Profile Generator (Airfoil) CustomFeature airfoil database has error for some common airfoil shapes.

john_longphre

Hi. This tool is super old but super useful for me.
The NACA 23015 and NACA 23018 are two of the most widely used airfoil sections on aircraft (from the Beechcraft Bonanza to the Focke-wulf 190 and tons of other aircraft). 
The ProfileGenerator Custom feature is great but it has a few errors in the source data for these two airfoils. Long lines are produced instead of proper airfoil shapes. 
The owner/creator of this feature has abandoned the feature. No response after multiple attempts to contact him.
How can we edit the airfoil coordinates database? (I am new to FeatureScript and am bewildered, frankly). 
In ProfileGenerator's Featurescript editor, I see this: 
"aerofoil" : lookupTablePath({ "Aerofoil" : "NACA 23015", "DataBase" : "UIUC" })

I think the custom feature's UIUC database must have an error for these two airfoils: 
From  UIUC Airfoil Data Site (illinois.edu)   ,the correct coordinates for NACA 23015 are: 

NACA 23015
1.0000     ......
1.0000     (0.0016)
0.9500     0.0112
0.9000     0.0204
0.8000     0.0373
0.7000     0.0525
0.6000     0.0661
0.5000     0.0774
0.4000     0.0859
0.3000     0.0905
0.2500     0.0908
0.2000     0.0892
0.1500     0.0852
0.1000     0.0764
0.0750     0.0690
0.0500     0.0589
0.0250     0.0444
0.0125     0.0334
0.0000     ......
0.0000     0.0000
0.0125     -0.0154
0.0250     -0.0225
0.0500     -0.0304
0.0750     -0.0361
0.1000     -0.0409
0.1500     -0.0484
0.2000     -0.0541
0.2500     -0.0578
0.3000     -0.0596
0.4000     -0.0592
0.5000     -0.0550
0.6000     -0.0481
0.7000     -0.0391
0.8000     -0.0283
0.9000     -0.0159
0.9500     -0.0090
1.0000     (-0.0016)
100.00     0.0000

The correct coordinates for NACA 23018 are: 

NACA 23018
1.0000     0.0019
0.9500     0.0132
0.9000     0.0239
0.8000     0.0440
0.7000     0.0618
0.6000     0.0775
0.5000     0.0905
0.4000     0.1004
0.3000     0.1055
0.2500     0.1056
0.2000     0.1036
0.1500     0.0986
0.1000     0.0883
0.0750     0.0801
0.0500     0.0692
0.0250     0.0529
0.0125     0.0409
0.0000     0.0000
0.0125     -0.0183
0.0250     -0.0271
0.0500     -0.0380
0.0750     -0.0460
0.1000     -0.0522
0.1500     -0.0618
0.2000     -0.0686
0.2500     -0.0727
0.3000     -0.0747
0.4000     -0.0737
0.5000     -0.0681
0.6000     -0.0594
0.7000     -0.0482
0.8000     -0.0348
0.9000     -0.0194
0.9500     -0.0109
1.0000     -0.0019

Is there some way to correct the database used by the ProfileGenerator custom feature?

GregBrown

Indeed it appears there is spurious data in the resource being used by the custom feature. This (I'm speculating here) may have been due to the scripts that were run to convert the UIUC data into the author's own format. For example the UIUC website source for NACA 23015 is https://m-selig.ae.illinois.edu/ads/coord/naca23015.dat which has a bunch of potentially unexpected characters. That last coordinate position of 100.0 0.000 is also way out of spec! This is the cause of the long line BTW.

The other problem with the old custom feature, aside from being largely abandoned, is the use of opFitSpline [edited to correct: skFitSpline is what I meant - same issue though] to create the splines between all the raw data points. If you look at NACA23024 (which does successfully build) you'll see an... um...  undesirable curvature plot. Zooming in you'll see issues at the leading edge (the two splines are not tangent) and so on. 
 

Fortunately there is likely to be a new custom feature (completely unrelated to the old one) coming out very, very shortly! You'll want to check that out when it launches. 

john_longphre

As always, thanks Greg.  I see that aberrant number "100" now. Makes sense. Looking forward to a new airfoil shape generating custom feature. 

jotham_barmentloo

Hi @GregBrown, I'm much in the same boat as John here with the curvature generated by this plug-in being a bit weird and wanting to use foils not in the database.

It is great to hear you're working on this! Just checking in it's been a few months - did it release anywhere at any point? Where could I find out more?

Eagerly awaiting any news. : )

Thanks

eric_pesty

jotham_barmentloo said:

Hi @GregBrown, I'm much in the same boat as John here with the curvature generated by this plug-in being a bit weird and wanting to use foils not in the database.

It is great to hear you're working on this! Just checking in it's been a few months - did it release anywhere at any point? Where could I find out more?

Eagerly awaiting any news. : )

Thanks

Check this thread, this might help:
https://forum.onshape.com/discussion/24730/new-custom-feature-havf-profiles-standard-airfoil-profiles#latest