A new dynamic wake model is developed to capture the complex nature of multirotor electric vertical take off and landing (eVTOL) wake systems. Blade element theory is coupled to an advanced dynamic inflow model which is used to inform the convection of the wake. The wake is then used to compute the high resolution inflow at the rotor blades, forming a loose coupling that can then be time-marched. This model is then applied to both an isolated rotor and a notional tandem rotor system at three shaft angles of attack, where the presence of the front rotor is shown to have a large effect on the development of the wake of the rear rotor. A modern free wake method is also applied to the tandem rotor vehicle. The relatively simple model developed in this paper shows good agreement with the free wake calculations for wake ages up to several rotor revolutions.