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Thread: Adding steel to a cinder block evaporator

  1. #11
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    Welcome Swingpure! I've only been doing this a half a dozen years, and I never built a cinderblock arch. I did build my own arch (out of an old wood-burning stove), so I did learn one or two things the hard way. I'll answer your post point by point.

    Quote Originally Posted by Swingpure View Post
    This is my first post. I am new to the maple syrup hobby/business and I am looking forward to this Spring when I can tap my first trees. I will start off tapping 16 trees on my property.
    For your first year, depending on how much time you have to devote to it, that seems like a manageable number of taps. I'll get more into estimating boiling times later.

    I plan to build a cinder block evaporator.. I will be poring a 6” concrete pad for it to sit on and will add sand on top of the pad. The pad is to help prevent any root fires as it will be built partially in a forest.

    My side walls will be three and a half cinder blocks long and three cinder blocks high, plus a four inch solid block on top to ensure I have enough clearance from the bottom of my pans and the stove pipe.
    That sounds reasonable to me so far, but maybe folks who do cinderblock arches can weigh in on how high the sides should be and what they should be made of.

    I plan to have a 1/4” steel end wall that the stove pipe will come out of (the pipe hole centered about 15” off the ground). I will have cinder blocks behind it to help support it.
    Seems to me you'd have more stability if you had the pipe coming off the top of a cinderblock, rather than out the back of an end-wall.

    I also plan on having a removable 1/4 steel front wall, that has adjustable air intake holes near the bottom of the plate.
    I wouldn't bother with adjustable air holes. You want a big opening that's open all the time. You need to have the same area of opening coming in as you have going out. So if you have a six inch stovepipe, that's 29 square inches. You need the same space for air in the front. If the arch is 20" wide, you will need at least 1 1/2 inches open along the whole width. Any less than that and you're starving the fire. Some folks add a blower to further increase the amount of air going to the fire, but you can get into that later if you decide to do that.

    The goal is to also have steel to help protect the side walls. I forget the official name, but there are steel strapping that can attach to the side walls, that you can then attach your steel to, that will create an airspace between the steel and the blocks, hopefully helping to protect the cinder blocks. The steel would be 3” off the bottom and from the top to help create convection currents between the steel and the wall.
    Your cinderblocks can tolerate the heat much better than steel. You do not want steel strapping in the fire, particularly if it's structural in any way. It will warp and fall apart. Anything in your arch made of metal (with the exception of the grate) needs to have the inside surface protected with insulation, and the outside surface exposed to air to help it cool. If it's in the middle of the arch, unprotected, with no air on the outside, it's going to get chewed up in no time. And the only reason why the grate can take it (sometimes - some people go through grates pretty quickly) is because it has cold outside air flowing up through it.

    I will have 1 1/4” heavy duty steel grate sitting on some 3” bricks on the ground, to help with the air flow from the bottom.
    Sounds good. Make sure your front "door" is set up so that all the air coming in is directed under the grate. Then have something that closes off the airflow on the far side of the grate, so the air can only take one path - up through your wood. Otherwise cold air will take the path of least resistance and go around the wood. That will cool down the inside of the arch and allow the fire to be starved for air. And as others said, the firebox - the part where the fire is (and the grate) should only be like 18 - 20 inches deep. So you only want wood from the front door, going back about 20 inches.

    Up top I will have four stainless steel 20x13x6” pans, which should encompass the entire length of the evaporator.
    Once you get this optimized, you should get on the order of one gallon per hour boiled off per square foot. So you've got about seven square feet. A good week mid-season may get you five or more gallons per tap. So that's eleven hours of boiling time. If you have that kind of time to put into boiling, you should be fine.

    Am I looking for trouble using all of this steel, or is it a good thing? Any advice on any of this would be appreciated. I am still in the planning stages, but will be pouring my concrete pad likely next week. I have my pans, pails, lids, spigots already. The trees are already marked, as I have many other species of trees in my forest.

    Thank you.
    Yeah, all that steel is a mistake. Can you say more about what you're trying to accomplish with it? I'm sure we can help you figure out how to do what you're trying to do without the steel in the arch.

    Also, figure out the inside of your firebox before you go any further. If you look around on here you can find examples other folks have given on how to make a "ramp" in your arch. If it were me I'd probably just add cinderblocks behind the grate, and fill in gaps with vermiculite or insulation or something. You're aiming for probably 1 1/2 inches between the bottom of the arch and the pans.

    Have fun!

    Gabe
    2016: Homemade arch from old woodburning stove; 2 steam tray pans; 6 taps; 1.1 galls
    2017: Same setup. 15 taps; 4.5 galls
    2018: Same setup. Limited time. 12 taps and short season; 2.2 galls
    2019: Very limited time. 7 taps and a short season; 1.8 galls
    2020: New Mason 2x3 XL halfway through season; 9 taps 2 galls
    2021: Same 2x3, 18 taps, 4.5 galls
    2022: 23 taps
    All taps on buckets

  2. #12
    Join Date
    Jul 2021
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    Parry Sound Area, Ontario
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    Thanks Berkshire for the detailed reply. I wish I read it earlier as I just bought $50 of steel for the walls and floor and I was so proud of my design. I was worried that having never read about steel in the firebox, that it was a bad idea. The whole point adding the steel, was to protect the cinder blocks.

    Looking at the concrete block evaporators on line, it always looked like they had a fire the length of the concrete and open flames touching the bottom of each of the pans. Only having burning logs for the first 20” or so is a radical change of thought for me.

    I will have to totally rethink the whole design, including moving the chimney to the top.. I still may be able to use the steel to help with the slope. I will also have to change the concrete pad it will sit on, as it will have to be deeper.

    Thanks for the response.

  3. #13
    Join Date
    Apr 2019
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    Nashville, MI
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    Depending on how much steel you purchased. You may be able to use it in the future towards the building of an arch and then get yourself really setup with a good stainless steel pan. Of course by then you'll be thinking to yourself, hmmm, now how can I grow my operation just a little bit bigger.
    By the way I will tell you that this becomes an addiction, an itch to grow, etc., etc,. Always though keep it fun and share with others.
    2004 - 2012 2x3 flat pan 25 to 60 taps
    2012 2x3 new divided pan w/draw off 55 taps
    2018 - didn't boil surgery - bought new evaporator
    2019 new SML 2x4 raised flue high output evap. 65 taps
    made 17 gal syrup
    2020 - only put out 53 taps - made 16.25 gal syrup
    2021 - going for 50 bags and 50 on tubing

  4. #14
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    Jul 2021
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    Parry Sound Area, Ontario
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    173A6C7B-4324-4301-AFEC-458BDA456B74.jpg

    I totally redesigned what I was going to build. This crude drawing is what is between the two side walls. The back wall will now be concrete blocks and there are blocks inside to aid the slope. I will include a steel plate that will go from the grate up to the top of one of the blocks to act as a slope. I will have another steel plate that will go from the last pan to the end of the concrete wall and the stove pipe will come out of that.

    The front wall will still be a metal plate, that I will lift to the height of the grate to allow air in. I will play with the exact height when the times comes.

    It will be interesting to see if I get addicted to making syrup and how many taps I will have in year two, but we are still at least 7 months away from year one, but I will be ready for it..
    Attached Images Attached Images
    Last edited by Swingpure; 07-22-2021 at 11:55 PM.

  5. #15
    Join Date
    Feb 2012
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    Fond du Lac, Wisconsin
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    For one it is not too late to get out before the addiction hits. After my first year with 12 taps cooked over a fire pit I was going to make a block arch. That turned into why not make a steel one as I had the rest of the year to get it done. First I figured a 2 X 4 would work but why not a 2 X 6 as long as I am building one. That went from going to do 40 taps to 126 taps. From there is went up to 425 a few years later and then I concentrated on being more efficient and am at about 400 now. This site is a great resource and you will learn a lot.

    Looking at your drawing it looks like you have the pans dropped into the evaporator. I would only have the bottoms come in contact with the heat and flames. By setting them in deeper you will scorch the sides of the pan above the sap level.
    Smoky Lake 2x6 dropflu pans and hoods on homemade arch
    Smoky Lake 6 gallon water jacked bottler
    Concentric Exhaust
    250 Deer Run RO
    325 taps

  6. #16
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    Jul 2021
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    Parry Sound Area, Ontario
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    Quote Originally Posted by Super Sapper View Post
    Looking at your drawing it looks like you have the pans dropped into the evaporator. I would only have the bottoms come in contact with the heat and flames. By setting them in deeper you will scorch the sides of the pan above the sap level.
    Virtually every cinder block evaporator I have seen on line has the lip of the pans on the edge of cinder blocks, and the pans sunken down below the top of the cinder blocks, including the gentleman I bought my pans from. My impression it helps to seal the heat in.

    As I build it, I may raise tbe last pan or two a couple of inches as they will only be 1.5” above the heat flow.79A5BB05-32A8-490C-AB86-6426AFE98BF0.jpg

  7. #17
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    Sep 2020
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    Corbeil, ON
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    I think the pan can be recessed to keep the sides warm however there should be something at the base of the pans to stop the fire from running up the sides of the pan. This can be achieved by using 8" wide block for the arch and 6" block for the top course. This allows the pans to sit on the 8" block and block the flames. The 6" block would need to be cut on the height if you are using 6" tall steam pans.
    2021 - Year one. 15 taps using 5/16" and drop tube into buckets. Homemade barrel evaporator with 2 steam trays. 4.7L syrup.

  8. #18
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    Jul 2021
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    In the attached pictures from on line, this person just offset the top row a half inch or so, to try and keep the flames off the ends of the pan.

    3968A976-C705-4979-91B1-E614D7257B9E.jpg

    I also see how he used some blocks instead of any metal plates to act as a ramp with an initial flat wall.

  9. #19
    Join Date
    Mar 2016
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    Central Wisconsin
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    Yeah keep the pans dropped down in. It will boil a LOT better. You'll get some scorching on the sides but it doesn't affect the taste like you think it would.

  10. #20
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    Jul 2021
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    Parry Sound Area, Ontario
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    Sometimes I wonder if I overthink the design of the evaporator. This video with this high energy, cheerful woman certainly simplifies things and makes the process seem even more wholesome.

    http://YouTu.be/uCts2DqzkJo
    Last edited by Swingpure; 07-24-2021 at 07:30 PM.

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