This report presents a method to calculate the frequency characteristics of a vessel that takes into account the dynamic interaction between the vessel and the Ampelmann system. Insight is provided into the dynamic interaction between the vessel and the Ampelmann system and the factors are identified that determine the changing dynamic behaviour of the vessel when the Ampelmann system is activated. Amplified vessel motions reduce the practical workability. The coupled frequency characteristics form input to Ampelmann's workability assessment and a more accurate estimation of the practical workability is obtained. An alternative compensation method is proposed that favours vessel motions and significantly increases the workability of the Ampelmann system on a vessel.