VOL 1. “Projectile Point
fracture experiments”
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Figure 1: The three
arrow shaft configurations tested (illustration by: Jeff-Burr Garetson)
Abstract:
In 1982, a series of
experiments were conducted to determine something about arrow shaft variability
affecting the breakage patterns of projectile points. Thirty identical points
were made from fused shale (a local meta-sedimentary SiO2), and then
hafted to three different types of arrow-shafts: 1) One-piece solid hardwood (Self
arrow with the nock cut into the shaft), b) two piece hardwood “footed arrow”,
hardwood spliced or inserted into the pile end as a fore-shaft, for durability
and balance, glued in hardwood nock, and c: two-piece hardwood and cane (also a
footed arrow). The three groups of arrows, ten of each type, were shot at
identical wood plank targets with hand held bow from a distance of 25 feet (8 m).
More than 90% of the points broke on impact
leaving the broken tip imbedded in the plank. Breaks occurred either at the tip
or midsection, sometimes accompanied by basal fractures (broken tangs). Both
hinge and languette (tongue like projection) fractures were generated but no
burinations or spiral fractures occurred in the thirty trials conducted.
Fracture type and location appear to be strongly correlated with hafting form
and style of shaft. Compound shafts of wood and cane seem to absorb more shock
on impact and therefore fewer points are broken. Also, breaks tend to occur
closer to the tip with compound shafts. Points with broken tips are easily re-sharpened
and reused, whereas medial breaks usually render the point useless as a
projectile point (Knetch 1997, Kelterborn 2001, Titmus and Woods 2006). Broken projectile
points from archaeological contexts may be understood more clearly if the cause
and mechanisms of use-fracture are better understood.
Keywords: projectile points; fracture patterns; Grimes
Canyon fused shale; experimental archaeology; North America, arrow shaft
variability.
Ray Harwood knapping projectile points at N.A.R.C. 1982 (Singer)
See also these fine online lithic publications:
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