Bricking Up the Arch with Friends

by Tig Tillinghast

We bricked up the “new” old arch in the sugarhouse. The maple syrup crew reconvened in the sugarhouse during exceptionally cold weather (otherwise we’d have been out in the bush putting up maple lines) and worked inside. We patched up the big holes in the windows – with quaint and scenic duct tape – and fired up a kerosene heater so that the mortar would have a chance to set before it froze.

It was nice having all the guys back together again working on a common project and poking fun at each other. I think it made us all eager for the proper maple syrup season to begin.

For those who don’t know why we’d be spending so many man-hours putting bricks into our steel arch, it’s because the special fire bricks insulate the outer parts of the rig so that the heat is mostly directed upward, where the maple syrup pans sit, transfering more energy to boiling the sap. Otherwise, the rig would act as a big radiator, using up a lot of that woodfired heat on warming up the sugar shack. Also, the firebrick protects the metal from the most seering of the heat, which prolongs its life.

Here is Robert wacking away at one of the bricks we removed before transporting the used arch. He’s removing the old mortar so they’ll fit nicely when put back in the new setup. You’re supposed to wear goggles when you do this.

Masons will cringe at what I’m about to say. The smoother and neater you put firebrick into an arch, the less turbulence is created in the air as it moves from the firebox, along the underside of the pans and then up the chimney, called a stack. Turbulence is good in this case. It allows more of the flammable gases to burn up and shed their potential heat nearer the maple sugar in the pans above. So here’s a look at the fine job we did “mudding” the bricks up to get some nice friction turbulence running along the sides and bottom. Will it make a difference one way or the other? Almost definitely not, but everything with sugaring has to be accompanied by a theory.

The part accompanied by most theories, though, is the baffles placed under maple syrup pans in order to ensure that the hot gases flow up into the pans corrugations – called flues – before being expelled out the stack. You can see from the picture below that Robert is messing with the first baffle, which is almost all bricked up, with the second one behind it still in metal. The pans sit on top of the side rails, so you can see that these baffles really force the flowing air up into the pan, and into the flue slots.

When boiling, the most vigorous maple sap bubbling action will be where these baffles come up. In this Grimm Lightnening model, the baffles are placed just about where the (cold) sap intake pipe comes into the pan, as well as the place were that sap gets expelled out of that pipe into the pan. I suspect that’s deliberate. Some people put Vermiculite or some other non-moisture-sponging and heat-resistent substance in a layer between the baffles to force the air into the flues the whole length of the pan. We’ll see how our draft is doing once we start boiling to see if we have room to play with such constrictions.

If we find we need more draft to be able to fiddle with such optimizations, we might add more stack height, which draws more air, or start improvising a blower system to introduce high-pressure air into the firebox. Given our natures, the blower is highly likely. Blowers reputedly increase performance by about 15 percent, both in terms of time saved and recovered energy release. The downside: most are very loud. Last year we introduced a cobbled-together blower for the little arch. We used a very quite Vornado fan and some clever ducting. It worked pretty well for the arch, but would be pretty outclassed by the size of this bigger one.