the online data for the airfoil (the SG6050) that i am using is somewhat lacking  , BUT it is real close to the NACA4415 ,which there is lots of data for , i believe i stated that earlier in this thread .
its not exact , but its close enough for me :)
the differences i can see are the sg6050 has a slightly pointier nose , it is a tad thicker , and lacks the slight camber twards the trailing edge , but like i said close enough for government work.
i agree the pressure, on the lower part of the graph ,is the pressure above the foil , from the incident wind side of the foil, even though they call it a coeficient it is really sort of a direct pressure reading from pressure sensors located on the upper and lower part of the airfoil ,i'll try and find the part in the pdf where they talk about  the pressure sensors and how the data is presented.

Three individual pressure transducers read tunnel total pressure, tunnel east static pressure, and tunnel west static pressure. Before the test began, these transducers were bench calibrated using a water manometer to determine their sensitivities and offsets. Related values were entered into the data acquisition and reduction program so the transducers could be shunt resistor calibrated before each series of wind tunnel runs.
The angle of attack potentiometer was a linear rotary potentiometer and was regularly calibrated during the tunnel pressure transducers shunt calibration. The angle of attack calibration was accomplished by taking voltage readings at known values of set angle of attack. This calibration method gave angle of attack
readings within ±0.25° of actual over the entire angle range.
Two ESPs were calibrated simultaneously using the DACU and PCU. At the operator's request, the DACU commanded the PCU to apply known regulated pressures to the ESPs and read the output voltages from each integrated pressure sensor. From these values, the DACU calculated the calibration coefficients and stored them internally until the coefficients were requested by the controlling computer. This calibration was done several times during a run set because the ESPs were installed inside the model and their outputs tended to drift with temperature changes during a test sequence. Frequent online calibrations minimized the effect.
Finally, at the operator's request, pressure measurements from the airfoil surface taps and all other channels of information were acquired and stored by the DACU and subsequently passed to the controlling computer for final processing.

Data Reduction
The data reduction routine was incorporated as a section of the data acquisition program. This combination of data acquisition and reduction routines allowed data to be reduced online during a test. By quickly reducing selected runs, integrity checks could be made to ensure the equipment was working properly and to enable timely decisions about the test matrix.
The ambient pressure and tunnel air temperature were manually input into the computer and were updated regularly. These values, as well as the measurements from the tunnel pressure transducers, were used to calculate tunnel airspeed. As a continuous check of readings, both the tunnel individual pressure transducers
and the ESPs, read the tunnel total and static pressures.
A typical datum point was derived by acquiring twenty data scans of all channels over a 1-second window at each angle of attack and tunnel condition. The reduction portion of the program processed each data scan to coefficient forms Cp, Cl, Cm¼, and Cdp using the measured surface pressure voltages, calibration coefficients, tap locations and wind tunnel conditions. All scan sets for a given condition were then ensemble averaged to provide one set. All data were saved in electronic form. The data were not corrected for any tunnel wall effects, etc.
Test Matrix
The test was designed to allow an extended angle of attack range of -60° to 230° and Reynolds numbers of 1, 1.5, and 2 million with and without LEGR. Tabular data in Appendix B contains the actual Reynolds number for each angle of attack. The angle of attack increment was four degrees when ����<-20° or ����>40°, two degrees when -20°< ���� <10° or 20°< ���� <40°, and one degree when 10°< ���� <20°. All test speeds and angles of attack were set for model clean and LEGR conditions.



For some cases, VGs were mounted at the 30% chord position on the model's upper surface only. The VG strips were provided by U.S. Windpower and were the exact type used on wind turbines in the field. Test conditions while the VGs were applied included clean and LEGR data at 1 and 1.5 million Reynolds numbers
over an angle of attack range of -20° to 40°.

Summary
A NACA 4415 model was installed in the OSU/AARL 7x10 subsonic wind tunnel and tested at three Reynolds numbers and with model clean, roughened, and with VGs. Table 1 is a summary of the aerodynamic coefficient data for the NACA 4415.