Hi Hisashi, welcome to the forum!
Network won't work on that current curve layout because of this area here - here:
The problem is having 2 blue curves that touch each other on one side. Basically for Network to work right, you need to have 2 sets of curves like you have here with red and blue curves, but they need to form a regular grid layout similar to how lines of longitude and latitude on a sphere unwrap to a flat 2D grid on a flat map.
It's possible for the lines to touch each other such as at the north pole or south pole on a globe, but if the lines touch, _all_ of them belonging to the same direction must touch each other in that spot, you can't have only some pieces touch each other's ends (like you have here) instead of all of them collapsing down to a single pole area.
So anyway that's what is confusing Network for your particular situation here.
Also it will be difficult to get a smooth result with having a non-smooth back shape with sharp points as part of the structure here:
If you were to do a Network with a readjusted layout, those sharp zones along that back side would basically cause the network to be formed in strips with one strip for each sharp corner there rather than as a big smooth surface.
Do you have any images of the kind of end result you're looking for? If you can post something it may help to give better advice.
Right now looking at your curve outline though, I'd probably advise to initially create a more simple blocky object and then use filleting to round off the shape in these areas where you've got tight bends in it like here:
Generally a tight bend like that in between 2 longer straight sides is better done as an edge fillet rather than trying to directly model the tight bend in a single surface construction by sweeping or network like you're trying to do here... It's difficult to control surfaces when you use shapes that go through tight bends like that, it's better for an individual surface construction to be a sort of broader more uniformly curved shape and areas of tight "transition curvature" are done by fillets.
Something similar to these steps - here I've started with a boxy shape and put on fillets to make rounded spots, put in the biggest fillets first and then smaller ones:
So notice there how the end result of the filleting gives the kind of rounded corner footprint like you have in your curves.
I'm not 100% sure that this applies to your shape though, the angular sharp cornered part on the back part kind of confuses me a bit.
- Michael
