hi michael,

thanks for taking the time to look into my problem, i appreciate it. here is the .3dm file. i have tried to fix the curves and give the curves that lead to the center of the vault the same structure as the outside curves, two points at the edges and a controlpoint in the middle to create the curvature while considering the curves tangents to the center of the vault. i doesnt help me to get a vault with a an even center, instead the three parts are slightly bulging to the middle.

regards
john