Explain to an idiot what spring lines are for

[Uncle Bob]

Originally Posted by Ballsnall

wtmf is correct in how spring lines should be set. The main purpose of spring lines is in the name. They act as springers to absorb shock loads from fore & aft forces and also from laterally away from the dock. The purpose of all dock lines is to hold the vessel in position but springers also have the advantage of being able to accommodate a wide range of tidal movement without affecting the vessels relationship with the fixed dock. You would set the springers to hold the vessel in the exact position and then set bow & stern lines loosely more as a backup should a stringer fail.
Generally, springers are made of larger diameter mooring line, approximately the length of the vessel or slightly more and with a large eye on one end, or for vessels using the same dock are made to exact size with eye each end and make regular docking a breeze. They are also the perfect line for bringing a vessel into and off of the dock lines in a cross breeze.

Hi, I would tend to disagree that springers should be of a larger diameter line, I believe that much like a snubber on an anchor chain, they should be of a size that allows a longitudinal elongation to absorb the energy of the boat surge, I use nylon line one size smaller than I would for a dock line. I have to admit that I keep my boat on a mooring and only utilize docks occasionally.

[TeddyDiver]

The brest lines eliminates the rolling and pitching movement of the boat, which just adds unnessery stress over the lines and cleats. Rolling and pitching doesn't move the boat anywhere in the slip as it's just a low frequency oscillation. Spring lines long enough have no effect for rolling but keep the boat in place with minimum stress..

[slug]

Originally Posted by ferrailleur

Don't understand the usefulness of spring lines when docked at a slip. I read many manuals and asked many sailors..... No cleat cut/definitive answer. I still don't understand. Am I missing something big or an I a total idiot?
Don't hold back your comments please.


My docking situation: I have two bow lines (secured on pilings) and two stern lines cleated on the pier.... (reverse situation if berthing the other way).

The boat can move a little fore and aft and side to side to adjust with a max three feet tide.

How in the world a spring line going to help with fore/aft movement of the boat which is already tied four way fore and aft?

Thanks

Springs keep you on your fenders ..without opposing spring lines .fore and aft ...the boat would saw back and forth ...and your fenders would loose their set

[Chas.7]

Hello,
A spring line is used for towing.
It is used to power the boat against the dock or to spring the stern out to leave a dock. These things are done in a commercial environment, but if your in a dock that you can't get out stern lines you may be able to get out a few springs.
Good luck

[stevengouch]

I think it looks awesome