Investigating force components

In this experiment, mass hangers were tied to both ends of a piece of string and then hung over clamp rods. In the middle, a third mass hanger was added. Graph paper was held behind the string and the set up was drawn so that the angles could be measured. It is clear that although 5.9N and 4.9N are pulling upwards on the string, you can't just simply add them because the sum needs to add up to 6.9N or else there would be a resultant force upwards. So we need to take components. Vertically the total is 5.9sin(40) + 4.9sin(31) = 6.3N. It does not equal 6.9N because there is some friction on the rods that provides the other 0.6N. The percentage difference between the measured total and the actual total = 8.7%.