LOG BUCKING METHODOLOGY

Bucking Logs to Cable model plot number 8• was selected to be bucked, and the Yarder Capacity Can results were used to illustrate the effectof alternatebucking rules on cable yarding efficiency and DecreaseYarding Costsand woodwastage. Forest model plot number8 is typicalof mosthard- Minimize Wastage wood stands:average dbh, 9.10 in.; averagemerchantable height to 4-in. top, 35.9 ft; number of Chris B. LeDoux, USDA ForestService, Northeastern Forest ,229; gross.volume,4,703 ft•/ ExperimentStation, Morgantown, WV 26505. ac; speciesmix, soft maple, red oak, white oak, black birch, yellow birch, hickory, beech, black Abstract.Data from selectedtime and mo- 1977, Wren 1965). Also, , cherry, walnut, ash, and yellow- tionstudies and a forestmodel plot, used in bucking,and have been poplar. A log bucking simulation a simulationmodel, show that analyzed as component costs model (seefootnote 1) was used to managersplanning felling, bucking,and within the harvestingsystem (King simulate bucking of the trees limbingfor a cableyarding operation must 1970, Schnell 1964). Others have within the plot. The model will considerthe effectof alternatebucking ruleson wood wastage, yarding production studied felling, bucking, and bucktrees into logsexplicitly con- ratesand cost, the number of chokerstoil? limbing of integrated sawlog- sideringlog grade, volume, and andtotal logging co•ts. Results emphasize operations (Gabriel yardingsystem payload capacity theneed to considerinitial loggingactivi- 1971) and cull trees (Gabriel and For any one , the simulation tiesin termsof effectson cableyarding Nissen 1971). The studies success- will attemptto buck logsto maxi- systemefficiencies and woodwastage. Re- fully quantified felling, bucking, mize log grade and volume while sultsalso emphasize the need to •mtchpay- and limbingtimes per tree,and in simultaneouslymeeting a yarder load(piece size) to cableyarder capacity. some cases,regression equations payload constraint. The end Resultssuggest that cable yarding costs can to predict time were developed. productof the buckingsimulator be decreasedby 20 to 32% by simply Detailed felling, bucking, and is as manygrade logsas possible, buckinglogs to yarder capacity. limbing techniquesused by pro- South.J. Appl.For. 10:180-I83, Aug.I986 givena specifiedmaximum allo•- fessional timber cutters in the Pa- ablelog weight. cific Northwestand other regions The results from 3 simulated The firststep in timberhar- are discussedby Bromley (1976), buckingrules are shownin Table vestingon steepterrain is the con- Conway(1973), FAO (1980), and 1. Buckinglogs for a maximum versionof trees to logs,which in- Pearceand Stenzel (1972). weight of 1,500 lb results in 974 cludes felling, bucking, and Generally,these past studies do 1ogs/acaveraging ! 1.4 fts per log limbing, usually with . not considerthe impact of alter- Buckinglogs to weightsof 3,000 Felling,bucking, and limbingcriti- nate buckingstrategies on cable and 6,000 lb increasesaverage log cally affect the amount of wood yarding efficiencies and wood sizeby 20.2% and 37.7%, respec- retrieved from a site and the effi- wastage.This articleillustrates the tively. The number of logs per cienciesof cableyardirig. If trees applicationof a methodologyfor acre for a 1,500 lb limit bucking are buckedwithout regard to end evaluatingthe. effect of alternate rule is 974, or 13.4% more logs use, value may be lost. Bucking buckingrules on hourly produc- per acre than a 3,000 lb rule, and big, long logs may result in logs tion rates, log distributions per 20.2% more logsper acre than a too heavyfor the yarding equip- acre,wood wastage, and total log- 6,000 lb rule. The percentageof ment to handle: conversely, ging costs.A simulation model products for a 1,500 lb rule is buckingsmall, short logsmay re- called THIN (LeDoux and Butler shownin Figure 1. sult in wood wastage and cable 1981) and a log bucking algo- Although forest model plot yarding inefficiency due to in- rithm • are used. The results can number 8 has a total creasedhandling time and costs be used by logging managersto volumeof 4,703 fts, only 3,23! fts resulting from small loads per determinefelling, bucking,and of merchantablewood (4-in. top) turn. limbin.gpolicies for cablelogging is realizedwhen using a bucking Regressionequations have been operauons. rule of 1,500 lb. Only trees with developedfor predictingfelling, •LeDoux, C.B. 1984. Hardwood Log • UnitedStates Department of Agriculture bucking, and limbing time (Jiles Bucking Simulator. Program on file, One-acreforest model plot data on file and Lehman 1960, Koger 1980, Northeast. For. Exp. Stn., Morgantown, Northeast.For. Exp. Stn., Morgantown, 1983, Martin 1975, Matthes et al. WV. WV.

180 sj^F 10(1986) Table1. Simulatedlog distributions by buckingrule for forest model plot number 8. a Bucking Logsize Ave. Number Merchantable ruleb Stand. log of volume (lb) Ave. Max. Min. der. length logsc removedac ...... (ft3) ...... (ft) ...... (fO)...... 1,500 11.4 24.8 0.50 8.4 28.5 974 3,231 3,000 13.7 48.2 0.70 12.9 33.1 843 3,360 6,000 15.7 86.5 0.90 18.9 35.8 778 3,556 ßAssumed weight per ft3 is 60 lb (all speciespooled). bMaximum weight allowed per log. = Numberof logsfor a 1,000- x 150-ftskyline corridor. dbh of 5.0 in. and greaterare con- significantlyaffect cable yarding 6,000-lb yarding logs bucked to s•dered merchantable.Log sec- productionrates. 1,500 lb flying 4 chokersproduces uons less than 4 ft are left on the 273.58 ft3/hr. Under similar con- site and not included in the total CABLE YARDING ditions, yarding logs bucked to merchantable volume. When PRODUCTION RATES 3,000- and 6,000-lb rules results in buckingrules of 3,000 and 6,000 hourly productionrates of 330.33 lb are used, the merchantable Hourly production rates for and 360.40 ft 3, increasesof 20.7% wood retrievable is increased from cableyarding are influenced sig- and 31.7%, respectively. Con- 3,231 to 3,360 and 3,556, in- nificantlyby the buckingrule. To versely, if an operator used a creases of 4.0% and 10.1%, re- illustratethese effects, the log dis- fi,500-1b rule instead of the 6,000- spectively.The increasesin mer- tributions shown in Table 1 were lb capacity,the abovepercentages chantable wood with the heavier input into the THIN simulation would representlosses. However, buckingrules are due to cutting model. The model was then used when similar runs were made with b•ggerand longer logs from re- to simulatethe hourly productivity unlimited number of chokers, the spectivetrees, minimizing wood rates and costs associated with hourly production rate for the wastage.Bucking to light bucking yardingeach log distributionwith 1,500-lb rule increasedby 29.7%, rules (1,500 pounds) results in a yarder capableof a 6,000 pay- from 273.58 to 354.89 fd, an in- many short logsand top portions load. The results are shown in creaseattributable to flying more of stems that do not meet the 4-ft Table 2. The simulations were run chokers(6 compared to 4). Simi- merchantability constraint. The with a fixed number of chokers larly, the hourly production rate gain in wood volumeis in the fire- and also an unlimited number of increasedfor the 3,000 bucking wood/pulpwood component chokers using bucking rules of rule, an increase of 11.2%, from (Figure 2). The number of logs !,500, 3,000, and 6,000 lb. For ex- 330.33to 367.22 ft•, againattrib- per acreas well as average size will ample, a yarder with capacityof utable to flying more chokers. Figure 3 illustratesthe increasesin productionrate by the number of chokers flown. Flying more chokers is not always desirable. For example, 66.09% when simulatingthe yarding of a OR PULPWOOD 6,000-lbbucking rule usingunlim- ited chokers,only 2.8 logs were hookedper turn suggestingthat 3 chokers would be enough. Re- peated simulations were used to show the optimal number of 9.12% chokersto fly by buckingrule and #3 numberof logsper corridor: LOGS Bucking rule No. logs/ No. optimal =2 (lb) corridor chokers SAWLOGS 1,500 980 6 485 4 SAW LOGS 323 3 3,000 843 5 420 4 278 3 6,000 778 3 Fzgure1. Percentageofproducts for buckingrule of 1,500lb, for forest model plot num- 389 3 ber 8. 258 3

SJ&F10(!986) 181 31.7% respectively.Clearly, the TOTAL BIOMASS advantage of bucking logs to •. 4703 AVAILABLE yarder capacity reduces yarding COSTS. PULPWOOD SAWLOGS'• & CONSIDERATIONS FOR • 4000 MANAGERS uJ

o Matching log size through bucking to payload capacity of uJ specificcable yarders is an impor- uJ 3000 tant cost savingsand should be considered.To apply the resultsto your situation,initially cruise the o proposedstand and determinethe uJ payloadcapacity of your chosen • 2000 yarder.Then fellersshould be in- structedto bucklogs to yarder ca- Z pacityas muchas possible.Such a practice will generally result m yardingtree-length trees. Yarding uJ tree-length wood to the landing 1500 3000 6000 results in an additional bonus; that BUCKING RULE, POUNDS is, bucking and sorting can be Figure2. Simulatedsawlog and firewood/pulpwood component of.merchantable volume done on the landing for the high- removedby bucking rule [or forest model plot number 8. value products most efficiently Tree-lengthlogging may result m damage to the residual stand xf Clearly, the resultssummarized limbing cost is only $165.38 per stemsare improperly felled. The are specificto forest model plot acreor 27.4% of yardingcost per buckingrule, however,is not the number 8 and will change for acre. The percentageof felling, only importantitem; for example, other stands; however, additional bucking, and limbing cost for a properlyoriented logs to the sky- simulations could be conducted 1,500-lbbucking rule to total cost line corridorhas shown significant for other conditions. Alternate isonly 11.8%,while yarding cost is gainsin yarding productivity(Le- bucking rules will also affect $603.89per acreor 43.1% of total Doux and Butler 1982). Good felling,bucking, limbing, yarding, logging cost. One may wonder managementand advancedplan- and total harvestingcosts. about the relative importanceof ning of the felling operation are felling,bucking, and limbingcosts crucial to cable yarding success TOTAL HARVESTING COSTS sinceas a percentageof total cost The skyline corridors should be they are quite low. However, al- identified and felled, and fellers The impactof alternatebucking though the impact of bucking should be instructed to fell trees so rules on total loggingcosts for a rules on felling, bucking, and that good extractionangles and specificset of conditionsis subtle, limbingcost is small(decreases of pathsare formed• but important(Table 3). The spe- 5.5% and 9.1% whengoing from Although the effect of high cific componentsby buckingrule 1,500 to 3,000 and 6,000 lb) the stumps, extraction paths, and are detailed, note the change in major contributionis in the reduc- limbingpractices on cableyarding felling,bucking, and limbingcost tion of yardingcosts. For example, cost was not quantitatively ex- to each component.For example, yardingcosts per acreare $603.89 plored in this study, felling and the yarding cost per acre for a for a 1,500-lb rule, $478.64 and buckinginstructions should con- 1,500-lbbucking rule is $603.89, $412.27 for 3,000- and 6,000-lb siderthese practices. The primary while the felling, bucking, and rules; or decreases of 20.7% and reasonfor not considerir/gthem quantitativelywas the lack of data. Table2. Simulatedhourly production rates by buckingrule for flyingfour chokers During the limbing process, andflying unlimited chokers for logsper 1,000- x 1S0-ftskyline corridor. many buckers will leave the un- Flying4 chokers Flyingunlimited chokers derlyinglimbs on a stem intact as Bucking Hourly Logs Hourly Logs this facilitatesliznbing. However, rule Logs prod. hookedper prod. hookedper for yarderswith low mainlinepull, (lb) corridor rate turn rate turn it would be highly desirable to (ft•/hr) (no.) (fO/hr) (no.) buck off these limbs to facilitate 1,500 974 273.58 3.5 354.89 5.2 lateral yarding.Even the smallest 3,000 843 330.33 3.3 367.22 3.8 underlying limbs can penetrate 6,000 778 360.40 2.8 361.33 2.8 the soil a few inches and cause

182 SjAF wood wastage;thereby, logging managers can make better deci- sions. [] 6CHOKERS 'ii.•4CHOKER$ Literature Cited

BROMLI•¾,W.S. 1976. Pulpwoodprodu. c- tion. The Interstate Printers & Pub- lishers,Inc., Danville,IL. 291 p. CONWAY,S. 1973. Timber cutting prac- tices. Miller Freeman Publications,Inc., Portland,OR. 192 p. FAO. 1980.Chainsaws in tropicalforests. PublicationsDivision, FAO,. Italy. 96 p. GABRIEL, W.J. 1971. Distribution of felling and limbing times for an inte- gratedsawlog-pulpwood operation. State Univ. New York, Coil. Environ. Sci. & ,For.AFRI Res.Note I. I p. GABRIEL,W.J., AND R. NISSEN,JR. 1971.A time study of felling cull trees in the southeastern Adirondacks. State Univ. 15•0 3000 6000 New York. Coil. Environ. Sci. & For. AFRI Res.Rep. 4.7. BUCKING RULE, POUNDS JILES, R. A., AND J. W. LEHMAN. 1960. Hardwoodlogging methods and costsin Figure3. Increasesin simulatedhourly production rates by bucking rule for four andsix the TennesseeValley. Tenn. Valley chokersfor forestmodel plot number 8. Auth., Norris,TN. Rep.232-60. 35 p. KING,W. W. 1970. Mountainlogging in the Tennessee Valley. Lumberman substantiallateral yarding delays. Although this work was based 221(2752):181-82, 184. 186, 188-89. Buckers should be instructed to on data from one forest model KOGERJ. L. Factorsafecting the produc- removeas many limbs as possible plot and one tree distribution, tion ratesof chainsaws. Tenn. Valley whenprocessing trees into logsfor similar analysis could be con- Auth., Norris, TN. Tech. Note B39. cableyarders. ducted for other conditions by 26 p. Stump height should also be simply making additionalsimula- KOGER,J. L. 1983. Observedmethods for considered.For example,approxi- tion runs. It is beyondthe scopeof felling hardwoodtrees with chainsaws. USDA South. For. Exp. Stn. New Or- mately 15% of total breakage this article to deal with all aspects leans,L4.. 7 p. occursduring the felting process, of fetling, bucking, and limbing LEDOux, C. B., AND D. A. BUTLER. 1981. the result of felling trees across trees into logs, and it is not envi- Simulating cable in young- stumps (Conway 1973). Lower sioned that results from field growth stands.For. Sci. 27(4):745-57. stumpswill resultin lessbreakage, studies as used in simulation LEDOux, C. B., AND D,-A. BUTLER. 1982. minimizewood wastage,and most models such as those summarized Prebunching?Results from simulation. J. tmportant, minimize timely and here will provide all the answers. For. 80(2):79-82. costlydelays due to turns of logs Such methods should illustrate the MARTIN, JEW A. 1975. T-H-A-T-S: Timber harvestingand transportsimu- hanging up on high stumps effect of alternate buckingstrate- lator. USDA For. Serv. Northeast. For. duringthe yardingprocess. gies on cable yarding cost and Exp. Stn. Res.Pap. NE-316. 31 p. MATTHES, KENNETH R., ET AL. 1977. Table3. Impactof buckingrules on total harvestingcost. production rates. 1977 Winter Meet. Am. Soc. Agric. Eng. Pap. Buckingrule (lb) 77-1575. 16 p. Harvesting component 1,500 3,000 6,000 PEARCS,J. K., ANnG. STENZ•L.1972. Log- ging and pulpwoodproduction. The ...... ($/ac) ...... RonaldPress Co., New York. 453 p. Felling, SCHN•LL,R. L. 1964. Harvestingcosts for bucking, hardwoodpulpwood in the Tennessee limbing 165.38 156.27 150.27 Valley.Pulpwood Prod. & Saw Mill Log- Yarding 603.89 478.64 412.27 ging. 12(2): 22, 24-25. Loading 76.17 78.13 80.16 Hauling 362.45 376.92 381.91 WREN,T.E. 1965. Estimatingharvesting Move in and costsfor wheel operationsin out plus delays 193.86 193.86 193.86 West Virginia. M.S. thesis,Dept. Indus. Total cost 1,401.75 1,283.82 1,218.47 Eng., WestVirginia Univ., Morgantown. 125 p.

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