Step 5. Construct Shelter Sidewalls and Side Bracing.
If the ground is other than granular soil, a 1 ½ foot wide, 1 ½ foot deep trench must be dug along the centerline of the shelter and partially backfilled with granular soil (sand or gravel) to a depth of 6 inches.
Run strings between the front & rear earth walls to mark the top edge of the shelter sidewalls. (Detail 5.1) At the top of the earth wall on the inside sheets of plywood, mark a line one-foot in from each side. Drive a small nail to the inside for each of these lines. Then run a string from the front earth wall to the corresponding rear earth wall. These strings should run parallel over the length of the structure exactly 6 feet apart. They will mark the top line for the sidewalls.
Repeat this process for the base of the front & rear earth walls. Dig a trench 6 inches deep and 6 inches wide along the two bottom string lines.
Plywood will be used as shoring walls for the shelter. Each shelter will use 40 sheets of ¾ inch plywood for construction of the sidewalls (20 per side). For each sheet of plywood (short side) mark the center (2 feet) mark and chalk between the two marks. On the long sides of the plywood mark the center (4 feet) mark and chalk between the two marks. Where the two chalk marks intersect is the middle of the plywood sheet. Mark the center of each of these sheets and drill a ½" hole. (Detail 5.2) The size of the hole should allow the ½ inch diameter hex screws to be inserted freely. This hole will be used for the center cross braces.
[If 4x4 cross braces are in short supply, 6-inch diameter logs can be substituted in their place. These logs must be straight and must be cut to 6-foot lengths with precision. This is for the middle bracing only.]
Each sheet of plywood comprising the sidewalls will be supported at 3 points with cross beams. The bottom of each sheet of plywood will be buried 6 inches into the ground to anchor it in place. (Detail 5.3)
Nineteen 4 x 6 beams and two 4 x 4 beams will be required for the top row of cross beams. Twenty 4 x 4 beams will be required for the middle row of cross beams. Each of these beams should be cut to exactly 6 feet. Take twenty 4 x 4 beams (middle rows) and drill a 3/8 inch hole in the center of each end. This hole should be drilled to a depth of 4 inches.
From 2 x 6 boards, cut 40 one-foot wide brace boards. In the center of each board drill a ½ inch hole.
The four corner sheets of plywood must be cut to mate properly to the earth walls. (Detail 5.4) This is to compensate for the top and bottom 2 x 4’s and the cables. Begin by cutting two rectangles 3 ¾ inches by 1 5/8 inches deep in accordance with the drawing. Position the plywood sheet against the earth wall and mark the position of the cables. Remove the sheet and cut "V" shaped notches for the cables.
Nail 2 x 6 boards flush to join the tops of the plywood together. (Detail 5.5) These boards will be on the outside of the shelter. Each side will be comprised of one unit that will attach to the front earth wall, one unit that will attach to the rear earth wall, four units that will attach to the middle starting from the front earth wall side, and one final unit (composed of 2 plywood panels that will complete the assembly. The other side will be a mirror image of the opposite side. After construction of each unit, drill ½ holes through the 2 x 6 top brace board and plywood. (Detail 5.6)
Start assembly of the shelter sidewalls at the front earth wall end. Raise the sidewall vertically. Mate the plywood cutouts with the earth wall 2 x 4’s and steel cables. The wall should be flush with the vertical 2 x 4 brace. Nail another 2 x 4 vertically for an outside brace. (Detail 5.7) After both sides are up, join them with a center support beam. (Detail 5.8) Align the ½ inch predrilled hole in the one-foot 2 x 6 brace board with the predrilled hole in the center of the sheet of plywood. The ½ x 6 hex lag screw will be inserted through the ½ inch flat washer, then the ¾ inch flat washer then through the one-foot brace board and then through the center hole of the plywood sheet and screwed into the end of the 6 foot 4 x 4 beam. After you complete installation of the three center cross beams, begin the assembly of the top crossbeams (one 4 x 4 and two 4 x 6). (Detail 5.9) (Detail 5.10) When you complete check levelness of the first wall segment and alignment to the string running from the front to back earth wall. Adjust as required.
The next step is to assemble the shelter sidewall segment that is adjacent to the rear earth wall. This will be assembled in the same manner as the instructions above.
Then continue by assembling each side wall segment starting from the front and working towards the rear. The last segment to be assembled is the 2 sheet plywood segment. Level and clamp the plywood segments together along the top and nail.
After all the sidewalls are assembled, check and adjust levelness and alignment. Fill in the six-inch trench at the bottom of the plywood. (Detail 5.11)
Finally, nail 2 x 4’s continuously from one earth wall to the other, just beneath the center 4 x 4 cross beams. These will be used for inserting the hook screws that will hold the hammocks. (Detail 5.12)