The kinematic model used by Dubins path determines the turn radius using following equation based on coordinated flight condition for a fixed-wing UAV:
(V is airspeed, ϕ is roll angle)According to your configuration AirSpeed = 0.1 m/s and Roll Angle = 1 radian, the resulting R = 0.00065519654 m, which is way too small and leads to the sharp turn you saw in the resulting path.
To get larger curvature, consider use higher airspeed or lower roll angle. In general, fixedwing UAV cannot fly at 0.1 m/s, which is too slow to generate enough aerodynamic force.
