Im building a frame for a hybrid solar car and i cant weld it or use swept feature to transform it on tubular to apply stress analysis, i made it from spine lines using the fairing has guide. The model is attached
Splines aren't allowed in Weldments...Don't ask me why, I have no idea why they haven't implemented it. But I've read that in 2020 the replacement for Weldments, Structure Systems will support them.
The only way I know how to do this is to insert a Reference Plane, perpendicular to each segment and then draw the profile of the tube on that plane then use Sweep. I have attached your file with one such sweep.
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