topic Re: Why does the thicken and the shell tool do this? in Fusion Design, Validate & Document Forum

Why does the thicken and the shell tool do this?

Quefelsees — Tue, 16 Dec 2025 13:39:52 GMT

Hello all,

I'm trying to create a body from a form surface. I could patch both holes and stitch the surfaces and then shell the resulting body. Or I can thicken it. However, both tools create a weird result at the nose of the fuselage.

My goal is top create the nose cone afterwards because I thought it would be computationally intensive. It's supposed to look like the "top view" canvas in the end.

Is there a better way? How can I stop the thicken and the shell tool from deviating from my form surface?

Re: Why does the thicken and the shell tool do this?

TrippyLighting — Tue, 16 Dec 2025 16:04:12 GMT

The results of the thickening operation are precisely what I would expect.

@Quefelsees wrote:

...

My goal is to create the nose cone afterwards because I thought it would be computationally intensive.

Based on what are you making that assumption?

Re: Why does the thicken and the shell tool do this?

johnsonshiue — Tue, 16 Dec 2025 21:18:15 GMT

Hi! The unnatural geometry is probably caused by the intersection edges at the relatively large thickness compared to the surface curvature. To get a more desirable result, Surface Modeling technique has to be used here.

You may offset the faces. Extend the offset surfaces. Create capping workplanes. Lastly, use Boundary Fill to solidify the body.

Many thanks!

Re: Why does the thicken and the shell tool do this?

TrippyLighting — Tue, 16 Dec 2025 22:07:12 GMT

@johnsonshiue wrote:

... To get a more desirable result, Surface Modeling technique has to be used here.

While surface modeling is undoubtedly an excellent option, it can be achieved with T-Splines. There are a few gotchas with both techniques.

Re: Why does the thicken and the shell tool do this?

Quefelsees — Wed, 17 Dec 2025 12:18:29 GMT

Well, I expected that it would follow the curvature of the model. Like at the back of the model. To me this is a result I would have not expected.

@TrippyLighting wrote:
Based on what are you making that assumption?

I've seen some people do the nose cone with surface modeling after finishing the t-spline model. So I thought that's the main way to do it. Also I had trouble welding the vertices at the nose after modeling the nose to almost 100% match my canvas. I could not get the result I desired. So I left it "open".

And I thought that the shell tool or the thicken tool would have trouble since the nose gets very thin and pointy.

Re: Why does the thicken and the shell tool do this?

Quefelsees — Wed, 17 Dec 2025 12:23:29 GMT

Thank you very much!

While this works and also looks like the result I would have expected from the shell tool or the thicken tool, would it be easier to model the nose first? And how would you do that? I kind of struggle to create the nose I want (probably obvious by now :D). Let me know if this would be a topic for another post instead.

Re: Why does the thicken and the shell tool do this?

Quefelsees — Wed, 17 Dec 2025 13:19:33 GMT

I would appreciate it very much if you could elaborate on this. What gotchas are you referring to?

Re: Why does the thicken and the shell tool do this?

TrippyLighting — Wed, 17 Dec 2025 14:27:31 GMT

@johnsonshiue did you compare the results of your technique with the result of simply capping and shelling the T-Spline based solid body?

They are 100% the same!

Re: Why does the thicken and the shell tool do this?

TrippyLighting — Wed, 17 Dec 2025 14:48:50 GMT

Here's how I'd model the nose in T-Splines. The trick here (I had to experiment with this myself) is NOT to weld the vertices at the tip.

Usually and regardless whether you are lofting (surface modeling) or using T-Splines it isn't good to loft into a point, which creates a mathematical singularity/ That is one of the gotchas. The Fusion team has done a great job to alleviate the usual problems associated with this in many cases.

It shells fine.

(view in My Videos)

Re: Why does the thicken and the shell tool do this?

Quefelsees — Wed, 17 Dec 2025 15:19:47 GMT

Aaaaaaahhhhhhh! I didn't know that was an option! Thank you so much!

That's good to know as well, thanks.