as a WB if needed (top of FB will be bottom of VC). I would also like to isolate the VC from the RF and use just the VC for smaller cooks OR use it as one large smoker - an RF with a VC at the end.

I have been doing as much research as I can into getting the sizing right to design my new build but I am not sure exactly what or how to input the data into the calculators or if this is even possible. If I input all the numbers based on using the smoker as one large unit then the FB is way too big if I just use the RF or VC by themselves.

Do I treat it as one large RF and use the VC as part of the chimney when in that configuration and have a chimney on each CC for when the are isolated OR do I treat them as two separate CC and not let the air flow through the RF into the VC but open dampers that allow the FB to feed both the RF and VC at the same time and another set of dampers to isolate them?

Can this be done and achieve consistent temperature throughout both CC's?

Lots more questions about this but maybe we just start with letting me know if this is possible.

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Re: Hybrid Smoker. Can it be done? How to calculate?

Post by ajfoxy » June 12th, 2019, 1:38 am

Very nice build that... hate to have to move it though... :D


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Re: Hybrid Smoker. Can it be done? How to calculate?

Post by mp4 » June 12th, 2019, 3:55 am

Only use the horizontal cook chamber in the calculations and you'll be good to go.



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Re: Hybrid Smoker. Can it be done? How to calculate?

Post by Frank_Cox » June 12th, 2019, 7:38 am

When you say Hybrid are you wanting one long cook chamber with half RF and half traditional offset?
When we design our style of hybrid we make the entire cook chamber able to cook as a reverseflow smoker or a traditional offset. We use our calculator (found at bbqpitcalculator.com) which works for both styles. then we cut the baffle plate into short pieces we call tuning plates ranging from 12" to 6" and install them on a rail in the cook chamber where the baffle plate would normally got. we place a smoke stack at both ends of the cook chamber. both are the size the pit calc recommends. when running the pit you move the tuning plates all to the firebox side and leave your gap at the opposite end. when running as a traditional offset remove one tuning plate and put gaps between the tuning plates to control your temp zones. the gaps are typically wider where you want the hot temp zones and shorter where you want the lower temp zones. As for the vertical cabinet, you do not need to factor that into your numbers like mp4 said. only the horizontal cook chamber.
Hope that helps!


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Re: Hybrid Smoker. Can it be done? How to calculate?

Post by Sleeman » June 12th, 2019, 8:34 pm

Hi Frank

Based on your explanation I think I have used the term "hybrid" incorrectly I just didn't know what else to call it.

Just like in a lot of your Smokerbuilder plans I have seen, I want to build a standard horizontal reverse flow smoker (rectangular chamber) with FB on the left (square) and a WB (rectangular) above the FB.

When used in this configuration what is the WB used for?

What I am wondering is if it is possible to do the following, using dampers or sliding doors to change the configuration of the smoker:

1. I would like to be able to isolate the horizontal RF from the WB and use the RF only.
2. I would also like to isolate the WB from the RF and use the WB as a VC for smaller cooks
3. Use it as one large smoker - an RF with a VC at the end.



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Re: Hybrid Smoker. Can it be done? How to calculate?

Post by Pete Mazz » June 13th, 2019, 3:31 am



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Re: Hybrid Smoker. Can it be done? How to calculate?

Post by Sleeman » June 14th, 2019, 10:10 pm

Peter

Thank you for sending me to that link, It is exactly what I am trying to do.

Frank

I am not a welder but I am a General Contractor so I can appreciate quality craftsmanship when I see it. I have followed a few of your builds on this site and I am impressed by your quality and attention to detail. I wish you guys were closer or I knew how to weld because there is no one near where I live that is building smokers like you guys do.

For calculating a smoker like this:

To calculate the FB, as mp4 said above, I should only use the horizontal cooker dimensions and not include WC but, do I include the size of the gap between the bottom of the smoker and the BP as part of the CC? I already have the outer dimensions of my horizontal smoker and WC so if the height of my horizontal smoker is 24" including the 8" space for that gap (arbitrary number, not sure how to calculate the actual size), I use 24" NOT 16"?

If I insulate my smoker and FB as you did in the Mack build, do I use the inner dimensions to calculate sizes?

Do chimneys need to be square or round? Can they be rectangle, or any shape as long as they have the same volume as the calculations say? Is there any benefit to dropping the chimney into the chamber?



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Re: Hybrid Smoker. Can it be done? How to calculate?

Post by Pete Mazz » June 15th, 2019, 3:16 am

I should only use the horizontal cooker dimensions and not include WC but, do I include the size of the gap between the bottom of the smoker and the BP as part of the CC?
Yes. Use the entire volume .
If I insulate my smoker and FB as you did in the Mack build, do I use the inner dimensions to calculate sizes?
Yes.
Do chimneys need to be square or round? Can they be rectangle, or any shape as long as they have the same volume as the calculations say? Is there any benefit to dropping the chimney into the chamber?
Round has the least friction loss. Use my Square Stack Calculator (see my sig) to get equivalent volume of a square or rectangular stack.

Some folks think it helps, others don't . Only figure the height of the stack above the CC


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Re: Hybrid Smoker. Can it be done? How to calculate?

Post by Sleeman » June 17th, 2019, 12:04 am

Looking through the posts on that build, Frank says that he only insulates his FB and not the CC or WB, I assume this is partly due to the entire smoker being built of 1/4" steel? If my CC and WB will be made of lighter gauge steel would it be a good idea for me to insulate?

How do you calculate the size of the openings from the

CC to WB - same size as the opening from the FB to the CC?

FB to WB - can this opening be small since it is direct from the FB?

How do you calculate the height from the bottom of the smoker to the BP? Is short and wide (4" H x 20" W) better that tall and narrow (8" x 10")?



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Re: Hybrid Smoker. Can it be done? How to calculate?

Post by Big T » June 17th, 2019, 7:50 pm

I made the opening on my CC to WC the same size as the throat (FB to CC) but I don't think that it needs to be that large. I believe that 60%- 75% would be plenty big enough to achieve any temp that I wanted in the WC or CC especially with the opening from the FB to WC. My current smoker is 24 X 48(round)with a 24 X 21 X 30(insulated floor) WC over the FB and I went with a 5 X 5 square opening from the FB to WC. I can run the CC and WC at the same temperature of completely different temps with no problem. I put a 6'' tall chimney on the WC and it takes a few minutes to get a good draft going if I'm cooking through the CC to WC and out the chimney. I plan on cutting the stack off and making it the same overall height as the one on the CC. I have a damper on the stack so I can choke it down if it drafts too hard but I think it'll help with establishing a good draft.


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Re: Hybrid Smoker. Can it be done? How to calculate?

Post by Sleeman » June 18th, 2019, 9:37 pm

Thanks Big T. That all makes sense.

Throat size is calculated in sq inches, and I read in others posts that the shape of the throat doesn't really matter as long as you have enough sq inches. So I can choose to make it square, rectangle, half-moon, round?

Is there a term for the area between the bottom of the smoker and the BP? The flow chamber?

Let's say the throat should be 100 sq inches and I decide to make it a rectangle - 5" x 20" - Do I make the "flow chamber" 5" x 20" all the way from the FB to the other end of my smoker? OR Do I make the "flow chamber" 5" from the bottom of the smoker to the BP and as wide as my smoker?

The online calculators are most focused on tank (round) smokers. Pete's Calculators include some that help with square (or rectangle) chimneys but I can't find info about how to calculate the Baffle gap in a rectangular smoker. Is it the same as the round?



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Re: Hybrid Smoker. Can it be done? How to calculate?

Post by Pete Mazz » Yesterday, 4:07 am

how to calculate the Baffle gap in a rectangular smoker. Is it the same as the round?

The BP gap should be the same as 75-100% of Throat size. There is a calc if you need it.

The area under the BP doesn't need to match the Throat. Just make it rectangular and the top of the BP is the top of the FB. That leaves maximum amount of room for grates, starting at 4-5" above BP.


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