I thought that I would have a go at making larch shingles using an 16" long section of nominal 12" diameter (38" girth) larch log cut from the base of a recently felled larch tree to make a long sill for our woodland cruck project.
The butt log was first quartered through the heart of the log using a large 14" froe and the sides cleaned using a Wetterlings broad axe.
The shingles were split out from the quarters and the sapy edges removed to ensure heartwood only shingles with the sapwood being recovered to make kindling
This resulted in the production of 28 shingles approx 0.75 - 1" thick x :-
6.25" wide x 4 off
5" wide x 4 off
4.5" wide x 10 off
4" wide x 4 off
3.5" wide x 3 off
2.75" wide x 3 off
i.e. a grand total of 13.55 sq ft [ 1.259 sq m]
or 0.903 cu ft from a 1.047 cu ft log resulting in a conversion efficiency of 86% shingles & 14% kindling.
After draw knifing and trimming the shingles were butted up tight on a flat floor resulting in a string of shingles 112" long x 16" high equivalent to 12.44 sq ft or 0.829 cu ft from a 1.047 log resulting in an actual conversion efficiency of 79.2% with 20.76% waste in the form of kindling and trimmings. A more accurate measure of conversion efficiency could be obtained by weighing the log before and the shingles after conversion.
The volume of timber needed to cover a 30 ft long x 16 ft high (slope) roof in shingles with 3 shingle overlap on 4" lath spacing is about 8640 shingles with a cumulative volume of 300 cu ft [9 cu m] i.e. as much and maybe a little bit more than is needed to make a 30 x 16.5 ft cruck timber frame.
Ken Hume
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