Peterson Portable Sawmills

Milling Trees from a Small Holding


By John Fairweather

Some smallholders now have millable trees on their properties. This article illustrates a recent example of small scale milling to produce sawn wood for the owner’s use. This milling job went well and illustrates some of the basic techniques and on-farm use, typical of what can happen on a smallholding.

The Milling Process

The milling took place on a smallholding about six kilometres north of Rangiora, North Canterbury. The property is used for horse riding and horse breeding. The owner wanted to enclose the horse riding arena and decided to mill some trees to provide the rails suitable for such a fence. The former owner had planted a variety of trees, including eucalypts that are now at least 20 years old. In addition, there were a number of large Macrocarpa around the hayshed. These provided some straight logs of good form and with minimal branching.

A local contractor felled three of the Macrocarpa to give six logs of three metres length. In addition, a large eucalypt provided four logs of four metres in length.

Most of the logs were easy to roll up to the mill although the eucalypt butt log was almost at the limit of manhandling. All logs were sawn into the largest possible cant then cut into 150 mm by 50 mm rails suitable for the fence. If the log was large enough we had a cant that was 300 mm wide and then cut this in half, rotating each remaining piece and cut at 50 mm thickness. The eucalypt was large for its age with the butt log having a mid section diameter of 52 cm. Tension in the log meant that when the large cants were cut in two through the pith area they each curved. When they were subsequently rotated and cut, the boards were curved.

Sawn Wood Recovery

The sawn wood was carefully stacked under the shelter of an adjacent row of mature trees. Each layer of sawn wood was separated with four spacers to allow some movement of air. Eucalypts need special care in the stack to slow the rate of drying, so we used the slab

wood to protect the wood at the top of the stack from direct sunlight, and toprovide weight to stabilise the stack and minimise movement. The latest Australian advice is to slow the rate of drying by keeping direct sunlight out and minimising air movement by covering stacks with a breathable plastic material.

The data in the table show that we had good recovery of sawn wood from both species. Recoveries are usually closer to 50 per cent and the higher rates obtained here were probably due to the small kerf of the band saw.

 
Rail width (mm)
Rail thickness
(mm)
No. of rails
Sawn volume cubic metres
Log volume
Recovery
Macrocarpa
150
200

75

50
50

25

49
14

4

1.55 2.71 57%
Eucalypt

 

150
150+ 150
50

50
25
37

4
3
1.28   2.27   56%  
Total
  2.82 4.98 57%

Fencing Options

We discussed some fencing options with the smallholder and worked out that for a single rail fence there was sufficient sawn wood for the Macrocarpa to make 189 metres of fence and for the eucalypts to make 164 metres of fence. There would be ample to fence the horse arena and to make another enclosure. We recommended using a preservative on the eucalyptus. This exercise shows how trees on smallholdings can be used. The Macrocarpa was easy to cut and stack while the eucalypt was largely good to work with but had some movement. The work was started early on a Saturday morning and was completed by noon on Sunday. The task was made easier with the help of Nick Ledgard who carefully stacked the sawn wood as it came off the saw.
John Fairweather is a North Canterbury woodlot owner and principal research sociologist, AERU, Lincoln University

© 2007 New Zealand Tree Grower
Reprinted with permission

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