Full Version: Anyone wish to develop a custom script?

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This is wonderful! I can now have my fantasy airplanes grounded in reality even more. :-)

I'll be glad to help with the MoI interface if you need any.

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Thanks,

Any help would be great. So far bemfarmer has been working on things. He would be the one to talk with if you like. Unfortunately, I don't know anything other than Fortran 77, so not much use. Just answering questions and testing things.

Anthony

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I converted the prop_design_geo into javascript, and used some factories.
However, absolutely nothing is displayed on the MoI screen, (except alert messages,) so there is some flaw in the javascript...
Either a factory is being (not) created by using non-points, or is being deleted by subsequent re-useage..?

There is the array index to zero issue. The "simple" math gets longer and longer, there are lots of parameters,
different data types....
Have not tried to add on any extra radius yet.

Also the rail points need to be sliced, like LineWeb script, (lengthwise,) into (3) curves.

Other than an alert text message, there is no debug window to display points ????

I think grafting on some of the SavePointFile script could be used to save some x,y,z values to see if they exist and what they are.

So now I am going to start with a small, very simple, display functioning script, and add on small pieces of prop_design_geo, until it breaks...
:-)

Edit: The new limited script will be called AirfoilPoints.js, use one factory, and only the airfoil parameters...

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Hi bemfarmer,

If you can make a closed curve from the airfoil points, that is the most annoying/boring part to keep doing over. You would have got the hardest part figured out.

Was the screencast any help to you?

Anthony

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Thanks Anthony

Yes, the screencast was very helpful. Going to watch it again, especially the initial portions.
Looks like you are getting good at using MoI.
:-)

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Well, after moving a few factory related scripts around, have (partly) succeeded in creating
a 13 point curve, for the airfoil, using interpret curve.

Edit oops, it should have 27 points,
(The airfoil is incorrectly indexed to TIP, at 13 points.) but happy to have something on the screen..........
Scaled up, it resembles the actual airfoil, sort of.

There is a hook on the end, but looking at the points, it seems like the last two or three points are created in the wrong order (???)
(??Is there any possibility that the fortran code is creating the last two or three points in the wrong order??)


(The rails are nonfunctional, and not at all right, but just need some javascript changes.)
The rails need a factory each for "top", "bottom", and "quarter ( or 3/4) cord".

The highly defective code, is NOT attached.

With MoI units set to meters, the curve is very small, 0 X .01 X 0.1 meters.

Image Attachments:
FirstAirfoiWithHook1.PNG 

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Hi,

There are a few points added so that you can create a circle at the top and bottom. Then using the last point of the real airfoil data, draw a straight line tangent to the circle for the last real control point for the airfoil curve. This is done at the top and bottom (from the right view). The larger circle at the top is the leading edge and the small circle at the bottom is the trailing edge. And yes, the trailing edge circle is really really small. This is why I'm having to use the millimeters unit system. Even the leading edge radius can be too small for MoI v2 on some examples. It won't find the tangent point, do the boolean operations, and other things when in the meters unit system. I posted an updated code that will output in the millimeters unit system.

Once the extra points are found then they are used as the start and end point of the airfoil spline, along with the other points that are in the .XYZ file. Then you mirror that curve. And lastly make arcs through the remaing points. Select the four curves and join them to make one closed curve. This is the curve that will be used for the sweep.

Merry Christmas/Happy Holidays to everyone.

Anthony

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Hi Anthony

In the Prop_Design_GEO of 12/22/2011, the third entry in AFYTAB is 0.0, which is inconsistent.(?) I would think it would be between
0.6880 and 1.0650. (?) (or is this one of the "extra" points?)

(I had AirFoil Points indexed incorrectly to TIP at 13. Was able to correct index up to 26, to generate (I think) 25 points, but going to 27
caused MoI to fail. Weird...
That is it for tonight... I'll have to re-read your post tomorrow...

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Hi,

Yeah sorry for the confusion, I believe that is one of the extra points for the circles. There are four exrta points to make the circles. Then you have to add two more points that are tangent to the circles manually. I was working on the picture attachments when you responded. Make sure to check the attachments again, as I updated them. It's hard to show, but hopefully between the pictures and the screencast it will start to make sense.

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Here is the actual NACA document with the points they specify. They have 0, 0 in there as well. But this isn't a point you would use for the spline. It is a point you would use for the leading edge arc/circle. If you compare the table of points in the Fortran code versus the NACA document, any differences are for the circles/arcs.

Edit; this document is now included airfoil_model.zip file in a later post or on my website.

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Thank you Anthony.

I'll need to study on the extra points, and arcs, and more on the "aerodynamics" and terminology.
The simple factory creates curves through existing surface points, (if they exist via the NACA,) so extra coding would be needed to deal with the arcs, and the extra points.

I'll add in the 1000 meter to millimeter scaling.

My missing 27th point, is actually a missing 1st element. The problem was due to the zero indexing in Javascript,
and the crash was due to trying to acces the 28th element in an array with 27 entries(I think).
So indexing M3 from 0 to <27, ++, should fix this. (I think).

:-)

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Attached is a script to produce the Air Foil portion of Prop_Design_Geo. The Rail portion is commented out, as it needs additional
LeadingFactory/Factories, TrailingFactory/Factories, and QtrChordFactory/Factories work, which should be fairly easy. :-)

The 26 original NACA points were restored to the AFXTAB and AFYTAB arrays, with (per original GEO,) AFYTAB element .019 rounded down to 0.0.
The two each center point coordinates were added to the END of the AFXTAB and AFYTAB arrays. Adding them to the end makes it easier to keep
them separate, (otherwise they could be extracted from their old locations, if it is necessary to keep them in the old locations.)


The two radius arcs have not been done. Can do mirror easy in MoI.

Image Attachments:
AirFoil1.PNG  LeadingEdge1.PNG  TrailingEdge1.PNG 

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As an amusement, I set up the NACA formula (for the symmetric non-cambered profiles) in Excel. It meant I could experiment with the X point spacing. Putting more of them at the front gives a more accurate profile. 26 points is not enough really. I found that 100 points gives a better profile when imported in to MOI, with the points biased to the front where the curvature is greatest.

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Hi bemfarmer,

I downloaded and setup your script. It is running too far to the right of my screen. My screen resolution is 1366 x 768. I attached a picture of the problem. I set it up so that Ctrl+P launches the script. When it launches it runs automatically and a message pops up. Is there a way to have it open but not run right away.

Thanks

Anthony

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Hi SteveH,

Does the equation you are experimenting with work for the NACA 65A009 airfoil? If so, could you share the equation with me. I would be interesting in trying it out. It could be a better way of doing things depending upon how it deals with the leading and trailing edge. I have modeled a bunch of blades using the data file I have, and haven't had any issues. MoI is easily able to curve fit the data from the NACA file. Creating a very smooth airfoil. But I'm always interested in a better way to do things. Perhaps your method will be better.

Thanks,

Anthony

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Here is the formula:



Y is half the thickness above the datum
t is the thickness of the aerofoil as a decimal of the chord

I have attached the spreadsheet I used. It shows the formula at the top as a picture. I have broken down the steps of the calculation to correspond with the formula. I am only showing 29 rows here but you can easily change this to whatever you want. The X figure is in mm direct.

I understand this formula works for all NACA symmetric aerofoils, the variance being in the thickness (t in in the equation). There is some maths rounding error here as in the sheet I have attached, at 500mm (the chord maximum), Y should be zero but calculates to -.225mm. This may be a limitation of Excel, as several of the factors of the equation are very small.

Attachments:
naca general.xlsx

Image Attachments:
Naca Formula.png 

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Just doing a quick google search that appears to be the equation for the NACA 4 series airfoils. Which are not good for transonic use (i.e. aircraft propellers).

I did another search and found a document that uses equations to obtain the ordinates for the 6A series. However, looking over it, I don't think its worth the effort to go that route. I already have the points I need. This wouldn't justify the effort to code.

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Yes, just realised that the equation I used was for the 4 series airfoil. Back to the drawing board.

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Here is the correct formula for a 65A. Too late and too tired to put this in Excel.

http://www.pdas.com/naca456thick6.html

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Oh thanks, I was just on that site, but didn't see that page. Way easier than the document I found.

Edit; Oh looking over it more, it appears to be the same. Rather involved. I don't think this will help me any, as I'm getting good results the way I'm doing it. However, its nice to know how the data points I was using were determined.

Thanks

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