Were my calculations off?

  • Some of the links on this forum allow SMF, at no cost to you, to earn a small commission when you click through and make a purchase. Let me know if you have any questions about this.
SMF is reader-supported. When you buy through links on our site, we may earn an affiliate commission.

gmh313

Fire Starter
Original poster
Jun 14, 2016
72
33
Portsmouth Rhode Island
Hi ya'll. I recently completed a 500 gal reverse flow smoker. Firebox is 3/8", baffle plates and all other material is 1/4". Calculations were based off of feldons:

500 gal tank

firebox is 42" wide, 28" tall, 32" deep, yielding 97.7% efficiency

6" ID exhausts, 66.58"needed, both exhausts are 33.25"

intake baffle is 6x18"which feldons told me I needed 1.05

opening from FB to CC is 27" in diameter.

baffle plate sits 4" below cook surface

I'm very familiar with charcoal smokers, however this is my first stick burner. I understand there's a learning curve, however I think I messed up somewhere and am seeking your advice. Before I spend hundreds to fill the smoker, I've been experimenting with small batches at a time: half a dozen racks of ribs, two flat briskets, couple whole chickens, etc. Granted a full cooker will hold temperature easier, I'm having trouble keeping the smoker "low".

I'm burning just a few sticks at a time, but I can't keep the smoker to run at anything lower than 300 without having too much smoke. See the photos for how closed the damper is... Is it possible I built the intake too large? The smoker is very tight, so I'm not getting air from anywhere else. I should note that I'm currently running kiln dried oak flooring scraps rather than true split wood... is this my issue, the wood is too "dry" ?

Any input is greatly appreciated. I have a 180# +/- pig for the 4th of July and want to be a little more confident with the cooker before then.





 
Add an upper air inlet to the FB door...  directly across from the FB/cc opening...  That allows for 2 important things....    The lower air inlet is then used ONLY to control the fire.....   The upper air inlet moves heat and smoke from the FB to and through the CC...    Just the a forced air furnace...   heating element and fan...  two separate functions...  working together for comfort...

It will take a bit to get the hang of the upper air inlet....   I would start with it 50% open and adjust the lower inlet to adjust the heat....  wait 15 minutes between adjustments...  Then mess with adjusting the upper air inlet to see what effects there are...   Once you get the hang of it...  You will be pleased with the control.....

Upper air inlet should be about +/- 20 sq. inches for a 500 gallon smoker..... 

.......
 
Interesting, so the upper vent will essentially "push" the heat through the chamber, and this will help attain LOWER temperatures?
 
The upper air inlet will even out the temps...   Cool an overheated FB...   It needs adjusting just like the lower air inlet...

Think of a forced air furnace...   The firebox makes the heat...    The fan moves the heat to uniformly warm the house..     Same deal....
 
Below is just one testimonial of the smokers members build on this site using the collective ideas put together by our members....

http://www.smokingmeatforums.com/a/reverse-flow-smoker-how-to-calculate-build-tutorial

Use the knowledge as you wish.....   Dave

80x80px-LS-952fa729_IMG_1875.jpeg

Hi Woody, does your smoker have any flap that covers the halfpie cut out in the fire box to control the smoke and heat? I saw one like that. Thanks, Pat
Hey pat. I just wanted to add to my last post. Right now I am smoking some cheese


Now I am truly convinced you don't need a flap or dampener between the FB and CC. It's holding temps steady at 80 deg left to right. I'm a true believer in DaveOmak's calculator.

http://www.smokingmeatforums.com/t/238321/short-fat-120-gallon-build
 
GMH, I would also try a different wood as this maybe part of your problem..

Try do a bit of fire management but using the least amount of wood posible to maintain temp.

It wouldn't take much to add a secondary upper air intake like Dave suggested. Everything just seems to work better and more stable when you have this.

In some of my latest builds I have not been using it, but this is for other reasons.  (I got tired of trying to explain how a secondary intake works and also time/cost when building for clients).

Smokey Todd      take a bunch of  pics and measurements and the folks on here will try to isolate your problem.
 
SmokingMeatForums.com is reader supported and as an Amazon Associate, we may earn commissions from qualifying purchases.

Latest posts

Hot Threads

Clicky