United States An Evaluation of Department of 

Agriculture

Forest Service Saw-Dry-Rip (SDR) Forest

Products

Laboratory for the Manufacture 

Research

Paper

FPL-435 of Studs from Small 

Ponderosa Pine Logs 

Robert R. Maeglin and R. Sidney Boone 
Abstract

Data show that the saw-dry-rip (SDR) 

method produces higher yields of 

STUD grade material than is produced 

by conventional sawing and drying or 

than has been produced in other 

studies using young-growth ponderosa 

pine. The studs are also more stable. 

Small logs were live sawn into flitches. 

The flitches were kiln-dried and then 

ripped into studs for planing. The SDR 

treatment with high temperature drying 

resulted in 77.8 percent of studs so 

produced meeting the STUD grade 

after 30 or more days of storage. 

Juvenile wood, compression wood, and 

less than optimum drying are discussed 

relative to problems yet remaining in 

the manufacture of studs from small 

ponderosa pine logs. 
United States 

Department of An Evaluation of Agriculture

Forest Service Saw-Dry-Rip (SDR)

Forest

Products for the Manufacture 

Laboratory1

of Studs from Small 

Research

Paper

FPL-435 Ponderosa Pine Logs 

August 1983 

ROBERT R. MAEGLIN, Supervisory 

Research Forest Products Technologist 

and

R. SIDNEY BOONE, Research Forest 

Products Technologist 

Introduction problem with black jack ponderosa pine desert southwest are most prone to 

compared different drying schedules severe degrading warp. Arganbright et 

Sawmill operators throughout the with and without top loading. The best al. (1) note that some mills record 

commercial range of ponderosa pine 

are increasingly interested in utilizing 

combination, conventional kiln drying 

and 200 Ib/ft2

 top loading, resulted in 

warp-caused grade reduction, as high 

as 60 percent. 

young growth, black bark, or “black 67 percent of the studs cut meeting the 

jack” ponderosa pine (trees less than STUD grade based on warp. STUD is The SDR system of stud manufacture 

100 years old and having black-colored a specific lumber grade established by was conceived, by scientists at Forest 

bark). However, lumber sawn from the National Grading Rule of the Products Laboratory in 1978, for use 

these trees warps excessively after it is American Lumber Standards Act PS- with hardwoods because of longitudinal 

graded and shipped. The study 20-70. The remainder were ECONOMY growth stress problems. It was devised 

reported here was undertaken at the grade or cull. to control excessive warping in studs 

Forest Products Laboratory to which has kept low and medium 

determine if the saw-dry-rip (SDR) In a similar study on black jack pine, density hardwoods from being used 

process would reduce warp in pine Blake and Voorhies (3) evaluated four commercially for structural lumber. The 

studs. elevated or high-temperature kiln success of SDR in manufacturing studs 

schedules for their effect on stud warp. has been documented for yellow-poplar 

Black jack ponderosa pines are mostly Their best combination was an (10,16), and aspen (17,18). The

small (6- to 12-in. diameter at breast 

height (d.b.h.), contain large 

elevated temperature schedule (190° F) 

with 112 Ib/ft2

 top loading. The 

promise for other species has also 

been explored, e.g., cottonwood, 

proportions of juvenile wood (22),2

 and treatment yielded 45.4 percent STUD sweetgum, black gum, and sycamore 

are prone to have compression wood grade pieces based on warp. (79) as well as basswood, soft maple, 

(2,21). Structural lumber, specifically willow, red alder and paper birch. 

studs, sawn from black jack pine may Both authors demonstrated that more 

be graded and sold at 19 percent warp occurred at lower moisture A comparative study of SDR and 

moisture content. But, as the lumber contents. The lumber manufactured by conventional processing of yellowdries below 19 percent moisture Arganbright et al. (1) had an average poplar (a hardwood), showed 

content, it often warps beyond grade final moisture content of 15 percent, reductions of 40 to 80 percent in 

limits, even to the point of becoming while that manufactured by Blake and average twist, bow, and crook for 

cull material. The excessive warping Voorhies (3,4) had an average final studs manufactured using SDR. Pieces 

problem is a plague to manufacturers, moisture content of 12 percent. This making STUD grade were 100 percent 

wholesalers, retailers, and consumers variation in moisture content may for SDR with high-temperature drying 

alike. account for the roughly 20 percent and 98.3 percent for SDR with 

difference in acceptable, STUD grade conventional drying (16,19). A

Several years ago, Arganbright et al. pieces between the studies. noncomparative study of aspen SDR 

(7) in an effort to overcome the warp studs showed 99.7 percent of studs 

Mills cutting and drying second growth manufactured met the STUD grade, 

ponderosa pine studs to 19 percent based on warp, initially after 

1

 Maintained at Madison, Wis., in cooperation with moisture content often have difficulties manufacture. After at least 60 days 

the University of Wisconsin. with their product when it is shipped to storage in an open-sided shed under 

2

 Italicized numbers in parentheses refer to and used in locations of low humidity. ambient conditions, 94.6 percent of 

literature cited at end of this report. Such studs shipped to locations in the pieces still made STUD grade (18,19).
Materials and Methods Table 1.—2 by 2 by 2 factorial study design for studying ponderosa pine studs 

Scope

This study was designed to evaluate 

the effect of SDR on the quality and 

yield of studs from small (5 to 12-in. 

diameter inside bark (d.i.b.) ponderosa 

pine logs. Increasing the yield and 

quality of graded studs from this 

resource could enhance the product 

recovery from logs and reduce the 

drain on the resource, allowing more 

trees to mature. 

Design

The design for this study was a 2 by 2

by 2 factorial, using two sawing 

methods, two drying methods, and two 

sampling locations. 

The two sawing methods were as 

follows:

Conventional (C) 

SDR live-sawing (S) 

The two drying methods were as 

follows:

Conventional (C) 

High temperature (H) 

These are combined in two-letter 

combinations where the first letter is 

the sawing method and the second is 

drying method: 

CC = conventional-sawing/ 

conventional-drying

CH = conventional-sawing/hightemperature-drying

SC = SDR live-sawing/conventionaldrying

SH = SDR live-sawing/hightemperature-drying

To avoid sample loss should a kiln 

malfunction during drying, two 

replications of each combination were 

used, table 1. 

Sample size was established on the 

basis of yellow-poplar data. The 

desired limits for sampling were a

detectable difference of 5 percent with 

a confidence of 95 percent. With a

sample size of 20 logs per cell, the 

probability of detecting a 5 percent 

difference in stud acceptance is slightly 

greater than 95 percent. 

Log Collection 

One hundred sixty woods run logs 

from small ponderosa pine trees (8- to 

12-in. d.b.h.) were equally selected 

from two different sites by personnel of 

Site 1 Site 2 

Sawing

method Conventional High temperature Conventional High temperature 

drying drying drying drying

ññññññññññññññññ Number of logs ––––––––––––––––

Conventional 10 10 10 10 10 10 10 10

SDR live sawn 10 10 10 10 10 10 10 10

the Coconino National Forest, Based on high-temperature-drying 

Flagstaff, Ariz. Log length was 8.5 feet, experience with hardwoods, literature 

and the top (merchantable) diameter on high-temperature drying of 

was about 5-in. d.i.b. At the Forest softwoods (6,12-15), and several trials 

Products Laboratory logs were with ponderosa pine, a highsegregated by site. Within each site temperature schedule was developed. 

grouping, logs were divided into 8 The schedule was 240° F dry bulb and 

groups of 10 logs each by butt and 190° F wet bulb for 24 hours followed 

upper logs, and diameter class (small by 24 hours of equalizing at 200° F dry 

end d.i.b., 4.6 to 5.5 in., 5.6 to 6.5 bulb and 188° F wet bulb (equalibrium 

in.–11.6 to 12.5 in.). The diameter moisture content 10 pct) and 16 hours 

distribution among the eight groups of conditioning at 195° F dry bulb and 

was as balanced as possible. After the 188° F wet bulb (equalibrium moisture 

groups were separated, they were content 12.5 pct) striving for an 

assigned to treatment by random average moisture content of 12 ± 3

selection. percent.

Sawing Ripping SDR-Studs Two sawing methods were used; a After kiln drying, the SDR flitches were conventional cant system and live straight line ripped to 2 by 4, 2 by 3, sawing. The conventionally sawn studs and 2 by 2 for best utilization with were cut using the centered cant emphasis on cutting 2 by 4’s. method and split taper sawing. A 4-in.

cant was cut from the geometric center

of the log, taking side boards off where Warp Measurement and Grading

the logs were large enough. The side After sawing, drying, and ripping, the

boards were cut 1-3/4 in. thick. Both studs were dressed to standard ALS

cants and side boards were ripped (American Lumber Standards) (23)

green into studs for drying. Side sizes and measured for warp (crook,

boards were ripped into 2 by 4, 2 by 3, bow, and twist). Crook is a deviation

and 2 by 2 for best utilization, with edgewise from a straight line drawn

emphasis on 2 by 4’s. from end to end of a piece. Bow is

deviation flatwise from a straight line 

Live sawing (through and through on drawn from end to end of a piece. 

one plane) was used to produce 1-3/4- Twist is a deviation flatwise, or flatwise 

in.-thick flitches for SDR. Full taper and edgewise, in the form of a curl or 

sawing, cutting parallel to one of the spiral so that the four corners of any 

outside faces of the log, was used, as face are not in the same plane. Each 

was a minimum 4-in. opening face. The piece was measured to the nearest 

flitches were edged green to 1/2 in. 1/32 in. for the three types of warp. 

wider than acceptable wane limits, and 

the presumed final edging line, to form 

a more compact and efficient kiln load. Acceptance of studs was determined 

using the National Grading Rule for 

Drying dimension lumber, STUD grade. Limits

Two drying schedules were used; a of warp for 2 by 4 and 2 by 3 are

conventional schedule and a high- crook 1/4 in., bow 3/4 in., twist 3/8 in.;

temperature schedule. Conventional and for 2 by 2, crook 3/4 in., bow 3/4

drying of studs and flitches was done in., and twist 3/16 in.

according to Forest Products

Laboratory Schedule T5-A5S (20), After initial measurement, the studs

striving for a moisture content of 12 ± were stored in an open sided shed for

3 percent. 30 days or more and then remeasured.

2
Statistical Analysis and Data 

Processing

Conventional analysis of variance for 

factorially designed studies was used 

to evaluate the effects of sawing, 

drying, and location on the yield of 

acceptable studs from ponderosa pine. 

Results and Discussion 

General Results 

General warp data are presented in 

table 2 for combined stud sizes (2 by 2, 

2 by 3, and 2 by 4) and in table 3 for 

2 by 4 only. Major differences in warp 

are primarily between CC and the other 

treatments. In table 4 we see that the 

only significant differences between 

treatments are for twist, where the 

difference is highly significant for both 

2 by 4’s and combined stud sizes. The 

Duncan’s multiple range test (table 5) 

shows no difference for crook or bow 

between treatments, but significant 

differences between treatments for 

twist (P=0.05). 

For 2 by 4’s only, a significant 

difference is shown between the CC 

treatment and all other treatments. 

There is also a significant difference 

between the CH treatment and the SH 

treatment. There is no statistical 

difference between the SC and the CH 

treatment or the SC and SH 

treatments. For the combined stud 

sizes, there are statistically significant 

differences between all treatments. The 

difference between warp types and 

treatment are shown graphically in 

figures 1 and 2 for 2 by 4’s and 

combined stud sizes respectively. 

Means by warp type and treatment and 

improvement by treatment over the CC 

results are shown in table 6. For crook, 

improvements are from 6.4 to 15.3 

percent; for bow, from 1.4 to 21.4 

percent; and for twist, from 25.0 to 

67.5 percent. The improvements for 

crook and bow are not significant, but 

a small change in average warp can 

lead to many more studs recovered. 

The values of twist are, however, of 

practical and statistical significance. 

While the average warp values are of 

interest and concern, the important 

question is, how many pieces make the 

grade? The standard used in this 

study, as previously mentioned, was 

the National Grading Rule-STUD 

grade. This was based only on warp– 

not on knots, moisture content, or 

Table 2.—Warp average, range,1 and number of rejects by treatment and area. Initial measurement after machining. All stud sizes 

combined (2 by 2, 2 by 3, 2 by 4) 

Treatment2,3

CC CH S C SH

Area Warp Average Range Rejects Average Range Rejects Average Range Rejects Average Range Rejects 

– – –1/32 in. – – – No. – – –1/32 in. – – – No. – – –1/32 in. – – – No. – – –1/32 in. – – – No.

1 Crook 5.6 52 17 4.7 31 10 6.8 52 18 4.7 33 11

Bow 6.4 31 3 5.9 22 0 8.1 82 6 5.8 29 2

Twist 3.9 22 4 2.7 25 1 2.1 11 0 1.1 7 0

2 Crook 6.7 48 14 6.0 35 17 5.0 28 14 6.4 33 23

Bow 8.4 34 4 7.2 30 4 6.0 27 2 6.2 36 4

Twist 4.3 18 4 3.4 15 3 2.2 13 1 1.2 10 0

Combined Crook 6.2 52 31 5.4

6.5

35 27 5.8 52 32 5.6 36

Bow 7.3 34 7 30 4 7.2 82 8 6.0 36 6

Twist 4.0 22 8 3.0 25 4 2.1 13 1 1.3 10 0

1

 Range is from 0 to value shown.

2

 CC = conventionally sawn/conventionally dried; CH = conventionally sawn/high temperature dried; SC = SDR live sawn/conventionally 

dried; SH = SDR live sawn/high temperature dried.

3

 Total number of samples per treatment: CC = 130, CH = 136, SC = 152, SH = 149. 

Table 3.—Warp average, range,1

 and number of rejects by treatment area. Initial measurement after machining, for 2 by 4 studs only 

Treatment2,3

CC CH SC SH

Area Warp Average Range Rejects- Average Range Rejects Average Range Rejects Average Range Rejects 

– – –1/32 in. – – – No. – – –1/32 in. – – – No. – – –1/32 in. – – – No. – – –1/32 in. – – – No.

1 Crook 6.4 52 17 5.1 31 10 7.3 40 14 5.1 33 8

Bow 6.1 30 3 6.1 22 0 6.5 28 2 4.3 25 1

Twist 3.9 14 3 3.0 25 1 2.6 11 0 2.0 7 0

2 Crook 8.4 48 11 7.3 35 17 6.2 28 13 7.2 33 21

Bow 8.4 30 3 7.4 30 3 5.2 27 2 5.5 26 1

Twist 4.9 18 5 3.7 15 3 2.8 13 1 1.5 10 0

Combined3 Crook 7.2 52 28 6.1 35 27 6.6 40 27 6.6 33 29

Bow 7.0 30 6 6.9 30 3 6.1 28 4 5.5 26 2

Twist 4.2 18 8 3.1 25 4 2.6 13 1 1.8 10 0

1

 Range is from 0 to value shown. 

2 CC = conventionally sawn/conventionally dried; CH = conventionally sawn/high temperature dried; SC = SDR live sawn/conventionally 

dried; SH = SDR live sawn/high temperature dried.

3

 Total number of samples per treatment: CC = 93, CH = 115, SC = 98, SH = 94. 

3

34
Table 4.—Analysis of variance of warp for area treatment and log position in tree 

Source DF Crook Bow Twist

All stud sizes combined 

Area 1 0.61 NS1 0.14 NS 1.46 NS 

Treatment 3 0.21 NS 0.44 NS 2

25.27**

Log position 

Area X treatment 

5

3

5.65**

1.86 NS 

2.04 NS 

3

3.12*

20.72**

0.60 NS 

Area X log position 4 1.17 NS 1.88 NS 0.69 NS 

Treatment X log position 12 0.56 NS 1.23 NS 3.69**

Area X treatment X log position 12 0.76 NS 0.52 NS 5.12**

2 by 4 only 

Area 1 1.64 0.34 NS 0.63 NS 

Treatment 3 0.32 NS 1.31 NS 10.21**

Log position 4 10.04** 3.77** 13.93**

Area X treatment 3 0.77 NS 2.59* 1.55 NS 

Area X log position 4 1.37 NS 1.10 NS 0.48 NS 

Treatment X log position 12 0.47 NS 1.20 NS 2.34**

– – – – –F value and significance – – – – – 

1

 NS = Not significant.

2

 ** = Highly significant, P = 0.01. 

3

 * = Significant, P = 0.05. 

Table 5.—Duncan’s multiple range test to evaluate the effect of treatment on warp, 

P = 0.05 

Warp Mean N Treatment1 Mean N Treatment

1/32 in. 1/32 in. 

Crook 2

7.2 93 CC 6.2 130 CC

6.6 94 SH 5.8 152 SC

6.6 98 SC 5.6 149 SH

6.1 115 CH 5.4 136 CH

Bow 7.0 93 CC 7.3 130 CC

6.9 115 CH 7.2 152 SC

6.1 98 SC 6.5 136 CH

5.5 94 SH 6.0 149 SH

Twist 4.2 93 CC 4.0 130 CC

3.1 115 CH 3.0 136 CH

2.6 98 SC 2.1 152 SC

1.8 94 SH 1.3 149 SH

2 by 4 only Combined stud sizes 

slope of grain. Table 7 lists the percent 

of recovery in the STUD grade, plus 

the improvement of the various 

treatments over the CC treatment. The 

apparent best treatment on initial 

measurement is CH. The yield of STUD 

grade material using CH varies from 73 

percent for 2 by 4’s only to 76.5 

percent for all stud sizes. These yields 

are better than those reported by 

Arganbright et al. (1) 67 percent, and 

Blake and Voorhies (4), 45.4 percent. 

While the above mentioned authors 

indicated higher warp for moisture 

content below 15 percent, the studs in 

the study reported here were much 

drier, averaging 9.4 percent moisture 

content. The highest average moisture 

content was for the SC treatment; 11.5 

percent.

Looking at the remeasurement data in 

table 7 we see that after 30 days or 

more storage the CH treatment 

showed up as best for 2 by 4’s, 

improving slightly in yield. The SH 

treatment for 2 by 4’s had a slight 

improvement in yield from 67 to 70.2 

percent, and was best for combined 

stud sizes with 77.8 percent yield 

percent.

Comparing Ponderosa Pine and 

Yellow-Poplar

The results of this trial may have been 

affected by the high-temperature-drying 

schedule, which was not quite 

1

 CC = conventional sawing/conventional drying; CH = conventional sawing/high 

temperature drying; SC = SDR live sawing/conventional drying; SH = SDR live sawing/ 

high temperature drying.

2

 Lines connecting values indicate no significant difference between connected values. 

Table 6.—Average warp and percent improvement over conventional sawing and 

conventional drying by treatment for second growth ponderosa pine 

Combined stud size 2 by 4 Studs 

Warp Treatment Average Improvement

over CC Treatment Average Improvement

over CC 

1/32 in. Pct 1/32 in. Pct

Crook SH 5.6 9.7 SH 6.6 8.3

SC 5.8 6.4 SC 6.6 8.3

CH 5.4 12.9 CH 6.1 15.3

CC 6.2 — CC 7.2 —

Bow SH 6.0 17.8 SH 5.5 21.4

SC 7.2 1.4 SC 6.1 12.8

CH 6.5 9.6 CH 6.9 1.4

CC 7.3 — CC 7.0 —

Twist SH 1.3 67.5 SH 1.8 57.1

SC 2.1 47.5 SC 2.6 38.1

CH 3.0 25.0 CH 3.1 26.2

CC 4.0 — CC 4.2 —

1

 CC = conventional sawing/conventional drying. CH = conventional sawing/high 

temperature drying; SC = SDR live sawing/conventional drying; SH = SDR live sawing/ 

high temperature drying, 

4

optimum. During the ripping operation 

flitches tended to pinch, indicating 

residual drying stresses. Any pinching 

results in the cut pieces warping in 

crook. Other evidence that some of the 

warp is induced by the hightemperature drying is the increase in 

acceptable pieces after storage. The 

lumber was exposed to an equalibrium 

moisture content of 15 to 20 percent in 

storage. The addition of moisture to 

the shell of the lumber would cause a

relaxation of the stress, and removal of 

some warp-enough to upgrade some 

pieces. Alternatives for the drying 

schedule to alleviate the case 

hardening might be to lengthen the 

conditioning period or to reduce the 

wet bulb depression (less spread 

between dry bulb and wet bulb) during 

conditioning. However, it has been 

noted that it is difficult to adequately 

relieve drying stresses when the target 

moisture content is above 11 percent 

(21).
growth ponderosa pine is directly 

related to anatomical properties of the 

wood and not to growth stresses. As 

mentioned earlier, black jack pine has 

considerable juvenile core and is prone 

to have compression wood. 

Juvenile wood of conifers has several 

negative characteristics such as high 

fibril angles, lower density, and shorter 

fibers than mature wood. These 

characteristics tend to result in greater 

longitudinal shrinkage than more 

mature wood and therefore more warp 

(22). These characteristics are not as 

easily manipulated as growth stresses. 

The other factor, compression wood, is 

not easily manipulated either. It, too, 

results in greater longitudinal shrinkage 

and warp when unbalanced with 

normal wood (21).

Perhaps a better yield of studs could 

be achieved through using heavy top 

weights, serrated kiln sticks, a modified 

kiln schedule, and the SDR process. 

Warp in Relation to Log Position 

Mean warp values by log position in 

the tree are listed in table 8 by warp 

type.

For average crook, the warp is nearly 

in progression from butt (log 1) to top 

(log 5), log 3 having the lowest crook. 

Duncan’s multiple range test indicates 

that log 1 has significantly more crook 

than the other logs, and that the other 

logs are not significantly different from 

one another. 

Figure 1.—2 by 4 ponderosa pine warp by 

treatment N = 400. CC = conventionally 

sawn/conventionally dried; CH =

conventionally sawn/high temperature dried; 

SC = SDR live sawn/conventionally dried; 

SH = SDR live sawn/high temperature 

dried. (M151900) 

While the results are encouraging 

compared to other research on second 

growth ponderosa pine, they are not as 

encouraging as the results from yellowpoplar. For example, average SH crook 

was about 6/32 in. and average SC 

crook about 6/32 in. for ponderosa 

pine, but less than 1/32 and 2/32 in. 

respectively for yellow-poplar. Average 

bow for SH and CH are respectively 

6/32 and 7/32 in. for ponderosa pine, 

but about 5/32 and 6/32 respectively 

for yellow-poplar. And, average twist 

for SH and SC are about 1/32 and 2/ 

32 in. for ponderosa pine, but 1/32 in. 

for yellow-poplar. 

The contrasts are also great when 

comparing the percentage of pieces 

making STUD grade. The data in table 

7 show the SH and SC treatments 

yielding 67.0 and 75.0 percent STUD 

grade pieces respectively. For yellowpoplar the SH and SC treatments 

yielded 100 and 98.3 percent, 

respectively. Achieving acceptable 

grade limits for moisture content was 

no problem with the yellow-poplar. 

Anatomical Problems 

The SDR process was developed to 

reduce the effects of longitudinal 

growth stresses on warp in studs. The 

success with hardwoods lies to a large 

measure in the regularity of stress 

distribution within trees and logs. The 

stresses are high in tension at the 

periphery of the tree, decreasing to a

Figure 2.—All stud sizes combined 

ponderosa pine warp by treatment N =

567. CC = conventionally sawn/ 

conventionally dried; CH = conventionally 

sawn/high temperature dried; SC = SDR 

live sawn/conventionally dried; SH = SDR 

live sawn/high temperature dried. (M151901) 

neutral zone and then changing to 

compression stress which is maximized 

at pith. When live-sawn flitches are cut 

for SDR, the stresses are balanced and 

restrain the tendency for the flitch to 

crook. However, as noted by Jacobs 

(11) the conifers don’t display such 

clear stress patterns. Jacobs states 

that, while all trees have tension 

stresses at the periphery, the conifers 

may or may not have compression 

stresses at the pith. He continues by 

saying that the only tissue 

demonstrating compression may be 

reaction wood. 

It may well be that the principal 

difficulty in sawing and drying young 

Table 7.—Percent of pieces making stud grade based on warp and the percent of 

improvement over the CC treatment 

2 by 4 Studs Combined stud sizes 

Measurement

Treatment1 Stud Improvement Treatment Stud improvement

grade over CC grade over CC 

– – – – – –Pct– – – – – – – – – – – –Pct– – – – – – 

Initial2 SH 67.0 11I.3 SH 74.5 11.4

SC 69.4 15.3 SC 75.0 12.1

CH 73.0 21.3 CH 76.5 14.3

CC 60.2 — CC 66.9 —

Second3 SH 70.2 12.7 SH 77.8 16.3

SC 64.3 3.2 SC 70.4 5.2

CH 73.9 18.6 CH 77.2 15.4

CC 62.3 — CC 66.9 —

1

 CC = conventional sawing/conventional drying. CH = conventional sawing/high 

temperature drying; SC = SDR live sawing/conventional drying; SH = SDR live sawing/ 

high temperature drying. 

2

 Measured directly after machining. 

3

 Measured after 30 days or more storage in an open sided shed. 

5
Table 8.—Duncan’s multiple range test to evaluate the effect of log position in tree on These data agree with the findings of 

warp, P = 0.05. Blake and Voorhies (3) and Hallock 

Warp Mean N Log position1 Mean N Log position 

1/32 in. 1/32 in. 

Crook 10.4 138 1 8.2 201 1 2

5.4 106 2 4.8 61 4

4.6 48 4 4.7 156 2

4.1 14 5 4.2 18 5

3.8 94 3 3.9 130 3

Bow 11.0 14 5 9.9 18 5

7.6 48 4 8.6 61 4

7.0 138 1 7.3 201 1

5.5 106 2 6.0 130 3

5.2 94 3 5.9 156 2

Twist 6.4 14 5 7.1 18 5

4.4 48 4 3.9 61 4

3.2 94 3 2.8 130 3

3.1 106 2 2.4 150 2

1.8 138 1 1.5 201 1

2 by 4 Only Combined stud sizes 

1

 1 = butt, 5 = top.

2

 Lines connecting values indicate no significant difference between connected values. 

For average bow there is no regular 

progression of means with log position. 

For combined stud sizes the top two 

logs of the trees had higher bow, while 

logs 2 and 3 had the lowest bow, and 

the butt logs were in the middle, but 

there were no significant differences. 

For 2 by 4’s only, Duncan’s test shows 

logs 4 and 5 are not significantly 

different from each other, nor are logs 

1 through 4. But, log 5 has significantly 

more bow than logs 1, 2, and 3. 

A reverse progression is found for 

twist, with more twist in the upper logs 

than in the butt log. Duncan’s test, for 

2 by 4’s only, indicates a significant 

difference between all means except 

for logs 2 and 3, which are not 

significantly different from each other. 

For combined stud sizes logs 4 and 5

are not significantly different from each 

other nor are logs 2 and 3. Log 1 has Figure 3.—2 by 4 ponderosa pine twist by significantly lower twist than the other log position N = 400. (1 = butt, 5 = top.) 

logs (fig. 3). (M151902)

(7,9) that show butt logs have more 

crook, moderate bow, and less twist 

than upper logs. 

Summary and Conclusions 

The SDR process, originally designed 

to manufacture studs from low- and 

medium-density hardwoods, was 

evaluated for use with warp-prone 

young-growth ponderosa pine. 

Compared to the results reported by 

Arganbright et al. (1) and Blake and 

Voorhies (4) the SDR process yielded 

more STUD grade lumber from young 

growth, “black jack” ponderosa pine. 

Arganbright et al. reported 67 percent 

STUD grade, Blake and Voorhies 

reported 45.4 percent STUD grade, 

while the study reported here had 76.5 

percent STUD grade pieces (77.8 pct 

after storage). Both Arganbright et al. 

and Blake and Voorhies showed that 

material dried below 15 percent 

moisture content warped considerably 

more; our results are for studs dried to 

an average moisture content of 9.4 

percent.

From this study we have concluded: 

1. SDR, with some additional 

modifications to the drying schedule 

with heavy top loading, and with 

serrated kiln sticks, may be an 

economical approach to utilizing warpprone young-growth ponderosa pine. 

2. The sources that accentuate warp in 

studs from “black jack” pine are 

primarily juvenile wood and 

compression wood, which are 

anatomical problems, not growth stress 

problems in the normal sense. 

3. It is possible to dry studs from 

“black jack” pine below 15 percent 

moisture content and still produce 

quality studs. 

4. Butt logs produce more crooked 

studs than do upper logs, but fewer 

twisted studs. 

6
Literature Cited 

1. Arganbright, D. G.; Venturino, J. A.; Goward, M. Warp 

reduction in young-growth ponderosa pine studs 

dried by different methods with top load restraint. 

Forest Prod. J. 28(8): 47-52; 1978. 

2. Barger, R. L.; Ffolliott, P. F. Factors affecting 

occurrence of compression wood in individual 

ponderosa pine trees. Wood Sci. 8(3): 201:208; 

1976.

3. Blake, B. R.; Voorhies, G. Kiln drying of young-growth 

ponderosa pine studs. Ariz. For. Notes No. 13. 

Flagstaff, AZ: North Ariz. Univ.; 1980. 14 p. illus. 

4. Blake, B. R.; Voorhies, G. Studies of kiln drying younggrowth ponderosa pine studs. South. Lumberman 

241(3002): 7-9; 1981. 

5. Boone, R. S.; Maeglin, R. R. High temperature drying 

of 7/4 yellow-poplar flitches for SDR studs. Res. Pap. 

FPL 365. Madison, WI: U.S. Department of 

Agriculture, Forest Service, Forest Products 

Laboratory; 1980. 9 p. 

6. Gerhards, C. C.; McMillen, J. M., compilers. Hightemperature drying effects on mechanical properties 

of softwood lumber. Madison, WI: U.S. Department 

of Agriculture, Forest Service. Forest Products 

Laboratory; 1976. 161 p. 

7. Hallock, H. Sawing to reduce warp of loblolly pine 

studs. Res. Pap. FPL 51. Madison, WI: U.S. 

Department of Agriculture, Forest Service, Forest 

Products Laboratory; 1965. 52 p. 

8. Hallock, H. Sawing to reduce warp of lodgepole pine 

studs. Res. Pap. FPL 102. Madison, WI: U.S. 

Department of Agriculture, Forest Service Forest 

Products Laboratory; 1969. 32 p. 

9. Hallock, H. Sawing to reduce warp of plantation red 

pine studs. Res. Pap. FPL 164. Madison, WI: U.S. 

Department of Agriculture, Forest Service Forest 

Products Laboratory; 1972. 27 p. 

10. Hallock, H.; Bulgrin, E. H. A look at yellow-poplar for 

studs. Res. Note FPL-0238. Madison, WI: U.S. 

Department of Agriculture, Forest Service, Forest 

Products Laboratory; 1979. 7 p. 

11. Jacobs, M. R. The growth stresses of woody stems. 

Commonwealth Forestry Bureau Bull. No. 28. 

Canberra; Commonw. For. Bur. Aust.; 1945. 63 p. 

illus.

12. Koch, P. Process for straightening and drying southern 

pine 2 by 4’s in 24 hours. Forest Prod. J. 21(5): 17-

24; 1971.

13. Koch, P. Serrated kiln sticks and top load substantially 

reduced warp in southern pine studs dried at 240° F. 

Forest Prod. J. 24(11): 30-34; 1974. 

14. Kozlik, C. J. Effect of kiln temperatures on strength of 

Douglas-fir and western hemlock dimension lumber. 

Rep. D-11. Corvallis, OR: Oreg. State Univ., For. 

Res. Lab.; 1968. 20 p. 

15. Kozlik, C. J. High-temperature drying of Douglas-fir 

dimension lumber. Inf. Circ. 22. Corvallis, OR: Oreg. 

State Univ., For. Res. Lab.; 1967. 31 p. 

16. Maeglin, R. R. Yellow-poplar studs by SDR. South. 

Lumberman 237(2944): 58-60; 1978. 

17. Maeglin, R. R. Could SDR be the answer to the aspen 

oversupply problem? North. Logger and Timber 

Process 28(1): 24-25; 1979. 

18. Maeglin, R. R. A new look at aspen studs. Timber 

Prod. (11): 36; 1979. 

19. Maeglin, R. R.; Boone, R. S. Manufacturing quality 

structural lumber from hardwoods using the SawDry-Rip process. In: Proceedings, 9th Ann. 

Hardwood Symp. Hardwood Res. Counc.; 1981 May 

26-28; Pipestem, WV. Asheville, NC: Hardwood 

Research Council; 1981: 29-45. 

20. Rasmussen, E. F. Dry kiln operator’s manual. Agric. 

Handb. 188. Washington, DC.: U.S. Department of 

Agriculture, Forest Service; 1961. 

21. Voorhies, G. Incidence and severity of compression 

wood in thinned stands of young-growth ponderosa 

pine. Ariz. For. Notes No. 15. Flagstaff, AZ: North. 

Ariz. Univ.; 1982. 11 p. illus. 

22. Voorhies, G.; Groman, W. A. Longitudinal shrinkage 

and occurrence of various fibril angles in juvenile 

wood of young-growth ponderosa pine. Ariz. For. 

Notes 16. Flagstaff, AZ: North. Ariz. Univ.; 1982. 

18 p. illus. 

23. U.S. Department of Commerce. American softwood 

lumber standard. Washington, D.C.: U.S. Department 

of Commerce; 1970. p. 20-70. 

2.5-7-8/83

7
Maeglin, Robert R.; Boone, R. Sidney. An evaluation of 

saw-dry-rip (SDR) for the manufacture of studs from 

small ponderosa pine logs. USDA For. Serv. Res. Pap. 

FPL-435. Madison, WI: For. Prod. Lab.; 1983. 7 p. 

The saw-dry-rip (SDR) method produced substantially 

higher yields of STUD grade material (77.8% meeting grade) 

than is produced by conventional processing or than has 

been produced in other studies using young-growth 

ponderosa pine. 

Keywords: Ponderosa pine, lumber, studs, saw-dry-rip, 

warp, live sawing, high-temperature drying.