The shape of the bench was dictated by the radius of the gravel area in the landscape plan. We selected an internal radius of 83 in with eight 1.5 inch wide rails spaced an inch apart. This gives an outer radius of 92 in and a bench “width” of 19 inches. We wanted the bench to extend for 90 degrees to fit in with the design and accommodate at least 5 people.
Step 1: Design
For this type of glue up you need to build a form so that the pieces can be clamped together while the glue sets.
To get all the dimensions correct and to design the form I decided to model the entire bench and the form using 3D modeling software.
The following picture shows the dimensions sketch which calculates the position of each rail from the internal radius, rail width and spacing. The second screen shot shows the 3D model created from the sketch including the posts and support beams.
Another advantage of creating a 3D model was to create an exact drawing for the location of the posts which helped the landscape contractor to install them very precisely - see the third screen shot.