To create corners you need to add more control lines to your corners. We will often add extra control lines at right angles. It tends to help the subdivision algorithms to maintain the shape you are try to develop.
Another option is adding a non-creased diagonal edge, connecting to point with the folding issues, *and* making that point a ”corner” point, can improve the problem.
Adding a creased diagonal edge connecting to point with the folding
issues, *and* making that point a ”corner” point, can fix the problem.
In some cases, a creased edge at that location runs contrary to what you are trying to do with your ship model, and in that case a
potential work-around is to have build the model using unconnected
Indeed, very often use unconnected faces as a matter of course,
especially with interior bulkheads and decks/cockpits