At my northern location, the horizontal and vertical components of the magnetic field are respectively 17.686 and 51.676 microteslas, meaning that the inclination of the field in the ground is 71.107°.
The results of these calculations are summarized in the following two figures, for positive and negative heel angles (with a zero pitch angle). Heel angle is considered positive when the mast leans to starboard.
It is interesting to note that there is one heading where the non-compensated compass will give a correct result, independantly of the heel angle: 270° for positive heel, and 90° for negative heel.
To reproduce these results for other locations, here are the equations to use.