ramp behind firebox

[SilverLeaf]

What is the purpose of the ramp behind the firebox that slopes up to the point where it levels off underneath the flue pan? (For example, in the typical 2x6, which has a 2 foot deep firebox with the next foot being where the slope slants upward to the point where it levels out underneath the back 3 feet of the flue pan) Is this feature necessary to get a good draft?

I just picked up my brand spankin' new 2x6 evap put together by a professional welder. She's a beauty! That brand new stainless steel shine just curls my toes. And the workmanship is absolutely top-notch. BUT, I totally goofed, and must not have explained it and diagrammed it correctly to the fellow - because there's no slope! :o The back wall of my firebox goes straight up, and then makes a 90 degree corner to be level all the way under the back 4 feet of the pans.

I'm not planning on using forced draft, at least not this year. Will this corner cause a problem for me to get enough draft to get around it and make it to the back of the flue pan (I'm not actually using a "flue" pan, just another flat pan back there for now)? If so, what can I do (besides use a blower) to make sure I get enough draft? I'll be using a 10" stack, so should have plenty of room for air flow there.

[smitty76]

Dan, I'm no expert but the slope is just a nice transition to the shallow area under the flue pan. Some manufactured(proffessional) arches have a vertical back to the fire box with a 90 deg corner at the top. Most that have a slope have firebricks laid in at the top of the slop mismatched on purpose to cause terbulance into the flues for better heat displacement and for a more complete combustion. your 90 deg corner just may do the same. The draft wont be a problem even with a blower. once you get the stove pipe hot it will take it all out and the 10" pipe will deffinetly get it done. That is what I run on my small brothers 2x6 and it works great.


good luck and have fun

Smitty

[SilverLeaf]

The draft wont be a problem even with a blower.

Hi Smitty, did you mean to say "without" a blower?

[WESTVIRGINIAMAPLER]

It should work fine as long as your pipe is big enough for sufficient draft.

[Maple/Cherry]

I have a 2 x 6 raised flue and I built the ramp to force the fire track up into the flue pan with in 6" of the front of the pan. Just big enough to get the flue brush in to clean. It ramps back down near the back. Email me if you want pictures of how I constructed it. woods@torchlake.com

[killingworthmaple]

I was using a 2x4 last year it had a homemade arch and I made a 90 degree turn on purpose to get the heat closer up to the pans. I even went one step more and copied what my 20 year old wood hot air furnace has. I made a shelf so that the hot smoke and fire had to travel to the front of the arch before it could start traveling down the pans. The smoke, fire, and hot gases had to make a C shaped travel. The results were great, complete boiling of sap from one end of the pans to the other. No problem with draft, don't worry you will be fine in my opinion. I have not seen this C shaped designed in any evaporators and am wondering why it's not done, it is used widely with wood stoves.

[smitty76]

Dan. It will work fine with or without the draft blower. I would run a blower as it will improve performance.

Smitty

[maple flats]

I would do a test boil with water. I made my bricking different from the owner's manual on my raised flue evap. I bricked up higher than the built in slope, to about 8" below the flues and ramped at about 30 degrees to just under the flues and then straight back until where i dropped down to make a chamber the go into the stack. When I boil it is very easy to get the front of my flue pan just having continuous geysers, shooting up as high as 18" or a little more. I think I forced too much heat up all at once to the pan rather than spreading it over a longer area. I will rebrick before the season to go closer to the original height and slope but I think I will be somewhat higher than original.
A test boil pushed real hard should answer your question. If you lose sap into the hood gutter and can't channel it back to the pan you are losing sweet. On mine I will try a new deflector design but it that fails i will re brick as I indicated above.

[SilverLeaf]

Thanks, all, for the comments! I'm feeling better in general about the situation. I don't have a blower now, so I will give 'er a test boil sometime without one and see how I can get 'er to crank. If for some reason it gets to be a problem I'll think about hooking up a blower...

[maple flats]

If it proves you are pushing the heat up too fast do not add a blower permanently at first. If too fast a blower will make it burn hotter still. You may not be too fast however. Just because mine is really does not mean yours will. Try it.