Building an Arched Wooden Bridge
Step 5. Making the sides of the bridge
Rip (cut) a length of 90 mm x 45 mm x 2400 mm (1 1/2" x 3 1/2" x 8ft) treated wood in half (lengthwise) to make
two pieces 45 mm x 45 mm x 2400 mm (1 1/2" x 1 1/2" x 8ft).
From that cut eight handrail uprights, each 600 mm (2ft) long.
Make eight wood washers 90 mm x 90 mm x 19 mm thick (3 1/2" x 3 1/2" x 3/4" thick).
Bolt the handrail uprights to the arch beams so that 4 uprights are spread evenly along each arch beam and so that each upright is at right angles to the arch beam.
Use the wood washers as well as metal washers and apply glue between the wood washers and the arch beams before tightening the nuts (see picture).
Drill and nail the handrail arch frames on top of the uprights. Secure each end with metal strap.
Step 6. Completing the bridge frame
Cut 3 spreaders 90 mm x 45 mm x 540 mm long (1 1/2" x 3 1/2" x 21 1/2" long) and fix them between the side frames, one in between the middle of the arch beams and one near each end. Secure with metal strap brace. (see picture).
Nail 3 temporary spacers on top of the handrail arch frame to keep them parallel until the decking boards have been nailed in place.
Nail and glue the shoes to the underside of the arch beams, one at each end.
Nail a temporary brace from shoe to shoe until the decking boards have been nailed in place.