Scribner Precision & Accuracy then and now

Transcription

1 Scribner Precision & Accuracy then and now Neal Hart, Jendro & Hart, LLC Timber Measurement Society Meeting, April 2016

2 Scribner Is it a more useful tool for log value then and now determination than cubic scale?

3 Scribner Precision: Capacity to differentiate between logs of different sizes Accuracy: Degree that measurement meets its objective actual lumber recovery then and now

4 Scribner then Designed for 19 th century technology and milling techniques ¼ kerf

5 Scribner s original design assumptions Ignored taper scaling cylinder only How precise & accurate is Scribner for logs 12 +?

6 Scribner 16 SED then 10 bf/ft 2-1 x x x 12 Slab 1 ¾

7 Scribner Scaling Cylinder LRF Cross-Sectional Area of Lumber Equal to Ratio of: Cross-Sectional = LRF Area of SED Log 120 in in. 2 = SED

8 Scribner Scaling Cylinder LRF : 120 Board Feet 12 = 10.0 Cubic Feet Scribner s Lumber Recovery Factor: = 0.60 scaling cylinder only 16.8 Cubic Feet

9 Scribner Scaling Cylinder LRF LRF for 16 Logs is Diameter (SED inches)

10 Scribner Scaling Cylinder LRF Rounding to 10 bf causes increasing variance in Scribner LRF as diameter decreases LRF for 16 Logs is ' 9' 10' 11' 12' 13' 14' 15' 16' 17' 18' 19' 20' Diameter (SED inches)

11 Scribner & Modern Empirical LRF Empirical Rough Green LRF (Whole Logs 8-20 ) Stud Mill Dimension Mill Scribner s scaling cylinder RG LRF 8' 9' 10' 11' 12' 13' 14' 15' 16' 17' 18' 19' 20' Diameter (SED inches)

12 Accurate Inaccurate Precise Imprecise

13 Precise, but inaccurate is correctable Ratio of Stud & Dimension Mill Empirical LRF to Scribner Scaling Cylinder LRF Avg +17% %

14 Scribner & Modern Empirical LRF Empirical Rough Green LRF (Whole Logs 8-20 ) Stud Mill Dimension Mill 34% 14% Scribner s scaling cylinder RG LRF 8' 9' 10' 11' 12' 13' 14' 15' 16' 17' 18' 19' 20' Diameter (SED inches)

15 Scribner 16 SED LRF then = 0.60 or 60% Slabs, Edgings & Kerf = 40% 10 bf/ft 2-1 x x x 12 Slab 1 ¾

16 Scribner LRF then = 0.53 or 53% 12 SED Slabs, Edgings & Kerf = 47% 5 bf/ft 1-1 x x 8 Slab 1 ¾

17 Scribner & Modern Empirical LRF Empirical Rough Green LRF (Whole Logs 8-20 ) Stud Mill Dimension Mill Scribner s scaling cylinder RG LRF 8' 9' 10' 11' 12' 13' 14' 15' 16' 17' 18' 19' 20' Diameter (SED inches)

18 Scribner When it comes to extensions of the rule, things get to be very confusing. Frank Freese, Statistician, Forest Products Laboratory Madison, WI USDA Forest Service A Collection of Log Rules

19 Scribner & Modern Empirical LRF Empirical Rough Green LRF (Whole Logs 8-20 ) Stud Mill Dimension Mill Diameter (SED inches) Scribner s scaling cylinder RG LRF 8' 9' 10' 11' 12' 13' 14' 15' 16' 17' 18' 19' 20'

20 Scribner & Modern Empirical LRF Empirical Rough Green LRF (Whole Logs 8-20 ) Stud Mill Dimension Mill Diameter (SED inches) Scribner s scaling cylinder RG LRF 8' 10' 11' 12' 13' 14' 15' 16' 17' 18' 19' 20'

21 Scribner & Modern Empirical LRF Empirical Rough Green LRF (Whole Logs 8-20 ) Stud Mill Dimension Mill Scribner s scaling cylinder RG LRF Diameter (SED inches)

22 Scribner & Modern Empirical LRF Empirical Rough Green LRF (Whole Logs 8-20 ) Stud Mill Dimension Mill LRF for 6"- 11" SED 1'-15' 16'-31' 32'-40' Scribner s scaling cylinder RG LRF Diameter (SED inches)

23 Scribner then 12 SED 5 bf/ft 1-1 x x 8 Slab 1 ¾ Boards 4 + in 2 increments No Wane

24 Scribner LRF - 12 SED by Length LRF Scaling Length

25 Scribner - Extension to 11 SED > bf/ft 2-1 x x x 10 Slabs 1/2 Drop One 1 x 4 Drop Both 1 x 4 s 4.17 bf/ft 1-1 x x x 10 One Slab bf/ft 1-1 x x x 10 Two Slabs 2

26 Scribner LRF - 11 SED by Length LRF Why 3 Models of Recovery? Scaling Length

27 Scribner - Extension to 10 SED < bf/ft 2-1 x x x 8 Slabs 1 Drop One 1 x 4 Drop Both 1 x 4 s 3.54 bf/ft 1-1 x x x 8 One Slab x x 5.6 bf/ft 4-1 x 8 Two Slabs ~2

28 Scribner - Extension to 8 SED < Drop One 1 x 4 Drop Both 1 x 4 s 2.20 bf/ft 2-1 x x 6 Slabs x 4.2 bf/ft 3-1 x 6 One Slab x 4 bf/ft 3-1 x 6 Two Slabs 2

29 Scribner - Extension to 6 SED < All Waney Boards One Waney Board One Waney Board 1.57 bf/ft 2-1 x x 5.4 Slabs < x 4 bf/ft 1-1 x 3 Two Slabs x 4 bf/ft 1-1 x 1.9 Two Slabs 1

30 Scribner - Extension to 5 SED (1 40 ) 0.65 All Waney Boards x 4 bf/ft 1-1 x 4.8 Two Slabs <1

31 Scribner & Modern Empirical LRF Empirical Rough Green LRF (Whole Logs 8-20 ) Stud Mill Dimension Mill 90% Diameter (SED inches) Scribner s scaling cylinder RG LRF 8' 10' 11' 12' 13' 14' 15' 16' 17' 18' 19' 20'

32 Scribner Precision: Capacity to differentiate between logs of different size characteristics

33 Logs Scribner 10 bf cf 1.9 cf cf 2.4 cf cf 2.7 cf cf 3.1 cf Cubic ft vol. in scaling cylinder %

34 Logs Scribner 20 bf cf 2.7 cf cf 3.9 cf cf 4.0 cf cf 5.2 cf Cubic ft vol. in scaling cylinder %

35 Logs Scribner 30 bf cf 5.3 cf cf 6.3 cf cf cf cf 6.6 cf Cubic ft vol. in scaling cylinder %

36 <12 Accurate Inaccurate? Precise Imprecise

37 To Use Cubic Instead! Cubic Board Foot

38 Questions or Comments? Neal Hart, Jendro & Hart, LLC Timber Measurement Society Meeting, April 2016