Using a simple absorption line model the phase dependent effects of ‘wind eclipses’ have been studied for the N IV 1718Â line in the WN4+05 binary, HD 90657. The varying strength of the absorption, as measured by the equivalent width, has been compared with the model for a range of wind parameters and assumptions. It is found that the fraction of absorbing atoms drops quickly, to the first or second power of the radius, and that a significant fraction persists beyond 60 R⊙.