The yacht basin at Marina Coruna is a little bouncy with northerly quadrant winds. We and everyone else are surging against our dock lines. There are comfort issues with jerking and noise which we have solved with a combination of dock line materials.
We are connected to the dock with three different types of rope. The small diameter blue lines are our normal Spectra 11mm (7/16″) material. As strong as the other lines of larger diameter Spectra has very little stretch which in this situation is uncomfortable.The braided material is a Gleistine “brait” a super stretchy nylon construction. It is being used as a bow line to minimize shock load when the boat rolls. The third line is a Yale Ropes polyester which is being used here for springs (the brait is too stretchy and would allow excessive surging). Both of the latter are 24mm (one inch).
A major consideration is the angle from the boat to the dock. That is why the stern line has been run across the dock. The angle is flat enough that we did not bother switching to a stretchier construction rope. Note that stern and bow lines are doubled up and adjustable from the deck.
Speaking of adjustments, you will no doubt have noticed the winches on deck. These are ideal for windy or surging docks where adjustment under load is a requirement.
Note the angle of the spring lines. These are attached to the widest part of the hull to minimize lateral angle, which is more comfortable than positions further off forward or aft which induce a side load as well as fore and aft load.
Both polyester springs are attached to the welded stanchion base. These are 50mm (2″) schedule 40 pipe welded all the way through the rub rail and very strong.
Finally, a shot of the normal spring, rigged for ease of docking and adjustment. The stanchion bases are used to position and turn the line, which is terminated at the deck winch. The bowline knot is about 3 meters (ten feet) off the dock so that we can reach it from the boat. In normal docking with these knots and bow and spring lines doubled up all four lines can be adjusted or cast off from the deck. However, if the boat is surging the lines squeak as they stretch slightly around the stanchion bases.