I have written about the best procedure for docking at the Suquamish public boat dock in the "Recommended Cruises" section. I mentioned that the best location to dock was on the West side of the dock so you would be protected from boat wakes coming from the Sound on the East side of the dock. On our recent trip to Sully's for lunch we took this advice and waited for a spot on the West side. We had just docked and secured the lines when we were hit with significant waves from a passing pleasure boat going fairly fast. The pilings on this dock traverse up through the dock itself with quite a bit of clearance between the dock deck and the piling. The result is a series of three different reactions to the incoming waves: the pilings moving with the wave, the dock itself bouncing off the waves and the pilings, and the boat bouncing off the dock. They do not move at the same frequency and the boat and dock are often out of sync and bouncing into each other. When moving apart, the dock lines are strained and any slack allows the boat to move significantly away from the dock. They are somewhat elastic and when the motion changes to come towards the dock, while the dock comes towards the boat, the result is a violent collision. The dock also rolls along it axis resulting in the contact points varying in height between collisions.
When the waves hit we could not adjust our lines since it it took all of our concentration to stay upright standing on the dock. We watched helplessly as the boat and dock banged together almost fully compressing the fenders. Fortunately we had plenty of fenders at the right height and in the right places and an stern and bow spring line in place. As soon as the waves subsided, we tightened up our lines significantly, especially the spring lines.
Next time I will put all of the fenders on the starboard side, stagger the height slightly to cover the entire hull of the boat and have the lines tighter compared to when we are tied up at the Marina.