Sand placement in 2x4 evaporator

[jroch]

I built my 2x4 evaporator last year, bought a phaneuf continuous flow pan and got great results. This year im trying to fix some "issues" i ran into last year. I was loosing a whole lot of heat right out the chimney so i added a key at the base of the stack hoping to keep more heat in. People told me to put down some sand on the flat part of the evaporator so i put a couple of mounds hoping to stir the fire before it leaves the stove. What do you guys think? Sorry about the sideways pics i cant figure out how to rotate them on my phone...
16173
16172
16174

[ecolbeck]

In order to push heat as close to the pan as possible the vertical area between the sand and the pan should be the same as the area of the stack.

[jroch]

So with my 6 inch stack, i should have about 3/4 o f space between the pan and the sand? Seems like that would cause me to lose even more heat then before. Whats the reason for using sand? Could i use firebricks to raise the bottom surface?

[maple flats]

Actually vermiculite under and fire half brick on top is best, sand adds much more weight and is not a great insulator. 3/4" will likely be best. If the pan had flues you'd want even less, to force the heat into the flues.
On my 3x8, raised flue I only have 1/4-3/8" space, that pushes the heat up into the flues, then at the back I have 14" front to back that is 6" lower, for the smoke (really is no smoke) to go out the stack. That 14", is 8" under the base stack and another 6" toward the front where the fumes can get to the stack.
To buy the vermiculite, go to a greenhouse supplier, not a garden center. The price will be vastly less. When I did mine it worked out that I needed about $500 (priced at Lowes in small bags) worth for my 3x8 raised flue, but at a greenhouse supply it was only $60 some.

[Millsy]

I have the same pan and an oil drum arch that I built. I have a 2" gap below the pan all the way back and it works quite well.

[Millsy]

http://mapletrader.com/community/attachment.php?attachmentid=16172&d=1490220498
This is too much space. Close it up straight back.

[claystroup]

I have done the same with vermiculite and ceramic blanket under the flat pan on my 2 x 5 Mason leaving about 3" under the back 3'. You can look in when its burning and see the flames getting sucked right through the 3" space up against the pan-pretty amazing. I think during this off season I am going to reduce that to about a 2" opening with another layer of ceramic blanket. I got a huge bag of vermiculite from the local masonary supply yard for about $18. It was more than enough to do my 2 x 5 and I have about a 5 gallon pails worth left over.

[maple flats]

That may be essentially what I paid. I got 3 giant bags and had about a bushel left over. I think each bag was 6 cubic feet.

[5 Oaks]

16187 This is how tight mine is. Its like this all the way to the rear.

[Sugarmaker]

Is this a raised flue, drop flue, or flat pan? Each one will need to be set up different. You need enough opening to get good draft.
Regards,
Chris

[BlueMaple]

Quick note; On your phone before you upload the pic edit the dimensions of the photo to a square and you'll be all set!

[jroch]

Thanks for the replies guys. I put down a couple of rows of half brick, because i had them on hand, and got the gap down to about 1 1/2". That'll have to be good for this year because i really dont like taking the pan off during the season if i don't absolutly have to. I boiled down about 60 gallons of sap yesterday and can't say i noticed any difference. The rest of the season will tell.