Closing a surface with 2 straight edges and 1 curved edge

Hi, I have done a model and now changed some of the outer edges to be curved edges, the surface has now gone, only the straight edge planes still have a closed surface. How do I close these surfaces in.

For info, it is a model of a Kite board fin.

F-One Fin Wider.stl (484 Bytes)

I don’t see any curved lines at all.

Share the .skp file, not the .stl

What version of SketchUp are you really using? Your profile doesn’t make sense. SketchUp Free (web) is not Desktop 2023. Are you actually using a cr acked version of SketchUp 2023?

first time using the community chat, that is not what it looks like on my screen, these are only the surfaces with flat edges, all the curved lines are gone, I will try loading the .skp file as suggested in reply below.

F-One Fin Wider.skp (98.9 KB)

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Sketchup geometry is made up of flat faces contained within edges, 3 being the basic number needed to form a face (a triangle). Even curved faces are made of flat faces with graphically softened edges.
So to form faces in the curved areas of your model you need to stitch edges together. Here you see I have divided the straight edge so it has the same number of segments as the arc. Then I join the dots and add a diagonal to complete the triangular faces. Once stitched I smooth the edges by toggling ctrl with eraser.
GIF 15-01-2026 8-31-54 PM

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Thanks, that make sense and will give it a try later.

Thanks, I have attached the .skp file in reply to first comment, and NO it is not a crack version, just the free version off the internet, nowhere on my profile does it say what version I have, I could not send request without choosing an option, so guessed!

I was just going by what you put in your forum profile.

The only legit free version off the internet would SketchUp for Web but it wouldn’t be 2023 Desktop.