In kit building when to use CA and when to use epoy?
Forget CA, use wood glue. Sets slower, but is every bit as strong (if not stronger), plus doesn't produce fumes that'll make you sick (thin give me a headache if I breath too many fumes). I've been using Titebond and the stuff is terrific. Wood breaks before the bonded area. In fact, I only use thin CA for hinges (using a hypodermic needle to reduce fumes) and thick (less fumes) for gaps now.
I use epoxy on area's of high stress as others have mentioned. Also use thinned epoxy (either using heat or alcohol) on any bare areas of wood that may see fuel or exhaust sputter.