firstly just like to say that it looks like you've got a great and helpful community, just what I was looking for with regards to CATIA! Ok, so I'm trying to design the nose section of a commercial aircraft eg. 737 / A320 size. I've generated the sketch profile which the nose is based on. (Don't worry about the pointy end / general design of it. I'm just trying to get it to work before I start worrying about little things!) The middle line is located at 2/3 of the diameter of fuselage measured from the top.
Now when I tried to surface this I ran into trouble. My first thought was to do it in two sections, the top and bottom halves. I was going to use sweep, with two guide curves. The profile would have been the fuselage arc, one guide curve in the horizontal plane and another in the vertical. Catia refused to compute the anchor points automatically and i couldn't choose the right ones to make it work!
After this i decided to try split the nose into quarters, instead of halves. I first tried to fill the quarter. Although the fill worked, the surface was "sucked in" or depressed in the center which wasn't what i wanted.
I ended up trying the sweep with two guide curves again. This time it worked! I used the same guide curves and the profile curve was only the quarter section of the fuselage arc.
Now there's a couple of things not perfect with this solution. Firstly, you can see that it's not ideal as each quarter section bulges out and then comes in where it meets the other sections. The result, not a smooth surface between the joins of each surface. The other thing was I had heaps of trouble giving the surfaces thickness. The two top quarters I used the pad function and that worked. For the two bottom surfaces I couldn't select a direction for the pad without encountering an error.
"The profile is locally paralell to the extrusion direction. The extrusion cannot be defined at that place. Chose a profile and a direction that are not parallel."
I sort of understand what this error means. But the wierd thing was that for the two top quarters, I chose the same direction for the pad and it worked. After this I tried to use thick surface instead, and got the following error.
"Current offset value leads to a local degeneration on a surface: body cannot be built"
So that's where I'm at. If anybody could offer some advice on this that would be great. Perhaps there is a better way from the start to go about it.