Airfoil alignment and dimensioning

[matt_bolty]

When I import a NACA DAT file to sketch an airfoil, I make a horizontal dotted construction line and select that. That part is fine.

But when I hit ok and the airfoil appears, the leading edge is not coincident with line itself. Why? When I close the airfoils trailing edge and draw a construction line from there to the leading edge, it's no longer horizontal.

How do I align the airfoil to be coincident with my horizontal construction line or how do I get to to be already coincident when I import it? How do I dimension or rotate it cleanly?

I want to avoid making a new centreline because it would no longer be horizonral and given how annoying it is to construct perpendicular planes on the damned software, I'd rather keep the original line!

@wersy

[Drewpan]

Hi,

There are a number of Airfoil extension Apps in the Fusion "shop" that can deal with various

Airfoil data types. I have a couple of different ones installed. These will often have a point

you can set as the leading edge of the airfoil and with some you can even manage twist angles.

In your specific case the airfoil is a collection of points and lines so I would simply group them

together and then use the co-incident constraint on the leading edge point and the origin. You

will probably need to do the same with the trailing edge.

While recently I have been hand designing an airfoil for a ducted fan, I normally get my airfoil

data from www.airfoiltools.com This has a great selection of standard airfoils and some not so

standard and data is easily available for each one. I then use the fusion Apps to incorporate them

into my design.

Cheers

Andrew

[wersy · Accepted solution]

The dat file is a disaster - unusable.

Where did you get it?
What's the name of the profile?
Which app did you use to import it?

[davebYYPCU]

I would simply group them together and then use the co-incident constraint on the leading edge point and the origin.

In Fusion? We have sketch blocks now?  How does this Grouping work?

I am well aware of measuring the chord incidence, to the origin axis with Measure.

Select all the airfoil, rotating to parallel with Move Tool, 

then Move LE point to Origin with Move point to point.

I agree I could not use that curve either.

Might help….

[matt_bolty]

I had the eureka moment that it was unusable last night! Thank you though. I deleted one of the points and everything worked. I only saw it when I was preparing a second question by zooming in a ridiculous amount and seeing a tiny loop at the leading edge from two points that were inverted. Once I deleted one, everything worked. This was incredibly drustrating given how much time I have sunk into just making a wingtip hahah!

How did you very it was unusable? I see all those jagged red lines but they don't appear on mine. Is there a way to check? 

I got it off Airfoiltools: http://airfoiltools.com/airfoil/details?airfoil=b737a-il

I am using the "Airfoil sketch from file" add-on for Autodesk Fusion. Got it from their website. Are there better add-ons that yield more consistent results? Perhaps one that lets me define NACA inputs and gives a singular curve instead of a multi-point spline? Although sketching from coordinates is useful for more complex foils 

[matt_bolty]

Thank you! I found out last night after zooming all the way that this airfoil is junk. The coords are wrong - somewhere two of the points are inverted, so they appear one over the other with a tiny loop at the leading edge. This little error was the source of so many woes! 

What are sketch blocks? Or what do you mean by them? And is "move point to point" a funtionality I need to turn on? How?

Thanks again

[TheCADWhisperer]

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@matt_bolty wrote:

How did you very it was unusable? I see all those jagged red lines but they don't appear on mine. Is there a way to check? 

---

Right click on the Spline and Toggle Curvature Display.

(This one is such a mess it won't make sense to you.  Create a simple 3-Point Spline and run the same command and you will see what the Curvature Display should look like.)

Sketch Blocks is something sorely needed in Fusion but somehow the developers are clueless about the utility of such functionality.

[davebYYPCU]

Move tool, has 5 options, for the type of function you are undertaking.

4th option is Point to Point.

So you are not making a life size Boeing 737?
For modelling scaled replicas, Airfoil library files and associated utility routines, are as you say, a timesoak.  
Draw your own. (in place)

You already have the chord length, you can calculate the required thickness / camber.  (There is a construction line in that pic for this)

Follow the latest pic example, I use a top and bottom curve, no more than four points as per pic, for the top, 

and no more than five points, (allows for undercamber) for the bottom curve.

LE points, coincident, and both tangent handles vertical.  Both thickness point handles horizontal.

Adjust the point near the leading edge, with position and handle, for the smooth curvature as shown.

Then the Fusion Loft, Sweep, Thicken, and Shell tools can be functional.

Might help….

[wersy]

I can't quite imagine that the .dat points are correct.

In addition, fitpoint splines are conceivably unsuitable for airfoils. That's why I trace the curves with control point splines, using only a few points. In doing so, I deviate by a maximum of four hundredths of a millimeter from some .dat points. In this case, I didn't even come close to succeeding.

I also tried SolidEdge, which has the best dat importer I know. It generates control point splines.
But even it couldn't conjure up smooth curves.

I was surprised that the curves didn't improve even at their original size. I would have expected more harmonious curves to result from the larger point spacing.

So if you want a visual model, @davebYYPCU  profile is very good.
If you want it to fly, you need to use different profiles.

By the way, maybe the root profile has a 1° angle of attack. That's the only way I can explain why it's published at an angle.