Understanding Chain Saw Reactive Forces

Transcription

1 Contents Acknowledgments... 5 Introduction... 7 CHAPTER 1: PREPARING FOR WORK... 9 Training and Experience Health and Fitness Potential Work Hazards Chain Saw Safety Personal Protective Equipment Work-Related Equipment Working With Others Are You Ready to Work? CHAPTER 2: TO FELL A TREE Basic Tree Felling Procedure Step 1: Assess the Tree and Felling Site Identifying Tree Hazards Identifying Felling Site Hazards Estimating Tree Height Determining Tree Lean Determining the Lay Establishing the Escape Route Step 2: Prepare the Felling Site Protecting People Protecting Property Preparing the Work Area Preparing the Tree Step 3: Execute Felling Cuts and Retreat Cutting the Notch Making the Back Cut Retreating From the Work Area Reading the Stump Cutting the Stump Putting it All Together Additional Felling Concerns and Precautions... 70

2 Contents CHAPTER 3: FELLING DIFFICULT TREES Felling Aids: Wedges, Levers, Poles, and Ropes Felling Wedges Felling Levers Push Poles Pull Ropes (pull line) Felling and Pulling Trees in Confined Spaces How to Safely Make a Bore Cut Bore Cutting Trees With a Heavy Forward Lean Felling Large Diameter Trees Felling Dead, Decayed, and Defective Trees Felling Multi-Stemmed Trees Felling Entangled Trees Felling a Set Back Tree and Freeing a Stuck Saw Dislodging a Hung-Up Tree Felling Storm Damaged Trees Additional Felling Challenges CHAPTER 4: LIMBING & BUCKING FELLED TREES Limbing and Bucking Hazards Basic Limbing Techniques Basic Bucking Techniques CHAPTER 5: MOVING LIMBS & LOGS Ways to Move Limbs and Logs Loading Logs Using the Parbuckle CHAPTER 6: SPLITTING & STACKING WOOD Splitting Firewood Stacking and Storing Firewood Appendix Firewood Comparison Chart Recommended Resources Equipment Suppliers Final Words Footnotes

3 Preparing for Work Understanding Chain Saw Reactive Forces Another critical safety concern for preventing chain saw injury is understanding the reactive forces that occur when the saw bar and chain make contact with wood or another object. There are three main reactive forces that can potentially occur at any given moment while cutting wood push force, pull force, and kickback. To be unaware of the constant presence of these forces is a surefire recipe for disaster, especially in the case of kickback, whose recipients receive injuries that are often severe or fatal. Push Force Whenever wood is being cut with the top of the bar, as when undercutting a log in bucking operations or in some instances to making felling cuts, the forward motion of the chain will tend to push the saw away from the wood and toward the operator. This can be a dangerous situation if you encounter such a force while using poor cutting stance, gripping the saw improperly, or are physically and mentally unprepared to respond to its effects, which can be powerful when operating a larger saw. Pull Force Whenever you cut wood with the bottom of the bar, which is the majority of the time, the cutter teeth making contact with the wood tend to pull the chain saw (and you) toward the wood. This can be especially hazardous when cutting smaller pieces of wood, which can be thrown forcefully toward the crotch area. (As the folks at Arborwear, designers and manufacturers of work clothing, would say, Protect your crotch. We can t stress that enough. I wholeheartedly agree). The effect of pull forces can be minimized by starting cuts under full throttle and with the bumper spike in contact with the wood. Be prepared for reactive forces by maintaining a good cutting stance and keeping a firm grip on the saw. A properly sharpened saw will also help lessen the effects of pull force. Chains in which the depth gauge (rakers) have been filed down too much tend to accentuate pull forces aggressively and dangerously. Push force Pull force 20

4 Preparing for Work Kickback There are two forms of kickback: rotational and linear (or pinch kickback). Rotational kickback occurs when the upper corner of the bar (kickback corner or no zone ) accidentally makes contact with an object. This contact forces the chain to a sudden stop and causes the saw to push itself off the object with a violent rebound toward the operator. Linear kickback is a more violent form of the push force previously described that occurs when the wood closes, pinches the saw chain in the cut, and pushes the saw toward the operator. In both cases (but especially with rotational kickback) there is no warning and little time to react when it occurs. From start to finish, the whole event takes place in a fraction of a second. Kickback corner or no zone Starting corner Avoid using the kickback corner ( no zone ) of the saw bar to avoid rotational kickback. Rotational kickback occurs most commonly while bucking logs and the bar tip makes contact with other logs piled behind the ones being cut or when using the tip of the bar to make bore cuts or to remove limbs close to the trunk. Wearing personal protective equipment will certainly help prevent or minimize injury if kickback does occur, but precautions must be taken to help prevent injuries from happening in the first place. These preventative precautions include: 1) keeping the bar tip clear of any obstacles, 2) avoiding use of the upper quadrant of the bar nose, 3) clearing the cutting area of any underbrush, branches, or other solid objects, 4) holding the saw firmly with two hands with the left thumb wrapped under the front handle, 5) using a low-kickback chain whenever possible, 6) using saws equipped with a chain brake, 7) keeping your chain saw properly sharpened, 8) maintaining a high saw speed when entering or leaving a cut, and 9) following the bore cut instructions on page 101 when it is necessary to use the bar tip. 21

5 Preparing for Work Work-Related Equipment The well prepared tree cutter is one who is also well equipped. This means having available at the worksite, and in good working condition, any tool that might make your work safer and more efficient. The kind of equipment you ll need will depend on the type of work you ll be doing and under what conditions. The tools for cutting trees in the back forty for firewood may be different than those needed for precision felling in tight residential areas. Though the equipment selection available to the modern tree cutter is diverse, I ve included in this book the ones I believe you will find most useful across a spectrum of felling situations. In subsequent chapters you will find additional information and illustrations regarding the application of these tools. Ten Essential Tools of the Trade We often go without a piece of equipment that saves time and energy simply because we never tried it or knew it existed. Therefore, in addition to your prized chain saw and the must wear PPE described on the previous pages, I have compiled a list of ten essential tools that I believe are indispensable for the type of tree work described in this book. 1. Felling Wedges Wedges are some of the most important felling and bucking tools you can own. They can help redirect a leaning tree and prevent your chain saw bar from getting pinched while bucking wood or when making a back cut when felling. You should have several wedges on hand ranging from 5 to 10 long and made of high-density polyethylene. 2. Single-Bitted Ax The single-bitted ax is an important tool for driving felling wedges into saw cuts. It can also be used to sound trunks for rot, strip off mud-caked bark, knock out deadwood from standing or felled conifers, or split firewood. A 3-lb. ax with a square flat end (to minimize wedge damage) and a 26 long handle is a good choice for meeting these needs. 26

6 Preparing for Work 3. Rope Trees with a significant back lean may require the additional leverage a properly placed pull line can provide. A direct pull from a single worker may be adequate in most cases to fell the tree, but it may be necessary to attach a winch, come-along, or pulley system to the line for more pulling power. 4. Pulleys, Biners, & Slings This gear comprises the main ingredients for assembling a pulley system to a pull line. Pulleys (or blocks) provide the means of gaining mechanical advantage, the carabiners (biners) are the connecting links, and the slings provide anchor points to which the pulleys can be attached. 5. Throw Line and Throw Bag This simple tool combination used by professional tree climbers has no equal for installing a rope at an effective height in the tree from the ground. The throw bag and line are tossed over a secure limb or crotch in the tree after which a rope is attached, pulled up into the tree, and tied off. This tool eliminates the need to climb the tree or use a ladder to attach a pull line. 6. Cant Hook At the end of the work day your body will thank you for employing this tool. The hook grabs hold of the wood while the long handle provides a mechanical leverage advantage making log rolling significantly easier. Cant hooks are also useful for rolling out a hung-up tree. Workers using two cant hooks in tandem can lift and carry logs to a more convenient location for cutting. 27

7 To Fell a Tree Basic Tree Felling Procedure The basic tree felling procedure presented in the flow chart below consists of three main steps Assess, Prepare, and Execute. Each of these steps is subdivided into additional steps of execution, all of which are presented in detail in this chapter. As stated on the previous page, some felling situations may not require carrying out every step of the procedure. It is essential, however, that you become familiar with and competent in performing all the steps of the procedure for the felling situations that do require them. STEP 1 Assess Tree & Felling Site 1. Identify tree and site hazards 2. Estimate tree height 3. Determine tree lean 4. Determine the lay 5. Establish escape route STEP 2 Prepare Tree & Felling Site 1. Protect people 2. Protect property 3. Prepare the work area 4. Prepare the tree STEP 3 Execute Felling Cuts & Retreat 1. Cut the notch 2. Make the back cut 3. Retreat from the work area N ORDER TO CONSISTENTLY PERFORM each step of the felling procedure I you should develop a means for remembering them. The method I use involves memorizing six key steps: hazards, height, lean, lay, escape, and execute (HH-LL-EE). Notice that the first five of these steps are the same five that are in step 1 above (assess tree and felling site). The last step (execute) involves executing the felling cuts and retreating from the work area (same as in step 3 above). So what happened to step 2: prepare tree & felling site? It s still there; I ve just collapsed it into step 1. As discoveries are made during the tree and site assessment I make a point of taking the necessary steps of action to protect people and property, and to prepare the work area and the tree itself prior to felling the tree. 36

8 Step 1: Assess Tree & Felling Site What You ll Do: Step 1: Assess Tree & Felling Site 1. Identify tree & site hazards 2. Estimate tree height 3. Determine tree lean 4. Determine the lay 5. Establish escape route No two trees are alike. Each has its own uniqueness and personality. In step 1 of the tree felling procedure your goal is to discover the personality or characteristics of the tree being felled and its surroundings (felling site) by applying five essential assessment factors. What you learn about the tree and site will profoundly influence subsequent decisions such as determining your equipment needs, which felling methods to use, and which hazards and obstacles will need to be avoided, protected, or removed. 1a. Identifying Tree Hazards Begin your tree assessment for potential defects and hazards from a distance, perhaps as you are first approaching it. Many hazards such as widow-makers (a lodged branch or treetop; see drawing on p. 39) or an overhead electrical line, may be hidden when viewed from directly below the tree. Upon reaching the tree, continue to inspect all sides of the tree starting with the base of the tree, along the trunk, and up into the canopy. Be attentive to any sounds as well that could indicate hazards such as the buzzing of hornets or other insects or animals. The tree hazard descriptions that follow on the next two pages will assist you in the tree assessment. Look aloft for tree hazards in the canopy. 37

9 Step 3: Execute Felling Cuts & Retreat Putting it All Together (Using the Open-Face Notch) 1 Position the notch on the trunk by sighting, or aiming the saw, in the exact direction you want the tree to fall. Aim the saw using the gunning sites marked on the top of the shroud or housing of the chain saw. It may be necessary to raise or lower the notch placement on the trunk to avoid obstructions (nails, etc.), cracks, or areas of decay. 2 3 Make the top cut of the notch by cutting at a downward angle of degrees (when using the open-face notch) to a point that is approximately one-third the trunk diameter or that provides a hinge length of 80% of the trunk diameter. Use the kerf created by the top cut as a window to sight down to watch for the emerging chain teeth when the bottom cut is made. Make the bottom cut of the notch so that it angles back and upward to cleanly meet the first cut. If the top cut is made at a 60- degree angle, then make the bottom cut at a 30-degree angle in order to obtain a 90-degree notch opening. Stop cutting as soon as the two cuts meet evenly. Avoid cutting beyond the top cut creating a potentially dangerous bypass notch º 20-30º 68

10 Step 3: Execute Felling Cuts & Retreat Inspect the notch placement on the trunk to ensure that it is still aimed directly toward the lay. Make any necessary corrections. Check notch placement by setting the bar flush against the back of the notch while looking down the felling sites of the saw. Check notch placement by standing back away from the tree and sighting it from the location you expect it to land. Make the back cut even with the apex of the notch opening (with the openface notch) leaving a hinge width 10% of the trunk diameter. Give a loud and clear verbal warning to others as you begin to make the back cut and again as the tree begins to fall. Cut inward evenly so the finished back cut runs parallel to the back of the notch creating a hinge that is of equal thickness along its length. Retreat from the work area along the planned escape route to a minimum of 20 feet away from the tree. Retreat as soon as the tree shows the slightest forward movement. Make your retreat opposite the lay at a 45-degree angle to the left or right side of the tree. Shut off the engine or engage the chain brake of your chain saw before taking it with you as you retreat from the work area. 69

11 Felling Difficult Trees Basic Wedging Principles The goal of wedging is to create enough lift in the back cut to move the tree forward past the tipping or pivot point so it will fall into the lay. This is perhaps the most basic and important wedging principle to understand. The three factors which influence this movement are 1) the amount of lift created by the wedge(s), 2) the tree s height, and 3) the tree s diameter (measured to the front of the hinge position or back of the notch). You can calculate how much forward crown movement, or crown displacement, as I refer to it, you can expect when wedging trees by using the formula below. Crown Displacement Formula: (WL X H) D = CD WL = Wedge lift (in inches) H = Tree height (in inches) D = Tree diameter (in inches to the front of the hinge position) CD = Crown displacement Consider for example, felling a 70-foot tall tree (H), having a 12-inch diameter trunk (D), using a single 1-inch thick felling wedge (WL). After plugging these factors into the equation, you can see from the results below, and in the illustration (right), the crown movement, or crown displacement (CD), is just over 5 ½ feet: (1" X 840") 12" = 70" (5.8 feet) In theory, if the tree had a back lean slightly less than this amount (5 feet or less to be safe) it would be a good candidate for wedging. As you apply this formula on the trees you wedge you will notice that as tree height increases and diameter decreases the amount of crown displacement becomes greater. Of course the opposite is also true as tree height decreases and diameter increases crown displacement becomes less. In some instances you may need to stack wedges to increase crown displacement or, if that isn t sufficient to overcome the back lean, use a pull line (see pages 84-99). A simple way to determine crown displacement on trees which have a trunk diameter of about 12 inches (measured at the front hinge position) is to remember the 1:1 rule. For every one-inch of lift (the average thickness of a single wedge) there is a corresponding one-inch of forward crown movement per foot of tree height as was seen in the example above (70 tall / 70 crown displacement). Remember, this ratio decreases as the trunk diameter increases. For example, a 70-foot, 16-inch diameter tree would have a crown displacement of about 52 inches and a 20-inch diameter tree of only 42 inches. As tree diameter increases I would advise that you revert back to the formula for more accurate results. 74

12 Felling Difficult Trees 70" Crown Displacement (5.8') Tipping point 70' Height (840") The Crown Displacement Formula (applied to a 70', 12" dia. tree) (1" WL X 840" H) = 70" CD 12" D 12" Diameter (measured from the front hinge position) (Wedge Lift) Three factors that effect crown displacement: wedge lift, tree height, & trunk diameter. 75

13 Felling Difficult Trees Installing the Rope: Throwing Procedure & Technique Step 1 Tie the throwline to the throw weight with a slipped figure eight knot or clove hitch. Though any good knot will suffice, these two provide a secure attachment and yet untie quickly when you are ready to tie on the pull rope after the throw. The slipped figure eight knot. Step 2 Aim for a suitable crotch or sturdy limb 2/3 up in the tree that can support the pulling forces that will be exerted on the rope. Select wide, u-shaped crotches whenever possible to allow the throwline (and attached rope, step 4) to pass through easily. Throw the line and weight using the single-hand toss method illustrated below. Make sure the line is free of tangles, ground litter, and your own feet. Tying a slip knot 2-3 feet up on the line helps you to grip and release the line better. The knot can be easily pulled out afterward. Alert others nearby that you are about to throw by shouting Stand clear! Aiming & throwing the bag. 86

14 Felling Difficult Trees Step 3 Allow the bag to fall back to the ground after a successful shot has been made. It may be necessary to first manipulate the bag over interfering limbs so the throw line runs nearly vertically along the back of the trunk. Remove the throwbag from the line and attach the pull rope using a pile hitch (fig. A). For a more streamlined effect, to facilitate rope installation in narrow crotches, add a series of half hitches and finish with a clove hitch (fig. B). Figure A Figure B Securing the throwline to the rope Step 4 Pull down on the throwline until the rope passes over the branch crotch and back down to where you can reach it and secure it to the tree (see page 88-89). Pulling the rope over the crotch. 87

15 Felling Difficult Trees Bore Cutting Trees With a Heavy Forward Lean Forward leaning trees are the least difficult to fall into the lay they are already headed in the right direction. Ironically, these seemingly easy trees pose a significant threat if the forward lean is too great, as the tree can start to fall before the back cut is finished. This can result in the tree barber chairing splitting at the back of the hinge causing the butt end to flip up dangerously toward the chain saw operator (see p. 70). Using the bore cut method instead of the traditional back cut offers the best protection against this threat. The hinge thickness can be setup without fear of the tree falling prematurely, which allows you to make the back cut when you are ready. Also, when using the felling option illustrated on top of page 103, all the felling cuts can be executed from the same position the notch is cut from. It is because of these reasons, that many people prefer to use the bore cut method almost exclusively. Bore Cutting When Trunk Diameter is Less Than the Saw Bar Length After cutting an open-face notch in the direction of the desired lay, begin the bore cut while standing on either side of the trunk. The side you cut from will depend upon personal preference (the side you are more comfortable making the bore cut from) and whether the tree has any side lean (if it does, cut from the good side of the tree). However, the cutting method described below, and illustrated on page 103, is the same regardless of what side of the tree you cut from. 1. Bore into the tree using the procedure described on page 101 (remember to initiate this cut by using the lower corner, or starting corner, of the saw bar to avoid kickback). Begin the cut even with the apex of the notch and just behind the desired hinge position. It is extremely important you do not accidentally cut into the predetermined hinge (reducing its thickness) while making this cut. Because of this concern, many tree cutters feel more comfortable staying several inches away from the back of the hinge when they make this cut. Once the saw bar has come out the other side of the tree, they then cut toward the hinge to fine-tune its thickness (10% of the trunk diameter at the cut). 2. The back cut can be made in one of two ways: by removing the saw after the bore cut is made and cutting the strap of remaining holding wood from the outside of the tree (Step 2, option A) or, if the tree has only a slight forward lean, by cutting straight out the back of the tree without leaving the strap (Step 2, option B). As you can see from the illustrations on page 103, the side of the tree you cut from determines whether the cuts are made with the top or bottom of the bar. One advantage of cutting the strap of holding wood from the outside is that it gives you time to get your wits together (get repositioned, double check the escape route, communicate with workers) before making the final back cut and puts you in a better position to make a quicker retreat when you suspect the tree will fall quickly. 102

16 Felling Difficult Trees Bore Cutting (trunk diameter less than bar length) Notch Step 1 The bore cut can be made from either side of the tree. In this instance, the cut is made from the right side of the tree as you face the lay (step 1). The back cut can be made in one of two ways: by leaving a strap and cutting it from the back of the trunk (step 2 option A) or by cutting straight out the back of the trunk (step 2 option B). Notch Notch Step 2 (Option A) Step 2 (Option B) Bore Cutting When Trunk Diameter is Greater Than the Saw Bar Length Begin by cutting on the bad side of the tree creating 50% of the calculated bore opening (#1-2 below). Finish the bore cut on the good side of the tree so that the cut meets (is level with) and extends beyond the cut made from the other side (#3). Cut toward the hinge setting up the same hinge thickness that was established from the other side of the tree (#4). Remove the saw and cut the strap of holding wood (#5). Notch Notch Note: The thickness of the strap should be at least 10 percent of the tree diameter. A thicker strap should be left when felling trees with an extreme forward lean or have decayed wood fiber. 103

17 Limbing & Bucking Felled Trees Bucking Wood Supported on Two Ends (Tension on Bottom) The illustration below shows the main trunk of the tree supported by the butt on one end and limbs on the other. This causes an upward pressure on the trunk creating a compression force on the topside and tension force on the bottom. Consider the three options that follow to deal with this situation. The main trunk illustrated below is supported by the butt on one end and the limbs on the other. T = Tension side C = Compression side C Open-face notch & undercut T 1st 2nd Option 1: Two Cut Combo Make a top cut (compression side) about 1/3 the way through the log. Finish with an undercut (tension side) so the two cuts meet. If you want the log to release slowly and with more control, make a shallow open-face notch on the topside and leave a hinge as you make the undercut (see inset above). On smaller logs you can get by with making an undercut only. Getting Attention F IT IS NECESSARY to interrupt workers I who are running a chain saw approach them from the front to avoid surprise or use a branch to gently tap them on the back or shoulder. When using the latter method, be careful that your attempt doesn t scare the daylights out of them and cause an accident. Use a stick long enough to put yourself a safe distance from the operator and the saw. Never try getting a saw operator s attention by coming directly up to them yelling or tapping them on the shoulder. 132

18 Limbing & Bucking Felled Trees Option 2: Felling / Bucking Wedge Begin by cutting from the top of the log or trunk and insert a wedge snugly into the cut as soon as room permits (hopefully this will be before the saw gets stuck). As you continue cutting downward, the wedge will prevent the saw bar from binding in the wood. It may be necessary to periodically drive the wedge in further to open the saw cut more. Option 3: Support Log Place a small support log under the log or trunk on the side you want to support. Next, make a top cut to a depth about 1/3 the log diameter. Make the undercut at a slight angle toward the top cut so the two cuts meet. This will allow one end of the trunk to drop away from the saw bar and onto the ground (the left side in the drawing above) while the other side remains on the support log. This method prevents both log ends from simultaneously collapsing to the ground. 133

19 Moving Limbs & Logs 1. Lift it 10 Ways to Move Limbs & Logs Even if you own all the fancy labor-saving tools described in this section, at some point you will bend over and attempt to lift a heavy piece of wood or other object by hand. If you don t do it properly you could end up with a debilitating back injury. Alternate starting position Basic Lifting Method 1. Plan ahead before lifting. Know where you are going with the object and know that you have a clear path there. 2. Examine the object for sharp edges, slippery spots, or other potential hazards you want to avoid grabbing. 3. Squat down close to the object with feet about shoulder width apart. Test the load to see if it can be safely lifted. 4. Grip the object firmly and begin slowly lifting with your legs, not your back, holding it as close to your body as possible. Keep your head up as you lift while maintaining normal back posture. Never twist your body during the lift, but rather turn by taking small steps after you have stood up straight. If you are straining to lift the object, it is too heavy. Set it down and get some assistance or try another method. End Over End Method Proper lifting technique. Wood sections that are too long or heavy to lift can be effectively moved by toppling them end over end. Begin by squatting down at one end of the log. Then lift the end by straightening your legs, keeping your head up and your back naturally curved. Finally, raise the log with your arms until it is nearly vertical before giving it a good push forward. Repeat the process until the log reaches its destination. 138

20 2. Carry it Moving Limbs & Logs Sometimes the most efficient way of moving wood and brush from the work site is to carry it out by hand. This is a standard procedure when working in residential areas where you wish to avoid damage to property with groomed lawns and landscaped areas. Also, carrying the wood keeps it from collecting dirt and mud that can dull the teeth of the chain saw and blades of the wood chipper. The Shoulder Carry 1. Stand the log on end, using the end over end method on page Put your shoulder on the balance point of the log. Tentatively lift the log to determine if it is positioned too high or too low. 3. Straighten up, using the legs, and using your arms to help lift and steady the log onto your shoulder. The log will almost lift itself horizontally into position if it is slightly back-heavy. Toss the log off to the side for easy unloading Using two cant hooks to lift and carry logs. Two-Man Carry You can take the guess work and back work out of lifting heavy logs by recruiting another worker to grab the other end. Better yet, use two cant hooks in tandem. This provides a better grip and allows both of you to face the same direction as you carry the log. Though log tongs can be used for the same purpose, it will require four people to accomplish the same task (see page 29). 139

21 Splitting & Stacking Firewood Step 3: Strike the Wood Though the ax is willing and the wood is waiting by this time, there are a few more things to consider before you let fly. Position yourself at a distance that will allow the ax (maul) to strike perpendicularly to the wood surface. Keep the splitting area relatively clear to avoid stumbling and maintain good footing while you work. Always face the wood you are splitting squarely to deliver the maximum energy from your swing. Also, if you should miss your target, this position allows the ax to swing between your legs instead of into them. Since split wood pieces (and loose ax heads) can fly 20 feet or more, make sure that onlookers are a safe distance away and coworkers are wearing the necessary PPE. Head protection and face shields may be optional, unless the employer requires them, but safety glasses should be worn to protect your eyes from wood chips or metal fragments. Wear work pants and footwear durable enough to withstand, or at least minimize the effects of any contact made with wood or ax (never split wood while wearing shorts). Check ax heads frequently to ensure they are properly secured to the handle. Refit and wedge the head if necessary. Aiming the Ax Up to 8 inch wood (halves/thirds) 8-14 inch wood (quarters/sixths) Over 14 inch wood (eighths ±) As you raise your ax to strike the wood (holding it off to the side as in the drawing on page 148 or, raising it directly over your head as some prefer, page 151) take aim where you want the wood to split. If any natural seams or cracks exist on the wood surface, aim for them, while avoiding any knots. But, where you strike the wood is determined primarily by the size of the wood being split and the size you want it to be split into. A general guideline for determining wood size based on wood diameter is as follows: wood up to 8 inch in diameter should be split in half (or thirds); 8-14 inch diameter wood quartered (or sixths); and for wood greater than 14 inch in diameter split into eighths (or more). Keep in mind, smaller firewood dries faster and is lighter and less bulky to handle. On the other hand, larger pieces of firewood mean less trips to the woodpile and woodstove. 152

22 Splitting & Stacking Firewood When splitting small diameter wood in half simply aim and strike at the center. Similarly, when re-splitting larger pieces with have been reduced in size, keep striking away at the center of the wood until you achieve the desired size. With a little practice you can get four sticks of firewood in two swings. This happens when the halved pieces remain standing after being only partially split, and the second strike splits both those pieces in half. A poorly placed second shot however, can sometimes cause handle damage. Splitting Large Wood As diameter increases, striking at the center of the wood becomes less effective. Two other techniques come into play at this point. The first method, involves striking an imaginary line across the face of the wood (fig. A). Your first strike should be centered on the far side of the wood. Subsequent strikes are made in a line across the face of the wood, one behind the other, working toward the side where you are standing. If it doesn t split after one pass of the ax, repeat the process (several times if necessary), striking across the same line. If the wood refuses to yield to your efforts try striking a new line in a different location, or flip the wood over and try the method on that side. Striking the line. 4th 3rd 2nd 1st Figure A 3rd 4th 5th 2nd 1st When you hear a dull thunk (or hollow boom as some describe it) after one of your strikes, it s a sure sign the wood is about to split. After it does, continue reducing the size of the wood by slicing pieces from the ends (fig. B) or by repeatedly splitting the wood in half (fig. C). Any time you split large, tough, and wet wood, be alert to the possibility that the ax or maul could rebound off the surface and strike you in the face or head. Figure B 3rd 5th Figure C 1st 4th 2nd 153