New Zealand Journal of Forestry (1982) 27(2): 207–218
©New Zealand Institute of Forestry
Some thoughts on efficient handling of smallwood
C. J. Terlesk , A. Twaddle and M. McConchie
The harvesting of smallwood of approximately 0.20 rn1 piece size has been well researched but, in spite of all modern technology, the cost oj smallwood handling is high and will remain expensive relative to largewood harvesting since smallwood is difficult to aggregate in load sizes which will effectively dejray the cost of the capital and labour used in the process.
Research effort in New Zealand and overseas has been directed at improving the productivity oj the labour and capital involved in smallwood production. Various labour production aids such as jelling levers, spring-loaded tapes, and safety helmets incorporating ear-defenders have been introduced into logging in New Zealand, but many did not meet with success. Extensive trials have also been carried out on a range of low-capital-cost machinery (the Holder AG 35 tractor, the Drabant and the locally developed Matthews Mini Skidder) in an attempt to reduce the cost of smallwood harvesting. However, time has shown that the low-capital-cost approach has generally met with little acceptance in the Bay of Plenty region and the machines have virtually disappeared from the scene. A technically significant trial was conducted using a Mercedes Benz twin-winch and 4 wheel-drive tractor but, although the system developed around the machine showed considerable promise with handling of small-piece-size, the approach did not capture the imagination of the industry at the time and the system disbanded.
Highly mechanised systems introduced into New Zealand about 1976 aimed at replacing labour with capital and reducing the delivered cost of smallwood. Low availability and utilisation percentages and sensitivity to piece size resulted in unacceptable cost of production and these systems, too, have been disbanded.
A fundamental problem in the handling of small piece size is load aggregation. In an attempt to ameliorate this problem, the Forest Research Institute Harvesting Group established extensive logging trials throughout the North Island in which the thinnings were concentrated into pairs of rows physically separated from pairs of final-crop rows. The thinnings were to be removed before they affected the growth of the pruned final crop stems. Worker measurement in three of the trial areas indicated significant productivity gains (15-30%) in the one cable system trial. Results on easy terrain, however, have not been as clear, although a productivity increase of 6-12% over conventional selection thinning was demonstrated.
The concentration of thinning stems to improve load aggregation in small-piece-size operations shows some promise where production thinning is considered essential. The effect of stand rearrangement of final-crop growth and values has not been established, however, and these critical factors must not be ignored in the effort to produce low value pulpwood at less cost. Much research effort has been directed at reducing the cost of smallwood harvesting, particularly the production thinning options, and some cost savings have been achieved, but inevitably at some sacrifice of final-crop values.