To design more efficient sailing boat sails and to analyze the efficiency of a sail trim on the water, it is very helpful to have the ability to obtain a digital copy of real-life sail configurations. As a step towards obtaining such digital copies, the Sailing Innovation Centre in collaboration with GeoDelta has created point cloud measurements from sails by placing physical markers on them. This paper introduces a physics-based reconstruction method that uses a known sail rest shape combined with this point cloud data to reconstruct the sail configuration at the time that the measurement was taken. By using a physics-based sail model and the knowledge that the sail is subject to gravity and wind forces together with a known sail rest shape, we can create plausible reconstructions even for areas in the sail where fewer to no markers are placed. Using measurements that were taken before this reconstruction method was proposed in combination with an approximated sail rest shape and material properties, our reconstruction method was approximated to have an average reconstruction distance below 1cm for a 2.5m by 4.5m sail. Taking new measurements following our proposed guidelines in combination with having a more correct sail rest shape and better knowing the sail material properties is very likely to yield even better results.