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Do Reverse Flow Smokers Need Drains?

post #1 of 17
Thread Starter 

Im about to build a Reverse Flow Smoker. I have seen some that do have drains, Ive seen some that dont. Is it needed?

post #2 of 17
They come in handy when rinsing out!
post #3 of 17

Depends.

There are two kinds of drains: grease drains and clean-out drains.

On a larger smoker when you are cooking a lot of meat over a long time, you will be rendering a lot of fat (grease) that has to go somewhere. The grease drain allows that fat to drain away and not cause problems (grease fires, etc).

A clean out drain allows you to hose out the smoker and drain out the dirty water, typically underneath the RF plate.

 

Necessity is in the eye of the beholder.

post #4 of 17
Thread Starter 

Thanks for replying. While your here, do you know if the intake is suppose to be under where the fire is in the fire box or above?

post #5 of 17

Your intakes should be below the level of the fire grate.

If the intakes are even with the grate, they usually work OK, but for best performance and efficiency, the intakes need to be below the fire.

If the intakes are too far above the fire grate, you will have a hard time getting up to temperature.

post #6 of 17
Thread Starter 
Can I put them on the side or do they have to be on the opposite side of the box from where it enters the cc?
post #7 of 17

You can put them on the side.

 

If you add a secondary upper air inlet for auxiliary air, it should be opposite the FB-CC opening.

Here is a good example of both:

http://www.smokingmeatforums.com/t/137442/and-the-mods-continue-for-my-rf-trailer-pit

post #8 of 17
Thread Starter 
Thanks. I saw somewhere that if you have a flat sided tank that you have to make a piece for it to curve. IS that required for it to work?
post #9 of 17

No, it will work with the flat end. Just make sure the opening between the end of the RF plate and the end of the tank is larger enough. It should be at least as big as the FB-CC opening.

post #10 of 17
Thread Starter 
Thanks, I've been rushing to check these things since I've started already.
post #11 of 17

Did you run all your numbers through the calculator? http://feldoncentral.com/bbqcalculator.html

 

You will need to increase the CC to FB opening by multiplying by 1.5 for reverse flow to get the correct opening, area under the RF plate, and opening at the end of the RF plate where the smoke turns up towards the grates.

post #12 of 17
Thread Starter 
I did use the website to calculate but didn't multiply by 1.5. This is the second time I cut that hole so I prefer not to and already put welds for the Rf plate.
post #13 of 17
Quote:
Originally Posted by LenDecaturAL View Post

Did you run all your numbers through the calculator? http://feldoncentral.com/bbqcalculator.html

You will need to increase the CC to FB opening by multiplying by 1.5 for reverse flow to get the correct opening, area under the RF plate, and opening at the end of the RF plate where the smoke turns up towards the grates.

So your saying if you use the calculator you still have to multiply the firebox opening by 1.5 ? For instance my smoker I'm building requires a 27.6" and I have to add 1.5 times the size to that ?
post #14 of 17

The short answer is yes. The calculator is set up for both standard offset and reverse flow; however, it gives the same value for both for the openings. Experience has shown that for the reverse flow configuration, additional area is needed to flow well. There are other issues with the calculator because all opening areas are calculated using the firebox size rather than the cook chamber size. Here is a thread on the forum that discusses the calculator.

 

http://www.smokingmeatforums.com/t/161795/is-feldons-calculator-really-flawed

 

What are the dimensions of your cook chamber and planned fire box?

post #15 of 17
My cook chamber is 37.5x 66" the firebox is 37.5 x 30" . Was planning about a 30" opening
post #16 of 17

Is the tank round? We need to start with a volume to put into the calculator, the same is true for the firebox and the result will come out as square inches for an opening. For example, if the tank is round and 37.5" in diameter and 66" long, considering a 100% firebox, it requires 195 square inches opening from the firebox to cook chamber  x 1.5 = 292 square inches so something must be missing from the numbers I'm using.

post #17 of 17
I am using a 500 gallon propane tank I cut 36" off I believe and I am going to use that as my fire box the cook chamber is 66" plus a lil but of the dome on each end.
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