3. Lumber less than 1 inch thick is considered an inch thick in measuring; over 1 in. to 1 in., as 11 in.; over 11 to 1, as 14 in., etc. Fractions of an inch in the width should be omitted and the nearest integer taken. 4. If a board or plank is wider at one end, the average width is taken as the width of the whole. From the definition of a board foot, the pupil will readily see that the number of board feet in a timber is the same as the number of square feet in one face, multiplied by the thickness in inches. If the board containing 2 board feet (shown above) be cut or sawed where the dotted lines are shown, there will be 2 boards, each containing 1 board foot. Take a piece of wood and show the actual work done. The pupil must understand just what a board foot is. To find the number of feet of lumber in any timber, Multiply the area of one face, in square feet, by the thick ness in inches. Probably the simplest way to remember the above rule is this: For all kinds of boards and timbers, write the length and width in feet and the thickness in inches. Multiply these three numbers, and the product is the number of feet in the timber. PROBLEM: How many board feet in a scantling 12 ft. long, 2 in. thick, and 4 in. wide! I wish to build a plank walk on one side of a lot 60 feet long. How many feet of lumber will it take, if the walk is to be 6 feet wide, 2 inches thick, and with four supporting timbers, each 4 by 4 (4 inches by 4 inches)? SOLUTION: Walk surface = 6 x 60 sq. ft., or 360 sq. ft. Supporting timbers = 4 × 60 ft., or 240 ft. in length. = 60 FT. To the Teacher: Have the pupil compute the cost of a sidewalk in the vicinity. Let him get the measurements and prices from the owner. NOTE.-M. is used to denote 1000 board ft., the way lumber is generally sold. The decimal point is moved two places to the left to show the number of M's. Drill on this method. PROBLEM: How much lumber, 1 inches thick, will be required for an open board fence, 4 boards high, boards averaging 6 in. in width, around a yard 6 rods square? SOLUTION: = One line of boards 24 rods in length. 4 lines of boards = 96 rods in length, or 1584 ft. If 1 inch thick and 12 in. wide, the fence would require 1584 board ft. Being 1 in. thick, and only 6 inches wide, it will require×× 1584, or 1188 board feet. For the Pupil : Suppose we put a tight board fence around the above lot, 6 ft. high, using 1 in. lumber, what would be the cost of the lumber, at $10 per M.? PROBLEM: How much lumber is needed for a bin 6 ft. deep, 10 ft. long, and 8 ft. wide? SOLUTION: 2 sides each 6 ft. x 10 ft. have... 2 sides each 8 ft. × 6 ft. have... Bottom 8 ft. x 10 ft. has... ..120 sq. ft. 96 sq. ft. 80 sq. ft. Total surface = 296 sq. ft. Hence, the bin will take 296 ft. of lumber. PROBLEM: What will the above lumber cost at $15 per M.? SOLUTION: 1000 ft. cost $15. 296 ft. cost .296 × $15, or $4.44. TALK: Many problems may be given in finding how much lumber is needed for various buildings. They should be made practical, and to that end, it is best to take actual buildings in the vicinity. Be care ful not to make the work too complex at first. Talk such work over with a builder or carpenter. Give considerable oral drill before proceeding to the written work. Be sure that the pupil knows what a board foot is, then proceed like this: 66 'How many board feet in each of these boards, all being one inch thick — 1 in. wide and 12 ft. long? 2 in. wide and 12 ft. long? 9 in. wide and 12 ft. long? 13 in. wide and 12 ft. long? 12 in. wide and 6 ft. long? 12 in. wide and 3 ft. long? etc." The following lumber measure reference table may be found helpful: |