Hemlock Dimensional Stability

Transcription

1 2010 Hemlock Dimensional Stability Test Evaluation Report Research & Development 9Wood, Inc. February 10

2 Abstract: This report analyzes the dimensional stability of Hemlock planks composed of various saw cuts (grain orientation) and relief cut applications. A total of 8 dimensional deviation readings were taken on 40 separate samples. The samples consisted of 10 Flat Grain Hemlock planks, 10 Flat Grain Hemlock planks with relief kerfs, 10 Vertical Grain Hemlock planks, and 10 Vertical Grain Hemlock planks with relief kerfs. The samples were subjected to moisture desorption and absorption to induce dimensional deviation (warp). Results showed that Vertical Grain had the least amount of overall average total dimensional deviation from flat (Bow & Cup combined) with an average inches of deviation over 5.25 inches of wood. Maximum deviation in cup is highly dependent on the type of grain used [p-value<0.01]. Maximum deviation in bow is highly dependent on the use of relief kerfs [p-value<0.01]. 9Wood, Inc. Abstract: ii

3 Table of Contents: Abstract:... ii Introduction:... 1 Literature Review:... 1 Figure 1: Depiction of Springwood and Summerwood. Figure also illustrates the three different grain directions of wood Figure 2: Depiction of the various types of warp... 4 Methodology:... 5 Figure 3: Relative Humidity and Temperature Data Logging Device... 6 Figure 4: Digital Depth Gauge... 6 Figure 5: Mini-Ligno DX Moisture Meter... 6 Figure 6: Depiction of the various Hemlock planks tested... 6 Table 1: Temperature and Relative Humidity of prep area before and after finishing when %MC readings were taken... 7 Figure 7: Depiction of Hemlock plank and labeled measurement markers... 8 Figure 8: Depiction of measurement scale for Deviation in Cup... 8 Figure 9: Depiction of measurement scale for Deviation in Bow... 8 Figure 10: Depiction of the stacked members on the fabricated sawhorse. Notice how the stickers are spaced with 1" blocks to allow the members to freely change in dimension Figure 11: Graph that shows the average change in Moisture Content, Temperature and Relative Humidity during Desorption (Hot/Dry chamber) over Time Figure 12: Graph that shows the average change in Moisture Content, Temperature and Relative Humidity during Absorption (Mockup area) over Time Discussion & Results: Figure 13: Graph that depicts the average deviation in Cup/5.25 for each sample type during acclimatization Figure 14: Graph that depicts the average deviation in Bow/52" for each sample type during acclimatization Figure 15: Graph that shows the overall Average Deviation from Flat (Bow & Cup) for each combination variable during Absorption and Desorption Figure 16: Graph that shows the overall Total Average Deviation from Flat (Bow & Cup Combined) for each combination variable during Absorption and Desorption Table 2: Analysis of variance of all variables and their significance on Maximum Cup (in) Table 3: Analysis of variance of all variables and their significance on Maximum Bow (in) Conclusion: Literature Cited: Appendices Appendix I: Measurement Data (inches) Sorted by Date Appendix II: Moisture Content Log Sorted by Date Appendix III: Statistical Analysis (ANOVA & Histogram) Wood, Inc. Table of Contents: iii

4 Introduction: Wood is highly unique for its physical, mechanical, and anatomical properties. It is an anisotropic, hygroscopic and viscoelastic material; that is, its dimensions are directionally dependent, it has an affinity for water molecules, and it properties exhibit both visco and elastic characteristics when undergoing deformation. Due to these properties, wood dimensional stability can be troublesome to manage unless considerations are made. The hygroscopicity of wood poses the most problems when trying to minimize dimensional change. Through diffusion, wood will come into equilibrium moisture content (EMC) with the surrounding air by absorbing and desorbing water vapor. During this transition, wood will change in dimension causing shrinkage or swelling due to the gain or loss of bound water within the woods cellular structure. However, dimensional change is highly dependent on the woods grain structure hence why wood is anisotropic. Thus, by changing the grain orientation through milling, dimensional changes can be manipulated. This study investigates the dimensional stability of 1 x 6 quarter-sawn (Vertical Grain VG ) and plain-sawn (Flat Grain FG ) Hemlock planks as they are subjected to changes in moisture content. The purpose of the study is to examine the effects of grain orientation and the application of relief kerfs when attempting to minimize warp. The objective of this report is to gain a better understanding on the feasibility of 1 x 6 Hemlock planks in efforts to constantly improve 9Wood s continuous linear systems. Literature Review: A fully saturated piece of wood is considered to be at 100% moisture content. This moisture is detained within the wood in two distinct manners bound water and free water. Bound water is moisture that is molecularly bound to the cellular structure of the wood. Free water, on the other hand, is essentially moisture that is freely held within the cell lumen (the hollow cell cavity). As wood dries, free water in the cell cavities is the first to be drawn from the wood. Once all the free water has been evaporated, wood is considered to be at fiber saturation point (FSP) or roughly 30% moisture content. At this point, any more moisture that is removed can have a substantial effect on dimension change. Shrinkage and swelling are present when any portion of a piece of wood loses or gains moisture below the fiber saturation point. In fact, every 1 percent change in moisture content, below the fiber saturation point, woods dimensions will inherently alter by a factor of one-thirtieth of its total dimensional change (2, 5). As wood changes in dimension, it is subjected to stresses and can become distorted, or strained. Fortunately, wood is viscoelastic, so it can conform to strain produced by shorttime stress below a certain limit (called the proportional limit). Strain below the proportional limit, elastic strain, will substantially disappear when the load is released; thus, avoiding serious damage. However, stress beyond the proportional limit, or stress below the proportional limit applied for long periods of time, produces some strain that does not disappear upon release of 9Wood, Inc. Introduction: 1

5 the load. This permanent strain will cause extensive damage and therefore, it is important to keep shrinking and swelling to a minimum (2, 5). Rules for shrinkage and swelling were characterized in the study held by the Forest Products Laboratory at Oregon State University. In the article, Shrinkage and Swelling of Wood in Use, it lists: Wood shrinks/swells the most in the direction of the annual growth rings (tangentially), less across these rings (radially), and very little, as a rule, along the grain (longitudinally). Formerly, the lesser radial shrinkage as compared with the tangential shrinkage was attributed to the wood rays, which are strips of cells extending inward from the bark. It was thought that these cells did not shrink much in length, and since their length lies in the radial direction, they were believed to oppose radial shrinkage. Now, however, it is known that the structure of the walls of the wood-ray cells permit large shrinkage along their length. The parallel arrangement of the springwood to the summerwood tangentially in the annual rings may account for some of the difference between tangential and radial shrinkage. Summerwood shrinks more tangentially than springwood. Because it is denser and stronger than springwood, the summerwood also forces the springwood to shrink more than it would if it were detached from the two adjoining bands of summerwood. The relative position of the springwood and summerwood, however, does not affect radial shrinkage (refer to Figure 1) Longitudinal Direction Radial Direction Tangential Direction Summerwood Springwood Figure 1: Depiction of Springwood and Summerwood. Figure also illustrates the three different grain directions of wood. Shrinkage not only differs with the three directions of grain, but also differs among species. It varies widely in material cut from the same species and even in material cut from the same tree. 9Wood, Inc. Literature Review: 2

6 In general, the heavier species of wood shrink more across the grain (transversely) than lighter ones. The over-all, or volumetric, shrinkage of wood also generally increases with an increase in specific gravity. Besides causing changes in dimensions, shrinking and swelling frequently have more harmful effects such as checking, warping, case-hardening, and honeycombing. (Information on the cause and minimization of such harmful effects is available in other publications of the Forest Products Laboratory). Since wood shrinks more tangentially than radially, quarter-sawn lumber (Vertical Grain lumber) shrinks less in width but more in-thickness than plain-sawn lumber (Flat Grain lumber). If a quarter-sawn and a plain-sawn board are placed edge to edge in the same panel, one may become thinner than the other with change in moisture content. Furthermore, plain-sawn lumber has a natural tendency to cup as it dries, because the position of the annual growth rings with respect to the two, faces of the board is not the same. Use quarter-sawn lumber if shrinkage across the width of a board is likely to be serious. A floor made from quarter-sawn material develops narrower cracks than one made from plain-sawn material. It should be cognitive; however, that quarter-sawn lumber shrinks more in thickness than plain-sawn lumber does. If a minimum of change in dimensions is highly essential, select a species having low shrinkage, such as eastern white and sugar pine for patterns, and the cedars in general for boat planking. Use a wood of as light weight as will have the necessary strength, because, as a rule, the lighter kinds of wood will not shrink and swell so much as the heavier kinds.(5) Warp in lumber can be defined as any deviation from flatness or straightness. Two of the most significant forms of warp are bow and cup. Cup, or cupping, is defined as the deviation from flatness transversely across the face of the board. Bow is the same type of deviation but in a lengthwise direction from end to end of the member (1). Other sources of warp include crook, twist, diamond, and oval. Bowing and Crook: Tension along the grain may have existed in the outer portion of the tree. In some cases, the tension was so great, that when flitches were cut, they would nearly split from end to end. Other possible explanations are that the longitudinal shrinkage of the sapwood may have been greater than that of the heartwood or that the wood toward the outer part of the tree was less dense and therefore may have had greater longitudinal shrinkage. As a rule, wood of low density shrinks more longitudinally and less transversally than similar wood of higher density (5). If the grain on one side of a board varies more from the longitudinal direction than the grain on the other-side, then the first side will have more transverse shrinkage in the longitudinal direction and the board will become concave on that side. In other words, the direction of bowing and crooking will be the same as that of the grain. Curly grained pieces bow and crook badly (5). 9Wood, Inc. Literature Review: 3

7 Cupping: The primary cause of cupping is the difference between the amount of shrinkage parallel to the growth rings (tangential) and that perpendicular to them (radial). An excellent way to compare the cupping tendencies of different species is to take from a shrinkage table the ratios of tangential to radial shrinkage for those species and then to compare the ratios directly. Since the tangential shrinkage is the greater, the cupping from this cause will usually be toward the sap side of the piece (5). Cupping (predominantly in Flat Grain lumber) can be easily predicted using the shrinkage ratios for a given species. The less difference between shrinkage tangentially (S t ) to the shrinkage radially (S r ), found by using the R/T ratio, will ultimately result in a more dimensional stable piece of lumber. Diamonding and Oval: Diamonding of squares or Oval of cylinders is also caused by the difference in tangential and radial shrinkage, and they too cannot be prevented. Naturally, the diamonding will be greatest for those pieces having growth rings running from corner to corner (5). Twisting: Twisting is mostly a result of other kinds of warp. A difference in bowing of two edges of the same piece or a difference in cupping of the two ends may cause the cocking up of one corner (5). Bow Twist Crook Cup Diamond Figure 2: Depiction of the various types of warp 9Wood, Inc. Literature Review: 4

8 There have been many efforts throughout history to minimize warp and the stresses caused by moisture absorption or desorption. The most controversial attempt is the applica tion of relief kerfs on the face of the board. Kerfs are shallow channels engraved into the face of the board that run the length of the member. Although there is no universally accepted explanation for the purpose of relief kerfs, some say that the kerfs are intended to release stresses in the board that are induced with varying moisture gradients. Others suggest that kerfs were originally intended to relieve effects of casehardening when lumber was dried in older kilns. Some say kerfs applied to floor boards help the members lay flat and hold a portion of the board away from a possible damp underlayment (7). Nonetheless, relief kerfs do alter the grain structure while increasing the surface area of the panel. Thus, unbalancing the member and allowing for more moisture absorption sites. Methodology: 1. Scope 1.1. Measure and record cup and bow (deviation from flat) on 40 various samples [100 2 bd. ft. /91ft ] of solid wood Hemlock planks. 2. Summary of Test Method samples of each cut variation (Flat Grain, Flat Grain with relief kerfs, Vertical Grain, and Vertical Grain with relief kerfs) were cut to the desired dimensions. Initial measurements and defects were recorded prior to the samples being sent through fire rating, and finishing to simulate practical production process applications Samples were then subjected to moisture desorption and absorption. This was achieved by acclimatizing the samples in a hot/dry chamber (average 89 F, 19% RH) to induce moisture desorption. Once acclimatized in the hot/dry chamber, the samples were then exposed to wet conditions (average 51 F, 69% RH) to encourage moisture absorption. During each acclimatization process, the samples were measured daily for member bow, and cup; other deviations in dimension (twist, crook, etc.) were recorded based on a visual appearance. 3. Significance and Use 3.1. This data will help us determine material selection and milling practices for our continuous linear, panelized linear, and grille ceiling/wall systems when 1 x 6 (or greater) members are used. 4. Apparatus 4.1. Mini-Ligno DX moisture meter (Figure 5) 4.2. Digital Depth Caliper (Figure 4) 4.3. Relative humidity gauge recorder placed in Heat Room and Mockup Area (Figure 3) 4.4. Straight edge. 9Wood, Inc. Methodology: 5

9 Figure 3: Relative Humidity and Temperature Data Logging Device Figure 5: Mini-Ligno DX Moisture Meter Figure 4: Digital Depth Gauge 5. Test Specimen 5.1. Solid wood Hemlock planks samples of 1 x 6 x 55 (nominal) FG Hemlock samples of 1 x 6 x 55 (nominal) FG Hemlock with relief kerfs samples of 1 x 6 x 55 (nominal) VG Hemlock samples of 1 x 6 x 55 (nominal) VG Hemlock with relief kerfs Vertical Grain w/kerfs Vertical Grain w/o kerfs Flat Grain w/kerfs Flat Grain w/o kerfs Figure 6: Depiction of the various Hemlock planks tested 6. Sampling 6.1. Constants: Flame stop Vinyl sealer Vinyl top coating (applied to one side only) Wood Species (Hemlock) Dimension of samples (1 x 6 x 55 (nominal)) 9Wood, Inc. Methodology: 6

10 6.2. Variables: Flat Grain Hemlock Flat Grain Hemlock with relief kerfs in backside Vertical Grain Hemlock Vertical Grain Hemlock with relief kerfs in backside 7. Procedure 7.1. Hemlock planks, with and without relief kerfs, were obtained from 9Wood s manufacturing facility and cut into designated dimensions (1 x 6 x 55 nominal) After samples were milled, they were labeled with the grain direction, presence of kerfs, and an ID number for reference. Samples were also marked at the center point for measurement purposes Next, Temperature and Relative Humidity of the prep area (ETO area) was measured and recorded Moisture meter readings were taken with a Mini-Ligno DX moisture meter while on setting 3 and with the long pins installed. Three reading were taken from side A on the panel face (one reading at each end and center of the panel). The readings were then adjusted using the temperature correction chart for the given temperature of the prep area (ETO area) Next, members were sent through the fire-rating and finishing process, simulating a normal production process NOTE: Boards were pre-sealed on both sides and only top-coated on one side (Side B ). By default, kerfed samples were topcoated on the kerfed side Next, moisture content readings were taken to ensure that samples had completely cured after fire rating and finishing applications (these processes can increase apparent MC% of the samples due to their water based solvent curing process). Temperature Relative Humidity Average Adjusted % MC Before Finishing 53.5 F 60% 8% After Finishing 53.4 F 77% 15% Table 1: Temperature and Relative Humidity of prep area before and after finishing when %MC readings were taken 7.7. Base measurements were then recorded along the length (bow) and width (cup) on both sides of the Hemlock members. (Note: measurements ±0.010 was recorded as zero). Members were labeled with the placement of initial measurements to ensure that future measurements were taken from the same spot (see Figure 7) Measurements were based off a positive/negative scale (refer to Figure 8 & Figure 9). Deviation on side A was recorded as a negative (-y). Deviation on side B was recorded as a positive (+y). This was done in efforts to categorize the deviation of warp for each side of the member. 9Wood, Inc. Methodology: 7

11 7.9. Next, members were placed in the hot/dry chamber (Heat Room) and stacked on saw horses with stickers between members to allow for maximum air flow (refer to Figure 10). To prevent stress on members, stickers were fabricated to allow for wood movement. Non-Topcoated Sided (Side A ) Cup 1a Cup 2a Bow 1a Cup 3a Topcoated and/or Kerfed Side of the board (Side B ) Cup 1b Cup 2b Cup 3b Bow 2b Figure 7: Depiction of Hemlock plank and labeled measurement markers Figure 8: Depiction of measurement scale for Deviation in Cup Figure 9: Depiction of measurement scale for Deviation in Bow hours after acclimatization in the hot/dry chamber, each sample board was measured for bow and cup (deviation from flat). Three samples boards from the top, middle, and bottom of the stack were also tested for moisture content and the chamber s climate conditions (relative humidity and temperature) were also recorded Once the samples had reached equilibrium moisture content (EMC), they were removed from the hot/dry chamber and placed into the Mockup area to induce moisture absorption. (Refer to Figure 11 for the change in temperature, relative humidity and moisture content during acclimatization in the hot/dry chamber). 9Wood, Inc. Methodology: 8

12 Figure 10: Depiction of the stacked members on the fabricated sawhorse. Notice how the stickers are spaced with 1" blocks to allow the members to freely change in dimension. Temp ( F) RH (%) MC (%) Temperature (ºF) and Relative Humidity (%) Due to absence, moisture content data was interpolated to obtain a running average Moisture Content (%) 0 0 Figure 11: Graph that shows the average change in Moisture Content, Temperature and Relative Humidity during Desorption (Hot/Dry chamber) over Time. 9Wood, Inc. Methodology: 9

13 7.12. Following the same data collection process, each sample board was measured for deviation in bow and deviation in cup. Three samples boards from the top, middle, and bottom of the stack were also tested for moisture content and the Mockup Area s climate conditions (relative humidity and temperature) were also recorded Once the samples had reached equilibrium moisture content (EMC), the data was analyzed. (Refer to Figure 12 the change in temperature, relative humidity and moisture content during acclimatization in the hot/dry chamber). Temp ( F) RH (%) MC (%) (ºF) and Relative Humidity (%) Temperature Due to absence, moisture content data was interpolated to obtain a running average Moisture Content (%) 0 25 Jan 26 Jan 27 Jan 28 Jan 29 Jan 30 Jan 31 Jan 1 Feb 0 Figure 12: Graph that shows the average change in Moisture Content, Temperature and Relative Humidity during Absorption (Mockup area) over Time Note: All raw data collected during desorption and absorption is listed in Appendix I: Measurement Data (inches) Sorted by Date After testing was complete, statistical analysis was performed to determine the significance of each variable. Grain (or saw cut) and the application of relief kerfs were tested for statistical significance against maximum deviation in both bow and cup by an analysis of variance (ANOVA) Conclusions were drawn from results. 9Wood, Inc. Methodology: 10

14 Discussion & Results: During the acclimatization process, each sample type behaved differently when exposed to moisture desorption and absorption (refer to Figure 13 & Figure 14). The following list characterizes the dimensional deviation of each variable tested (refer to Figure 15, Figure 16, Table 2 and Table 3 for vis ual interpretation of results). Cup: Deviation from Flat (change in dimension / 5.25 ): Grain had the most significant effect on maximum deviation in cup [p-value<0.01] On average, Flat Grain cupped more than Ver tical Grain during acclimatization even when relief kerfs were used The least amount of overall average cup was present in Vertical Grain (average total deviation = inches) The largest amount of overall average cup was found in Flat Grain (average total deviation = inches) The use of relief kerfs in Vertical Grain substantially increased the overall average cup (deviation from flat) by 75%. However, there was no immediate effect on the overall average cup (deviation from flat) in Flat Grain when relief kerfs were used. Bow: Deviation from Flat (change in dimension / 52 ): Relief kerfs had the most significant effect on maximum deviation in bow [p-value<0.01] On average, the use of relief kerfs decreased the overall average bow (deviation from flat) in each grain type. Vertical Grain had an average 39% increase in overall average bow over Vertical Grain with Kerfs and Flat Grain had an average 57% increase in overall average bow over Flat Grain with Kerfs. The least amount of overall average bow was present in Flat Grain with Kerfs (overall average = inches) The largest amount of overall average bow was present in Flat Grain (overall average = inches) Total Deviation from Flat Bow & Cup Comb ined (change in dimension / 5.25 ): Vertical Grain had the least amount of overall total warp (overall average = inches) Flat Grain had the largest amount of total warp (overall average = inches) On average, Vertical Grain showed higher signs of dimensional stability compared to Flat Grain. 9Wood, Inc. Discussion & Results: 11

15 Flat Grain Flat Grain with Kerfs Vertical Grain Vertical Grain with Kerfs Average MC 16.0% Absorption (Mockup Area) 14.0% 12.0% Deviatio n in Cup (in) % 8.0% 6.0% Moisture Content (%) 4.0% Desorption (Heat Room) 2.0% % Figure 13: Graph that depicts the average deviation in Cup/5.25 for each sample type during acclimatization Flat Grain Flat Grain with Kerfs Vertical Grain Vertical Grain with Kerfs Average MC 16.0% Absorption (Mockup Area) 14.0% 12.0% Deviation in Bow (in) % 8.0% 6.0% Moisture Content (%) 4.0% Desorption (Heat Room) 2.0% % Figure 14: Graph that depicts the average deviation in Bow/52" for each sample type during acclimatization. 9Wood, Inc. Discussion & Results: 12

16 Average Bow (Deviation/52") Average Cup (Deviation/5.25") Deviation from Flat (in) Flat Grain Flat Grain with Kerfs Vertical Grain Vertical Grain with Kerfs Figure 15: Graph that shows the overall Average Deviation from Flat (Bow & Cup) for each combination variable during Absorption and Desorption. Total Average (Deviation/5.25") Deviation from Flat (in) Flat Grain Flat Grain with Kerfs Vertical Grain Vertical Grain with Kerfs Figure 16: Graph that shows the overall Total Average Deviation from Flat (Bow & Cup Combined) for each combination variable during Absorption and Desorption. Note: Deviation in Bow for Figure 16 was converted to change in deviation over 5.25 inches in efforts to standardize the total amount of deviation for each sample type. This is done depict which combination variable showed the highest signs of dimensional stability. 9Wood, Inc. Discussion & Results: 13

17 ANOVA Analysis for Maximum Deviation in Cup/5.25 Source Sum of Squares Degrees of Freedom Mean Squares F value p value A: Grain Type 2.31E E B: Relief Kerf 4.61E E AB: Grain Type and Relief Kerf 2.05E E Table 2: Analysis of variance of all variables and their significance on Maximum Cup (in). Note: The ANOVA table decomposes the variability of Maximum Dimensional Deviation (in) into contributions due to various factors. The contribution of each factor was measured having removed the effects of all other factors. Since 2 p-values are less than 0.05, these factors have a statistically significant effect on Maximum Cup (in) at the 95.0% confidence level. ANOVA Analysis for Maximum Deviation in Bow/52 Source Sum of Squares Degrees of Freedom Mean Squares F value p value A: Grain Type 8.05E E B: Relief Kerf 5.71E E < AB: Grain Type and Relief Kerf 4.28E E Table 3: Analysis of variance of all variables and their significance on Maximum Bow (in). Note: Since 2 p-values are less than 0.05, these factors have a statistically significant effect on Maximum Bow (in) at the 95.0% confidence level. **Refer to Appendix III: Statistical Analysis (ANOVA & Histogram) for statistical analysis** These results signify that each variable (grain/saw cut and relief kerfs) have their own unique effect on dimensional stability. If the desire is to minimize cupping, Vertical Grain WITHOUT relief kerfs is the application to use. If the desire is to minimize bow, Flat Grain with relief kerfs is the application to use. However, it is important to balance the cost and benefits of each application. Flat Grain may be a cheaper consideration, but the application of relief kerfs add production costs. For this reason, it may be more beneficial to use Vertical Grain WITHOUT kerfs given the total amount of deviation throughout the whole member (bow and cup combined) is essentially lower than any other grain and relief cut combination. 9Wood, Inc. Discussion & Results: 14

18 Conclusion: Vertical Grain Hemlock members significantly improved dimensional stability with an overall ave rage 40.5% decrease in total dimensional deviation from flat to i ts closest competitor (overall total average dimensional deviation over 5.25 was inches). Vertical Grain members had the least amount of overall average cup w ith an average value across all Vertical Grain members of in ches in deviation from f lat (75% lower than closest competitor). Flat Grain significantly increased the maximum dev iation in cup compared to Vertical Grain [p-value<0.01]. Flat Grain members with relief kerfs had the least amount of overall average bow with an average value across all Flat Grain with relief kerf members of inches in deviation from flat (1.2% lower than its closest competitor). The application of relief kerfs significantly decreased the maximum deviation in bow in both grain types [p-value<0.01]. Note: A confounding variable was created in the test due to the fact that topcoating was only present on one side of the me mber. This may or may not have skewed the res ults and therefore data presented in this test is specifically related to Hemlock members with top coating applied to one side only. 9Wood, Inc. Conclusion: 15

19 Literature Cited: 1. Knight, Edwin. The Causes of Warp in Lumber Seasoning. Western Pine Association. Pages McMillen, J.M. Stresses in Wood Drying. Forest Products Laboratory; U.S. Department of Agriculture, Forest Service. No Revised Seasoning Dimension Stock. United States Department of Agriculture. Forest Service; Forest Products Laboratory. Madison 5, Wisconsin. University of Wisconsin. Revised June Stamm, A. J., and Seborg, R. M. Minimizing Shrinking and Swelling. Forest Products Laboratory. U.S. Department of Agriculture, Forest Service. University of Wisconsin; Madison Wisconsin. R November Torgeson, O. W. Shrinkage and Swelling of Wood in Use. Forest Products Library. Forest Research Laboratory; Oregon State University. August 1957; No. 736 (5) 6. Uneven Coatings on Wood Cause Warping. Forest Products Laboratory; U.S. Department of Agriculture, Forest Service. Madison 5, Wisconsin. Technical Note number D-12. Revised December Woodweb Online Forum. Wood web.com. Why is Wood Flooring Kerfed on the Bottom Face? 11/17/2009 < Bottom_Face.html> 9Wood, Inc. Literature Cited: 16

20 9Wood, Inc. Appendices Copy of Test Data and Statistical Analysis Test Evaluation Report Research & Development January 10 9Wood, Inc. Appendices: 17

21 Appendix I: Measurement Data (inches) Sorted by Date 9Wood, Inc. Appendices: 18

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28 Appendix II: Moisture Content Log Sorted by Date 9Wood, Inc. Appendices: 25

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30 Appendix III: Statistical Analysis (ANOVA & Histogram) Maximum Deviation in Cup: Design-Expert Software Max Cup Normal Plot of Residuals Color points by value of Max Cup: Normal % Probability Internally Studentized Residuals Design-Expert Software Max Cup Design Points X1 = A: Grain X2 = B: Relief Interaction B: Relief B1 Yes B2 No 0.02 Max Cup FG VG A: Grain 9Wood, Inc. Appendices: 27

31 Maximum Deviation in Bow: Design-Expert Software Max Bow Normal Plot of Residuals Color points by value of Max Bow: Normal % Probability Internally Studentized Residuals Design-Expert Software Max Bow Design Points X1 = A: Grain X2 = B: Relief 0.2 Interaction B: Relief B1 Yes B2 No 0.15 Max Bow FG VG A: Grain 9Wood, Inc. Appendices: 28

32 Descriptive Statistics: Histogram Plots: 35 Flat Grain Histogram of Frequency Wood, Inc. Appendices: 29

33 70 Flat Grain with Relief Kerfs Histogram of Frequency Vertical Grain Histogram of Frequency Wood, Inc. Appendices: 30

34 80 Vertical Grain with Relief Kerfs Histogram of Frequency Wood, Inc. Appendices: 31