making steam hoods

[bowtie]

i would like to make a steam hood that hangs suspended about 2 ft above my evap. i do not want a "tight" hood as i am not looking to pre-heat with it just looking to vent steam out the roof. i have currently cut a approx. 7ft long by 8" hole in the ridge of the garage i am boiling in and the steam really backs up alot. so i would like to funnel the steam out. what gauge ss should i use and would 2-6" stacks be enough vent for my evap. i am currently using the garage of the house i purchased across the street from my house as a temporary shack and want something that i can move when i build my new sugar shack hopefully this summer or fall. any help is appreciated.
also has any thought of using the stack as a source for pre-heating sap, i thought about running my stack under my ss sa ptank to warm it up a little not sure if it practical or not. just can't help but think there has to be some way to use all that "wasted" heat going out the stack.

[mapleack]

My guess is that yes two 6" pipes would be enough for your 2x4 as they would give you slightly more area than one 8" pipe. If this is a completely temporary set up, frame your hood out of wood and cover it with plastic. It won't look pretty but it'll get the steam out. I'd nix the preheat idea, you don't want sap in the head tank to be hot, bacteria would explode.

[Dill]

If you put a copper pipe preheater in the hood it will still heat the sap some even if its not tight to the evap pan. I think the wood with plastic is a good idea.