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Hardwood Group Offers Training,Tips for Bucking Logs for Grade
Bucking Hardwood Logs: The Hardwood Value Improvement Project provides suggestions for bucking hardwood logs, including how to ‘look for the best log’ that can be cut from the stem.
Date Posted: 9/1/2007
(The following article on hardwood log bucking is based on a series of articles produced and provided by the Hardwood Value Improvement Project (HVIP). The HVIP is a collaborative effort among the Ohio Forestry Association, U.S. Forest Service and a collection of businesses, trade associations and extension agencies to offer hardwood log bucker training throughout the 30-state hardwood region.)
Know Your Markets
The golden rule used throughout training by the Hardwood Value Improvement Project (HVIP) is: ‘know your markets.’
Hardwood log markets can vary considerably by species, buyer and region. A quick glance through publications such as The Sawlog Bulletin bears this out. While a particular mill or buyer may have a general set of specifications for the grades of logs they purchase, often there are species-specific requirements as well. Knowing these specifications and requirements is essential in bucking hardwood logs for grade.
Knowing your markets means knowing the physical size requirements for the logs you produce, the quality requirements, price differentials for various grades and how all these specifications will be applied and interpreted by the scaler or buyer.
Physical requirements include minimum diameters (e.g. 14 inch minimum for veneer logs), acceptable lengths (e.g. 8 feet, 9 feet, 10 feet only or 8 feet, 10 feet, 12 feet, 14 feet and 16 feet) and trim lengths (e.g. 4 inches, 6 inches, etc.).
Quality requirements refer to the number, type and position of defects that are allowed. Quality requirements tend to specify the number of clear faces (or length and number of clear cuttings) and the amount of sweep, heart, holes, etc.
Mills demonstrate that they want better logs by assigning progressively higher prices for better grades. The differences in prices between grades are readily available, and knowing the change in percent from one grade to the next helps you to understand when it makes sense to sacrifice volume for grade.
Communication and interactions with buyers is an essential aspect of knowing your markets. Ask log buyers questions so you understand how they grade logs and make deductions for various defects.
Hardwood logs may be better or worse than they look at first glance. A little extra care in cutting out logs can ensure that they make the best possible impression on the buyer or scaler.
The red oak log in Figure 1 has root flair. In this case it gives the log an exaggerated appearance of sweep and tends to make the heart look off-center, which might rule out a veneer grade. From a practical standpoint, it makes it difficult to load this log on a truck or in a container. Trimming off the root flair in this case would reveal that the heart is indeed centered. The red oak log in Figure 2 came into a sawmill yard with a significant amount of root flair; yard workers trimmed away the flair in preparation for showing it to a veneer buyer.
Buyers prefer logs that are squarely cut to accurate lengths. This attention to details signals to the buyer that you have taken the time to carefully buck out your logs. This positive impression can have a strong beneficial effect over the course of scaling and grading an entire load of logs.
The Quality Zone
In producing valuable hardwood logs from tree stems, it is important to understand the potential of logs to produce lumber and other valuable products. Producing a rectangular object like a board from the naturally irregular shape of a log is challenging enough. When this is combined with common defects, such as knots, holes and seams, the sawyer will need considerable skill to produce the most valuable lumber. Removing slabs from the log and squaring them up for further sawing leaves us with a portion of the log known as the ‘quality zone,’ shown in Figure 3.
The quality zone has been defined as the portion of the log between the heart zone (the center 40% of the log’s diameter) and the slab wood (the outer inch of the log’s diameter). This quality zone is where high quality boards are sawn. These ‘jacket boards’ tend to have large defect-free areas.
Defects that impact the quality zone will lower the yield of the higher grades of lumber. The various grading systems that mills and other buyers use reward logs with fewer defects and penalize those with more. The differences in prices between grades represent the greatest potential gains and losses during the bucking process.
Look for Best Log
One of the rules of thumb for optimal bucking of hardwood logs developed at Michigan Tech by Jim Pickens and Scott Noble for HVIP is to look for the best log that can be cut from the stem and then work around it.
For most of our valuable hardwood species, there are significant price differences between grades. Most often, there is one potential log in the stem that will contain the majority of that tree’s value. Comparisons made with the HW Buck log bucking software bear this out.
To test this rule of thumb, 25 hard maple stems were bucked using the optimization process in the HW Buck software. In this process, HW Buck compares every possible combination of log bucking options for each stem, using pre-defined grading rules and prices. The bucking pattern that results in the highest value is presented, showing the value of each log created.
For each of the 25 trees used in this example, the value and volume of each log was recorded. In this small sample, optimal bucking patterns resulted in production of one to four logs from each tree. On average, the best log from each tree represented 68% of that tree’s value. Taking this a step further, for trees where three or more logs were created, the best two of these logs, on average, represented 91% of that tree’s value.
This example used the International ¼-inch log rule and seven grades of logs, ranging from veneer to scragg wood in price and quality. Note that similar results could be expected regardless of the price schedule, log rule and species, as long as the relative differences in prices from one log grade to the next that are commonly reflected in the market are used. Historically, percent differences among prices by log grade have remained similar.
Look for the best log in a tree that can be made and work around it in making your bucking decisions. Capturing the value of this best log goes a long way toward realizing the full potential value of each tree.
Value and Volume
When does it make sense to make a log shorter in order to make a step up in grade?
A common assumption is that the more scaled volume in a log, the better. In situations where producing the most value is the goal, it often makes sense to sacrifice volume in favor of upgrading a log into a higher paying grade.
A log can be shortened by 2 feet (e.g. 12-foot log bucked back to 10 feet) as long as the increase in price to the resulting grade is at least 30%. This is true of Doyle, Scribner and International ¼-inch log rules alike. This assumes no increase in the diameter of the log. If the diameter increases by 1 inch, a smaller increase in price is all that is needed to increase the value of the log. Specifically, increases of 18% for International ¼-inch rule, 15% for Scribner rule and 16% for Doyle rule are all that are necessary.
Let’s consider an example. Suppose you are considering bucking out a 12-foot #1 grade hardwood saw log; we will assume it is 14” inches in diameter (100 board feet, International rule). At a #1 grade price of $600 per MBF, this log is worth $60 (0.100 MBF x $600). Alternatively, you buck it into a shorter 10-foot Select grade log. Assuming that this shorter log is also 14” in diameter, it would yield 80 board feet. If the Select grade log sells for $900 per MBF, this smaller log is worth $72 (0.080 MBF x $900), and the 2 feet that you did not put on the end of this log are probably the butt end of the next log.
Are all these calculations necessary before making the bucking decision? Not really. All you needed to know is that the $900 price is 50% more than the $600 price. It is often possible to jump more than one grade in price by shortening a log, resulting in more dramatic value increases.
Communication with log buyers is important. Some prefer to buy the log in a longer length but are willing to pay you for the shorter, higher value log.
When a logger is working on a production-based contract, the focus is going to be on providing the highest volume of logs, negating the whole question of volume versus value. Mills and buyers who contract out production should take a close look at their price incentives to ensure that maximizing log value is a logical course of action for the contractor.
Sweep and Crook
It is important to understand the impact of sweep and crook on the volume that can be sawn from a log. Sweep and crook will lower the scaled volume of a log, and excessive sweep or crook will result in a lower price grade for the log.
Some sweep is unavoidable, based on the shape of the tree. In most cases, one or two potential logs close to the butt end of the tree will contain the greatest share of the potential value of the tree. Minimizing sweep on these logs is most critical in ensuring the highest possible grade, even if this means cutting out otherwise useful sections of the stem.
Consider the challenge in bucking the red oak stem in Figure 4. This stem is 39.5 feet long, and there are six potential log grades available (A Veneer, B Veneer, Prime, #1, #2, & #3).
The first bucking approach emphasizes volume and expediency. Four 8-foot saw logs are cut from the stem in successive order. The butt log has the highest potential value, but this bucking pattern leaves 4 inches of sweep in it, creating a log worth only $18. Overall, this bucking pattern produced 208 board feet and just $67.50 in value.
The second bucking pattern focuses on minimizing sweep in the most valuable logs and maximizing the total value of the stem. By bucking off a section of the tree to eliminate most of the sweep, the butt log now has only 1 inch of sweep, enabling it to grade out as a B Veneer worth $58.50. Overall, this bucking pattern produced 191 board feet and $117.30 in value, a 74% increase in value over the other bucking pattern. Note that this approach resulted in three short sections cut out of various locations on the stem rather than one long one at the top.
This bucking comparison was accomplished with HW Buck software used in HVIP log bucker training.
Hardwood Defect: An imperfection in the slab zone, quality zone, or heart center resulting in the reduction of sound wood volume and quality.
One of the most important aspects of the Hardwood Value Improvement Project’s training package is an emphasis on understanding hardwood defects. Workshop participants learn to recognize log surface indicators of internal defects and understand their impact on value and bucking patterns.
The Hardwood Defect Trainer is an important resource that participants take home with them. The self-contained Web page includes a step by step tutorial that explains many types of defects along with an extensive photo gallery and defect index. An online version of the Hardwood Defect Trainer can be found on Michigan Tech’s Hardwood Research Group Web site: www.forest.mtu.edu/research/hwbuck/hardwood_defects/index.html).
Some defects that are generally ignored in saw logs are serious enough to prevent an otherwise acceptable log from making a veneer grade. Gum in the growth ring of a cherry log, for example, can seriously devalue the appearance of the veneer. Veneer-only defects tend to include items like single adventitious buds, mineral streaks, curl, defoliant rings, slight ingrown bark, and tension streaks. Some defects are species specific.
The presence of defects that immediately rule out veneer grades will often change the ideal bucking pattern for a particular stem. For instance, when a clear 10-foot butt log has its veneer log potential ruled out by an interior defect visible on the end, such as gum, a 12-foot saw log may be the next best alternative.
Making a careful appraisal of external defect indicators is a good first step in judging the best potential logs that may be cut from a stem. Knowing how to recognize these defects is an important skill in making bucking decisions.
Defining Hardwood Veneer Log Quality Attributes (Wiedenbeck et al, 2004) is a free U.S. Forest Service publication containing many high quality color images of veneer defects, supplementing a very good description of the hardwood veneer industry in North America. You can download a copy at www.fs.fed.us/ne/princeton/publications/index.html.
HW Buck Software
The Hardwood Value Improvement Project uses HW Buck log bucking software as a training tool in log bucking workshops. This software was first developed by Dr. Jim Pickens and others at Michigan Tech and then more recently enhanced by both Pickens and Scott Noble to provide a more realistic and user-friendly experience.
This Windows program allows you to look at 150 different tree stems, rolling them around on screen to see the shape of each one, along with its defects. The user can then place accurate cuts to decide how each stem should be bucked. The program gives you the result of your bucking decisions, including the board foot volume of each log and its value, as well as the overall value created in bucking the stem. One popular option allows you to compare your result against the optimal bucking pattern for the stem.
HW Buck software is a great way to practice log bucking techniques without expensive mistakes, safety hazards or sawdust. Users will find that patterns of sound bucking decisions become evident after using the program for a while. Comparing individual results to the optimal results provided by the software reinforces how much profit could be gained by making better bucking decisions.
HW Buck is not a perfect representation of the real world, but it is a very good way to practice cutting up logs and see the immediate results. Like any software, a little bit of time must be spent in learning how it works. Many of us have a younger and more computer-friendly person around the house to lead us through it.
To download a free public version of HW Buck Software, visit Michigan Tech’s Hardwood Research Group’s Web page (www.forest.mtu.edu/research/hwbuck/downloads.htm). This version has a limited number of log market options but does include all the log bucking options. For a more enhanced version of this software, along with several other important hardwood log bucking resources, please attend an HVIP log bucking workshop. For a sampling of hardwood log buck training, visit the HVIP channel on YouTube (www.youtube.com/HardwoodVIP).
(Editor’s Note: To schedule, host or promote an HVIP log bucking workshop or to suggest a bucking instructor candidate, visit the Web site at www.hardwoodvip.org or call project manager Steve Bick at (315) 369-6424.)