removable insulation under raised flue?

[SilverLeaf]

Ok. I think I'm gonna do it! upgrade from 2x6 flat pan to 2x4 raised flue/2x2 finish pan.

Question: Current evaporator has 4" airspace under flat pan, which works well. That spacing is made via a layer of vermiculite. For raised flue though I know I'll need to ramp it up to just under the flues. Never seen a raised flue in person before so not exactly sure how it's typically done.

Conundrum: I don't want to make it "permanent". I'd like to have the flexibility (if its a bad year; or if I burn my pan - :cry: - or something) to quickly switch back to the flat pan. So whatever insulation I stick in there to raise it needs to be easily removable (and reinstallable).

I was thinking ceramic blanket might work? - at 1" thick I'd just have to roll like 4 layers of it in place. And it'd be super easy to remove. But I've never worked with ceramic blanket before. Anything about having 4" of ceramic blanket sitting on top of a layer of vermiculite that might be a bad idea? How heavy is it - will it compress ok (will some of the draft find its way between the layers, rather than stay on top by the flues)?

Any other ideas?

[red maples]

First GOOD IDEA. that will drastically improve your GPH rate with that 2x6.

yes you are going to need to move that up. I added forced air to my 2x6 Drop flu and wanted to move the ramp up as well so I added a few bricks to front at a steep angle, then filled it with vermiculite put a piece of 1" ceramic blanket over it and just put split bricks on top to hold everything in place and it worked great as I was able to adjust things to play around with height and where the start of the ramp should be.

found out 1.5 inches was about the best most even boil. but that's my rig. not sure what the raised flu distance should be.

[millscrest]

This maybe a dumb question, it there a different type of vermiculite you can use or is it all the same? I have been thinking of putting some inside of my arch as well.

[SilverLeaf]

it there a different type of vermiculite you can use or is it all the same? I think its all the same. You can get big bags of it for pretty cheap at Home Depot or any big box hardware store.

[millscrest]

Silverleaf, thank you very much. I will get some and try it this year. Thanks again !!!!!

[SilverLeaf]

put a piece of 1" ceramic blanket over it and just put split bricks on top to hold everything in place how many bricks do you have holding it down? are they just in front or do you have a couple scattered back aways too?

[PerryFamily]

I bricked each end to within a 1/2" from the pan. On the stack end I only left like 2" for the smoke / gas to get into the stack. Between the bricking I used vermiculite from agway, 2 bags I think. Then a layer of dry refractory cement sprinkled with water which settled quite a bit. So I used a layer of ceramic blanket to take up the difference. It actually just touched the flies. Worked awesome.

[farmall h]

Silver Leaf. You can fill your arch flush with vermiculite. The whole idea of raised flues is that the flame goes through them. You will never go back to a flat pan again so make it permanent. Besides..burning a raised flue back pan would mean you ran dry of sap..fell asleep..passed out drunk. Be sure to have plenty of sap on hand. Gravity flow with an adjustable float. Sap level in the back pan is generally an inch above the flues at all times. Boil water once you get it all installed..that's the best practice. Good luck.

[maple flats]

I agree pretty much with farmall h. While you can get vermiculite at Lowes or Home Depot, it is much more expensive than finding some at a commercial greenhouse supply. While you won't need as much, when I did my 3x8 raised flue I calculated the volumn and went to Lowes garden section. They only had small bags. I did the math (needed 16 cu ft) and it was going to cost me over $400 to get that at Lowes. Then I sked a greenhouse where they buy theirs and I was given the name "Milikowski Greenhouse supply". I called them and I paid about $50 for 3 bags at 6CF each. Milikowski has been bought out, but the new co., Griffin has it. They have several locations. Link: www.griffins.com They will carry at least 2 versions, small curd and large curd (No it's not cottage cheese). You can use either, for our purpose it makes no difference, just compare the price and get the cheaper if there's a difference. Vermiculite will hold up to a few thousand degrees. It is very light, you do need something to hold it from going up the stack. If you want, 1 layer of ceramic blanket will do, but I see little chance of you deciding to remove it to use the flat pan. I'd put layer of half brick on it and a 1/4" layer of dry refractory cement on top. Then use a misting bottle and lightly dampen it. Don't let it freeze, add some heat (heat lamp?). Repeat when dry and partially cured, re dampen and repeat. Do this 3x and you will be good. Worse comes to worse, the layer will break easily, lift the bricks, use a dry shop vac to remove the vermiculite and you can switch back to your2x6 flat set up. I really doubt that will ever be needed.

[farmall h]

Screened sand works well also. Mine has been in the arch since 1988. Sand is cheap too..just be sure not to have road salt in it. :)

[maple flats]

It would work, but be sure to support the sand, it will be heavy. For a 2x6 with a 2x4 raised flue pan, you might have upwards of 5-6 CF of sand. Depending on the coarseness of the sand, dry sand weighs between 80-100 lbs/cf. As such, you could have 5-600 pounds of sand in that arch. Then you put sap in the pans and you might get as much as 550# or so in the arch, which is only supported under the fire box and at the other end. If doing that route, just be sure to support the weight. Remember, raised flue has much more fill than drop flue.

[farmall h]

Maple Flats...I'm surprised mine is still standing after all these years. Keep in mind that the area filled w/sand is probably 4" deep. I believe we may have fixed a sheet of 1/4 steel from where the bricks ramp up ...to the back of the arch. Did this new in '88. Less sand to fill in. Been so long I vaguely remember the details.
Not that I'm that old !

[SilverLeaf]

So it seems the consensus on here is that I will never ever ever go back to my old flat pan. :)

A question, then: what do you at the end of the season? Do you shut it down, let it cool, drain the flue pan and replace it with water, and then finish the syrup off with just the front pan? That's more or less what I do now with my flat pan (it's two 2x3 flat pans) but its not such a big deal there. With a 2x4 flue pan I would think there's a whole lot more sap to drain and it would take awhile to finish all that off just using the front 2x2 pan.

[maple flats]

My calculations were for the depth measurement of my arch for a raised flue. If you create a void it will of course cut that weight.

[farmall h]

SilverLeaf. At some point you need to connect your flue pan to your finishing pans. The purpose of the flue pan is to concentrate your sap (remove the H2O via steam evaporation) and then it is moved to the front pans for finishing (syrup). Maybe Millscrest can explain it better to you since he has a 2 x 6 mason.
Cleaning it is something that has been discussed many times in the past here on the Trader....

[millscrest]

Silverleaf. With my 2x6 mason I have a 2x4 flue pan and a 2x2 syrup pan. At the end of the day boiling, I always leave my pans sweet. If I have a few days where the sap is not running, I will let the evaporator cool down and remove the sap from the rear pan and put into the syrup pan and finish it there while I fill the flue pan with plain water. I hope this helps