i am trying to find the widest point

[carlweitman50]

Hello, I am trying to find the widest point of an airfoil, which is a pretty complex shape. Is there anyone who could help me?

[davebYYPCU]

Can’t access the file for a while yet.

Draw horizontal lines across top and bottom, > measure.

Might help….

[TrippyLighting]

Extrude a surface -> Right-click on the body and select properties. Look at the bounding box size.

[etfrench · Accepted solution]

The bounding box is not very precise.  The airfoil section is also not symmetric so the widest point may or may not be at the same point above and below the centerline.  Trimming the horizontal lines created using measurements from the bounding box(es) fails because they are not tangent to the airfoil.

[davebYYPCU]

Thanks, that is what I meant.

[TrippyLighting]

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@etfrench wrote:

The bounding box is not very precise. 

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I am aware of that. Why would you need a "very precise" dimension form a free-form fit point spline? 

[etfrench]

Even using the full 9 decimal place precision, the horizontal line created with the bounding box data is not tangent with the airfoil.  When zooming in, the horizontal line and the airfoil are nearly parallel, so visually determining the high spot is still not very precise. 

You can refine it by:

1. Draw a vertical line at the guess point.
2. Draw a horizontal line centered on the bottom endpoint of the vertical line (coincident with the airfoil) .
3. Draw a horizontal line from the upper endpoint. This is just to store the position of the vertical line.
4. Delete the original vertical line.
5. Trim the horizontal line that is coincident with the airfoil.  If that endpoint is coincident with a vertical line drawn from the endpoint of the stored position horizontal line, undo the trim, and trim from the other end. 
6. Repeat until you're satisfied with the position.

As @TrippyLighting says, this point may not have a lot of value given the use of a fit point spline.

[Drewpan]

Hi,

How was the airfoil generated?

Airfoils are typically created using a formula and so in theory you should be able to calculate the max and min from

the formula you used. Try using data from this site: http://airfoiltools.com/ There are many tools on the site and one of

them may assist you to find what you want.

An airfoil file used to create the shape may also help, it is the point data to draw the splines. How accurate do you

need your solution? The highest and lowest data point may be what you want or the spline curve might be a tiny

amount more or less. Certainly drawing horizontal lines from these points might be a guide to the measurements.

Cheers

Andrew

[TheCADWhisperer]

@carlweitman50 

This doesn't precisely answer your question, but drag the construction circle center point left or right and observe the Driven Dimension...

...it would be nice if we could make the circle tangent to the spline, but can't do that...

dragging the circle right or left.