3d sketch anomalies with complex tube structure

[ea425019]

I am having a problem with 3d sketching a fuselage tube structure.  Here is what I have tried:

1) 2d sketch lower plane, then upper, then join the two with 3d sketch 'middleparts'

    a) It kept doing projections, whereby geometry changes split the coincident constraints apart from the upper and lower planes.

2) (shared example) 3d sketch the entire thing, allowing the lower plane to be planar with the origin XY plane, then building up from there.

   a) It seems to not constrain the sketch despite efforts, it remains blue line.

    b)  It secretly constrains things whereby I cannot move them.

In the attached screencast you see me trying to move the upper body relative to the lower back and forth via dimension, then via 'move' it does not allow movement via dimension, yet I didn't apply or witness any constraint prohibiting this. I have had several unconstrained elements refuse to move, or advise me to delete the dimension to move it. I can point to others, but wanted to keep the video brief.

Final question:  What is the best practice in doing a complex tube structure?  Last year I did one by components, defining each tube and angle, it was painstaking, I default to consider that 3d sketch, then 'pipe' command, then 'split body' to miter the tubes is the best choice. I welcome your experiences.

Thanks,

https://autode.sk/39fVg6I

[davebYYPCU]

That frame has no need of a 3d sketch, 

most of the lines are duplicated on each side of the frame, and then joined by cross member.

Stick to 2d sketch.

If those frame lines are centre lines, you will strike grief with pipes not reaching the mitre extent.

Might help....

[ea425019]

Yes, so I typically "extend - extrude" such tubes past the juncture, then 'split body' then delete all the fragment bodies.  

With 2d sketch I had the problem of it not being dynamic, change one thing, and the sketch planes disconnect.

[wersy]

I would start it with planes:

[davebYYPCU · Accepted solution]

Use a Sweep for closed frame paths and the mitres are done for you. 

Cross members Extrude 2 sides to object and the coping cuts are done for you.

2d sketches are way more dynamic, when fully constrained (black articles in this colour scheme) and change the articles you wish, should not break anything.

Sketch a side frame, mirror to other side, then add centre line construction, and connect the oblique members.

Few offset planes, got it covered.

Many ways to skin the cat.

Might help...

[ea425019]

Thanks!  So I did a left, mid, right, top, bottom plane.  These built the 2d sketches up.  Movements/changes movements work OK now.  I did have to use a 3dsketch for some non-planar tubes, but it seems when 3d sketches contain fewer lines, it works according to the proper logic.