Yeah well you’ve got to name it something. There are three arches in this project. I figured I could use the middle arch as a form for both the top (cap) arch and the bottom or inside arch. The plan was to make a template of the middle arch and matching bending forms for that part using a jigsaw for the rough cut and a flush trim bit to make the plywood uniform. So back to the second entry in this series. Calculating by both Sketchup and the Chord/Rise equation gave an outside radius (the top of the middle arch) of about 120”. Since the headboard posts are 3 1/2” wide I wanted to make the arches match this width so the inside radius is 116 1/2”. This is a lesson I learned from another Lumberjock jlsmith5963 regarding segmented arches. There are a number of ways to cut an arch’s radius, but I still prefer to use a router and swing arm.
I lined up my workbench perpendicular to the assembly table and used one of the large holes as a pivot. I scrounged around and found a drain pipe and shimmed it with duct tape for a better fit. I used a 1/4” diameter router bit so the center of the holes were placed 3 1/2” apart plus and minus 1/8”. The outside radius was cut with the inside or bottom of the bit while the inside radius was cut with the outside or top of the bit (relative to the pivot). Whew… to technical. The end result of all the cutting would produce three pieces so I screwed them all down to a a scrap sheet of mdf making sure the screws would not be in the way of the cutter. After cutting the top arch I repositioned the pivot in the hole to cut the inside arch.
After a little light sanding the pattern was smooth and it was an easy task to mark the curves in the plywood, rough cut the line, and smooth it to a perfect match with the flush trim bit. Next up on the New California Workshop, the first lamination is cut and glued.
-- tim hill www.newcalshop.com