For the master thesis ‘Thermal optimization of competitive sailing gear’ research and design was done to improve the thermal comfort of sailing gear for the Dutch Olympic team. The research starts by defining the ambient conditions, target group and the basic human body heat balance. It was found that not the core temperature of a body is the result of heat drawn (cooling) or added to the body (warming) by the environment. The design is focused on single-handed dinghy sailors, as they face the most extreme conditions and exercise levels. Heat generated in the body by exercising is conducted through the skin and the suit materials to the suit surface. At the surface, heat is exchanged with the environment, particularly by evaporation of (spray) water from the surface and convection (wind). Ideas to control these heat transfer modes are applied in a range of suit concepts. A simulation model is made to evaluate the effect of a sailing suit on the body’s thermal balance during a race. Using this model, concepts are evaluated and further detailed. The model is further detailed and validated, to be able to predict the properties and performance of a suit during a match. With this simulation model, the suit design is optimized for a sailing match during the 2012 Olympics in Weymouth. The result of this master thesis are a sailing suit and a simulation model for sailing gear. The suit is designed and optimized using this model, proving both the model’s functionality and the suit’s expected properties.