I recently came up with another airfoil to which I cannot locate coordinates to.
The model plan says it used an N.A.C.A. 65018 airfoil. My thought is that it resembles a N.A.C.A. 65A015. But not exactly thick enough. Anyone have better coordinates than I have been using?

Wm.

You can multiply the y-ordinates you have by the difference between the thicknesses and arrive at the proper shape.
18% is 20% thicker than 15%, so use a 1.2x factor,

You can use javafoil to generate coordinates for any NACA airfoil.

http://www.mh-aerotools.de/airfoils/javafoil.htm

I have Compufoil and Airplot7. With both, the thickness can be altered a few percent, However, when done the altered ones do not resenble the foil shown on the plan. The come out always too thin and too blunt nosed.


Wm.

The "A" is the culprit then. The 65018 and 65A018 are not the same. Javafoil also lets you specify that modification or not. Here are the coordinates generated (no A modification):

1.00000000 0.00000000
0.99726095 0.00027138
0.98907380 0.00111974
0.97552826 0.00264174
0.95677273 0.00497904
0.93301270 0.00829152
0.90450850 0.01272445
0.87157241 0.01837336
0.83456530 0.02525122
0.79389263 0.03326198
0.75000000 0.04218423
0.70336832 0.05166773
0.65450850 0.06124429
0.60395585 0.07035277
0.55226423 0.07837701
0.50000000 0.08469334
0.44773577 0.08872392
0.39604415 0.08999086
0.34549150 0.08836999
0.29663168 0.08448896
0.25000000 0.07906202
0.20610737 0.07269250
0.16543470 0.06583322
0.12842759 0.05876755
0.09549150 0.05161156
0.06698730 0.04433498
0.04322727 0.03679746
0.02447174 0.02879447
0.01092620 0.02010687
0.00273905 0.01054763
0.00000000 0.00000000
0.00273905 -0.01054763
0.01092620 -0.02010687
0.02447174 -0.02879447
0.04322727 -0.03679746
0.06698730 -0.04433498
0.09549150 -0.05161156
0.12842759 -0.05876755
0.16543470 -0.06583322
0.20610737 -0.07269250
0.25000000 -0.07906202
0.29663168 -0.08448896
0.34549150 -0.08836999
0.39604415 -0.08999086
0.44773577 -0.08872392
0.50000000 -0.08469334
0.55226423 -0.07837701
0.60395585 -0.07035277
0.65450850 -0.06124429
0.70336832 -0.05166773
0.75000000 -0.04218423
0.79389263 -0.03326198
0.83456530 -0.02525122
0.87157241 -0.01837336
0.90450850 -0.01272445
0.93301270 -0.00829152
0.95677273 -0.00497904
0.97552826 -0.00264174
0.98907380 -0.00111974
0.99726095 -0.00027138
1.00000000 0.00000000

It's also possible that the airfoil on the plan isn't what it's labeled.
Profili will generate a NACA foil..
The 65A015 and 65A018 look like this..
Profili won't accept a 65018... needs a dash or letter between the 65 and the thickness
I tried the Java-foil at Martin's site.. it locked up the computer.

Wm:
Here are a couple of exerps from the NACA Tech Report #824 "Summary Of Airfoil Data".
The first attachment shows the lift characteristics, shape, and coordinates for the 63-015 and 63-018 airfoils. The second attachment is a partial section of the numbering system for the 6-series airfoil.

WS.....

I copied what you noted and placed into Compufoil then into Autocad. The initial 70% fit right over the drawn lines from the plan. The last 30% was too thin. -Which is normal for models. I had to thicken up the area around the T.E. to fit available balsa wood stock and DuBro hardware items.

Overall it fit better than the 65A which had been generated via a library file.


THX


Wm.