Wind tunnel test data's validity at low reynolds numbers depends on the accuracy of the test model, the low turbulence level of the tunnel, the instrumentation, etc. I heard Dr. Selig talk at one of the MARCS National Sailplane Symposiums about 1989. He expressed the idea that people who have done wind tunnel testing tend to question the results but, others tend to take the data more seriously than they should.

Martin Heperle was complaining on his web site about some wind tunnel test data for the MH 32. He felt that inaccuracies in the test model made the MH32 look worse than it should in some series of wind tunnel tests.

Another case in point is shown in Fig. 2.14 of Soartech 8 on page 34. The figure compares FX60-100 tests at Stutgart in 1980 with Princeton tests in 1989. The drag coefficient results at the same lift coefficient and reynolds number disagree by as much as 60%!!!!

It sure makes you wonder.