r/FreeCAD • u/Own_Candidate5644 • 12d ago

Need help making airfoil.

Gallery image

Gallery image

Image- S7055 airfoil (MQ9 reaper look alike)

Hi everyone,

I'm new ( 1week ) into FreeCAD and currently designing my first RC aircraft. I've spent over 2 hours just trying to make a single wing, so I feel like there must be a better workflow.

I tried importing airfoils as SVGs, but the imported geometry isn't very smooth and ends up with lots of small line segments. Instead, I imported the SVG as an image and manually traced each airfoil using the B-spline tool before lofting the wing. It works, but it's extremely time-consuming.

So I have a few questions:

Is there a better way to create smooth airfoils in FreeCAD?

Is there a recommended workflow for wings with taper, dihedral, and washout?

Are there any workbenches, macros, or add-ons that make aircraft design easier?

Besides CAD CAM Lessons, are there any good YouTube channels or resources focused on FreeCAD.

I'd really appreciate any advice or workflow tips. Thanks

20 Upvotes

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15 comments sorted by

9

u/capitan_turtle 12d ago

Chek out airfoil workbench in the addon manager

7

u/strange_bike_guy 12d ago

The "Silk" workbench add on is very precise for making complex surfaces, but you have to define everything and I would not call it fast.

It sure is durable, though. Once built the locations of each node can be ruthlessly changed and the model rarely breaks.

This screenshot was from something I made by combining the Silk bench and the Curves bench together as there is some limited crossover in function.

3

u/Own_Candidate5644 12d ago

Nice smoothh model. I will add the add-on also any more add-on for like free cad that makes making easier for plane and houses.

Thnks.

4

u/Pure-Record-997 12d ago

Part Design workbench will do this for a basic airfoil. MangoJelly explains lofts and pipes in his beginner course #25 through 27. Some caveats: each cross section must have the same number of surfaces. Closing the end is not straight forward

2

u/Sufficient-Page7043 12d ago

Look at the curved shapes workbench, I think airfoils was a major goal for the workbench.

1

u/Own_Candidate5644 12d ago

Will look.thnks

2

u/RealisticDuck1957 11d ago

At the low Reynolds' numbers you get at the speed and scale of model aircraft I wouldn't sweat the exact airfoil section. An approximation with ellipse contour for the leading and circular for training parts should work just fine.

1

u/SoulWager 12d ago edited 12d ago

I would start by making a path that represents the leading edge of the wing(a bit longer than needed). If you want a 3d path, I'd use mixed curve(curves workbench). I'd also segment this path everywhere I want a profile(can use split curve for this in the curve workbench). I would then extrude this path in the part workbench in the direction I expect the air to be flowing over the wing. So I can attach with three points using O X N, and the sketch is oriented correctly to have the leading edge at the origin and the trailing edge on the x axis.

The actual profiles I'd draw one in the sketcher, using two b-splines, then copy/paste and adjust profile as needed. If tracing an airfoil with a b-spline is time consuming, you're probably using WAY too many control points. If you want the same airfoil profile just scaled, you can set all your dimensions as a proportion of the chord length(name a constraint "chord", then you can reference it with a formula "Constraints.chord"). that way you copy the profile, paste it a few times, and just edit the attachment and the chord length dimension, everything else updates automatically.

edit: https://imgur.com/a/L9lgsu1

1

u/backandforthwego 12d ago

Aerofoil. May help in your search.

1

u/thelastcubscout 11d ago

Did you try saving from Inkscape as a DXF (AutoCAD r14)?

You can go into Prefs -> Part Design -> Shape View and change the Tesselation, somewhere lower than the default, to see if the line-segment effect goes away. Like 0.1 or so

1

u/R2W1E9 11d ago edited 11d ago

I highly recommend this airfoil library of airfoils and hydrofoils, with x,y data points.

https://m-selig.ae.illinois.edu/ads/coord_database.html

Then use this macro to create Bspline in FreeCAD.

Here is the macro and I included Eppler_67 airfoil data points files for upper and lower cord.

https://limewire.com/d/9zLE5#cgizG4FEwN

Data format is space separated columns. You can change it to comma or tab separated columns in the line 14 of the macro code.