ORIGINAL: redcommander
...When crabbing, you are aiming a component of force (propulsion system) to oppose the wind force. How would you do this on a neutrally stable airplane?? first you would have to input rudder to set the crab angle. A directionally stable airplane will set the crab angle for you....
A crab angle is the difference between an airplane's heading and it's ground track. Normally, crab angles are set with normals turns until the desired ground track is acheived. A crab is NOT holding rudder continuously against a crosswind.
An airplane flying with a steady crosswind component will have a ground track that is downwind of it's heading. A steady crosswind does not cause the airplane to turn, so no rudder or aileron pressure is required against a wind. If the airplane's true airspeed, and the windspeed are constant, the airplane's resultant path over the ground will be straight (or would be if the world was flat - actually it's a geodesic, but we'll ignore that).