Inventor General Discussion

Inventor General Discussion

19 Posts
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Registered: ‎01-03-2013
Post 1 of 4
Accepted Solution

Equation curves

945 Views, 3 Replies
01-29-2013 10:18 AM



I found tutorial for symmetrical equation curve for NACA Airfouil in Inventor 2013.


I need to create assymentric airfoil. I am wondering if there is a possibility to put equation in Inventor which looks like the one I attached in doc file.


If it is not possible that's OK as I can use coordinate generator in the internet and put coordinates into inventor so I can draw it but It would be nice to put set of the equations rather than manually put 100 points. 

I know that those equations are more complicated and I don't know how to start with them in Inventor





I will follow your advise. I will generate coordinates in the NACA tool and put then through MS Excel into inventor


Thank you very much

Distinguished Mentor
734 Posts
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Registered: ‎05-23-2002
Post 2 of 4

Re: Equation curves

01-29-2013 11:51 PM in reply to: PiotrekL1

I'm not in front of Inventor right now, so can't check the syntax for the equation curve editor - but I would say "yes", this is possible.  For now, I'd just recommend inserting points from Excel.  Inventor will draw a spline through the imported points for you - it's like the poor-mans Equation curve editor!  Have a look at the expanded tool-tip for the format of the Excel sheet.  (It's on the Sketch > Insert panel.)

19 Posts
0 Kudos
Registered: ‎01-03-2013
Post 3 of 4

Re: Equation curves

01-30-2013 12:43 AM in reply to: pcrawley



I will follow your advise. I will generate coordinates in the NACA tool and put then through MS Excel into inventor


Thank you very much

Active Member
7 Posts
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Registered: ‎02-20-2011
Post 4 of 4

Re: Equation curves

05-13-2013 06:43 PM in reply to: PiotrekL1

Been working on this to...


My end goal is to have an assembly with n number of NACA 4 digit (and others) profiles. This will allow the user to quickly develop a surface model to export to a CFD program.


Parameters to control (between each section):

  • Sweep
  • sweep
  • dihedral angle
  • span
  • twist

Parameters to control (For each section):

  • NACA Type
  • NACA Parameters
  • Camber length

Step 1: Developing NACA 4 digit profiles


Approach 1: Sketch Equation Curve

Following equitation on, I was successfully able to develop the mean camber line (with two different equation curves). While trying to add the equations for the top and bottom of the profile, I ran into many issues most of which resolved after time, although not all.



  1.  The parametric equations are not fixed in space (i.e.. you can drag them around) and I have not been able to successfully relate all 6 curves, trailing edge, and leading edge (approx. as a circle).
  2. The beginning of the forward curves approach div by zero and are as such not useful.
  3. Very cumbersome, extremely hard to use and error prone.

Approach 2: Thickness Circles + mean camber line = Spline (kinda)

Using my sucsessful mean camber line, I added 10 circles along the mean camber line and demendsioned their linear poisiton along the mean cambber line using the x_u parametric equations, and their heigth demension from the x-axis using the y_u parametric equations.



  1. After passing the max mean camber position, things started going badly. It turns out that inventor was not parsing the equations correctly. This could be a program or user error, the jury is out on that one. See post here: 
  2. Cumbersome (seeing a trend here). While I could type all the equation in the tiny window and get it work corretly, I feel I have better things to do in my life, and there is probably a better approach.

Propossed Approach 1: iRule/iLogic/API

The title is garbled because I don't know enough about each of those, but my preliminary research shows this may be the correct approach. The plan is to create a set of point using the parametric equations to define a spline.


If anyone has any questions/comments/advise please let me know.


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