20" RF Plans?

[Barrion2018]

More questions!

After using the Smoker Builder calculator, and finding out the area of the throat I need. I still did'nt have any measurements for height and width. So I Googled it and found the website below, and got the following measurements.

Throat Calculators
Website: https://planetcalc.com/5155/

Throat Calculator for Overlapping Cylindrical Tanks
(I used ID measurements)
Tank 1 Diameter: 9.25" ID
Tank 2 Diameter: 9.25" ID
Throat Area from the PitCalc: 50.27 sq. in.
Dam Height: 0

Overall Height of cut-out: 5.527”

Cut-out Width: 13.5”

Equals Calculated Throat Area: 51.38 sq. in.

If I use the height measurements from the Throat Calculator, the ID “Cut-out Height” should be 5.527”
I’m not sure what my actual height should be??
.5 = ½” of an inch., .5625 = 9/16” of an inch (see chart below).
I was thinking of rounding up to a cut-out height of 5.5/8”.
My question is, will rounding up a ~1/8” of an inch from barely over ½”, to 5/8” make that much of a difference?

Or, should I round it down to 5. 1/2" since they are showing "Throat Area: 51.38 sq. in."?

[Barrion2018]

Sorry! ID measurements 19.25" NOT 9.25"

[Dirtytires]

How bout 17/32 for you cutout?

[Barrion2018]

How bout 17/32 for you cutout?

THANK YOU!

But I don't have a tape measure that goes that small/precise of increments, the smallest increments on my tape measure is 1/16" increments.

I guess I need to buy me a better tape measure

Thanks again Dirtytires!

[Big T]

Relax, it's a smoker, not a NASA rocket, just get it close using the tape measure that you already have. If they had to be that precise, none of the ones that I've built would've ever worked. I would opt for the little bit larger on the throat rather than smaller and I'd go for a little bit smaller on the BP gap when you get to that. It's just fractions of an inch so it's not going to hurt anything and truth be told most of my cuts are probably off by a fraction of an inch here or there.

[Barrion2018]

Unfortunately, my daughter wasn't able to work on her smoker Saturday, so we didn't get as much done as we had planned over the weekend.

Fortunately on Sunday, her two brothers showed up to help. Her one brother is the only one who knows how to weld, and is teaching her.

It was a great day Sunday having them all at the house, every one had a great time.

Below are some pictures, the first one is of my daughter getting ready to start welding.

She didn't feel comfortable welding on the legs and bracing due to the differnt angles since i just learning, so she asked her brother to do it. She did weld the feet/pads on the legs.

My daughter cleaning and preping some used 1" OD black iron pipe that will be used as bracing and the lower wood rack.

[Barrion2018]

Relax, it's a smoker, not a NASA rocket, just get it close using the tape measure that you already have. If they had to be that precise, none of the ones that I've built would've ever worked. I would opt for the little bit larger on the throat rather than smaller and I'd go for a little bit smaller on the BP gap when you get to that. It's just fractions of an inch so it's not going to hurt anything and truth be told most of my cuts are probably off by a fraction of an inch here or there.

Thank you again for your advice Big T. You have been a great help!

I'll follow your advice.

[Big T]

Heck yeah!! That's awesome having the family help out.

[Dirtytires]

A 32 of an inch is just half way between each 16th. Measure to the half inch point, which is 16/32, and then halfway before the very next 16th is 17/32. No need to buy a new tape measure.

[Barrion2018]

A 32 of an inch is just half way between each 16th. Measure to the half inch point, which is 16/32, and then halfway before the very next 16th is 17/32. No need to buy a new tape measure.

Thank you Dirtytires.

Math is not my strong point.

[Barrion2018]

It's called a shadow plate, mounted at the top of the throat just below the BP. Most guys run them about the first 25% of the length of the BP so 12" will work fine. There should be an inch or so air gap between the plates for it to be effective.

Big T,

Will it make a diiferance if the shadow plate is 3/6" thick and longer than 12", say 14"? BP will be 1/4".

I found a scrap pieces of 3/16" that will work perfect, but I need to cut it down to 12" ,if 14" is too long.

I plan on installing it after work today.

[Dirtytires]

I would like to see 10-12 inches long but 14 would probably be ok.

[Barrion2018]

I would like to see 10-12 inches long but 14 would probably be ok.

I'll cut it down to 12 inches.

Thank you

[Barrion2018]

Got the shadow plate and BP installed, going to cut out the door next.

[Big T]

[Barrion2018]

Got a little more done on my daughter's RF. She was not able to come over this weekend to help due to here kids weekend sporting events.

I cut out the door and tacked one of the end plates on. I'll have her finish welding everything the next time she is here.

Below are some pics of what I got done.

[Barrion2018]

Question when it comes to placing the stack, I have read that it is personal preference. But one of the replies I read from another post, really got my attention. The post was by Zimbomike, Subject title "New Reverse Flow 20 x 45"

In Zimbomike's post, he asked pretty much the same thing I'm asking now, and the one reply that got my attention was by Dirtytires, this is what he said, (Post by Dirtytires » February 24th, 2022, 8:03 am) "Disadvantage of a top mounted exhaust is you shouldn't place meat below it to prevent any dripping or crud falling on it. With that said, I have not had good luck with a low mounted exhaust on previous pits I've had so will stick with a top mounted in the future."

Dirtytires, if you read this, will you explain a little more on why you prefer a "top mounted" stack?

I don't know anything about RF smokers, and I'm just trying to decide which works the best before I get to adding the stack.

[Dirtytires]

Happy to add confusion to your build...lol.

To answer your question, the exhaust is often times a place where creosote and soot build up so placing meat directly below increases the chance of particles dropping onto the food. This is easily avoided by simply not putting meat below the stack. Another method is to stop the cooking grate 6 inches short of the end of the cook chamber and use this last 6 inches for the exhaust. Not having grate in this last 6" also prevents food and drippings from falling into the baffle plate gap, which is a pain to clean out if it does.

My old pit had an exhaust that opened at grate level. The smoke would rise in the cook chamber and get trapped because it couldn't get out. As it slowed down, it tended to drop the creosote and soot onto the meat and I experienced an odd, bitter taste to some of my cooks. My new pit is a top exhaust, 24x48 reverse flow. The airflow is much more "fluid" and allows it to keep the creosote trapped so that it doesn't fall on my meats.

My experience with both pits over the last 20 years has convinced me that the top mounted exhaust is far superior but it is your decision. Help this helps....

[Barrion2018]

Thank you for the info Dirtytires! I'll mount at the top.

My only problem is, I made my door to wide, and I don't have enough room to put the stack.

I did see how SheffSmoker made a "small plenum for the stack" for the RF he was making.

I hope SheffSmoker dosn't mind that I'm using his picture of his "small plenum"?

This is SheffSmoker's picture of what he built:

What are your thoughts on doing something like this, since I didn't leave myself room on the "top dead center" of my CC?

Hopefully SheffSmoker will chime-in, and let me/us know how good it works.

[Barrion2018]

My apologies Big T.
I went back through your “The Ugly Stick” post and saw that you have a similar “small plenum” as SheffSmoker.
It looks and sounds like that design works; I’ll give it a try.
Thank's again Big T

[SheffSmoker]

Thank you for the info Dirtytires! I'll mount at the top.

My only problem is, I made my door to wide, and I don't have enough room to put the stack.

I did see how SheffSmoker made a "small plenum for the stack" for the RF he was making.

I hope SheffSmoker dosn't mind that I'm using his picture of his "small plenum"?

This is SheffSmoker's picture of what he built:

Stack Idea .PNG

What are your thoughts on doing something like this, since I didn't leave myself room on the "top dead center" of my CC?

Hopefully SheffSmoker will chime-in, and let me/us know how good it works.

Of course I don't mind you using the photo - that's what we all do in case it can help others out - sharing is caring

Life has got in the way of my build, so I can't comment on how it runs yet as it's not finished! I do concur with DT though on the stack "droppings" - my current offset I placed the stack at the far end of the CC at the top on the bell end, it's a few inches clear of the cook rack and the amount of black creosote looking shavings that end up collecting in the bottom of the CC under it... I even pull my stacks through with a sponge on a wire every so often and it still happens.

[Barrion2018]

Thank you for the info Dirtytires! I'll mount at the top.

My only problem is, I made my door to wide, and I don't have enough room to put the stack.

I did see how SheffSmoker made a "small plenum for the stack" for the RF he was making.

I hope SheffSmoker dosn't mind that I'm using his picture of his "small plenum"?

This is SheffSmoker's picture of what he built:

Stack Idea .PNG

What are your thoughts on doing something like this, since I didn't leave myself room on the "top dead center" of my CC?

Hopefully SheffSmoker will chime-in, and let me/us know how good it works.

Of course I don't mind you using the photo - that's what we all do in case it can help others out - sharing is caring

Life has got in the way of my build, so I can't comment on how it runs yet as it's not finished! I do concur with DT though on the stack "droppings" - my current offset I placed the stack at the far end of the CC at the top on the bell end, it's a few inches clear of the cook rack and the amount of black creosote looking shavings that end up collecting in the bottom of the CC under it... I even pull my stacks through with a sponge on a wire every so often and it still happens.

Hello SheffSmoker!

Thank you for allowing me to use your photo.

I totally understand about life getting in the way, it happens to me all the time.

Can't wait till you get the time to finish your smoker and see pictures of when it's finished, plus how she cooks.

Thank's again!

[Big T]

I've mounted a few exhaust stacks with that style plenum and they work great. Just be sure that it doesn't cause a choke point by making it too small.

[Barrion2018]

I've mounted a few exhaust stacks with that style plenum and they work great. Just be sure that it doesn't cause a choke point by making it too small.

I'll make sure to make it a little bit larger.

Thanks again Big T!

[Barrion2018]

Another question:

Is wider and taller better when it comes to the stack on a RF?

I have both 4" ID pipe and 6" ID pipe for a stack.

I was planning on using the 4" ID pipe and making it a few inches longer then what the calculator says.

If I use 4" ID pipe as a stack, the calculator says the stack needs to be 25.1". I was thinking closer to 30" above CC.
Is going taller a bad idea on RF smokers?