Unwrapping a conic loft airfoil section...

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LVAeronautics
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Unwrapping a conic loft airfoil section...

Post by LVAeronautics »

I first want to thank all for helping me get on track with my original airfoil posting.

But, I came into another problem today attempting to "unwrap" a section.
Unwrap attempt fail.jpg
Unwrap attempt fail.jpg (42.78 KiB) Viewed 969 times
Here is my workflow:

1. Import .dat file, complete with trailing edge gaps
2. Draft WB
a. Scale & Place as required
3. Curves WB
a. Select Wire; select Join Curve (Curvature Combing, as suggested by @hammax in my previous post, did not work [or I did not do it correctly])
i. TE gap disappears
4. Draft WB
a. Select Draft to Sketch
5. (Repeat as required for additional airfoils)
6. Part WB
a. Place all Sketch airfoil drawings into body
b. Loft as required
7. (All seemingly well at this point)
8. Part WB
a. Select lofted section
b. Select “Create Copy”
i. Select Create Shape Element Copy
9. Mesh Design WB
a. Select Copied Shape Element
b. Select Create Mesh from Shape
i. Select OK to accept default values
c. Select Mesh product
d. Select “Unwrap Mesh”

I am inclined to think that the lack of a flat piece on the trailing edge, as a result of the Join Curve, is to blame. However, if I attempt to B-Spline the wire drawing, the trailing edge ends up all kinds of distorted.

In my previous posting, the drawing file Wing Loft Practice 3 that was done for me showed a couple things:

1. The flat trailing edge
2. A line separating the upper and lower surfaces on the leading edge (see below; please show me how I can do this)
Unwrap 2.jpg
Unwrap 2.jpg (37.82 KiB) Viewed 959 times
Long story short, was able to do a successful unwrap on this drawing file.
Unwrap success.jpg
Unwrap success.jpg (39.12 KiB) Viewed 969 times
To summarize:

1. Where did I go wrong on my workflow?
2. How do I maintain the flat trailing edge?
3. What is the workflow for a successful Curvature Combing?

I hate to be a pain, and I am sure it is due to the fact that I am still learning, but if you guys can point me in the right direction, I would be most appreciative.

Thank you once again in advance!
Attachments
Wing Loft Practice 3.FCStd
(705.22 KiB) Downloaded 12 times
Wing Section Unwrap Practice.FCStd
(589.65 KiB) Downloaded 10 times
"Testing leads to Failure, and Failure leads to Understanding" -Burt Rutan
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onekk
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Re: Unwrapping a conic loft airfoil section...

Post by onekk »

You are forgetting to post "full FreeCAD version info" as explained in:

http://forum.freecadweb.org/viewtopic.php?f=3&t=2264

As you use even Curves WB it will be interesting to have versions of WB you have installed, as some things could change between versions.

A proper "full FreeCAD version info" will give these information and much more.

Regards

Carlo D.
GitHub page: https://github.com/onekk/freecad-doc.
- In deep articles on FreeCAD.
- Learning how to model with scripting.
- Various other stuffs.

Blog: https://okkmkblog.wordpress.com/
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hammax
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Re: Unwrapping a conic loft airfoil section...

Post by hammax »

... trying it with up and down sections of "flying wing"
per facebinder => meshing it => unwrap => and position it by placement => get an unrolled surface.
(why do you need that? => cutting of planking ?)

FlyWing_2.png
FlyWing_2.png (45.85 KiB) Viewed 873 times
Attachments
Wing Loft Practice 7.FCStd
(296.79 KiB) Downloaded 12 times
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LVAeronautics
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Re: Unwrapping a conic loft airfoil section...

Post by LVAeronautics »

onekk wrote: Thu Dec 01, 2022 6:19 am You are forgetting to post "full FreeCAD version info" as explained in:

http://forum.freecadweb.org/viewtopic.php?f=3&t=2264

As you use even Curves WB it will be interesting to have versions of WB you have installed, as some things could change between versions.

A proper "full FreeCAD version info" will give these information and much more.

Regards

Carlo D.
Certainly-

FreeCAD 0.20.1
Curves Workbench 0.6.1

Using this on Windows
"Testing leads to Failure, and Failure leads to Understanding" -Burt Rutan
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LVAeronautics
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Re: Unwrapping a conic loft airfoil section...

Post by LVAeronautics »

hammax wrote: Thu Dec 01, 2022 7:02 am ... trying it with up and down sections of "flying wing"
per facebinder => meshing it => unwrap => and position it by placement => get an unrolled surface.
(why do you need that? => cutting of planking ?)


FlyWing_2.png
Unwrapping the wing sections is needed to create the section sheet metal cuts required to make the molds. They'll then be 4-roll formed, joined together via electron beam weld and placed into fixtures. Multiple molds for the wing & centerbody upper & lower surfaces.

I'll give facebinder a shot; I haven't tried it yet. Will this give me that leading edge 'line' I have see in your product?
"Testing leads to Failure, and Failure leads to Understanding" -Burt Rutan
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onekk
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Re: Unwrapping a conic loft airfoil section...

Post by onekk »

LVAeronautics wrote: Thu Dec 01, 2022 12:38 pm Certainly-

FreeCAD 0.20.1
Curves Workbench 0.6.1

Using this on Windows
What is so obscure in this post?

http://forum.freecadweb.org/viewtopic.php?f=3&t=2264

This is a simple request to add a "proper version info".

like this:

Code: Select all

OS: Artix Linux (openbox)
Word size of FreeCAD: 64-bit
Version: 0.20.1.29410 (Git) AppImage
Build type: Release
Branch: (HEAD detached at 0.20.1)
Hash: f5d13554ecc7a456fb6e970568ae5c74ba727563
Python 3.10.5, Qt 5.15.4, Coin 4.0.0, Vtk 9.1.0, OCC 7.6.2
Locale: Italian/Italy (it_IT)
Installed mods: 
  * QuickMeasure 2022.10.28
  * Assembly4 0.12.4
  * fasteners 0.4.24
  * toSketch 1.0.1
  * Curves 0.6.1
  * Help 1.0.3

As you could see there are much more informations and some of them are "crucial" to solve some problems, as example some methods could not be implemented or have errors on some OS versions, or maybe some "core" libraries could be not correct or have bugs.

A "full FreeCAD Version info" chould show even maybe which one of the different possible building you are using, maybe this is not your case, but as example for Linux there are many ways of obtaining FreeCAD or even running It, even on Windows, you could use "Portable Builds" or a different method.

If you feel brave you could even put the appropriate "FreeCAD full version info" even in the first post editing it using the "edit post" icon that on most styles is a "little pencil icon", this way simply seing first post will give an idea of what version you are using.

Regards

Carlo D.
GitHub page: https://github.com/onekk/freecad-doc.
- In deep articles on FreeCAD.
- Learning how to model with scripting.
- Various other stuffs.

Blog: https://okkmkblog.wordpress.com/
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LVAeronautics
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Re: Unwrapping a conic loft airfoil section...

Post by LVAeronautics »

onekk wrote: Thu Dec 01, 2022 4:23 pm
LVAeronautics wrote: Thu Dec 01, 2022 12:38 pm Certainly-

FreeCAD 0.20.1
Curves Workbench 0.6.1

Using this on Windows
What is so obscure in this post?

http://forum.freecadweb.org/viewtopic.php?f=3&t=2264

This is a simple request to add a "proper version info".

As you could see there are much more informations and some of them are "crucial" to solve some problems, as example some methods could not be implemented or have errors on some OS versions, or maybe some "core" libraries could be not correct or have bugs.
My apologies; I am learning this new system, and did not know how to pull this information. Is this what you are referring to?

Code: Select all

OS: Windows 10 Version 2009
Word size of FreeCAD: 64-bit
Version: 0.20.1.29410 (Git)
Build type: Release
Branch: releases/FreeCAD-0-20
Hash: f5d13554ecc7a456fb6e970568ae5c74ba727563
Python 3.8.10, Qt 5.15.2, Coin 4.0.1, Vtk 8.2.0, OCC 7.6.3
Locale: English/United States (en_US)
Installed mods: 
  * A2plus 0.4.60e
  * AirPlaneDesign 0.4.0
  * Assembly4 0.12.4
  * CurvedShapes 1.0.4
  * Curves 0.6.4
  * ExplodedAssembly
  * fasteners 0.4.24
  * FeedsAndSpeeds 0.5.0
  * LCInterlocking
  * Plot 2022.4.17
  * Pyramids-and-Polyhedrons
  * sheetmetal 0.2.59
  * Ship 2022.4.11
It seems to look the same as your suggestion.

Now, back my initial distress call....

I think I have found a way to get the flat leading edge retained on the airfoil. It involved the following sequence:

a. Importing .dat file (Scale as appropriate)
b. In the Draft WB, change the Wire into a Sketch
c. In the Sketcher WB, manually delete the vertical line at the TE
d. Turn the Sketch back into a Wire in the Draft WB
c. B-Spline the Wire
d. Manually add a vertical line
e. Change into a Sketch

When I did this, I was able to clone this particular airfoil, loft in the Part WB and ultimately unwrap it via the Mesh WB. I assume I can simply import, modify & place my multiple airfoil geometries in the same manner as the previous, and get the result I am looking to get.
Getting Closer.jpg
Getting Closer.jpg (35.01 KiB) Viewed 669 times
Am I off-track on this, or is there an easier/more practical way?

Also, how do I place that leading edge line that separates the upper and lower surface?
Attachments
Unwrap practice 2.FCStd
(69.96 KiB) Downloaded 9 times
"Testing leads to Failure, and Failure leads to Understanding" -Burt Rutan
edwilliams16
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Re: Unwrapping a conic loft airfoil section...

Post by edwilliams16 »

@LVAeronautics
What .dat file are you using and how did you import it? Is the plan to loft multiple different sections? If so it won't flatten without distortion. Is the plan to cut the profile into upper and lower sections and loft them separately?
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LVAeronautics
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Re: Unwrapping a conic loft airfoil section...

Post by LVAeronautics »

edwilliams16 wrote: Thu Dec 01, 2022 6:29 pm @LVAeronautics
What .dat file are you using and how did you import it? Is the plan to loft multiple different sections? If so it won't flatten without distortion. Is the plan to cut the profile into upper and lower sections and loft them separately?
I am importing the Selig format .dat files generated on XFLR-5. Here is the format as shown on Notepad; 100 points total:
Airfoil Format.jpg
Airfoil Format.jpg (99.02 KiB) Viewed 634 times
I imported them while using the Part Design WB (upper left pull-down menu, Import). Is there another way?

The intent is to individually loft individual sections (12 over the halfspan; airfoils are interpolated between the root and tip, are similar but different in shape), separate them into upper and lower halves, and unwrap them. Because you are dead-on that doing a singular loft will absolutely create an inaccurate distortion that will be useless for a CNC sheet metal cut.

How do I separate the upper and lower halves? With that, is the workflow I described in my previous post in incorrect/redundant technique?
"Testing leads to Failure, and Failure leads to Understanding" -Burt Rutan
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Re: Unwrapping a conic loft airfoil section...

Post by edwilliams16 »

@LVAeronautics
A simple python script could import the upper and lower halves of the airfoil separately. This is likely easier in the long run that trying to repair and split the existing wire. Could you upload the file? The uiuc database doesn't appear to have that particular airfoil. I assume it is typical.

So if I understand you, you plan on lofting different but similar airfoils in short enough spans that the flattening distortion can be neglected?
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