Building the Traditional Hewn-Log Home

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The half-dovetai l is the primary hewn-log notch, and we'll be discussing it at length in the following paragraphs. The half-dovetail notch offers the advantages of a traditional, attractive appearance; tight, strong corner joints that require no spiking; ease of layout and cutting (with Peter's method of working from longitudinal centerlines, the logs can be prenotched and dropped into position on the walls with little subsequent adjustment required); and a tendency for the joints to actually tighten as the structure ages.

FIRST THE MATH

In spite of the half-dovetail's complex appearance, each log end requires the cutting of only two angled notches. Viewed from the end of the log, the top notch slopes downward from the inside to the outside face-while the bottom notch slopes up and in. Both notches have the same pitch and, with Peter's method, are laid out with the aid of a template.

In the old days, half-dovetail notches were cut mostly by experience and educated guesswork. The log was lifted into position on the wall and scribed to match the log below . . . taken back down and recut . . . refitted on the wall . . . and so forth until a reasonably close fit was achieved. Surprisingly, no one ever came up with a better way to go about laying out and cutting notches-until Peter Gott came along.

The key points in Peter's unique half-dovetail notching method are [1] chalking a centerline along the length of each face of every log, and [2] using a couple of relatively straightforward algebraic formulas to determine a common depth for all the notches in a round.

Thus, instead of laying out approximate notch depths by measuring from the top and bottom of a log in toward the center, Peter lays out exact notch depths by measuring carefully calculated distances out from a centerline that's common to all four logs in a round. (Which, when you think about it, means that the term notch depth is used very loosely here; in fact, we're talking about the amount of wood left between the deepest parts of the top and bottom notches, rather than the amount of wood removed to form the notches.)

The beauty of taking all measurements from chalk lines snapped along the vertical centers of both faces of each log in a round is that small variations in the diameters of the logs—and even differences in the diameters of the butt and tip of each log—can be ignored. Instead, we can calculate a common notch depth (that is, the distance from the centerline to the peak of the lower notch) for each round by using a formula having three variables: [1] average log height (obtained by measuring the height of each log at its longitudinal midpoint, adding the four figures, then dividing by four to come up with the mean height); [2] the width of the chinking gap between rounds (an arbitrary figure—we'll use 1" as an example); and [3] rise (viewed from the end of a log, rise is the vertical distance from the lower edge to the upper edge of the slanted top notch).

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