Some basic facts: Most modern engines such as Lycoming, TCM and Rotax, which are commonly installed in modern aircraft, rotate to the right. Asymmetric thrust and the helical path of the propellor slipstream means that a permanent yaw to the left is always present. Manufacturers deal with this is many ways: offset engine thrust line and/or an offset fin. Cessna also commonly provide a fixed trim tab at the foot of the rudder which is bent so deflecting the rudder as required.
All the above are only going to be effective as desired with a given RPM and airspeed combination. The factory therefore arranges this to suit the RPM/speed for the most common cruise combination: i.e. the period that the pilot is most likely to spend time. When flying more slowly then the offsets begins to dominate and causes a yaw to the right.
When assessing the basic aeroplane it is important that all the references used are not in error. Until the mounting of the balance ball tube, turn Ind./turn Coordinator and the Attitude Indicator is serviceable and proven to be correct they should not be used. You need a stable day with a clear horizon. At the POH recommended cruise RPM and speed then check the wings are absolutely level with the natural horizon and that the nose remains fixed constantly on a distant reference point. It doesn't matter at this stage whether you need to maintain wings level and zero yaw with ailerons and rudder. The important thing is are you able to do so whilst maintaining a constant heading with the wings level. We are establishing by doing this check whether or not the fuselage is twisted or deformed. If it is you will not be able to maintain a constant heading with the wings level and will also have a difficulty with maintaining height. A series of heavy landings overtime can do this to the fuselage or a single heavy landing.
The aircraft logbooks should have recorded any accident damage and repair but ....?. I've lost count of the number of aeroplanes in this condition that I've discovered during pre-purchase flight surveys, This is the first thing I look for because just about everything else can be fixed. With your hands and feet off and the aeroplane flies straight and level the fuselage is good and all variable settings are also correct. Note; some aeroplanes have a fixed trim tab on the right aileron which may need adjusting, by bending as with the rudder fixed trim tab. These fixed trim tabs can only be adjusted on the ground of course and can take a number of flights to get spot on. These above checks need to be completed first before any other checks or you could be chasing your tail, so to speak.
You haven't told us the aeroplane type and model and the type of engine installed. There will be many who can help you knowing the particular characteristics of your aeroplane. There is a lot more to add but we need detail to help further. I don't want to go further without those details.
I'm not sure that you are using the terms "skid" and "slip" correctly so that needs some clarity. Also the term "turn" we need to separate this from "yaw" - in physics they can be the same thing I know but for flight we usually keep them seperate. Yaw then is a swing around the normal axis but turn describes a change of direction of the flight following a roll to an angle of bank. Pilot Dar has already explained "adverse aileron yaw" which causes a swing away from the direction of the intended turn but it is yaw and is only prevented by the proper amount and the correctly timed application of rudder.
Last edited by Fl1ingfrog; 1st Aug 2020 at 18:00.