One of the main challenges of cutting an arch is figuring out the dimensions and glue angle of straight boards from which an arch can be cut. Fortunately, this time around I’m using Sketchup. As you can see in the picture it is pretty easy to figure these out, although I’m still searching for a formula to calculate the dimensions. The vertical angle is 15 degrees. I drew a line intersecting the bottom of the middle of the arch with the bottom of the right side. I then made a copy of this line and dragged it to the tangent of the upper curve of the arch. I connected these with vertical lines in the middle and side. I used the Protractor tool to read the angle.
For this project I made a full size template out of Luan ply. I plan to later cut this down and use it to laminate the copper sheet. I like to use the jig saw for rough crosscuts on this size lumber. It is fast and saver than a circular saw. I also used paper to layout the segment to make sure it would cover the arch. This gate is a little wider and taller than the first. The top of the arch is based on a 30” radius curve, and since the sides are 7 1/4”, the bottom curve is based on a 22 3/4” radius. Both curves use the same pivot point. (See Segmented Arches discussion in the Gate I blog).
Just like the first gate, I used the cross cut sled with the angled cutoffs to trim the segments.
Next time on The New California Workshop, we’ll cut the mortises. Stay tuned.
-- tim hill www.newcalshop.com