cant lomchevak without a rudder http://www.waterstruck.com/AS/mvc-302v.mpg

again you need rudder for ground control. when landing in a cross wind rudder can help keep the plane straight, co-ordinating turns to keep the nose from dipping or climbing in a turn, and alot of aerobatics require rudder input to pull off (snap rolls, hammer heads, lomchevaks, knife edge, point rolls, rolling circle, torque rolls, etc etc etc)

when you get the hang of flying around expierement with the rudder (at a high altitude) one of the easies to try is a stall turn. bring the nose of the plane to almost striaght up (about 70 degrees) and let the plane slow down to were it just about stops. give it full left rudder and full power. the plane should fall over sideways till its pointed straight down. release the rudder and pull out to level.

for a true hammer head turn you want to be full 90 climb until the plane stops. then when the plane stops and starts to fall backwards full rudder and the wash from the prop will kick it over to the side to a straight down. really cool to see both full sized and RC exp with smoke system going some planes can take it to a next step and do a DOUBLE hammerhead.. thats one and a half times around.. thats alot of rudder.

here is a clip of a FULL SCALE aircraft doing this

http://www.bulldogairshows.com/video...ublehammer.avi

if you look close you can see the rudder in full deflection.

(note with a trainer or other plane with dihydral in the wing you may need to feed in ailerons to keep the wings "level" through the manuver.)