Problem selecting cross sections for Multi-Section Surfaces

[WK95]

When I try to select the first curve, I instead end up selecting the entire sketch of that cross curve. When I then select the second curve, I select just the curve I need and not the entire sketch. Why is this happening?

 

[itsmyjob]

that's why I do not like working with sketches that much, they give you the feeling that design is easy, but the real curve tools are in 3d not in sketch.

a quick solution for you:

once you have all your sketches, make some "Extract" with proper continuity from each section, then use those extract in your Multi sections surface.

Another way would be to define output profile in the sketch.

the choice between 2d sketch outputs or 3d curves like extract depends on you need to control vertices. If you need to remove them, then you will have to go 3d with an extract then a smooth curve (but then you could be slightly off your sketch).

I've been working with curve sections for a nacelle loft optimization (for cross wind / drag and other stuff) and I had a mix of sketches, 3d curves, smooth curves, connect curves, conical curves, joins... all kind of functions and optimization.. then finally one nice multi section surface as I had to stay within GSD for possible VBA compatibility (FSS API are not available).

you don't have much option in the surface creation, so all the real work need to be done at the curve level.

Eric N.
indocti discant et ament meminisse periti ​

 

[itsmyjob]

as for the why you have this behavior, I ll let you analyze the geometry you have in your sketches, the truth is out there...

Eric N.
indocti discant et ament meminisse periti ​

 

[WK95]

Itsmyjob,

Which workbenches and tools in CATIA would be best for doing this sort of thing?

To model the fuselage, my preferred method is modelling side views, top views, and cross curves and then modifying them individually as needed. How else could I do this without the use of sketches?

 

[itsmyjob]

i use GSD with planes, points and curves

Eric N.
indocti discant et ament meminisse periti ​

 

[WK95]

https://www.youtube.com/watch?v=u5CBv_qXATE

In this video, the GSD workbench is being used to make a bicycle seat. Curves are made within sketches.

In your approach, would you instead not use any sketches at all but place points on a plane then connect them with non-sketch curves?

 

[itsmyjob]

yep. so when i move points or change curve parameter I see all my analysis 'live' (porcupine/surfacic curvature...) If you do your curve in a sketch, the analysis will update only when you exit the sketch (like in the video), unless you have next version of CATIA (and maybe some additional license). Also some curve functions are not available in sketch : spine/ curve by equation...

But this is me... if you like using sketches please do.

Eric N.
indocti discant et ament meminisse periti ​

 

[WK95]

Thanks a lot itsmyjob. I'm trying to use the Extract tools right now and it works just fine for me so far. However, I'll take your suggestion and try to also make the fuselage using curves to see which one works best.

 

[JeniaL]

man are you building an UAV? the government will contact you soon. just kidding.
try to build only points in sketch and then outside a sketch use spline or whatever to connect points.

 

[WK95]

Not a UAV. It's an aircraft of my own design I've been working on for conceptual design.

So suppose I want to make some cross sections which use conics. How do I get some points from this which I use then connect to with splines?

 

[JeniaL]

do you use sketch tracer?

 

[WK95]

Yes, but only for the side view to trace a drawing I made.

 

[itsmyjob]

well for conics, some functions are only available in sketcher only: Hyper/Parabola by focus. Hope you looking only for generic conic curve.

You do conic curve in sketch the same way you do them in 3D. Based on points and tg line.

Eric N.
indocti discant et ament meminisse periti ​