Trim results in invalid solid

In the attached model I have two components/solids. They both validate as correct with Solid Inspector^2.
I am attempting to trim the long (horizontal) component with the shorter (vertical) one. That is, the vertical is solid 1, the horizontal is solid 2. After trimming, the horizontal is no longer a solid and Solid Inspector^2 can’t fix it. One of the large faces develops a split and the area above the split is missing. I’ve tried scaling 10X and the problem persists. I’ve scaled 100X and the trim claims to succeed, but in fact nothing is trimmed.

trim_problem.skp (861.5 KB)

No problem here, but using 2018, down saved to 2014

You selected the “handle” first then the curved rafter?

trim_problem.skp (898.6 KB)

Thanks for trying this. However, at least in 2014 the result is again not a solid. Solid Inspector reports two surface border errors that it can’t fix. Two of the resulting faces seem to have some sort of invisible edge. When you select the face, only a portion is highlighted:
error

The pair trimmed fine for me.
Try
View > Hidden Geometry > ON
Then use a temporary Section Cut to see inside etc…
Delete the problem parts…

It is possible to trim two solids and get a messed up [non-solid] result - especially when you get near to the 1/1000" tolerance limitation…

The problem is the geometry is slightly non coplanar.
While the Faces appear fine, their existence is rather tenuous.
The subsequent Trim operation causes SketchUp to automatically triangulate to preserve Faces.


Here, one corner has been moved to the Origin.
The coordinates tell the tale.


After the Trim operation, with Hidden Geometry on.


@pcmoor’s version exhibits the same result.


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Second Issue … Misuse of SketchUp’s Layer System


See this training video

Looked at this very late last night… got the same results as George. George explained the issues far better than I ever could…

Sorry about the layer screw-up. somehow I messed up the layers while stripping the model down to the area of concern.
As to the non-planar issue:
Yes, I suspected as much. But why is the face non-planar? It was created by drawing the front face, which lies in a plane, then push/pull. And since it’s not planar, why does it fill in? Regions bounded by non-planar edges don’t fill.

SU does have a tiny window of tolerance where noncoplanar Edges will support a Face.
As in this case, such Faces tend to fracture during secondary operations.
Notice if you delete the long side Face, no amount of retracing will heal it.

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