Is it on the same plane, or a vertical one?
I’m having a good experiment, and your inspiration is taking me down simpler paths I hadn’t considered — so, progress, thank you! I can’t work out how you got to design4 above though, even when playing with the shell tool.
I think they actually recommend using Loom here for videos, although I’ve used it for a couple of years anyway. Delightfully simple experience, can work on iPad and desktop too…
I made a rectangle. Added a circle on one end and drew a random wavy line over the other end. It’s ALL about the sketches.
Yes simple takes time-
What is it? Lotus 7 ? Morgan? Might help to pull back a little with your pictures to provide some context to both ends of the curve, which looks like it might be flared too.
Are you simply planning on filling the opening? Or is there another function to it?
I think it might be helpful to try to model the curves of the car, which might provide some clues as to the geometries you might need to work with, but I think you’re doing fine-
Everything takes time-
It’s a 7, yes @jb7
The picture in this post should give a clearer context.
Long story short - I just want to create a temporary “cover” for this gap. It’s when I swap between air filters; this particular one not being the same size as the other.
I want said cover to have a similar curve to the bonnet itself, and it needs to have a “base” wider than the hole so I can stick it on behind the hole. The base needs a curve at the rearward point to attach properly, really. And I’m struggling with making a curved base with a raised top section.
But I think @Oregonerd has given me a better approach in using an offset edge. As I said at the beginning, I’m new to this game so I don’t have the experience to know what’s the best option. I love how creating things in CAD often means thinking around a shape though 
It really makes you think about objects from a different perspective.
Extruding the shape, complete with curved base, then cutting an edge in with offset edge is an approach I’d not tried.
Although the other challenge I’m having is the front section - near the foam filter - being more raised than the rear section. To be really need it needs to taper, which is a whole other challenge for me 
So I extruded the first shape. Then I used the Chamfer/fillet tool to make the round edge. Then I selected the top face and extruded that (design3)
Then I used the Chamfer/fillet again to smooth the shape. Then use the shell tool to get design4. The shell tool makes a wall at the end (open end). Simply select the interior face and extrude it gone to get the open end.
I think I under-utilise chamfer/fillet. This approach seems to make things so much simpler than what I was doing!
Thanks again @Oregonerd, your input has been incredibly valuable, and appreciated.
Thanks for the clarification about the 7-
I’ve had a lot of problems relating to a very simple issue redesigning scuptural cowl shapes on my motorcycle, so I sympathize-
However, since your question was about design, might you not be tempted to remove the trim around the opening to allow you to design directly around the opening in the metal?
I think the geometries of the metalwork might be simpler to work with, compared to the convoluted turns of the trim.
I realize I’m not helping, but simple is as simple does, and adding a curved profile around some trim seems to be complicating mattters. Perhaps you might have a better result by having only one junction, a cleaner one between your printed part and the bodywork?
I’ve printed petg cf, and it’s pretty stable in UV, but I don’t know how I might be able attach it to metal bodywork-
Oregonerd is helping you way more than I am-
Have you considered TPU? If you remove the trim you might be able to conform a panel to the metalwork-
Thanks for the extra thoughts @jb7, all angles are welcome to help my thinking and approach 
The trim is only there to stop you taking a limb off on the sharp metal 
so to be honest, it won’t make any difference taking it off to model. I pretty much know what I want to do, and to an extent I have a solution, but I couldn’t help thinking it was overblown (and will take a long time to print).
I made a simpler, hollowed out shell, structure this week which took 5 hours to print (versus the predicted 20 for my detailed model) — so with a little tweaking thanks to @Oregonerd direction, I think I can produce something that will suffice.
Cheers!
