A curve radius tool is nice to have but you don't really need it. Same thing with parallel spacers.
As Jim said, a wooden yard stick can do the job of a radius tool. Just put a nail in one end, say at 1", then drill holes big enough for a pencil or pen at several spots toward the other end, say at 25", 27", up to 35". You can easily draw arcs up to 34" radius.
Hey, just call me cheap. I'm always looking for cheaper ways to skin a cat.
