Abstract:
Results of a recent production study indicate that a four man
crew thinning young growth Douglas-fir [Pseudotsuga mensiezii (Mirb.)
Franco] with an Iglarid-Jones Trailer Alp can produce 1360 to 1460
cubic feet (38 to 41 cubic metres; 8160 to 8750 bd. ft.,) per eight
hour day on slopes of 10 to 50 percent with average slooe distances
of 150 to 300 feet (46 to 91 metres) and average lateral yarding
distances of 30 to 50 feet (10 to 15 metres). The stand studied was
thinned from 226 stems per acre (558 stems per hectare) to 130 stems
per acre (321 stems per hectare). The average tree size removed was
19.4 cubic feet (0.55 cubic metres) and the average log size yarded
was 12.9 cubic feet (0.36 cubic metres). A standing skyline system
was used with a haulback line attached to hold the carriage in
position during lateral yarding.
The cost of a four man crew felling, bucking, and yarding this
material with an average slope distance of 250 feet (76 metres) and
an average lateral yarding distance of 35 feet (11 metres) is
estimated at $36.63 per cunit ($12.93 per cubic metre; $61 .04 per
Mbf.). A three man crew operating under the same conditions would
produce only 1160 cubic feet (33 cubic metres; 6950 bd. ft.) per day
but the unit cost of production would be lower at $35.30 per cunit
($12.46 per cubic metre; $58.83 per Mbf.). During the study,
operating delays accounted for 26 percent 0f total study time and
skyline road changes accounted for 10 percent of total study time.
The use of intermediate supports can successfully extend yarding
distance on unfavorable slopes and can facilitate efficient decking
if placed within 100 feet (30 metres) of the landing.
