Smoke stack size

[mapleknollman]

Hey, I built a arch and pan last year and wish I had found this site while building it. Anyways I put together a 4'x9' and am having problems with the back half of the pan not boiling. I have a forced air unit that blows throught the grate I built and that makes the sap pretty much hop out of the front of the pan with a good load of dry pine in 3 foot lenghts. The space from the arch to the pan in the back is about 2" and i have ceramic blanket in the whole back half with fire brick in the front. I didnt have the time to do different pans so its just one 4'x9' flat bottom pan with 4 dividers back and forth. Anyways a friend of mine came and told me that my smoke stack was not big enough and that was why my boil was only on the front half of the pan. I have a 8" pipe coming out of the base colector. Do any of you think that if switching to a 12" colvert for a smoke stack will make the back half of the pan come to life. I build it twards the end of the season and didnt have a whole lot of time to tinker with it but would like to make it come to life a little more than it is now. Thanks alot,
Joseph

[dschultz]

You should have a 16" on that size setup.

[mapleknollman]

Would a 16" culvert work or does it not really matter? If not any other cheap ideas on pipe? Also do you think thats going to open it up in the back end?

Thanks
Joseph

[Father & Son]

The length of the stack should also be considered. The rule of thumb is the stack should be at least twice the size of the evaporator, in your case 18'. That may influence what you use for stack and how you will support it.

Jim

[mapleknollman]

So 20' of 16" culvert, 400' of 3/16th guy wire and then the back end will light up into a raging boil? How does adding air over fire affect things along with smoke stack size because I would like to rig something like that up at some point in the future when I actually make some profit off this extreamly addictive and costly hobby. Then maybe my wife will see that trudging around in the snow and cold is a good idea and want to join me right?

Thanks for your replys,
Joseph

[whalems]

Profit on maple syrup???:lol::lol::o

[Jim Brown]

These's no money in maple syrup!!

[sweetwoodmaple]

You will need to watch the stack length if it is single wall and outside the building. Wind and other factors in uninsulated pipe can diminish the effect of the extra height. I would not go longer than 20', especially with culvert.

Also, the corrugated sides may reduce the actual cross sectional area and create turbulence. I think I would try to get smooth pipe if possible.

Just my two cents.

[Jeff E]

4x9 is 36 sq ft of area. My 3x12 is the same and I have a 14" stack, that is 22ft long. I have really good draw.

From what I have read, over air in the fire box will help you get you temps up by burning more of the combustible gases, getting you a better boil. Just adding air under will not give you alot unless you have a real tight firebox and you are 'pressurizing' the fire box.

Trust me, pressurizing a fire box that is not sealed will be a mess!:mad:
I have gone to pressurized nozzles into the fire box this year, rather than just a high volume of air.

I am also trying to maximize the boil in my rear pan as I have a piggyback unit on it, wanting to soak up all the steam energy it can get.