Best wel leuk en inderdaad zonder yaw servo's.
It's a Futaba 10C. You need a 4-way 90 degree swash mix in Heli mode. My 10C has two versions of 4-way mixes ... for "+" or for "X" configurations (see an early post in my Siimple Quad thread). Up to this point it's the same as a Signguy Triocpter but with an extra motor, and requires one or two yaw servos and tilting motors for yaw control (with gyros on them for yaw stabilisation).
To get rid of the tilting motors, you sumperimpose some more mixes which achieve yaw effect by slowing two opposite motors and speeding the other two, keeping overall thrust constant. This last set of mixes took a while to get right (as I'm not an expert TX programmer!). You also need to tilt the 4 gyros, so that each gyro stabilizes yaw as well as stabilizing the rise and fall of the arm. This last bit was my "flash of brilliance".
