raised flue on homemade arch

[redneck mapler]

I purchased a 30" by 5ft. raised flue pan this year. I put it on a homemade arch that I had from last year. My pan last year was 30" by 6ft. but a flat pan. I put fire brick in arch and it has a 6" smoke stack. Everyone tells me I should get between 40-50 gallon and hr. boil off. I might be getting 10-15 if lucky. Does any one have any suggestions to increase this. I am going to purchase a new arch and finish pan so I have the complete set up for next year but just looking for ideas to get through this year. Any and all ideas would be appreciated. thanks

[jmayerl]

The stack is way to small, should be a 12". That is the majority of you problem, no draft. Second. Do you have a proper ramp built up to the flue pan. A picture or much better description would help.

[redneck mapler]

Thanks, I actually added a 4" stack last night and made a big difference. I did also raise the height closer to pan and built a slope up to. I am going to buy a new arch for next year. thanks a million though, I just want to keep expanding and know Im getting more sap than I can boil.

[I Luv Stainless]

You are doing the right thing, asking questions and experimenting.

I am always looking for a better way.

Keeping good notes will also help.

I write new ideas and notes to myself in chalk all over the arch as I think of them.

[maple flats]

Does the arch have a wide stack to start. It should be about 24" wide as it leaves the arch, then taper to 12". Are you just using the raised flue or do you also have a syrup pan in front of that?
As a rule of thumb, the stack should be at least 2 times the length of the arch. Also, on a raised flue pan you should ramp up behind the firebox at 30-45 degrees until you only have 1/2" space under the flues to force the heat into the flues. Then split your wood wrist size (must be dry) and fuel it by the clock. Many find every 7 minutes the best. Once you get used to running it, try to keep the sap just 1" max over the top of the flues (I run about 3/4")

[redneck mapler]

Thanks a lot Maple flats. To answer some of your questions. No on the taper straight out with a 6" and I added 4", this helped. I am just using the flue pan. Was going to add a boughten arch and finish pan for next year, thinking this will solve most of my problems. Thanks again for all the help. On the depth you said to keep it at an 1" My cousin has a drop flue with a syrup pan on front. He runs about 3" said he can go any lower because when he draws off needs that much. Will I have the same issue with mine next year?

[jmayerl]

Your cousin does not understand how to run an evaporator if he needs to run it 3" deep. 1-1.5" is the common depth, any deeper and it's just a big batch boiler, shallower and it gets dangerous fast if your not always watching.

[redneck mapler]

Do you get faster boil off when you run at 1-1.5" depth? I just cant wait until next year when I have my complete rig set up. thanks a lot for all your input. definitely learning a lot on this site. I was reading another forum and will the shorter boils help keep my syrup lighter in color? thanks to all

[jmayerl]

Yes the shallower the higher the boil rate. On a 2x6 it could be 35gph at 3" and maybe closer to 40 at 1" deep. Also is running very deep it will be nearly impossible to get a proper gradient established and then when drawing off you may gets huge 3 gallon draw and then surges will make for a very inconsistent running of the evaporator.