# Russian Airfoils Data

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#### Norman

##### Well-Known Member
HBA Supporter
In this airfoils families, Ordinates of the cambered lying sections are obtained by laying off the thickness distributions "perpendicular to the mean lines".
That method introduces more problems than it solves. There have been many discussions about how to properly offset the surfaces from the mean line. Here's one, take note of the little spike in the pressure distribution at the leading edge of the NACA airfoil section, that is caused by the NACA's shortcut to draw in the leading edge radius, there's also a link to the Xfoil archive in post 24 of that thread in which Dr. Drela explains why he didn't implement the rolling circle method in Xfoil.

Because this, scale in one direction, plot mean line by midpoint "Y" ordinates and anything else of this type is only misinterpretation about airfoil section generation and the plot that you obtain is not any related airfoil.
Yep, if you want a thicker version of an existing airfoil the best way to do it is find an acurate thicknnes form of the same family and add the mean line from the airfoil you started with so that you preserve both the camber and thickness distribution. Just multiplying the Y ordinates by 1.n will change the mean line and blunt the leading edge. By blunt I mean that, if you start with an airfoil that has a simple arc segment leading edge, after scaling the Y values the leading edge will be an ellipse with its major axis perpendicular to the chord.

#### wizzardworks

##### Well-Known Member
ultralights, I looked around on you-tube and found a second way to enter multiple points.It starts as you outlined above by opening in something like notepad wherte you replace the space between the
columns with a comma and save as a .txt file rather than the originasl .dat file extension. Then in Rhino they suggest tools/commands/read from file to make the airfoil. Looking closely at it the points
they are connected by straight line segments if you zoom in fairly close. This seems solvable by drawing a control point nurbs curve by selecting the points or end of line selection. Much quicker than
data entry and intuition tells me since the same points are used it would be an identical curve.
I tripped over something else while looking for multiple point entry. When I loft a wing with different root and tip airfoils with both curves closed the results are often strange twisted things. When I
use edit/rebuild on all the airfoils to get the same number of points it always lofts. The testelation lines look like a ruled surface but the 3D surface is fine rendered. The problem with doing this is that all
points on the airfoil are evenly spaced rather than closer together near the faster changing shape of the leading edge like the original .dat file started with. This is where the new bit comes in. If I use
analyze/surface/curvature analysis the leading edge curvature is all ragged and crossed up. Then when I use the surface for a variable radius wing fillet it is a real struggle. I figure saving the curve unrebuilt
I can add it as an overlay and get the fillet command to be more cooperative. Just a thought.

wizzardworks

#### ultralights

##### Well-Known Member
Thanks all very much for your opinions.
I could get a complete report about R-III airfoil from Warsaw Politecnic University.
The report is in polish, I will work a time to translate this.:ban:

#### simflyer

##### Well-Known Member
I wonder if anyone knows the data for the following Russian airfoils:

TsAGI R-3a (or CAGI R-III A-15?)
TsAGI P-III-12
TsAGI P-IIIA-15

searching the internet I was able to achieve the following links:
Airfoils characteristics and coordinates
TsAGI R-3a (12%) (tsagi-r-3a-il)
I want to get more accurate data and the original reports with the exact coordinates it is possible to draw profiles.
Here are coords for TsAGI R-IIIa-15 and some other TsAGI airfoils and data:

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#### renxxx1981

##### Well-Known Member
Thats why P-III equals R-III and P-3 and R-3.... depending on what origin is the printed source for the airfoil.

P-III airfoil was used on vintage russian biplace record breaking sailplane Stahanovec.

On many Russian forums I found out that airfoil P-III is very popular even today. Almost any ultralight or light plane/glider uses that airfoil. And as far I was able to observe Aeros Rigid Wing Phantom, even his airfoil seems to be pretty close to the P-III....and that gives a clue (I am not sure but suspect) also about Alatus AL-12 ultralight sailplane airfoil, as D box is taken from Phantom D-box molds.

Mitja
That's very precious info Mitja! Thanks!

#### pwood66889

##### Well-Known Member
I love the international flavor of this forum!!!!
Percy in NW FL, USA

#### Norman

##### Well-Known Member
HBA Supporter
I love the international flavor of this forum!!!!
Percy in NW FL, USA
We're all stuck on the same rock, Percy, it's just geographic isolation that separates us and that's getting pretty weak.