# Splines - I can't figure them out
**URL:** https://discourse.shapr3d.com/t/splines-i-cant-figure-them-out/38040
**Category:** Modeling Questions
**Created:** [May 20, 2025, 12:38am UTC](https://discourse.shapr3d.com/t/splines-i-cant-figure-them-out/38040 "2025-05-20T00:38:00Z")
**Posts on this page:** 6
**Page:** 1
### Author:  [@Rtfm00](https://discourse.shapr3d.com/u/Rtfm00)
#### Post date: [May 20, 2025, 12:38am UTC](https://discourse.shapr3d.com/t/splines-i-cant-figure-them-out/38040/1 "2025-05-20T00:38:00Z")
OK - I am trying to use splines to smooth out an airfoil shape created by Sketchup. The Sketchup generated edges are quite large, and I thought that tracing the points using a spline would give me a nice, un-faceted surface. But I can’t get this to work.
I managed to create a single spline for almost all of the top surface, and similarly almost all of the bottom surface. With each new spline point my laptop slows down to the point where it will not add a new point. Hence the top and bottom splines.
Then I thought all I need to do is to add a third spline to fill in the gap, but this Shapr refuses to do. Online tutorials show Break and Join badges popping up when points are clicked on. This doesn’t happen on my S3D. So there seems no way I can either create a third mini spline, or to join it to the existing splines.
Finally, I can’t figure out how to “extract” the splines from the existing (faceted) airfoil shape. If I try to extrude the airfoil, it comes out beautifully smooth on the surface, but underneath there are zillions of little triangulated facets.
So I’m stuck.
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### Author:  [@JST](https://discourse.shapr3d.com/u/JST)
#### Post date: [May 20, 2025, 4:54am UTC](https://discourse.shapr3d.com/t/splines-i-cant-figure-them-out/38040/2 "2025-05-20T04:54:26Z")
For me the best way is to create the profile outside of shapr from a dat. file and then import it as a template rib, in step form. For real flying models.
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### Author:  [@Xdrakosha](https://discourse.shapr3d.com/u/Xdrakosha)
#### Post date: [May 20, 2025, 6:39am UTC](https://discourse.shapr3d.com/t/splines-i-cant-figure-them-out/38040/3 "2025-05-20T06:39:36Z")
I don’t know anything about aircraft but quick search gives me this photo
This form can be easily recreated with controlled spline with 9-10 points
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### Author:  [@JST](https://discourse.shapr3d.com/u/JST)
#### Post date: [May 20, 2025, 9:18am UTC](https://discourse.shapr3d.com/t/splines-i-cant-figure-them-out/38040/4 "2025-05-20T09:18:17Z")
> [@Xdrakosha](#):
>
> I don’t know anything about aircraft but quick search gives me this photo
Unfortunately, it’s not that simple, a profile can be designed for multiple purposes. Since most of us are not aerospace engineers, we use well-established profiles in simulation programs (Profili, Xlfr5). In these, you can specify the density of the points for the best possible line drawing, and the coordinates can be saved in a .dat file. If you just need to draw something, your solution might be good, for example for a model on the top of a cabinet
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### Author:  [@Xdrakosha](https://discourse.shapr3d.com/u/Xdrakosha)
#### Post date: [May 20, 2025, 9:39am UTC](https://discourse.shapr3d.com/t/splines-i-cant-figure-them-out/38040/5 "2025-05-20T09:39:33Z")
In that case making that in CAD from scratch is waste of time. This topic has no sense at all. So using external specialized software is only reasonable way.
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### Author:  [@Rtfm00](https://discourse.shapr3d.com/u/Rtfm00)
#### Post date: [May 21, 2025, 6:05am UTC](https://discourse.shapr3d.com/t/splines-i-cant-figure-them-out/38040/6 "2025-05-21T06:05:59Z")
Hi, and thanks for your reply. The original question was “can I create an airfoil profile in Shapr3d from a DAT file” The answer seems to be “No” That’s fine. Fusion can do it, and I can import it as a step file. Problem solved.