On-the-ground harvest unit layout, especially in skyline-thinning operations, is critical to meeting multiple resource objectives of the land manager and maintaining the economic viability of the timber harvesting operator. This phase of an operation can optimize the layout and harvesting of a sale or unit. Detailed layout by a knowledgeable...
This paper describes a mathematical formulation and a computer program
in basic language for analyzing the load carrying capacity of skyline
systems using the effects of log drag. The actual log and ground geometry
are used in the analysis of the payload capacities for standing, live and
running skylines. The...
Published February 1984. Facts and recommendations in this publication may no longer be valid. Please look for up-to-date information in the OSU Extension Catalog: http://extension.oregonstate.edu/catalog
Initially, a small experimental study was undertaken to examine the influence of incline on the frequency of taut cables. The experiments consisted of exciting a short cable at angles of incline from zero to 90 degrees and at various tensions. The results from these experiments shows a small effect due...
Three skyline carriage types are analyzed on the basis of their operating characteristics and limitations. Their effect on productivity
is expressed as cubic feet per hour yarded to the landing. These carriage types, tested as part of Oregon State University's School of Forestry Smallwood Harvesting Research Program represent those which...
In recent years, a great deal of research in North America has been directed toward refining methods of assessing the load-carrying capability of skyline systems. Little effort has been directed, however, toward field measurement of cable tensions for skyline logging systems to facilitate initial tensioning of unloaded skylines or to...
Yarding delays add significantly to the time and cost required to obtain a given quantity
of timber. In this study, they increased total yarding time by as much as 28 percent. As yarding system complexity increases, the frequency of delays can also be expected to increase. For one balloon yarding...
Research on skyline machines and techniques currently available for yarding smallwood is reviewed. Three categories of machines are discussed: used yarders (with a low initial cost) adaptable to smallwood, new and versatile yarders (with a high Initial cost) manufactured in the United States, and new, foreign-built yarders (with a low...
The forest products industry often uses intermediate-support cable logging systems to transport logs from the harvest site to a staging area. A method is presented to assist in the analysis and design of these cable systems. The method determines tensions in individual cables, forces on and stresses in the support...
Designing timber harvesting units is a challenging task. The task requires decision making on logging equipment, landing site, cable road profile, road location, and transportation system. Traditionally forest planners have done the task manually. However, the manual method makes it difficult to examine many alternatives and the harvest plans depend...
Commercial thinning young growth forests is an increasingly
important silvicultural technique for improving second growth
management of Douglas-fir stands. Research aimed at advancing the
efficiency of skyline logging operations in small wood timber stands
is essential in order to make thinning these young stands economical.
The purpose of this study...
This project was one of several studies conducted during the summer of 1981 that were part of the Smallwood Harvesting Research Program administered through the Department of Forest Engineering, Oregon State University. The study looked·at the feasibility of falling and yarding whole trees as a combined activity in a cable...
The purpose of this study was to determine the significant
variables influencing the damage levels sustained by the residual
stand after skyline thinning of coniferous stands. Damage levels were
measured in ten study areas in western Oregon that had received their
first commercial thinning.
For this post-logging study, 38 units...
This paper shows how ten easy-to-use linear skyline thinning production rate equations were obtained by transforming existing but more cumbersome turn time equations using the THIN simulation model [11). The equations provide reasonable approximations of delay-free hourly production for several cable yarders operating skyline thinnings under a variety of conditions....
Road changing i.s the activity of moving operating lines
on a cable yarding operation to permit access to logs in an
unyarded portion of a logging unit. The time required to
perform this activity varies widely and may consume a significant
portion of the total yarding time.
With rising costs...
This study compares the production rates and yarding costs of prebunching
with a low investment skyline yarder and swinging with a larger
skyline yarder to full-cycle thinning with the larger yarder The study
analyzes two slackpulling techniques (manual and haulback assisted) and
two carriages (a multi-span carriage and a clamping...
Multispan skyline logging systems are cable systems designed to yard logs over steep terrain having a constant or convex slope. An intermediate skyline support is used to raise the skyline high enough to achieve ground clearance without overstressing the skyline. Certain improvements in performance can be realized by providing intermediate...
Carriages may be classified as slackpulling or non-slackpulling, and the slackpulling carriages may be further classified by how they accomplish the slackpulling function. Slackpulling carriages provide the skyline with lateral yarding capability and therefore can be used in a variety of silvicultural prescriptions. Non-slackpulling carriages can include either chokers or...
A computer program package to estimate cable yarding
payload capability was made. The package was intended to
expand applicability of existing packages and to be user
friendly. It has six system options: live skyline, standing
skyline, running skyline, slackline, multispan and highlead.
In the standing skyline and multispan analyses, load...
The popularity of gravity-return skyline logging systems is now increasing in the Western United States. Simplicity seems to be the basis for their success. While two drum yarders are most commonly used, ·some systems, such as the Wyssen, use only a single drum for yarding. Carriages commonly used with these...
In the Pacific Northwest, loggers are faced with the problems of changing from logging old growth to second growth. This is due to the shrinking old growth timber supply and increased entry into the· second growth stands. Beuter (1 980) indicated that in western Oregon 70.2 percent by volume of...
Timber harvesting is a common activity on many small woodland
properties. Whether a harvest is large or small, landowners
must carefully evaluate their overall goals and objectives before
beginning. A well-conducted harvest will help realize those
goals, but a poor job may lead to disappointing results that have to
be...
The objective of this paper is to develop a methodology for determining running skyline yarder performance based on the mechanical characteristics of the yarder and its interaction with the load and the terrain. A code for implementing this procedure on the HP-9020 will be prepared .
Tension relationships were determined in steel cable passed through a stump notch and anchored to another object. Tensions were measured in the cable coming into and leaving the notch with one full wrap on the stump. Data was collected from two sites with two test stumps (15.7 to 37.5 inches...
Whole tree and tree length thinning are two alternatives which are likely to be more productive and may prove to be more cost effective
than conventional log length thinning. The purpose of this study was to evaluate and compare log length, tree length, and whole tree thinning techniques in terms...
This paper describes the results of a time-study conducted
near Grand Ronde, Oregon, to determine the production
rates and total harvesting costs of a cable thinning in a
young stand. The stand had a species mix of 48 percent
western hemlock (Tsuga. heterophylla- (Raf.) Sarg.), 45 percent
Douglas-fir (Pseudotsuga meuziesil...
This paper describes the analysis of data from a three-year gross time study of skyline, balloon, and helicopter yarding systems operating in Western Oregon. Data collection activities were designed and supervised by the Pacific Northwest Forest and Range Experiment Station, U.S.D.A. Forest Service. The specific logging systems studied were running...
This paper describes the analysis of data from a three-year gross time study of skyline, balloon, and helicopter yarding systems operating in Western Oregon. Data collection activities were designed and supervised by the Pacific Northwest Forest and Range Experiment Station, U.S.D.A. Forest Service. The specific logging systems studied were running...
Procedures are developed for integrating short-term,
area-based plans with long-term, strata-based harvest
schedules. These procedures were tested on a 4000 hectare
tract of forest land in British Columbia. It is shown that
a combination of these two approaches to forest planning
provides a spatially feasible short-term solution that is
also...
The development of bioenergy from biomass has dominated the minds of forest engineering researchers over the last decade. One of the main themes that has been generated from that research is that bioenergy from biomass has major operational hurdles to overcome before becoming economically feasible. More directly, the impact of...
This study evaluated the impact of using a rubber-tired skidder to keep the landing clear by sorting and decking the logs along the road prior to loading by a self-loading truck. The evaluation was accomplished through detailed time studies conducted on a Koller K-300 yarder, a Crown Super 3000 self-loader,...
This paper presents an evaluation of the cable loading
support capacity of red alder, Alnus rubra Bong., Sitka
spruce, Picea sitchensis (Bong.) Carr, and western hemlock,
Tsuga heterophylla (Raf.) Sarg., tail trees. Capacity is
measured in terms of combined stress resulting from
compression and bending, rather than the traditional methods...
This paper documents the development of a model which determines multiple stump anchor system displacement as a response to skyline load for four anchor rigging configurations: 1. Series multiple, 2. Tieback, 3. Elevated tieback, and 4. Equalizer block. It also documents the field testing of four two stump anchors rigged...
An analysis of forces on two tree intermediate supports is presented. The analysis is in two parts:
The maximum force that the support jack will experience. The movement and forces created in the two tree support by the skyline and carriage. The maximum force on the support jack occurs when...
Western hemlock and Sitka spruce are relatively thin-
barked species and susceptible to damage during thinning
operations. Damage to the wood allows decay-causing fungi
to enter resulting in loss of merchantable volume at the
time of final harvest. Cable yarding systems are needed for
much of the thinning because most...
Forest managers in the Blue Mountains, of northeastern Oregon are currently faced with
vast areas of forests with health problems and high fuel loadings. These conditions
resulted from a combination of insect infestations, past management practices and the
elimination of fire from the local ecosystems. These forests are now overstocked,...
Strip thinning is recognized as a way of commercial thinning
young-growth stands. strip thinning has been used worldwide. The
purpose of this study was to explicitly evaluate the costs and benefits
associated with skyline strip thinning in young Douglas-fir
(Pseudotuqo menzesii Franco) stands in the Pacific Northwest and to
compare...
There is much interest in the State of Vermont in cable harvesting. Since there are no time studies available for cable harvesting with various machines in Vermont, it is necessary to arrive at production and cost levels by a different method.
The method chosen for this paper is made up...
This paper describes the results of a project conducted to determine
the magnitude of and the parameters affecting the magnitude of the
cable tensions generated during lateral yarding operations in a cable
thinning. Specific emphasis was placed on measuring mainline tensions
as a function of turn weight, turn length, mainline...
Young Douglas-fir stands were commercially thinned to achieve vegetation- and wildlife-related objectives. Harvesting and forwarding production and costs were compared among three mechanized thinning treatments: light thin [(115 residual trees per acre (tpa)], light thin with 0.5-ac openings (92 residual tpa), and heavy thin (53 residual tpa). The sites were...