Date Subject Software System
17th March 2021 CAD Tutorial FreeCAD 0.18.4 Ubuntu 20.04 LTS

FreeCAD: Make a Smooth Wing Part from an Airfoil Section - Part 1
This article shows how to make a smooth wing part in FreeCAD from an airfoil section shape defined by coordinates in a file.

The wing has sweep, taper and twist and the thickness to chord ratio varies across the span. The result is a smooth 3D shape that follows the shape of the loaded airfoil section.

In part 1, we make a sketch of the planform. This is not strictly necessary, so you can skip straight to part 2 if you just want to see how to make the wing.

Description
Intro: Here is the part that we will make. There are several ways to make this shape in Freecad. This method uses a short macro to load the airfoil section from a text file.

There is also a youtube video accompanying this description (embedded at the end of this page).

The macro, airfoil section and a freecad file containing the final shape are also available to download from the link in the footer.

I don't have comments enabled on this site, but if you have any comments or questions, please feel free to leave them at my youTube channel after the video for this tutorial.

Freecad version: I'm using Freecad version 0.18.4 running on a fairly standard Ubuntu 20.04 LTS. I've added curve and surface modules to Freecad but I don't use them here so the standard Freecad 0.18.4 install should be ok.

Planform outline: The first thing I do is make a sketch of the planform. I don't actually use the sketch to make the wing shape but I like to have it to guide me during the process.

Create a new project, select Sketcher , create a new sketch and then select the XY plane as the working plane. Select the Create 2 Point Line tool and make 4 disconnected lines roughly in the shape of a wing as shown. It's not important if they're accurate as we constraint them to the shape we want in the next steps.

Freecad may automatically create horizontal and vertical constraints on the lines. If they are not created, add horizontal constraints for the top and bottom lines in the image. Remove any vertical constraints.

Planform join lines: We constrain all the lines to be connected. Select the point constraint and then for each corner point, select the two points to connect in turn and they should snap together.

Do this for each of the corners. Then constrain the top left point to the origin in the same way.

You should end up with a connected shape similar to the image but we still haven't fully constrained the shape so yours might look different.

Planform final constraints: Select the horizontal distance constraint and then the top line. This will be the wing root. Set the value to 100mm.

Repeat for the lower line, which will be the tip chord. We'll make a tapered wing so set this to 25mm.

Next we'll set the leading edge sweep. The left line will be the leading edge so select the angle constraint and then the top line followed by the left line. The angle we are setting is 90 minus the leading edge angle so for a leading edge sweep of 35 degrees, set the angle to 55.

Finally, we set the semi-span with a vertical distance constraint on the right hand line. Set this to 90mm. The lines will turn green, indicating the sketch is fully constrained.

Guide Line: I also add one more guideline to help me with the tip chord rotation and positioning. Add one more line to the sketch, constrain it to a horizontal distance 12.5mm from the tip chord leading edge and then constrain each end with a vertical distance of 5mm from the root and tip chord trailing edge points.

The final sketch should look as shown. Close the sketch .

This is the end of part 1 of this tutorial. Continue to part 2 to complete the wing part. There's also a video version of this tutorial below.

I don't have comments enabled on this site, but if you have any comments or questions, feel free to leave them at my youTube channel after the video for this tutorial.

Go to Part 2

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Video Walk-through of this Tutorial


Downloads

WingFromAirfoil.zip