Step 4: Seat back
Plane all the outer edges of the timber only to the point marked in Fig. 4. Do not plane below this point as it will create an entry point for moisture into the storage chest part of the seat. The curved back of the seat is not cut until all the framing is place.
Lay all the 19mm seatback pieces, planed side up, in the order shown in Fig. 4, ensuring that they fit snugly against one another and rearranging if need be to achieve this. Fix the bottom and top framing 70mm x 35mm pieces at the points shown in Fig. 4, using 2 screws per paling in both the top and bottom piece. Flip the seat back and reinforce the framing with a third support, as shown in Fig. 5, again fixing with 2 screws per paling. Now that all the framing pieces are in place, use your tape measure to mark up the curved back of the chair. Mark the first 140mm wide piece at either end of seat back at 690mm, and trim using the jigsaw. Find the midpoint of the 1500mm seat back and mark it. The curved graduates from this point down on either side to meet the edge of the straight cut outer 140mm pieces. Use a piece of string centred in the very middle of the seat back and tied to your pencil to ensure your curve is symmetrical and smooth. Trim along you pencil line to create the curve. You may choose to create a square, or more rectangular shaped back – the choice is yours as long as you don’t dip below the back support frame. Lastly, install the two 320mm x 70mm x 35mm side frame supports at either end, as shown in Fig. 3.