Sunday, October 26, 2014

Layover Valley Rafter Hexenschnitt #2

English translation for Witches Cut

In the book
Das neue Buch vom alten Wissen der Schiftung
The new book on the ancient knowledge Schiftung
The new book on the ancient knowledge Roof Framing
The new book on the ancient knowledge Roof Framing Geometry
by Bernd Küppers

Does this make sense?
Witches cut: Hexenschnitt:

Example 3: The true witches cut using the basic method

On unequal pitched roofs the hip- or valley rafter is inclined less than the rafters or jack rafters and it gets the so-called witches cut eave cut (tail cut). This witches cut only occurs on tail cuts that are not plumb cuts at the eave line. If the unequal sloped main and adjacent roof rafters have a right angle rafter tail cut (square tail fascia) and this cut direction is transmitted to the hip rafters, one speaks of a true witches cut.

To illustrate a cross-sectional direction it requires two points at different heights. The eave line as height 0 (zero) offers itself as the first point in elevation.

The second elevation line, in the example image -30 cm, you can choose at will. The farther they are away from each other, the more accurate the scribing. It is important that the same elevation line height is chosen in all profiles.

If you now extend the direction of the tail cut, down to the elevation line, there are two points of intersection.

Firstly, the cutting direction with eave height and on the other one is the cutting direction with elevation line -30 cm.

Drop plumb lines from these intersections at the elevation line and run them through to the ground plan, until they meet the edge of the hip rafter ground plan.

The newly acquired points you plumb back to the hip rafter profile in elevation, its height accordingly, and connecting the point with the one at the hip rafter elevation line.

If you connect the intersection of the elevation lines and the intersection of the eaves, there is the resultant edge of the witch’s cuts in the ground plan.

If you bring the two points, of its height according, to the hip rafter profile, you get the actual view of the completed work at the hip rafter tail cut.


Note: I used 150mm in my example drawings for the elevation line.

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