# How to scale airfoil coordinates to achieve the required size?

I'm using airfoil data that is generated by a program. The generated airfoil has a chord length of 1 unit. I want to know how to scale up this airfoil to required chord length. My airfoil series number 638xx. NACA five digit series.

This is a simple math question. Multiply your x and y coordinates by the scaling factor you want. Say your chord length is 100mm. To make it 150mm, multiply all your values by 1.5. If you have a picture of an airfoil, just scale the image by 150%.

• What about the y coordinates ? Feb 28, 2017 at 16:09
• Multiply both x any x values by your scaling factor. Feb 28, 2017 at 16:11
• Did that do the trick? Feb 28, 2017 at 16:13
• No, I was a following a video tutorial done by some guy on youtube. He shared his airfoil section coordinate files. When I check the scaling factor for the airfoil coordinates, it is different for x and y coordinates. For reference I'm adding pastebin link and the original coordinates data Feb 28, 2017 at 16:23
• he is using NACA 4415 Feb 28, 2017 at 16:23

MountainClimberi is correct. Multiplying both x and y coordinates by the same factor will scale your airfoil correctly. Using a different factor for each will result in a different aspect ratio and a different(stretched) version of that airfoil that will not match its published properties.

Also remember that after scaling the data, your reference location will have moved if it was not (0,0). This may require a translation operation if you need to adjust it.

Per Scaling(geometry) wiki: "The scaling is uniform if and only if the scaling factors are equal (vx = vy = vz)"
Willamate.edu has a good article on 2D transformations including scaling.
Python would be a good language to manipulate this data with. Here is an SE python scaling question.