cinder block arch

[On the ledge]

I'm planning on building a cinder block arch, would it be a bad idea to build a concrete slab to put it, or would the heat cause it to crack. I go to a clambake every year in Gil Ma. and they had put down a concrete slab and the heat from the fire caused the slab to explode there was concrete flying everywhere do you think the same thing would happen with an arch ?

[buxtonboiler]

Based on my experience with block evaporators. I would say, generally yes, bad idea. But, if you put some half bricks (firebrick) over it, it should hold up. Also would depend on the height of you grate, higher up would allow for it to stay cooler. The blocks themselves will also need protection from the heat with firebrick or insulation. I went through about 10 blocks last year that cracked or broke from th heat.

[On the ledge]

Thanks for the input. I don't think I'm going to get the cinder block arch built in time for this year.This is just my second season tried 10 taps last year, will have about 30 this year. How bad was it using a turkey fryer for 30 taps? How much propane did you go thru. I figure I should get a pan before I build my arch. With the trees on my property I'll probably max out at 50 taps, so I figure if I get a 2x4 divided pan and build a cinder block arch it should be adequate.

[brookledge]

As long as the fire itself isn't sitting on the concrete you should be fine. Every evaporator I've had sits on a concrete pad. If you build it with some grates in it so that ashes and air can come in then the concrete will never pop. As for your side walls you might want to consider putting in fire brick along the sides to protect the cinder blocks and keep them from cracking.
Keith

[KenWP]

Was the cement under the clam bake getting wet by any chance. Sounds more like rocks full of water then to much heat. If the cement is kept reasonabbly dry it should not explode.

[Haynes Forest Products]

On The Ledge lets just use 2x4 as a size for the pan. Take some of the cheap roll insulation and strip off about a 2 " layer and lay it down on the cement. Lay down cement blocks holes up on top of the insulation the size of the arch you want. Full block completely filling the floor with block. Lay another layer of insulation thinner this time over all the blocks and lay down a second row of block holes up. NOW on the 3rd row lay another layer of insulation thin like the last one and build the arch walls AND a solid area 1/2 way back so the heat is directed up. Then the last row of blocks will be all wall that will support the pans. NOW GO POUND SAND Really take a stick and poke holes in the insulation so you can fill all the holes with sand. Now you will have a insulated arch that will not crack the cement and will hold alot of heat in.

If you want to get fancy find a pallet strap tool and the strapping and run a band around the rows of blocks to keep them together. We are not talking about alot of money for the block, insulation and sand. Find someone to weld up a frame for the fire door or just install a steel Lintel and you will have a good working arch. Build it up so you can work at a comfortable level and not be bent over all day long

[Maplebrook]

On the Ledge,

I built my first wood fired evaporator out of concrete block. Using 8x8x16" block, it was 3 blocks wide, 41/2 long , 4 high and housed 2 24X32" flat bottom pans. The base was lined with concrete patio blocks and the firebox lined with fire brick. I didn't have a problem with the concrete blocks and heat, although the occasional one cracked. The patio blocks on the other hand...
The first day I fired up, the fire was building, the boil was coming on nicely, my poor man's preheater (see other thread from last week)was warming the sap and I was feeling quite proud of my handy work. Then BOOM, and once the surprise settled and the concrete pieces came back to earth - I'm sure they exited from more places than just the draft - I discovered that the patio blocks objected to the heat. (see thoughts on maple below!!!)
The new base was gravel and the collected pieces of concrete. Once that was out of her system, that rig worked great for 3 years.

Darren