On Sat, 02 Dec 2006 21:36:48 +0000, Scott
wrote:

I could not find info on a plain old Y-15. Did find some references to
the Clark Y, Clark YH, Clark YM15, etc. They all apear to have a
slightly curved bottom plot all the way back to the trailing edge,
whereas the Y-15 in the Georgias plans is flat from about 15% back from
the leading edge all the way to the trailing edge.

Scott wrote:

Ok, I ran into a little problem...

I'm laying out the rib design for a 1931 Georgias Special and it uses a
Clark Y-15 airfoil. The coordinates (stations if you will) for upper
and lower surfaces start at the leading edge and go back to the rear
edge. Chord is supposed to be 48". Adding up the distances in the
drawings (the 1931 Flying and Glider Manual, reprinted by EAA) add up to
54 inches. So...does anyone have the airfoil coordinates for this
airfoil (and I assume they would be expressed as something like 2% (aft
of leading edge), bottom =0.75" lower surface and 1.5" upper surface, 5%
(aft of leading edge), bottom surface = 0.25", upper surface = 2.25",
etc.)? It would be even easier if someone had the coordinates for one
with a 48" chord

Thanks for any help!

Scott


what you need scott is the abbott and von doehnoff classic book.

clark Y has a flat bottom and the ordinates are from a line through
the flat bottom.
the more usual ordinates are from the chord line.
NACA 4415 is the 15% clark Y with the ordinates referenced to the
chord line.

if you are carving a prop the naca 44xx series IS the clark Y at
various thicknesses.

dont ask how we know this but there is an aero engineer who will smile
at the thought of the discussion/argument we had before we realised
this.

btw the clark YH is a modification to the standard clark Y to
constrain the centre of pressure. the clark Y has a cp that wanders
with speed and angle of attack making for an aircraft that requires
constant trim attention. the YH was supposedly an improvement.

if you want a really sweet flying classic aerofoil the naca23012 with
washout to tame the stall is superb.

Stealth Pilot