_ United States

,i**$ Department of ,‘.L!&’ Argriculture

f-n7, a Forest Service hWiDmimim wu i

w Southern Forest

Experiment Station

so-297

August, 1983

Observed Methods for Felling Hardwood Trees with Chain Saws

Jerry L. Koger

SUMMARY

The angles and lengths of the cutting surfaces

made by chain saw operators on hardwood tree

stumps are described by means, standard deviations, ranges, and regression equations. Recommended felling guidelines are compared with observed felling methods used by experienced timber

cutters in the southern Appalachian Mountains.

Additional keywords: Chain saws, felling.

INTRODUCTION

Chain saws are commonly used by loggers in

the southern Appalachian Mountains to fell, limb,

top, and buck trees. The relatively low initial cost,

light weight, and fast cutting speed of chain saws

favor their use for felling trees on rough and often

steep mountain slopes. Detailed information concerning the felling methods used by timber cutters

in this region is very limited.

The felling methods observed in this study are

typical of those used by experienced timber cutters

in the southern Appalachian Mountains. After determining the direction of tree lean, the brush

around the base is usually cleared and the facecut

is made. In this study, only the conventional facecut

(fig. l), consisting of an approximate horizontal

basecut made toward the tree center and a downward sloping notchcut that intersects the basecut,

was observed. Generally, the facecut is made on

the side of the tree having the greatest lean, prepondence of crown, or desired direction of fall. On

steep slopes, the facecut is almost always on the

downhill side of the tree. Next, the backcut, an approximate horizontal cut located on the opposite

side of the tree, is made toward the center of the

tree.

METHODS AND MATERIALS

Stump height, diameter, and cutting surface

measurements were made to the nearest tenth of

an inch. Merchantable stem length measurements

were made to the nearest tenth of a foot. Diameter

measurements of the felled trees were made at the

butt and merchantable ends, at dbh, and at approximately a-foot sections along the stems. Angle

measurements of the cutting surfaces and ground

slope were made with a clinometer to the nearest

one degree. in addition, the distance the felled tree

was separated from the stump and the distance the

timber cutter moved away from the stump were

measured.

The data on the cutting surfaces were collected

during a study on the production rates of chain

saws (Koger 1980). Cutting surface data were

collected on 82 hardwood trees in north Georgia,

western North Carolina, eastern Kentucky, eastern

Tennessee, and southeastern Virginia.

Definition of Variables

The following definitions were used in this study

to describe cutting surfaces and tree characterisSouthern Forest Expariment Station/T-10210 U.S. Postal Services Bldg., 701 Loyoir Avenue, New Ortesns, La. 70113

Forest Service, U.S. Department of Agriculture.

Servlng Alabama, Arkansas, Louisiana, Mississippi, E. Oklahoma, Tennessee, E. Tsxas, Puerto RICO, U.S. Vlrgln Islands

1
Figure 1 .-Virglnla Umber cutter making a conventional facecut.

tics. The relationships of the cutting surfaces and Notchcut:

variable names to the tree are shown in figures 2 8 1 = the angle that surface B (figs. 2 & 3)

and 3. makes with the Y-Z axis.

Facecut: 82 = the angle that surface B (figs. 2 & 3)

Basecut: makes with the Y-X axis.

83 = the angle that cutting surface A (fig. 3) T = the maximum thickness of the pie-shaped

with the Y-Z axis. notch.

84 = the angle that cutting surface A (fig. 3) VN = the volume of the pie-shaped notch.

makes with the Y-X axis.

SHL = the height from the base of the facecut

to the ground.

LUC = the length of the base of the facecut,

measured from the outside of the bark

toward the center of the tree.

D C = the distance from the intersection of the

basecut and notchcut to the center of

the tree.

Y

= 2T(RB-DC) d RB’RB - DC*DC

Backcut:

85 = the angle that surface C (fig. 3) makes

with the Y-Z axis.

86 = the angle that surface C (fig. 3) makes

with the Y-X axis.

SHU = the height from the base of the backcut

to the ground.

The author is a Research Engineer at the Forestry Sciences Laboratory, maintained by the Southern Forest Experiment Station,

USDA Forest Service, at Auburn, Alabama. The author gratefully acknowledges partial support from the Division of Land and

Forest Resources of the Tennessee Valley Authority (TVA) at Norris, Tennessee.

2
Y

X

Ci

f-+-X

Bockcutt

/‘-Notchcut

#--%.psecut i 7

4

\ T

St-IL

3 I

Figure P.-Measured variables and axis orientation.

3
Figure 3.-Selected views of the cutting surtaces.

Table l.-Summary of observed variable characteristic8

Variable

locatlon Variable Unit Minimum Average Maximum Std #

Facecut

Undercut

Notchcut

Sackcut

Miscellaneous

83

64

SHL

LUC’

83

82

T

VN

85

ee

SHU

LBC’

D B

DBH

TML

DSE

DM

DF

87

88

dw

dw

in

in

deg

incu in

de9

in

in

in

in

ft

In

ft

ft

0 8.8 1 8 5.2 8 0

0 8.1 3 4 5.9 8 1

4.0 17.3 4 8 8.2 8 1

4.0 10.9 24.0 4.7 8 2

0 8.8 2 8 8.3 8 0

2 30.2 5 8 10.1 7 1

0.0 3.1 8.8 1.4 7 2

0.0 172.8 1019.5 190.1 7 2

0 8.0 2 8 5.3 8 0

0 10.2 3 2 8.3 8 1

4.0 13.7 48.0 8.1 8 1

5.0 11.0 21.8 3.8 8 2

11.8 22.7 37.1 6.0 8 2

8.1 18.4 33.3 5.3 8 2

12.1 41.0 80.3 13.8 8 2

3.5 13.0 25.8 4.8 8 2

1.7 5.8 8.7 1.2 2 3

0.0 7.2 121.2 8.2 3 5

0 1 5 3 5 1 1 8 1

0 2 8 7 0 1 9 61

‘Is the length along the cut surface

4
LBC = the length of the base of the backcut,

measured from the outside of the bark

toward the center of the tree.

Non Cutting Surface:

DB = the diameter of the tree at stump height

(outside bark).

RB := the radius of the tree at stump height

W/2).

DBH = the diameter of the tree measured at 4.5

feet above the ground on the uphill side

of the tree (outside bark).

TML = the merchantable length of the tree as

determined by the timber cutter.

DSE = diameter of the tree, measured at the

end of the merchantable length (small

end, outside bark).

DM = the distance the timber cutter moved

away from the stump as the tree started

to fall (measured with ground slope).

DF = the slope distance from the butt of the

felled tree to the center of its stump.

87 = the angle, in degrees, of the ground

near the tree stump.

88 = the percent slope of the ground near

the tree stump.

RESULTS AND DISCUSSION

The means, standard deviations, and ranges for

the variables measured are shown in table 1. There

are several differences between the recommended

(Wackerman 1949; Simmons 1951; Employers Insurance of Wausau 1965; Pearce and Stenzel 1972;

Table 2.-Developed rsgresslon equations

Conway 1973; Pollini 1982; Bentley 19??) method of

felling trees and those observed in the study. The

major differences between the observed methods

(table 1) and the recommended methods involved

the slope of the facecut and backcut and the length

of the facecut. The base of the observed facecut

sloped downward at 6.1 degrees and the base of the

backcut sloped downward at 10.2 degrees. Further,

the length of the base of the facecut was made almost to the center of the tree. A comparison of several recommended methods versus those observed

in this study are shown in figure 4. Since the existing

recommendations were not developed specifically

for hardwood trees, direct comparisons between

the recommended and observed methods may not

be meaningful.

The timber cutters in this study often continued

making the backcut after the tree had started to fall.

This could explain their moving only a short distance

(5.6 feet) from the base of the tree after completing

the backcut. Their apparent purpose was to: (1)

reduce splitting of the butt log and possible kickbacks and (2) fine tune the direction of tree fall.

The falling momentum of the tree combined with

the slope and nature of the ground surface can

cause the butt of the felled tree to be separated

from its stump by several feet. In this study the

average slope distance separating the center of

the stump and the butt of the felled tree was 7.2

feet.

The general equation model, 83,84,SHL, etc. =

f(DBH, TML, & GSD), was used in the STEPWISE

procedure and FORWARD selection option of SAS

Location Variable* Equation R-SQ C.V.

Faceout

Undercut

Notchcut

Backcut

Mlacellaneoua

$3 = 7.274.21’DBH+O.O8’TML 0.09 73.80

84 = 10.744.35’DBH+O.l5’(j7 0.10 94.73

SHL = 6.20+0.32’DBH+0.36’1$~7 0.30 41.43

LUC = 0.49+0.62’DBH4.02’TML 0.47 31.75

81 = 6.324.12’0SH+O.ll’TML 0.07 70.65

,92 = 24.18+0.54’DSH4.20*,j7 0.06 35.36

T= -0.24+0.18’DBH 0.57 25.79

VN = 1,60+9.42’DBH 0.49 89.76

85 = 9.154.27’DBH+0.06’TML+0.09’~7 0.08 70.00

fj8 = 14.044.05’DBH4.15’TML+O.l9*~7 0.16 81.61

SHU = 9.59+0.21l DBH+O.O04*TML 0.04 44.17

LBC = 3.17+0.40’DBH 0.31 28.80

OM = 2.80+0.17’DBH 0.18 18.86

DF = l-26+0.21 ‘198 0.44 53.73

*See table 1 for variable units (in, ft, etc.)

5
RETREAT AT 43’ANGLE FROM DIRECTION O F

FALL, AND AT LEAST 25 FEET BACK FROM

STUMP.

rlAKE NOTCH OPENING 20% OF STUMP DIAIETER. MAKE QASECUT LEVEL.

AAKE BACKCUT LEVEL AND I-2” HIGHtR

rHAN BASECUT. LEAVE l-2” OF HINGEYOOO.

AAKE BASECUT 25% to 33% OF STUMP

)IAMETER (STUMP HEIGHT OF 12”). 3

OBSERVED

RETREAT WAS hT 180OANGLE FROM DIRECT

tON OF FALL, ANO AVERAGED 5.8 FEET

FROM STUMP.

_._ - -- YOTCH OPENING WAS 17Yo OF STUMP DIAUETER. 8- ---- -- l

. ..a- ----- ASECUT .____ -- WAS MADE AT A .a. - l - s. 5.1° DOWNWARD ANULL [e4].

I BASECUT

lACKCUT WAS AT A lO.2O DOWNWARD ANGLE

06) AND 2.0” HIGHER THAN BASECUT. ONE

NCH OF HINGEWOOD WAS LEFT.

BASECUT WAS 48% OF STUMP DIAMETER

,STUMP HEIGHT WAS 13.7”).

Figure 4.--Recommended versud observed

6

techniques.
@AS Institute Inc. 1979). Only variables that met

the 0.5 significant level for entry into the model are

shown In table 2. Significant differences (Duncan’s

multiple range test) in cutting surface measurements were caused by different chain saw operators

and tree species. However, class or dummy variable

codes were not used, because a meaningful and

consistent grouping could not be found.

The dbh of the tree was a significant variable in

all the equations predicting cutting surface angles

and lengths. In the three equations predicting cutting angles between the x-y surfaces (82,84,86), the

variables dbh and ground slope were significant.

in the three equations predicting the cutting angles

between the x-z surfaces (81,63,65), the variables

dbh, ground slope, and merchantable tree length

were significant.

CONCLUSIONS

The angles and lengths of the different cutting

surfaces made by chain saw operators when felling

hardwood trees have been described by means,

standard deviations, ranges, and regression equations. The low r-squares in the regression equations

indicate that factors other than those measured influenced felling techniques. For example, tree lean,

not measured, would certaintly have an influence on

felling technique. Time consuming measurements of

tree lean would have interfered with the timber cutter. In addition, felling accuracy was not measured.

The major difference between recommended and

observed felling methods was that the base of the

facecut was made to 48 percent of stump diameter.

A facecut between 25 percent to 33 percent is commonly recommended. Another recommendation is

that the base of the facecut and the base of the

backcut be horizontal. In this study the base of the

facecut sloped downward at a 6.1 degree angle and

the backcut sloped downward at a 10.2 degree

angle.

Other average findings based on the results of

this study were:

1. Stump ‘height on the uphill side of the tree

was 13.7 inches (12.0 inches recommended).

2. One inch of hinge wood was left between the

facecut and backcut (one inch to two inches

recommended).

3. The base of the backcut was two inches higher

than the base of the facecut (one inch to two

inches recommended).

4. The notch opening was 17 percent of stump

diameter (20 percent recommended).

5. The timber cutter moved 5.6 feet away from the

stump as the tree was failing (25 feet recommended).

6. The momentum of the falling tree combined

with ground conditions caused the butt of the

felled tree to be separated from the stump by a

distance of 7.2 feet.

The average values determined in this study for

the different cuts used in felling hardwood trees are

not given as recommendations. However, these

averages do reflect the cutting techniques of experienced timber cutters in this region,

LITERATURE CITED

Bent@, A. R. Logging safety. Georgia Casualty and

Surety Company, Atlanta, Georgia, 80~.

Conway, Steve. Timber Cutting Practices. San Francisco, California: Miller Freeman Publications

Inc.; 1973. p.67-87.

Employers Insurance of Wausau. Safe use of power

chain saws. Employers Insurance of Wausau,

Wausau, Wisconsin, 11 p. 1965.

Harkonen, Pekka [Pettersson, Bengt. ed.] The chainsaw-use and maintenance. The National Board

of Forestry, S-551 83, Jonkoping, Sweden, 67~.

1979.

Koger, Jerry L. Factors affecting the production

rates of chain saws. Division of Land and Forest

Resources, Tennessee Valley Authority, Norris,

Tennessee, Technical Note No. 839, June 1980.

p. 22-23.

Pearce, J. Kenneth; Stenzel, George. Logging and

pulpwood production. New York, New York: The

Ronald Press Company: 1972. p. 212-217.

Pollini, Claudia. Techniche di abbattimento e allestimento in foresta. Consiglio Nationaie Delle

Ricerche. lnstituto Perla Technologia Del Legno.

S. Michele a/A - Trento, Italy. 106 p.

SAS Institute Inc. SAS user’s guide. 1979 ed. SAS

Institute Inc., Raleigh, North Carolina, 494 p. 1979.

Simmons, Fred C. Northeastern loggers handbook.

USDA Forest Service, Northeastern Forest Experiment Station, Agriculture Handbook No. 6, p, 47-

66.1951.

Wackerman, A. E. Harvesting timber crops. McGrawHill Book Company, Inc.; 1949. p. 93-120.

*U.S. GOVERNMENT PRINTING OFFICE: ,9g)- 669-OS/53

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