Charlotte Birchall 18/2/13
Establishing Professional Practice Sketch up
If you want to make a door or a window onto a curved surface, you make the curved object and the separately to the side make you window or door and then select the object and extrude it so it goes all the way through the curved object.
Once you have done that you then place the object in the middle of the curved object.
Select the object and right click on it and select intersect faces with model, and this should make an outline on the model.
Charlotte Birchall 18/2/13
Establishing Professional Practice Once made an outline you can then delete the outside of the object to create your window/door.
Animation View > Animation > Add Scene