from scratch?! Why? lol i understand building planes from scratch, i do that but a heli is a different story...especially if you havn't built/flown one already
Generally the scale ones you see are regular heli's such as the trex except people have put on a jet ranger shell (or what ever shell) and maybe done some other little things to make it look right. The heart of the helicopter is still a trex or what ever model they put the cover on.