Dock Line Tension

[deblen]

I was taught,in commercial fishing, to tie bow,stern & springs "tight enough to squeeze the fenders" ,when tying to a floating dock or another boat.
No slack allowed or lines will part with surge. Chafe gear may be reqd,but not usually,if using good 3 strand nylon with vessel's cleats very close to chocks-so there is little, if any,stretch motion between cleat & chock.
Keep the stretching off the boat & off anything else that it can chafe on.
If possible,run bow & stern lines up & down the dock like a spring,rather than at right angles to boat.
Works for me,but..
whatever works for you.

[delmarrey]

As usual, everyone has their own option. If possible I try to go w/o fenders. I don't really like side ties unless I'm tied up to a guess dock. I prefer tying off to 4 corners, depending on cleat position. I've seen too many worn spots on the sides of boats. And mine is painted, which makes it even worse.

When living aboard I've spent plenty of stormy nights retrying up neighbors boats who's lines were so loose that the lines just chaffed and snapped. Just like with a sea anchor, you want to keep the chaffing and shock down to a minimum.

FSMike, Navy small craft very seldom have a slip. Usually side tied to a barge or another vessel. In Vietnam (PBR's, Swift's, Mic's and tugs) the only time they were tied up was to check in or pick up ammo/supplies. As for the big ships, we would just go out to sea in typhoons, point up wind and just idle along.

Guy, like I said below, it's common knowledge once something starts moving around in a storm it just gets worse. And that's synonymous with dock lines.

And BTW, show me a marina where one is not going to get hit with foul weather, eventually. Maybe, San Diego or L. A. is the best I know of. Every marina is different, and didn't Boston get hit with Sandy a couple years ago. Boats are only safe under a responsible owner, and even then there are uncontrollable conditions. Boats are always in danger, either by man or nature.

[UNCIVILIZED]

The docks to which you're tying the boat up to are pretty flexible, & change their dimensions & shape quite a bit with each wave striking them, or boat tugging on them. With even the pilings to which they're connected flexing a decent amount when the weather pipes up. Such isn't at all difficult to see. So since the docks & pilings move around like that, you have to allow for some range of motion via your lines.

[markpierce]

With eight attachments (four on each side) to the floating docks, I don't worry much, making sure opposite lines aren't "fighting" each other creating noise and unnecessary wear.

[markpierce]

Note slack on leeward (starboard) side and tension on windward (port) side. Avoiding noise and unnecessary wear.



Sorry, didn't notice previous post worked after receiving internet failure.

[Cruisingscotts]

I have to say snarkyness and disagreements aside, alot of good information showing the norm to local areas and marinas and the respective weather they see.

[Dockhead]

Originally Posted by deblen

I was taught,in commercial fishing, to tie bow,stern & springs "tight enough to squeeze the fenders" ,when tying to a floating dock or another boat.
No slack allowed or lines will part with surge. Chafe gear may be reqd,but not usually,if using good 3 strand nylon with vessel's cleats very close to chocks-so there is little, if any,stretch motion between cleat & chock.
Keep the stretching off the boat & off anything else that it can chafe on.
If possible,run bow & stern lines up & down the dock like a spring,rather than at right angles to boat.
Works for me,but..
whatever works for you.

That's exactly what I was taught as best practice.

The main thing is snatch loads, which can develop if the boat is allowed to move freely, and which can break lines.

In some cases you can't avoid having some slack in the lines, for some specific local reason (dock doesn't float, tied to something which moves differently from the boat, etc.), but in usual cases you should make them as tight as you can. I run the boat in forward to take out slack in lines running forward towards the dock -- tighten, then run in reverse to tighten the rest.

As Deblen wrote, perpendicular lines ("breast lines") should be avoided on small boats except in very calm weather, and doubling bow and stern lines is good practice if it's going to be rough. The angle of the lines helps shock absorption because it magnifies the force, but the same effect can overload the lines if they are not sized properly.

Rubber snubbers work wonders in a really rough harbor.


I spend winters in a harbor somewhat exposed to the NE (Cowes on the Isle of Wight), and after having had lifelines broken there and topsides scratched the first winter in a storm, I had to improve my technique. I went through hurricane force winds in the same harbor, just this spring. Rubber snubbers really help a lot, although keep in mind when you're deciding how to deploy them that they have limited energy absorption ability. I use them not on the main bow and stern lines, but with lighter nylon lines which I run from bow and stern cleats, but at a more direct angle to the dock than the regular bow and stern lines -- to control snatching and not to provide the main holding force.

Whatever you do, don't just leave your dock lines slack. This will allow snatch loads to develop which greatly increase the forces and stresses on cleats and lines. What you are trying to do is control the motion of the boat so that the lines are absorbing the forces before snatch loads can develop.

[Snowpetrel]

Originally Posted by roverhi

On a floating dock, leave the fore and aft lines a bit loose. Snug up the spring lines, however. Don't want the boat surging fore and aft but dancing around on the bow and stern lines takes a load off the cleats, both on the dock and boat, and cuts down on chafe at the chocks.

Why are you looking at power boats for guidance?? Them stinkpottere don't know nuthin.

This is how I do it. Tight long springs to stop surge. They have enough elasticity and length to cope with some up down movement.

The shorter bow and stern lines need a bit of slack to cope with the bow pitching in a sea or wake.

If there is much tide on a non floating dock enough slack is needed for low water.

Sent from my SM-G930F using Cruisers Sailing Forum mobile app

[GILow]

We had some serious weather hit us here last month. During which our boat broke her lines in the pen, despite the lines being theoretically significantly oversized, particularly in comparison to the boats around us. In the ensuing mayhem, a live-aboard opposite us managed to get a few lines onto our boat, but by the time I got down to the club no fewer than five lines had been snapped. They were breaking as fast as he could attach them.


Luckily I had the set of lines that were used to tie the boat down in cyclone season up North in Australia, so I hauled these out of the forward locker and tied the boat down with them. Then I was able to sit back and observe what was going on.


It became quickly apparent that my enemy was kinetic energy. An unusual wave motion was coming into the club, and being right at the entrance to the club, we were copping the worst of it from the port rear quarter (while sheltering the boats downwind of us). The 17 ton boat was describing a circular motion at the stern, and when the upwards motion combined with the sideways motion at the top of the circle, the strain on the lines was clearly enormous. So I used a sheepshank hitch to haul the boat down tight to the dock finger and could immediately see the peak force on the lines reducing, (the woven lines were the sort that collapse inwards under strain so show the relative load clearly.)


Since then I have kept the boat very tight in her pen, although those weather incidents are a once in 25 year phenomenon, any good statistician will tell you that the once in 25 year events can occur tomorrow.


Matt

[The Garbone]

Fixed dock with tidal swing, no way you can keep them tight unless your boat is in a cradle. snug enough to give the fenders a workout.

[barnakiel]

Our lines are generally pretty slack. If the boat moves too much, I would add a soft small diameter line (say 8 mm nylon, etc) as a sacrificial snubber. The snubber I keep it zero slack then.

b.

[1000 islands]

Once when the weather was not great and the waves rising about 3-4 feet, I decided to tie my boat up as tight as possible to the dock so it wouldn't be bouncing around all night.

Sometime around real dark, windy and raining I awoke to feel the boat bouncing like a trampoline.

I grabbed a light and went out to see what was going on and to my surprise two of the dock cleats had become de-attached to the dock and all that was holding the boat was the spring line.

Lesson learned.....never, ever tie up tight always leave a bit of play.

[zeehag]

i was taught not to make boat too tight as damages happen. tugging and jerking must not happen as those cause damages. i prefer my boat to move in its slip. natural action.
causes much less damages to lines docks and boat.
tugging and jerking cause damages just as much as tight lines do. .
my dock neighbor in patriciacane had tight lines and snapped 3. i had loose lines and only lost my mahogany boarding ladder. oops . yes was a loss, but the boat did not break nor did my aged lines. the only line i used that chafed was the heavy hawse line i placed around the stbd piling. i did pop one cleat, windward side, bow, but i had 4 other lines in play and the line around that piling did not chafe, by miracles....winds were clocked at 200 mph plus gusts.....
always use spring and breast lines to secure boat. the more the better, and make sure there is no tugging nor jerking with motion of boat.

oh yes i use both sides of dock for affixing my boat.

[deblen]

Originally Posted by The Garbone

Fixed dock with tidal swing, no way you can keep them tight unless your boat is in a cradle. snug enough to give the fenders a workout.

Yes-fixed dock in tidal area requires different tactics.