smoke

[tcross]

I have a question. my arch is a home made 4'x4' with a flat pan on top. I have an 8" stack that is 12' high and a auf blower. I get a good burn. each time I fire the arch (between 4 and 7 minutes depending) I shut the blower off, but I still get smoke/flames blowing back at me when I open the door. I've tried shutting the blower off and waiting a few seconds hoping the draft would pull the smoke, but no luck. would adding more stack help this issue. Anyone know of a way I can get this to not happen? it's not a huge deal, but breathing in smoke all day gives me a headache, and ash blowing in my syrup isn't preferred!

[bowhunter]

If smoke and flames are coming out when you open the door you don't have enough draft. You probably need more stack or you may have some restrictions in the stack. If you have a stack damper make sure it's wide open. If you have more than one elbow that could be a problem. Make sure something in the arch isn't partially blocking off the opening into the stack.

[tcross]

thanks! I was assuming that I'm not getting enough draft. however it's odd, because I have almost 3x the amount of stack vs. the length of my arch. but i'll add another section and see if it helps. guess i'll check and see if some insulation got sucked in the path of the opening first!

[TerryEspo]

Is there enough space leading into the stack from inside the arch ?

Its possible that the stack is choking before even getting into the stack.

Just one thing to look for.

[maple flats]

A 4x4 arch needs more than an 8" stack. It should start with a near full width base stack and then taper down to at a minimum 14", maybe even a 16" stack. If you have a 4x4 area all burning, you will not get enough draft from 50.24 sq. " of stack cross sectional area. My little 3x8 with a 24" x 32" firebox has a transition from 32" wide x 7.5", down to a 12" round stack 6' above the base of the transition. With a 4' x 4' fire you need lots more. It may be even more than 16" you need. Maybe someone with a 4' wide arch can shed some light on what theirs has. My little 2x6 had an 8" stack and that was smaller than many. On that the firebox was only 14" wide at the bottom and 20" wide at the top and was 24" deep.

[tcross]

i guess I never really associated my arch with a full size arch when thinking of smoke stack/draft. I assumed if it was so much shorter then the traditional 4' arch it would act accordingly... guess not, cuz your math makes sense! thanks maple flats for the good explanation/info! i'll add another couple lengths of stack and hope it "helps" for this year! the plan is to upgrade to a 2x8 or 2.5x8 within the next year or two!

[maple flats]

Even with a block 4x4' arch, you can improve the draft and make sort of a transition. Try opening the whole width on the back and start stacking the blocks (best if using solids for this) to taper in. Have the base be full width up to pan level, then start adding blocks gradually closing in, With 16" long blocks you can step in 4" on each side at each tier until you get up to what your metal stack will be. Remember to keep a solid front and bach, just taper the sides that will form the open flue. Tie in layers so you don't have 3 separate stacks. Then when you work up to the final (for this year) size, put your stach up. Be sure to guy it so it can't fall, then no top.
For ideas how to offset, just look at some old brick chimneys in old attics, they used to side step to go thru the peak because that was the easiest place to seal against leaks.

[Sugarmaker]

Yea I seen another post somewhere like this I agree that a large base stack maybe 32 x 8 tapered up to about a 12 inch dia stack might be the answer to the draft issue. 4 x 4 is a big bunch of wood on fire at one time! I have 12 inch stack on my 3 x 10 rig, which is longer arch but the fire box is about 32 x 50 inches long.
Regards,
Chris

[maple flats]

Another idea for 1-2 seasons max, get an old wide file cabinet, cut out enough in the back to receive the smoke, place it up against the block arch, and cut out the opening in the top to accept your 8" stack, make it 6" circle, then cut 1" deep slits around the circle and fold the tabs up at 90 degrees, then set the 8" stack on it, again, brace it well with guy wires for support. That old file cabinet or metal wardrobe should last for 2 years if you keep it dry between seasons.
If seams or gaps leak, just seal them using a tube of furnace cement.

[tcross]

I like that filing cabinet idea. i'll have to figure that one out... seems easy enough. my arch is actually not a block arch. it is a welded up angle iron arch with steel sides. however I can cut a whole out the back end that's larger and taper down the stack after that. i'll put my crude welding skills to the task and see what I can come up with! thanks for the ideas guys! the smoke is sort of a minor issue because the arch actually preforms really well! I get around 25 gallons per hour with my preheater, hood and blower. it'd just be "nice" to not have a puff of smoke blow at me each time I fire!

[maple flats]

With my air over fire, it never gets shut down from shortly after lighting until after about 45 minutes past last fueling. I get no sparks out the front or the stack.

[mellondome]

Do you have your arch oriented so that the stack is downwind in relation to the normal air patterns where you are boiling?

[DocsMapleSyrup]

Maple Flats:

I had my first firing of my 2x8 AOF/AUF arch. I attempted to open the door with the blowers on and man, I just about singed the little hair I have on my head. How much stack are you running? I only have 8' on my arch right now because of no natural draft, but I'll be adding more once I build a sugar shack. I'm hoping to find the sweet spot but it wasn't to be today.

[tcross]

my stack is pretty much cross wind of where the predominant winds come from in my area. I added two more pieces of 2' stack to it this weekend... figured I'd see what would happen since I needed to drain my pans and clean them up before this week! the extra 4' of stack seemed to really help a lot! still get a little smoke, but nothing compared! I'm happy for this year!