Rubber boards can theoretically be fabricated to any length. At the Noble Foundation, we've fabricated boards up to 30 feet long. Boards longer than 30 feet are not recommended because of their excessive bulk and weight.
To produce a rubber board, select a group of tires having similar tread width. Start by cutting a small slit in the sidewall close to the tread large enough to insert a jigsaw blade. Make one cut through the tread of each tire using the jigsaw equipped with a hacksaw blade.
Next, remove the sidewalls using the jigsaw. Cut as close to the tread as possible but avoid cutting into the steel bolts located in the tread. This produces sections of tread 5 to 7 feet in length and 6 to 8 inches in width, depending on tire size.
Based on the length of board needed, arrange the appropriate number of tread sections on your work bench end-to-end, making sure tread is facing down. Working from one end, slide the second section under the first section 6 inches and secure with four sheet metal screws. To insure a strong union, place a screw in all four corners of the overlapped sections of tread, being careful to not get too close (within one inch) to the edge.
Place the third section of tread under the second and overlap 6 inches. Secure this second union in a manner like the first.
Slide the fourth section of tire under the third and fasten. Repeat this procedure until the desired length of board is obtained. Adjust the length of the last section by cutting or simply overlapping the excess with the previous section.
Form a tight loop at both ends and secure with a minimum of two sheet metal screws. The loops need to be of sufficient size to accept a 5/8-inch diameter piece of rebar.
Using a jigsaw equipped with a hacksaw blade, cut 6-inch-wide pieces of rubber from sections of tread. The use of a tread-cutting jig makes this task easier.
Place these pieces of rubber on the board, tread facing up. Space the pieces on 18-inch centers and secure each piece with two screws, one placed an inch from the left edge and the other an inch from the right, equidistant top to bottom.
Rebar stakes inserted through these "pockets" allow the board to stand erect and be anchored to the ground. Overlapping sections of tread also serve as pockets. Take this into consideration when spacing the small pieces of rubber on the board.
When the board is finished, flip it over and remove the screw points, using a grinder. Repeat procedure for each additional board required.