New reverse flow build

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joecool
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New reverse flow build

Post by joecool » December 2nd, 2018, 1:50 am

Greetings fellow pitmasters from the land down under.
I’m about to embark on a new reverse flow build and have a couple of questions for the experts out there. My cc is 18 x 48 inch pipe and my fb is 18 x 24 inch pipe The online calculator is telling me that the fb is at 150%. Is this ok to use or should I shorten the fb pipe. My understanding is the fb can be bigger than needed all you do is make a smaller fire.
I would like it to be dual purpose whereby using just the fb as a griller when needed so would prefer not to shorten if posssible. Any advice appreciated.



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ajfoxy
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Re: New reverse flow build

Post by ajfoxy » December 2nd, 2018, 4:00 am

Welcome to the crew.

Trying to make a dual purpose smoker/grill generally is not a good idea. One is hot and fast and the other is less hot and a lot slower. That which makes the low and slow smoker work efficiently works against the grill dynamics. Best advice I can give is to build two separate units. That way you get two good results instead of one device deliverying two less than satisfactory results. Just my 2c worth.


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Dirtytires
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Re: New reverse flow build

Post by Dirtytires » December 2nd, 2018, 12:00 pm

I would follow the calculator. You are looking for about 110%. We restrict the airflow to keep the fire small but an oversized firebox already has all the air it needs so is much more difficult to controll.

And, AJ said it all, build a separate grill if you want one but this here is a smoker!



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Big T
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Re: New reverse flow build

Post by Big T » December 2nd, 2018, 1:59 pm

Welcome aboard!!


Measure Twice.....Cut Three Times.

joecool
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Re: New reverse flow build

Post by joecool » December 3rd, 2018, 2:32 am

Thanks all for your quick replies. I will adjust the firbox size accordingly.
My next question is when joining the two pipes together does the opening need to be
football shaped or is a half moon shape ok.



joecool
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Re: New reverse flow build

Post by joecool » December 3rd, 2018, 2:34 am

Thanks all for your quick replies. I will adjust the firbox size accordingly.
My next question is when joining the two pipes together does the opening need to be
football shaped or is a half moon shape ok.



Chromeski
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Re: New reverse flow build

Post by Chromeski » December 3rd, 2018, 2:47 am

Half moon should work. Make sure the size of the hole matches recommendation of the calculator



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Pete Mazz
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Re: New reverse flow build

Post by Pete Mazz » December 3rd, 2018, 4:47 am



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joecool
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Re: New reverse flow build

Post by joecool » December 3rd, 2018, 5:04 am

Thanks Chromeski much appreciated. I’ll post some picks once I get started. I’m just trying to arm myself with as much info before slicing and dicing. When measuring for cutout from pit calculator do you measure down from central horizontal or measure up from bottom of tank?



joecool
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Re: New reverse flow build

Post by joecool » December 3rd, 2018, 5:12 am

Thankyou very much Pete Mazz for smoker calculators.I’m sure they’ll come in very handy.



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Re: New reverse flow build

Post by joecool » December 3rd, 2018, 5:40 pm

G’day fellow pitmasters. Just wondering if someone could answer a question regarding the throat cut program. Its telling me I need a cutout of 12 inches by 4 inches for two overlapping round tanks. I’ve reduced cc to 40 inches and fb to 16 inches to get me around 115%. Is the 4 inch measurement calculated when both tanks are joined or will it be 8 inches when joined. So basically will the football be 4 inches or 8 inches wide at its widest point.
Thanks in advance.



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Pete Mazz
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Re: New reverse flow build

Post by Pete Mazz » December 4th, 2018, 5:35 am

If you did your calculations for the adjusted sizes the throat (football shaped) will be 4" high on each piece.


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joecool
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Re: New reverse flow build

Post by joecool » December 5th, 2018, 1:51 am

Ok thanks for your reply. A couple more questions before I commit to cuttting please.
My BP is going to be about 5 inches off bottom of tank at FB end and about 4 inches at far end allowing for fall. I have cut two pieces of 1/4 inch plate for BP and tacked them to 2
inch angle which will be the drain. My cutout according to calculator is 4 inches high and 12 inches wide meaning the space below BP at far end is the same as cutout.Is this ok like this or should I raise the BP. The next question is regarding the opening at the far end. I have scoured through other posts on this site and have seen answers from 50% to more than 100% of FB cutout as being acceptable BP opening. What are your thoughts on this.
Thanks in advance for your time.



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Pete Mazz
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Re: New reverse flow build

Post by Pete Mazz » December 5th, 2018, 4:55 am

No real need to slope the BP as this sometimes leads to airflow issues. Most RF guys simply scrape off any goo after a cook with a 4 or 6" putty knife. I would keep the BP gap the same as the throat. You could always add an extension if you feel like experimenting.


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Re: New reverse flow build

Post by Big T » December 5th, 2018, 7:39 pm

:yth:


Measure Twice.....Cut Three Times.

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