Hello zoomad,
Prop wash steering effects is
![Smiley :)](http://forum.shipsim.com/Smileys/default/smiley.gif)
, translated by "coup de fouet" ie "whiplash", and named "kickstartforce" in SS2006 ... That effect exists indeed as long as the available turning moment can stall the hull.
Also thanks to your answer (and after some Googling) I learned that propeller walk, propeller effect, asymmetric thrust and asymmetric blade effect, are still some more translations of the French "effet de pas d'hélice" or "prop pitch effect".
As for the explanation given in this
Wiki, I am not quite sure, because the effect does not decrease with an horizontal shaft, whether ahead (zero rudder shifted 1 or 2° starboard) or astern.
Also, the ship needs to go ahead/astern for any wake to exist, and the side thrust (prop in reverse) is nevertheless strong enough to be the major turning force at low speeds (no wind!) or being stopped.
Anyway, it is due to an asymmetric thrust like you mention. For instance, I was told (teached?), many years ago, that it was due to the important loss of efficiency (unsteady flow) around the blades passing nearest to the surface with regard to the immersed ones. It is a pity one cannot find more precise answers on the internet about such a discernable effect, although largely known and used by many thousands of sailors.
Ill search further...
Regards,
Luc