They were real bad compromises to keep the radiator as close as possible to the engine and were poor setups. There are lots of examples of what I am talking about. Figure 2 shows the side and front view of the plane. The solution to the problem was a big, ugly forward set radiator. The propeller is forcing the air back, but by thrashing through the air it creates a lot of turbulence and strong flow around the fuselage.
Every blade creates a pulse when it comes by the radiator.
Go back to Fig. 1 and look at the trailing edge of that airfoil. The air behind the airfoil is turbulent and disturbed, at least three chords wide behind the airfoil. So anything three times the chord ofthe propeller blade, away or closer to the propeller, is in that turbulent area and gets the pulse of the blade. You will notice the wind blowing throhgh the car. Imagine the car being the radiator.