Dear new friends, I want to take this opportunity to introduce myself. I am retired due to health problems and I lost my last job as an employee about a decade and a half ago. So to keep the muscle located between my ears busy I decided to reengage into modelism but due to the tougher financial situation I decided to go for building a sailboat model. they are less prone to crash! Now I have used the project of building such a model, I am getting to complete one decade working on it, as a platform that gets me in touch with the most diverse technologies. Additionally, as a former fan of Apple Macintosh computers I like to evangelize people by sharing the thoughts and a certain amount of knowledge I keep building myself. I started promoting the use of self build electronics with the goal to help naval modelists to overcome the inhibition to deal with self build electronics by promoting a tutorial of a friend of mine that did introduce newbies to, starting from en electronic circuit on paper build their own experimental board and such to learn that with some few building blocks a lot an be achieved. Now a lot of time has passed since I started and in the course of my work on my model sailboat, called Carina, I made up my mind to define a concept for a sheet control system of my own. A sheet control system is a system that allows a user on a R/C transmitter to control the position of the sails by setting how much sheet or lines are available for the sail to open. Now my model Carina follows the example of a sailboat called Endeavour and this meant that it has to be able to change the length of the sheet by 8.4 meters. This picture shows the pulley consisting of 7 drums in 6 blocks through which the sheet runs from the boom of the sail to the deck, where in a model a winch translates the instructions given by the operator on his R/C transmitter. This picture gives you a first impression about the complexity of my sheet control system. Due to reasons I can present on request, I received a lot of warnings from seasoned naval modelists specialized in sailboats why my system is not going to work. Additionally, myself reflecting over the concept have discovered a number of issues that set additional demands for the implementation of my system. One of the consequences of this was, that I had to assume that as I would go more and more into the details of the implementation, I might find more critical issues. As my model sailboat Carina works taking its energy from batteries on board it became evident that the energy efficiency of the design would be an important aspect to take into account while designing the implementation of my sheet control system! During the investigations and analysis I did i discovered a methodology called "Design by Modelling" and so I decided to apply this methodology to design my sheet control system. So, and this I plan to present in a thread of its own, not being sure yet where in this forum I have to place it. So I have decided to start with a relatively simple part of my sheet control system, the pulley as shown in the first picture I included here. This is pure physics, in detail it is what is called "System Physics" and it applies methodologies coming from the "Dynamic Systems" science. I basically plan to model a single drum around which the sheet lays around and find by combining the models, one instance per each of the 7 drums that make up the pulley so that I can find out at which strength of the wind blowing into the sail, taking into account in which angle it is blowing into the sail the forces from the boom of the sail pulling the sheet is equal to the sum of the forces resulting from the friction between the sheet and the individual drums. So I know from which effective wind strength on the sail of my model Carina will be able to pull more sheet against the sum of the frictions between the sheet and the 7 drums. I understand this is just part of my goal, but a nice way to teach myself the techniques involved! Just to give you an advice that might wake up your interest. I will not be dealing with forces but with impulses, reservoirs and flowing dimensions!