Knife edge loop?
lol Dean you made that pic too small.
Enter on knife edge, add enough rudder to begin the climb, but take it easy.... to recover (ie once past the top) add full rudder, and you might need a fair bit of power too. Correct KE with aileron and elevator all the way around. You'll probably find you haven't got man enough engine, CG too far forward, rudder throw too little or model just too heavy.
Maybe soemone else could add more, i'm not that familiar with the maneuver, I've not yet owned a model that'll do it.... sure I have an overpowered Cg ultimate but I don't have a good rudder servo, so again, out of the question. My CAP 232 used to manage half of one, and it's just about to get a YS 63 so hopefully it'll complete one too!