Rf Plate questions

[Suicycle]

I'm trying to do all the homework I can to determine dimensions and design of my first build. I'm looking at a cook chamber of 20x40 or maybe even slightly larger diameter. Might go as large as 24 dia and possibly as short as 36" in length. This should be a one and done and outlast me. I really want a reverse flow but nothing I can find says the plate should be thick or thin for any real reason. Is it just duct and should be thinner or keep it at same thickness as CC walls? I have plate and access to roll it. All I need are decisions on which way to go, well and buy the rest of the material.

 

[civilsmoker]

1/4 inch is the ideal thickness for the reverse flow plate..... ie 1/4 is also the typical for the cooking chamber as well. Some higher end RF units use 3/8s for the cooking chamber for heat retention, but they take a bit to heat up. To me a 3/8 fire box and 1/4 inch CC and RF plate would be near perfect, if you had the choice up front on anything.

All that said.....My copper pot build has 3/8 FB, 1/8 CC (double 1/8 on the round end), and 3/8 RF plate....
https://www.smokingmeatforums.com/t...h-vertical-cabinet-aka-the-copper-pot.268790/

 

[Suicycle]

1/4 inch is the ideal thickness for the reverse flow plate..... ie 1/4 is also the typical for the cooking chamber as well. Some higher end RF units use 3/8s for the cooking chamber for heat retention, but they take a bit to heat up. To me a 3/8 fire box and 1/4 inch CC and RF plate would be near perfect, if you had the choice up front on anything.

All that said.....My copper pot build has 3/8 FB, 1/8 CC (double 1/8 on the round end), and 3/8 RF plate....
https://www.smokingmeatforums.com/t...h-vertical-cabinet-aka-the-copper-pot.268790/

I have a 5/16 plate I'm considering using for the CC since it's not being used. And depending on dimensions I could get the FB out of it to. My desire after talking to my wife is buy a 3/8 plate for FB and CC and use the thinner for end caps and possibly RF plate and the collector/plenum.

 

[civilsmoker]

I wouldn't hesitate to use the 5/16 for the FB or CC and/or get 1/4 for the CC and RF plate....Its just what you would like to do. Just know once you go above 1/4 the fab/welding takes a lot more time.....wieght to.

 

[flatbroke]

24 inch diameter will allow you to place a rack of ribs on top shelf front to back instead of sideways if that matters to you at all. 20 inch won’t.

 

[radioguy]

1/4 to 5/16 material is good for heat retention, takes while to get it hot, but stays hot in windy conditions.

RG

 

[LanceR]

Quarter inch plate weighs 10 pounds per square foot with each additional 1/16" adding 2.5 pounds per square foot.

A 24" interior diameter cook chamber will come in at around 70 pounds per lineal foot plus racks, attachments, the firebox, fire grate, ash pan, exhaust stack, RF plate etc. So, at a minimum, your looking at several hundred pounds.

Going to 3/8" plate overall will add 50% to your finished weight. Which begs the questions: will it be stationary, a hand moved patio build or trailer mounted so you need a garden tractor or other vehicle to move it?

And if your lot or driveway are sloped or lack a level spot to use the smoker that needs to be considered, too.

 

[Smokin Okie]

24 inch diameter will allow you to place a rack of ribs on top shelf front to back instead of sideways if that matters to you at all. 20 inch won’t.

I have a 20" and lay ribs crossways a lot . And 20" will have better air flow.

 

[flatbroke]

I have a 20" and lay ribs crossways a lot . And 20" will have better air flow.

I dont know how to determine if the 20 inch flows better then a 24 inch diameter pipe with a reverse flow so will take your word on it. I do know that the top rack in a 20 inch diameter pipe with a reverse flow plate such as a lang with racks spaced to allow for a large piece of meat like a butt on the bottom rack wont fit a rack of ribs on the top rack front to back, but only allow sideways on top rack unless the racks are trimmed shorter. that can be an issue for some people and is why i pointed it out.

 

[Smokin Okie]

I dont know how to determine if the 20 inch flows better then a 24 inch diameter pipe with a reverse flow so will take your word on it. I do know that the top rack in a 20 inch diameter pipe with a reverse flow plate such as a lang with racks spaced to allow for a large piece of meat like a butt on the bottom rack wont fit a rack of ribs on the top rack front to back, but only allow sideways on top rack unless the racks are trimmed shorter. that can be an issue for some people and is why i pointed it out.

Aaaahhh, the top rack. I was thinking the main cooking grate. My bad.

 

[LanceR]

It isn't accurate to say that any particular diameter will flow better than any other diameter.

Airflow in any particular pit is a symbiotic function of firebox size and layout, fire grate placement, vent size and placement, cook chamber shape, exhaust stack design and placement, the quality of the door seals, rack placement, the shape and size of air current passageways, fire and firewood management; and often, a pinch of magic.

Or, just follow the well beaten path to the pit calculator at the head of this forum and avoid all the pole vaulting over mouse turds that we all seem to be guilty of occasionally...... maybe me more than most......

Suicycle , if you are going to be in anything up to about the 24" range you could do a lot worse than to cruise Amazon for some of the better gas grill grates. You can buy some pretty heavy duty ones made of a good grade of stainless steel for less than buying the material. Then you can decide whether to use them as-is as drop in grates, to build a sliding frame for a movable rack, etc.

I cut one end off of a 20-1/2" OD propane tank a few months ago for a smallish trailer mounted reverse flow smoker with a warming/cooking cabinet above the firebox and sized the layout of the cook chamber and warming cabinet around commercially available gas grill grates. When it cools off a bit here in North Carolina I'll get some pictures and get on with the build.

Here's an example of off-the-shelf grates that might serve well in a smoker of roughly 20x40":

https://www.amazon.com/gp/product/B07Y49LQXV/ref=ox_sc_saved_title_2?smid=A3RFCB56HIHPI8&psc=1

And some for a 24x40 smoker:

https://www.amazon.com/gp/product/B07JDM8NKV/ref=ox_sc_saved_image_4?smid=A1DHHQN3Q1UIA7&th=1

Best regards to all,

 

[Smokin Okie]

Self delete, not worth it

 

[civilsmoker]

To me a 24x36 to 40 is about the perfect patio home cooker there is. It’s big enough you can smoke for a big party, if it has two shelves you can do under pan smoking with larger proteins

As mention above an average rack of ribs is about 18 inches in length so putting them front to back vs long ways will provide for a more even cook.

The losses will be less on a 24” than a smaller dia so it will be less sensitive during operation. A reverse flow has a lot of friction losses which are different than a simple offset and the thermodynamic airflow friction losses are more critical to be aware off.