I've just finished a build of a largish X8 setup using the quanum 700 frame, its using multistar 268kv motors with 15x5 props running 6S using 30A escs ( http://rctimer.com/product-1323.html )
Now, ive tuned up countless 400-600 class quads and hexas with no worries but this rig is giving me a nightmware.
With default PIDS its pretty much unflyable unless holding a tight level with the sticks. If i whack the P up to around 0.3 and the D up to 0.2 it becomes a little more controllable but again only around the level. As soon as i try to pitch or roll with any enthusiasm it bobs and dives with a noticable overshoot. I have stab and pitch rate at around 5, moving this up to 8 or 9 only seems to help around the +-5deg rolls and still when rolling with any authority it bounces around.
So theres that, would be up for any ideas. Also Im having an issue with being underpowered. I know its not underpowered as my AUW is only 3.5kg and I have 8kg of potential thrust, i have even tested this by going into esc setup mode on the APM, and giving it the beans, it wasnt to rocket off into the sky. However when flying it barely wants to climb. Hover is around 70% stick, whereas theoretically it should be around 40%.
Whats going on then, any ideas welcome.