Explain to an idiot what spring lines are for

[valhalla360]

Originally Posted by Scorpius

No, I've not had the same slip for 35 years. However I'm sure that in that time, counting both local and offshore cruising, I've moored to/at well over 100 different long docks and slips - probably several times that number. And yes, some of them were pretty hairy - sometimes having to run lines ashore, or across fairways, or running out an anchor, to get Scorpius safely out, or having to use the hydraulic anchor winch to pull the bow into the dock when the current was trying to rip it away (Port Neville off Johnston Strait at 2am - effectively single-handing. Don't ask).

Again, you are focusing on lines used for manuvering. This was a discussion of securing a vessel.

[Dockhead]

I'm surprised no one has mentioned the other purpose of spring lines -- not only are they intended to prevent movement fore and aft, but the fact that they go off at an angle dampens lateral motion. If you rig your bow and stern lines as breast lines -- perpendicular to the dock -- then they will snatch up if there is any wave action. Better rig these also at an angle, as proper bow and stern lines, and then once you've added your spring lines, then you are holding the boat against the dock but with plenty of elasticity in the system so you don't have snatching

[valhalla360]

Originally Posted by Dockhead

I'm surprised no one has mentioned the other purpose of spring lines -- not only are they intended to prevent movement fore and aft, but the fact that they go off at an angle dampens lateral motion. If you rig your bow and stern lines as breast lines -- perpendicular to the dock -- then they will snatch up if there is any wave action. Better rig these also at an angle, as proper bow and stern lines, and then once you've added your spring lines, then you are holding the boat against the dock but with plenty of elasticity in the system so you don't have snatching

Unless it's a very wide slip, spring lines normally go almost parallel to the boat providing negligible lateral resistance.

Already mentioned that bow and stern lines need to be long enough to provide some stretch and avoid snatch loading. Ideally, crossing bow/stern lines helps with this (port cleat on boat to starboard cleat on dock and vice versa)....though on monohulls this can be difficult on a narrow bow and some really don't even work for stern lines.

[Dockhead]

Originally Posted by valhalla360

Unless it's a very wide slip, spring lines normally go almost parallel to the boat providing negligible lateral resistance.

Already mentioned that bow and stern lines need to be long enough to provide some stretch and avoid snatch loading. Ideally, crossing bow/stern lines helps with this (port cleat on boat to starboard cleat on dock and vice versa)....though on monohulls this can be difficult on a narrow bow and some really don't even work for stern lines.

As long as there are enough cleats on the dock, you can choose at what angle to put your spring lines. There is no law that they need to go all the way to the bow or stern. I would not rig a spring line parallel to the boat, myself. You lose this function of the lines without any advantage in the other function.

[valhalla360]

Originally Posted by Dockhead

As long as there are enough cleats on the dock, you can choose at what angle to put your spring lines. There is no law that they need to go all the way to the bow or stern. I would not rig a spring line parallel to the boat, myself. You lose this function of the lines without any advantage in the other function.

I've had people run spring lines to the far side of fingers to get a better angle...makes for a tripping hazard. Asked them to rerun them to eliminate the issue.

If you are a 12' beam in a 15' wide slip, at most you can get 1.5ft of offset on the spring lines (assuming you want the boat centered in the slip). Even with a relatively short 15ft spring line, that's a 1 on 10 angle and will provide almost no lateral resistance.

Do you have a sketch? I suspect we are thinking of different things.

[ferrailleur]

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

Please allow me to repost my original question with a crude drawing which shows that I'm not mooring alongside a dock... Please answer my question in blue.
Thanks

[Sailmonkey]

How long are your current lines?

A spring tied from the front piling to a stern cleat has a lot of stretch. The purpose is to absorb shock rather than snap or snub the boat.

This allows you to leave your existing lines a little more slack and let the springs take the load of surge.

[Yellowtulip]

Originally Posted by ferrailleur

Please allow me to repost my original question with a crude drawing which shows that I'm not mooring alongside a dock... Please answer my question in blue.
Thanks

Have you spent time on your boat on the mooring in winds of 30 knots plus? With the setup you have in the diagram it will snatch a lot. Springs add elasticity as others have pointed out. Also if just one of your lines or cleats fails your boat will move around a lot putting more strain on the remaining lines. If you have any swell where you are, then even more so.

[Woodland Hills]

Originally Posted by Dockhead

As long as there are enough cleats on the dock, you can choose at what angle to put your spring lines. There is no law that they need to go all the way to the bow or stern. I would not rig a spring line parallel to the boat, myself. You lose this function of the lines without any advantage in the other function.

I prefer to separate out the jobs of the lines: springs fore and aft parallel to the boat and crossing and then bow and stern lines as close to 90* as possible. That way each line does it’s task in as efficient a manner as possible with the least strain as possible. The springs keep me from moving forward and backward and the bow and stern from moving from side to side. During hurricanes I add another set of springs on the opposite side and double up the bow and stern lines crossing the sterns for more length and more shock absorbing effect during surges. If I could do it without chafing I would cross the bow lines too during storms when I double up the lines.

[valhalla360]

Originally Posted by ferrailleur

Please allow me to repost my original question with a crude drawing which shows that I'm not mooring alongside a dock... Please answer my question in blue.
Thanks

If we are talking about say a 35ft boat and each of those lines is 15ft long and really running at a 45 degree angle, the boat is probably reasonably safe (assuming no line fails...there isn't a lot of redundancy in the setup).

It may not be comfortable in some conditions as that setup won't stop the boat from rotating in place.

Of course, if the drawing is accurate, it's probably not convenient to get on and off as you can't pull it in close to the pier or finger dock without leaving some of the lines too loose.

Is there a reason you are opposed to using spring lines? Once you get the hang of it, hardly takes any time.

[El Pinguino]

Originally Posted by ferrailleur

Please allow me to repost my original question with a crude drawing which shows that I'm not mooring alongside a dock... Please answer my question in blue.
Thanks

I see no need to alter anything in that set up which is essentially a 'Mediterranean moor'
That is almost exactly ( buoys not piles ) how I have been tying up in Ecuador, sometimes with a small finger sometimes without.

Only thing I do different is... when a short finger is on offer ... rig a 'Lazy line' from midships to the end of the finger to haul in when wanting to step on or off

[Dockhead]

Originally Posted by ferrailleur

Please allow me to repost my original question with a crude drawing which shows that I'm not mooring alongside a dock... Please answer my question in blue.
Thanks

I agree with Ping -- no spring line needed there.

[JC Reefer]

Simple, Longer lines stretch more. Dock lines should stretch to allow the gradual release of energy as the vessel bobs about from passing boats and waves.

You should avoid having super tight bow and stern lines to account for tides but the spring lines can be snobed up a bit more, locking the boat in place without ripping out the deck gear.

Nylon is really stretchy compared to other materials. But if it’s 5 feet long then your still not getting enough of that cushioning i think boats need. Check the specs!

[Dockhead]

Originally Posted by Woodland Hills

I prefer to separate out the jobs of the lines: springs fore and aft parallel to the boat and crossing and then bow and stern lines as close to 90* as possible. That way each line does it’s task in as efficient a manner as possible with the least strain as possible. The springs keep me from moving forward and backward and the bow and stern from moving from side to side. During hurricanes I add another set of springs on the opposite side and double up the bow and stern lines crossing the sterns for more length and more shock absorbing effect during surges. If I could do it without chafing I would cross the bow lines too during storms when I double up the lines.

You may be able to get away with 90 degree breast lines (which is what you described are properly called; bow and stern lines go ahead and back at an angle) where you sail, but I would rip cleats out of the dock and snap dock lines where I am if I did that. The way I tie up, all lines are doing work in both lateral and longitudinal directions, and none of them are set at an angle which would create big snatch loads, that is, anywhere near 90 degrees.

[El Pinguino]

Originally Posted by ferrailleur

Please allow me to repost my original question with a crude drawing which shows that I'm not mooring alongside a dock... Please answer my question in blue.
Thanks

You could 'tame the stern' by crossing your stern lines..ie take from stbd cleat to port quarter and v.v. but that always carries the risk of fouling stetn ladders and the like.
Likewise if there was a lot of surge in the berth or you wanted more security you *could* run midship springs... or you could just double up your head and stern lines.