Filling rear end of evaporate with sand or vermiculite

[tgormley358]

A question has been bugging me, please solve my mystery. I've got a new Lapierre Jr 2x5 (5" raised flues in the flue pan) which i'm now setting up with board and brick. it comes with a bricking plan which i'm following. The arch design and the bricking ramps up from the fire box, levels off for about 12-13" where the bricks hit right under the rails, makes sense so far. But then it drops off from there about 6" down and 17" to the back of the arch, the first 9" or so of which is under the flue pan and the rest is under the stack.

So then why do I read in so many threads about adding sand or vermiculite to the back portion, i assume after the leveled off area, to bring it also up just under the rails? Is that what I should be doing with mine? If that's where we want the top of the material, then could i also just add bricks up to that level (i have a bunch extra)? If i don't raise it up like this will it decrease the boil in the back of my flue pan?

One other question: the arch board is all 1", but the Lapierre design calls for 1/2" board on the side walls of the fire box area, and I don't have any. Have others used 1/2" rather than 1", and where did you get it? I'm wondering why Lapierre calls for 1/2" rather than 1", and I'm guessing it's to maximize the firebox area for heat under the syrup pan ... adding full bricks on top of the 1" board does seem to cover over a bit of the opening between the grate and the side. Could i use blanket material instead of the 1" board for this to get closer to 1/2"? Will it provide enough protection for the SS sides? Thanks!!

Tom

[Haynes Forest Products]

I built my arch for my raised flue and you need the downward space so the hot gases can exit the raised flue bulkhead and exit down around and out the flue stack. that space needs to be equal to the area of the flue spaces. You would cause back pressure if the exit is smaller. I would use fire blanket instead of sand or any other loose material that will blow out over time or with forced air.

[jrobida]

CDL has a good video on YouTube on bricking an evaporator. The arch he is bricking is just like ours. He uses 1 inch fire board but I’m going to use 1 inch blanket. He uses full bricks up the sides and a half brick under the top rail. Under the flue pan, he uses vermiculite with blanket on top, check it out.

[Russell Lampron]

When I got my new W F Mason air tight arch he supplied fire blanket that is about 3/8" thick to be put between the bricks and sides of the arch. I used vermiculite to fill the space behind the ramp to where it tapers down about 6" from the stack opening. I covered that with fire brick because I had some left over. You do want that area filled to the arch rails so that the flames stay in the flues.

[maple flats]

You will get the best boil if you push the heat up into the flues. On a raised flue type, that brings the floor under the flues up to about 1/2" or less. If you fill that void with sand you have a huge amount of weight on the arch and they are not designed to hold that much weight. Vermiculite fills the space but if you don't cover the surface the draft of the stack will pull some of the vermiculite up and out. Thus it must be covered, ceramic board or blanket works good, but so does a flat layer of firebrick. I used the brick method. Then where I had any spots that still expose the vermiculite I used dry refractory cement and leveled it, then I used a fine mist of water to lightly dampen the surface a few days in a row. I chose the brick route because I thought the flue brush to clean the underside of the flues would mess with the ceramic insulation.
For knowing what space you want under the flues, I just went with 1/4", because the area in the flues was essentially the same as the volume of the stack.
To buy vermiculite it will cost a fortune if you need to buy small bags from a Lowe's or Home Depot, but then it depends on how much you need. On my 3x8 I calculated the number of bags at Lowe's and it would have cost me $500, I then called a wholesale greenhouse supplier who was only 25 miles away, and I paid $63 total for 3 huge bags, and I had a little left over. That was 10-11 years ago.
On a much smaller arch you might be able to use the small bags but check out the BIG bag cost at a greenhouse supply before you choose. Then do the math, including delivery or your driving costs (time and fuel) for pick up to compare.

[tgormley358]

Ok I need to first thank all of you for your responses. Really appreciate it. I’ve start bricking and went with blanket of about 1” on the sides of the fire box, which Maple Guys supplied. I don’t think it’s much different from the 1” board but maybe a little. Thanks for the explanations of the purpose of the vermiculite and vs sand (weight). I plan to experiment with it this season, starting with just brick, then add some vermiculite and blanket on top and see what happens with th boil. It’s what I call in my profession “Plan-do-study-act”. I’ll look for an ag supplier for the vermiculite. I plan to hang some buckets this Saturday and tubing 45 taps and might have my first boil Monday or Tuesday. I’m figuring out s lot of things last minute including transfer pumps and collection tanks but hey it’s not rocket science right! Starting to feel the excitement of the season.

[Greg MacWilliam]

vermiculite is available from U line supply as packing mtl for hazardous mtl.

[maple flats]

Their price is quite high and you need to order a minimum of 2 bags at 4CF each. That would put many smaller producers out of the picture unless you can go in with another producer who also has a small evaporator needing some. As I said above, my 3x8 raised flue used almost 3 bags (mine were 6 CF). Before you order from u line do some searching for other sources, and by all means, calculate how many cubic feet you need.
I just did a quick google search and came up with http://www.greenhousemegastore.com/product/vermiculite-4-cubic-foot-bag/soil-additives?gclid=CjwKCAiAqvXTBRBuEiwAE54dcMEs2CA7h3 5SjTpTyyCS_P9aF5WVsfRgxtb0Zxh2Y5BUCqJok3yzmBoCUjUQ AvD_BwE
There may be other sources too, check around, but if there is a commercial greenhouse supply in reasonable driving distance that will be the best.

[Russell Lampron]

I bought a 2 cu/ft bag at Home Depot for $21. I don't know if that's a good price or not but it was the amount that I needed to fill the space in my arch.

[maple flats]

Here's another source, 4 CF delivered for just under $28 https://www.amazon.com/Coarse-Vermiculite-cubic-foot-bag/dp/B015RXB9HW

[Sugarmaker]

A lot of the threads on sand and or vermiculite may be for drop flue arches. Different animal and requires different arch prep than your raised flue with the hump in the arch.
Regards,
Chris

[BSD]

Here's another source, 4 CF delivered for just under $28 https://www.amazon.com/Coarse-Vermiculite-cubic-foot-bag/dp/B015RXB9HWi bought two bags from amazon last week. just right to dial in my 30"x10'. price was good too. much cheaper than local option