A buyer should understand the production system before choosing individual machines. Choosing a machine first and then discovering which system it belongs to is how fleets become unbalanced.
Cut-to-length harvesting
The classic CTL production chain is:
The harvester performs several jobs in one cycle:
- grabs the tree
- cuts the tree
- feeds the stem
- delimbs the stem
- measures diameter
- measures length
- determines log assortment
- crosscuts the logs
- places logs by assortment
The forwarder then loads those logs and carries them to roadside.
Commercial advantages
CTL can reduce the number of machines required at the harvesting site, and it keeps logs off the ground during extraction. Potential advantages include:
- reduced log contamination
- better assortment control
- reduced soil dragging
- accurate production data
- good thinning capability
- good utilisation of each stem
- integrated measuring and optimisation
Commercial disadvantages
The equipment is highly specialised. If the harvester stops, wood production stops. If the forwarder stops, roadside supply eventually stops.
The head alone contains numerous expensive systems — saw motors, feed motors, measuring sensors, feed rollers, delimbing knives, computer systems, control valves, a rotator, wiring and hydraulic hoses. Downtime can therefore be commercially severe, and the dealer support arrangement is not a soft factor in this system. It is part of the machine.
Full-tree and tree-length harvesting
The alternative system may look like:
This separates the harvesting process across several machines.
Commercial advantages
Individual machines can achieve extremely high production because each does one task very quickly. A feller buncher cuts and bunches trees. A skidder extracts stems. A processor converts stems into logs. That specialisation can produce very high throughput.
It also distributes risk differently: a failure in one machine does not necessarily stop the entire system, provided there is buffer inventory between stages.
Commercial disadvantage
Every machine becomes part of an interdependent production chain. If the contractor owns:
- a $700,000 feller buncher
- a $400,000 skidder
- a $500,000 processor
- a $350,000 loader
but the processor fails, a large amount of capital can effectively become unproductive. Fleet balancing is therefore crucial.
The bottleneck principle
A harvesting system produces only as much as its slowest critical stage. This is the single most important principle in forestry machinery procurement, and it is routinely ignored.
Consider a system with the following stage capacities:
The practical system cannot continuously deliver 100 tonnes/hour. Its commercial capacity is closer to 55 tonnes/hour, because truck supply is the bottleneck.
Buying a larger feller buncher would achieve little. It would increase capital, increase depreciation, increase fuel and increase transport cost, and deliver no additional tonnes at all.
The better investment might be:
- another truck
- improved loading
- better landing design
- increased processor capacity
Before any machine purchase, model every stage of the chain and identify which one actually constrains output. If the machine you are about to buy is not the constraint, you are buying capacity you cannot sell.
Test it before you sign. Write down the hourly capacity of every stage in your system. Circle the smallest number. If the machine you are quoting is not that stage, explain — in writing, to yourself — what the purchase is actually going to change.
Choosing between the systems
Neither system is generally superior. The choice is made by four conditions, and it is usually already narrowed before machine selection begins.
Stem size and form. Uniform, well-formed stems suit cut-to-length, where the head does the work of felling and processing in one cycle. Large or irregular stems favour full-tree, where the difficult processing happens at a landing with a machine dedicated to it.
Terrain and access. Full-tree needs a landing that can be established and reached by trucks. Where landings are hard to place — steep ground, sensitive sites, restricted access — processing at the stump is the practical answer.
Product specification and sorting. Sorting at the stump is cheaper than re-handling at a landing. Where a mill requires multiple products cut to length and sorted, cut-to-length has a structural advantage; where the product is whole stems or a single assortment, that advantage disappears.
Residue management. Cut-to-length leaves residue distributed through the coupe, which can serve as brash mats and reduce compaction. Full-tree concentrates residue at the landing, which suits a biomass outlet but requires a plan for it.
The most useful practical question, though, is which system the estates you can actually win work in already use — because the system determines the product specification you will be paid against, and a contractor equipped for the other one is quoting against a mismatch.
Balance is worth more than capacity
A production chain delivers at the rate of its slowest critical stage, and pays for every stage regardless. That statement is obvious and routinely ignored in purchasing, because machines are compared individually and bought into systems.
The practical discipline is to measure each stage's sustained output over a full week in representative conditions, in a consistent unit, and to add capacity only at the stage that is actually limiting. A feller buncher with 20% more capacity than the skidders can clear has not added 20% of production; it has added capital, fuel and depreciation to a chain that still produces at the rate of its extraction. Stems simply accumulate until the landing fills and felling stops anyway.
Two further points are worth stating because both are frequently missed.
Trucks are a stage. Truck supply sets production as effectively as any machine you own, and chains constrained by haulage look balanced on paper while producing roadside stock in practice. Include haulage in the chain whether or not you own it.
The bottleneck moves. It shifts with haul distance, stem size, weather and truck availability. A chain balanced at 200 metres of extraction can be extraction-limited at 600.
Fixing a constraint without capital
Before adding a machine, exhaust the levers that cost nothing:
- Landing placement and layout — shorter hauls, better truck access, more sorting space
- Snig track and corridor planning — reducing the longest extraction distance rather than the average
- Shift patterns — matching machine hours to truck availability rather than to the working day
- Maintenance scheduling — moving planned downtime out of productive hours
- Operator training at the constraining stage specifically — where the variation between operators is largest
A bottleneck moved by rescheduling is a bottleneck moved cheaply. Where these are exhausted and the constraint persists, the honest alternative is sometimes to reduce capacity at an over-specified stage rather than add it at the constraint — a smaller machine where capacity is idle releases capital without costing output.
See cut-to-length versus full-tree for the detailed comparison, and use the bottleneck analyser to find the constraint in your own chain.
Whole-tree chipping and biomass systems
A third system sits alongside cut-to-length and full-tree, and it is easy to miss because it produces a different product entirely. In whole-tree chipping, stems are felled and extracted much as in a full-tree operation, but instead of being processed into logs at the landing they are fed whole into a chipper or grinder.
The system's economics are unlike either of the others in one important respect: the product specification is set by a buyer rather than by a mill's log schedule, and it is unforgiving. An out-of-specification load is rejected, not discounted. That makes the offtake agreement the first decision in the chain rather than the last, and it changes what the bottleneck is — feed rate to the processor, rather than felling or extraction.
Where residue from a conventional harvest has a biomass outlet, the same logic applies to the residue chain: landing layout and stem presentation have to be planned for it in advance, because a landing designed only for log processing makes residue recovery expensive.
Steep-slope and assisted systems
Where slope, soil or stability prevent conventional ground-based work, the available systems change and so do the economics.
Winch-assist tethers a ground-based machine to an anchor, extending the slope on which it can work safely. It adds capital and a second machine to the chain, and it converts terrain that would otherwise be unavailable into workable ground — which is the whole commercial case for it.
Cable systems extract by cable rather than by machine travel. They are slower and more capital-intensive per cubic metre than ground-based extraction, and they are the answer where the alternative is not extracting at all rather than extracting more cheaply.
Both are best understood as access purchases rather than production purchases. The question is not whether they are efficient — they are not, compared with flat-ground work — but whether the resource they unlock is worth the cost of reaching it. That calculation belongs to the estate as much as the contractor, and it should be had before a machine is specified.
Balancing a chain, with numbers
The bottleneck principle is easy to agree with and hard to apply, because it requires measuring each stage rather than estimating it. Worked through, it looks like this.
A full-tree chain is measured over a representative week and produces these sustained rates:
Feller buncher 100 t/h
Skidders (2) 80 t/h
Processor 65 t/h
Truck supply 55 t/hThe chain delivers 55 t/h — the truck figure. The three machines above it have a combined 245 t/h of capacity, of which 190 t/h cannot be sold.
Now consider the two available "upgrades":
| Change | New system capacity | Effect |
|---|---|---|
| Larger feller buncher (100 → 120 t/h) | 55 t/h | None, plus more depreciation |
| Faster processor (65 → 80 t/h) | 55 t/h | None, plus more capital |
| One more truck (55 → 70 t/h) | 65 t/h | +18%, limited by the processor |
| One more truck and processor capacity | 70 t/h | +27% |
The cheapest capacity in this chain is haulage, and it is the last thing most contractors consider because it is frequently someone else's machine. That is the practical lesson: include every stage in the measurement, including the ones you do not own.
Shift patterns are capacity
Before buying capacity, check whether the capacity you have is available at the right time.
A chain constrained by truck supply is frequently constrained by truck supply during a particular window — mill opening hours, weighbridge queues, or a haulage contractor serving several clients. Moving machine hours to match the window, rather than to match the working day, can lift delivered volume without any capital at all.
The same applies to maintenance. Planned servicing performed during productive hours consumes the scarcest thing in the operation. Moved outside them, it costs the same money and no production. Over a year that difference is substantial, and it is available to any operation willing to schedule deliberately.
Use the bottleneck analyser to work your own chain, and see cut-to-length versus full-tree for choosing between the two main systems.