New reverse flow build

[joecool]

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.

[ajfoxy]

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.

[Dirtytires]

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!

[Big T]

Welcome aboard!!

[joecool]

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]

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]

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

[Pete Mazz]

https://planetcalc.com/4580/

[joecool]

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]

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

[joecool]

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.

[Pete Mazz]

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

[joecool]

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.

[Pete Mazz]

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.

[Big T]

[joecool]

G’day all, best wishes for christmas and the new year.
Managed to get a couple of free days to work on the smoker so we’re up and running.
Ive made the baffle plate and fully welded her in place and have mostly cut out the door opening bar a bit at each corner, which leads me to my next question. I’m using 1/4 inch by 2 inches for the door banding and am wondering what you guys do with the top door band.
Do you put a crease in it to follow tank radius or just leave it flat. If flat does it seal ok.
Also what type of hinges do you guys recommend for a 32 inch door openg

[Dirtytires]

Leave it flat. I tried to kinda split the difference of the gap that the flat-on-round created. Once my gasket was installed, it seals great and looks perfect too.

[joecool]

G,day and a happy new year to all.
Work is slowly progressing on the smoker build. Had a couple of minor drama’s but have managed to overcome those roadblocks. I’ve got a quick question regarding the chimney. I have some heavy wall pipe that I was planing on using that has an internal measurement of 21/2 inches, is this ok to use providing it has the length specified by pit calculator or would a larger diameter be more appropriate.Taking lots of happy snaps along the way will post some pictures soon. Thanks in advance for your replies.

[Pete Mazz]

Less than 4" may be too restrictive

[Dirtytires]

Never disagree with Pete on numbers...he said too small!

But....just for fun, let’s assume you ran the numbers thru the calculator and determined you needed a 30” long piece of 4” diameter pipe. If you were going to use 2.5” your legnth would be close to 76” to get the same volume. Even if you run two stacks, you are at 38” so I would probably run 3 at 25” so it would fit in a garage door.

With that said, it’s easier to get a piece of 4 inch pipe than to run 3 small dia stacks. It doesn’t need to be heavy wall.

[joecool]

Ok 4 inch it is. Thanks for your quick replies.

[Dirtytires]

Good choice....it will look better, function better and be easier to work with.