To give you some insight in the various types of ropes, the properties and the relation between all this, we have been doing some research on this and looked at a few practical situations and what this means for you. 

Conclusion

Choosing a line can be a tricky job if you want to use properties of a rope and compare them with other rope - since virtually none of the ropes are exactly the same. Not only stretch is important but also the difference in stretch when the load is slightly higher or lower is important. When the wind is getting stronger and the load on the sail is increasing, the load on the rope is also increasing. These types of load are very hard to state. A most obvious place to ask for these load is the sailmaker of the shipyard.

Next, there is significant difference in stretch between Dyneema and Polyester (at least 50%) whith comparable ropes.