Mother's Heat Grabber Is Back

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So here's MOTHER's Heat Grabber all over again . . . only this time we're mostly fabricating the unit out of wood. The bad news is that It'll take you about six hours to construct this version. The good news is that [1] it'll cost you only $2.50 per square foot tops-and far less than that if you can scrounge up your lumber-to build this one, [2) this is a more rugged unit, [3) you should have no trouble finding everything you need for this version, and [4] we've added some refinements and improvements that-if anything-make this second MOTHER's Heat Grabber even more efficient than the first.

Before you start putting your own Btu-catcher together, though, remember this Important fact: For maximum effectiveness, you should "custom design" your Heat Grabber to rest In a window at an angle up from the horizon equal to your latitude plus 10°.

This adds up to 45° for MOTHER's North Carolina offices (which are situated 35° north of the equator). And that's what we get when we cut both sets of boards on the sides of the unit (where the "collector" portion of the Heat Grabber meets the furnace's "window box") off at an angle of 67.5°.

In Miami, however-which Is located about 25° north-a collector should be angled up at 35° to the horizon . . . which, In turn, means that the 67.5° cuts specified in the accompanying drawings should be 72.5° Instead. Likewise, the cuts should be 65.75° for Washington, D.C. . . . 61.5° for Seattle . . . and 54.5° for Anchorage. (You can calculate the specific "cut angle" for your own location merely by subtracting your latitude-plus10 from 180 and dividing by two . . . or just average it out from the figures given here. The angle is critical, but not that critical.)

And a word of warning: The panes of glass used on the "face" of MOTHER's Heat Grabber are single strength. As such, they're just as susceptible to accidental (or intentional) breakage as the single-strength glass you'll find in almost every residential window and door on the continent. Make sure your window furnace is installed with this caution In mind.

LET'S BUILD!

MOTHER's second-generation Heat Grabber consists, basically, of (1] a box shaped frame that is Insulated on the back, covered with glass on the top, and designed to hook over the lower sill of a window, and which contains [2] a divider Inside. This divider is composed of a main body (which separates the box into two chambers) and some airflow passages that run up the top surface of the divider's main body underneath a sheet of aluminum attached to that top surface.

Start construction of the frame by cutting two 87"long and two 27"-long 1 X 8's. Rout a 3116" X 318" groove (314" In from one edge) down the length of the two long boards and one of the short ones as shown. Measure down 14" from the "top" ends of both long boards and scribe two 67-112° marks (one "ahead of" and one "behind" the 14" measurement) on each board. Then cut out the wedge of wood you've just marked, so that the two 67-112° angles are left (see drawings).

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