How Do I Loft With A Curve?

[glencandle]

I have a large profile being lofted down to a smaller profile.  The loft is linear but I would like the effect to be curved (i.e. the second pic below). I'm not sure rails is what I'm after, but I also don't know how to achieve this with a sweep.

What would be the best method to pull this off?

[For clarity: instead of the top being a straight grade down to the bottom, it would roll gradually and then get exponentially steeper toward the bottom.]

[jeff_strater]

Is this what you are looking for?

I used a rail to get this.  It is in Sketch4 (see attached)

[glencandle]

This is almost it, thank you, I didn't realize it could be that easy.

I am, however, having an issue with the curved face it seems to create in the middle of the downward ramp.  Is there any way to keep this face flat?

Notice the ridge down the middle:

[glencandle]

The curved face is easier to see in a section analysis:

[TheCADWhisperer]

@glencandle 

Can you File>Export your *.f3d file to your local drive and then Attach it here to a Reply?

Why not a simple Extrude?

[glencandle]

Hi, I did post a project file originally, and now the issue I am referring is based on the file that Jeff just posted above. 

Doing a loft with rails gets me close, but there is the strange curvature I mentioned.  

When you say simple extrude, to which step are you referring?

[jeff_strater]

Interesting.  I do not see that curve in the model I posted.  Here are a couple of cross sections:

and, I do not see the crease, either:

Now, the side walls are curved, but I think they have to be to meet the requirements as I understand them.

re-adding the model FYI

[glencandle]

I apologize for the confusion, I forgot that I actually did work on the file:

In your file the face at the end of the cavity was curved, so I added a rail to straighten it (see below).  But for some reason the addition of the rail added the ridge I mentioned above and I'm not sure how to get around it.

Project file attached.

[jeff_strater · Accepted solution]

Try this version.  I added more rails (and removed the original one).  4 total rails.  Basically, that is the main lever you have in Loft - adding rails.

[g-andresen · Accepted solution]

Hi,

No loft needed

günther

[glencandle]

Rails on the sides!  Oh man it's so obvious now that I'm kicking myself for not going there.  Thank you, after this interaction I have a much greater understanding of rail logic now.

[glencandle]

Thanks for this, I also accept this as a solution.  More than one way to skin a cat!  I never use the Surface tools, and I'm still not totally clear on how they work, but after flowing through the timeline and the sketches you've made it does make a kind of sense to me.  Extruding a line to make a surface is an interesting solution and one I've never considered.

[g-andresen]

Hi,

Here is another model that uses planes instead of surface bodies for extruding to an object and additionally a concave channel profile.

günther