whats wrong with my ship?

[mrjohndoe]

Hello,

I have launched a first part of a space station (downloaded from internet) and want now to add my first own module. This should be a extender for docking small crafts to the station. I have launched the ship using mechjeb but have the problem that after staging the main tanks the ship doesn't react to steering except rcs. But the autopilot then burns all rcs for the maneuvers.

I have seen other ships without that problem so what is it at my ship?

Can someone please look and give me advices? Maybe some tipps for a better ship, too?

Thanks.

https://www.dropbox.com/s/eeex6cs6jkpeqpk/Cobra%20Bucht%20MK2.craft