Noob question joining curve to line


I am very new to SketchUp and do not know my way around it very well. I am trying to build a rib to 3d print and have all the parts in .dxf format. I have copied the part I need and pasted it on its own into new drawing and saved this as riib1.skp and have uploaded it with this.rib1.skp (158.1 KB)
I have ‘welded’ all the individual lines together until i ended up with just 2 lines. One is the curve and one made up of lots of individual segments, but i am unable to find a way to join these together to close the object. I was hoping to do this and then use ‘Push/Pull’ to set the thickness of the rib.
Any advice on how to do this would be much appreciated ( i have spent many many hours googling and am still stuck)
Thanks in advance for any replies


Do you mean like this?

rib1.skp (241.0 KB)


If you do mean like that, your problem was that you had grouped a portion of the curve within the overall group of the wing. All I did was to explode that group, draw a line across the void to create a surface and then erase the temporary line. Bingo!


thanks very much i can use push/pull now. Was it in the curvy part in that little box that appears just around the small section and did you have to ‘weld’ the parts together once you had done that? (sorry for more questions :)) i will go back to my file and try and see if i can do what you did. thanks again.


If you’re new, you probably won’t have used Outliner much yet. It’s useful for telling you how your model is made up. It also allows you to move things around and navigate directly to parts. Very handy. In this case, it shows you have a group (the blue box) nested within another. Here’s what I did:


Thanks for the reply and video, it has helped me a lot and i have successfully done it now :slight_smile: . What i don’t really understand is why it works when the 2 parts are joined with the tempory line and then select the 2 areas and then remove the line and you can select it all as one area. Why does it not see the original as closed, using the full perimeter to the right, instead of drawing a line to split it into 2 sections.
It is a long long time since i used a CAD app, last time was when autocad R13 was around and then i only used it when i had to as i found R13 a very hard program to use intermittently, but i bought a Creality CR-10S last week and need to get my knowledge on modern day CAD a lot. I am using Cura to convert the drawing for the printer.
Thanks again :slight_smile:


It’s important to remember that SU is a surface modeller. Also that what you might think of as a line is in fact an edge. SU allows you to have unconnected edges but as soon as you connect up 3 or more in the same plane, a surface will be created. However, SU is not quite clever enough to monitor edges that have been drawn separately and then joined together. That’s why you have manually to join them. Actually, you can achieve the same result by drawing over an existing line. That’s actually simpler because you then don’t have anything to erase.

Apart from AC, I don’t know the other programs you use. I assume Cura is 3D printing software. For 2D, use Layout.


Only the people with access to the source code could definitively answer this, so you’re not likely to get a complete answer.

There are many situations where SketchUp fails to recognize an area as a face. The “Draw a edge across the area, then delete the edge” is a frequently referenced workaround. But it’s actually the second thing you should try! The first is to simply draw over one edge that bounds the area you think should be a face. If the desired face is created, congrats! You’re done!

If that doesn’t work, then there is likely a problem with the enclosing path of edges - and it generally comes down to one of:

  • Two edges don’t actually meet or
  • The bounding edges aren’t co-planar

For both of these, the “draw an edge between two points” method can help you narrow your search for the problem as follows:

  1. Draw a new edge across the area
  2. Check for plane creation - 1 “side” of the edge didn’t create a face
  3. Your problem is in the area where the face wasn’t created - treat this as a the new “problem” area
  4. Goto step 1

At some point, you’ll discover either a gap, or a place where 2 faces ARE created, but the faces aren’t co-planar. Fix as appropriate.

Occasionally, it can get really frustrating - especially if the desired face can’t be made because it isn’t planar - and the error is a very shallow angle. There will come a point where starting from scratch and redrawing is a better use of your time.


Thanks for taking the time to explain this all to me and the very fast reply.


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