Here's a way to tackle the job of making your home more energy-in-dependent . . . even if you're low on cash and short on welding skills.

BUILD YOUR OWN (900/0 EFFICIENT!) FIREPLACEthey found its efliciency to be virtuallyequal to that of the "Bolshevik behe-moths". (ln all fairness, we should pointout that, although the efficiency of thelarge and small models is about the same,the volume of heat rendered by either roomoven will vary according to the amount ofwood burned . . . and the larger hearth is,of course, capable of absorbing morelher-mal energy before releasing it !o the livingarea.)

HOWTHEY DID ITThe Southwesterners'secret is not an

intricate interior labyiinth (their molded re-fractory firebox is almost Spartan in thisrespect . . . though its metal flue pipe lssomewhat convoluted), but thd fact thatcast masonry stores and liberates heatbetter than does metal. The team opted tofabricate the stove from Kast-Set, a relrac-tory clay (available locally, or by writing toA.P. Green Co., Dept. TMEN, Green Boule-vard, Mexico, Missouri 65265), because [1]it's easy to work with, [2] it's strong, [3] itcan withstand 2500'F temperatures, and[4] it doesn't require kiln drying.

First, the two gentlemen made a mold

-using 3/4" plywood and 2 X 4 braces-and cut it in half horizontally. Next, theylined the form with thin-gauge sheet metaland covered the inner "plug" in the samemanner. Since the rear section of the fire-box supports the flue pipe, they also hadto devise a reinforced cardboard bung toprovide for that piece of exhaust hardwarewhen casting the "aft" portion of thestove. Then they worked up a mold for thesimple arched slab that forms the backwall of the f irebox.

The trickiest part of the stove's con-struction, its designers found, was the ac-tual casting and curing. The refractory claymust be mixed with enough water to giveit the consistency of wet sand that willhold its shape when squeezed. Accordingto Bob and Alex, it's best to be thoroughwhen dampening the mix ... in fact, theyfound that three gallons of water per bag

-though it's more than the manufacturerrecommends-makes the strongest blend.

Since the "mud" is too stiff to pour, ithas to be caref ully spoohed into the molds(which ought to be thinly layered withgrease beforehand to make them easier toremove later) and firmly tamped between"servings"-being sure all the corners arefilled-with a piece ol 1 X2. The mixturestarts to sel in about 20 minutes, so it'sbest not to dawdle at this stage.

When all the molds are full, excess claycan be skimmed off the top and a sheetof plastic placed over them. The castingsshould be allowed to stand for one weeklike this, at temperatures over 50'F. Then

-since proper curing requires that theKast-Set be kept slightly damp for at leasttwo weeks after forming-gently removethe molds after the first seven days, andseal each "gr.een" piece into a plastic gar-bage bag. Allow the sections another weekin that moist environment. Finally, removethe shrouds altogether and sun-dry theparts for a fortnight,or two ... or until

they're compleiely air-cured (naturally, ex-posure to rain and coridensation shouldbe strictly avoided during this final stage).To save time, it'd be a good idea to orderor fabricate an adjuslable, vented, 3/16" X16" X 16" steel firebox door while waitingfor the molded components to harden.

The New Mexican stove builders haveassembled their creations either over bedsof bricks or on poured concrete slabs. Tohold the various components together,they use thin layers of Kast-Set as mortarin the joints, though they say refractorycement will work, too. (Another two weeksof air-drying will cure the seals.)

The f lue installation is very important tothe stove's ability to transmit heat proper-ly. ln a standard room with seven- to eight-foot'ceilings, a 16-foot length of 6'pipe-equipped with an airtight damper and ar-ranged in a serpentine pattern-seems towork best. Too much stovepipe will resultin excessive convolutions, and there maynot be enough hot exhaust flow to allowthe stove to draw properly. (Of course, aswith any heat-producing appliance, thefirebox and flue stack should be 36 inchesaway from all combustiUe surfaces, and aventilated wall thimble should be used.)

TRY IT OUTOnce the assembly is completed and

checked, it's ready for the initial confla-gration. Fuel for the first five fires shouldprogress from a single sheet of newspa-per to a healthy handful of kindling . . . inorder to complete the curing and condi-tioning process. Afterward, the stove canbe used normally.

According to its builders, the fireplacewill-when loaded with five pounds ofwood and lighted-give an instant dose ofheat to the room through its stovepipe. Anhour and a quarter later, the outer surfaceof the firebox will reach nearly 200'F. Andsix hours after that, its masonry "hide" willstill be above 100'F ... though the fluepipe will have long since cooled. Bob andAlex suggest a fast, hot fire at first . . . un-til the coals stage begins, usually afterabout 35 minutes. Then they recommendthat the flue damper be shut, to allow onlya slight flow. (Normal store-bought "flap-pers" are too "dratly" ... but you canmodify such a unit by simply placing asolid sheet-metal disk over the existingplate.) This mode of operation allows thefireplace to absorb heat rather than dumpit out the chimney.

When the two designers tested theirstove, they came up with efficiency fig-ures as high as 92.6%. And, even if this in-credible percentage figure doesn't panout for everyone, the "ceramic stove"could be about the closest thing to home-heating perfection available . . .-especiallyfor a couple hundred dollars and 19 hoursof easy labor!

David Gustalson

The "rebirth" of wood heat has been areal education for a good many peoplewho grew up thinking that winter warmthis created by a turn of the thermostat. Notonly has the growing popularity of fire-places and woodstoves forced a numberof folks to put a time-and-sweat-rath-er than a dollars-and-cents-price tag ontheir fuel, but it's also stirred up the curi-osity of a few individuals regarding the ac-tual levels of performance that can be ex-pected from the "new" appliances.

INCREASED EFFICIENCYSurprisingly enough, the folks who have

looked into such matlers have found thatlhe elliciency of the woodburners (calcu-,lated by measuring the amount of heatvented into the atmosphere, subtractingthat figure from the total number of BTUavailable in the given weight and kind ofwood used, and converting the result to apercentage) can range anywhere from nearzero (with a poorly designed fireplace) toa high of perhaps 72% (in a good airtightstove).

Not long ago, in an effort to learn whysome heaters work better than others-and with the eventual goal of building aneffective, affordable woodburning device

-New Mexicans Bob Christensen andAlex Sanchez began to research variousstove designs. The pair initially concen-trated on modifying the basic shape andconfiguration of the "standard" firebox... but when they discovered that platesteel couldn't be easily conformed to thepattern they wanted, the inventive South-westerners decided to try a different tack.

Coincidentally, the New Mexico Energylnstitute at the University of New Mexico(an Albuquerque-based research organiza-tio4 dedicated to the promotion of alterna-tive energy) was conducting a workshopproject on so-called "Russian fireplaces". . . devices which were testing oul al g0o/o

elliciencyl The excellent performance ofthese unusual.heaters stems from twocharacteristics: They contain enough ma-sonry to provide a massive heat sink, andthe inlerior flue path of each unit is ar-ranged in a serpentine pattern so that hotwaste gas has plenty of time to transferits thermal energy into the walls of thestove. Unfortunately, the typical Russianfireplace weighs about 11 tons, standsseven feet tall, and can cost as much as$2,000 if built by a professional mason.

A TEMPEST IN A TEACUPNevertheless, using information they'd

gleaned from the university's seminars-with the aim ot remedying the disadvan-tages of the design-Christensen and San-chez designed and built a five-piece, cast-clay firebox tllat weighed only 280 pounds,cost them $244 in new materials, and tookup'an easy-to-live-with 18'.X 18' X 27'space on the living room floor. Best of all,when the two tinkerers condi.rcted per-formance tests on their compact creation,

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EDITOR'S NOTE: Bob and Alex have put?together a set ol comprehensive building iand installation plans f or their stove. To or- ider, send.S75 fo Stoyes, Dept. TMEN, P.O.ABox 1 575, Belen, New Mexico 87002. e E

THE MOTHER EARTH NEWSO