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Boat Bondage!

8K views 15 replies 14 participants last post by  CaptTom 
#1 · (Edited)
I was at a public dock with major surge this weekend. My strategy with surge (and in general for that matter) is to use big fenders, spring lines, and give the boat lots of dock line so she can move independently from the dock. Another boat owner saw my boat dancing around, and asked if I shouldn't pull the boat tighter to the dock. I explained my method, and he seemed to buy it.

An impressive 60-70 foot power yacht was tied to the same dock. IMO, it didn't have large enough fenders (and possibly the wrong type), and was taking a beating from the surge (yeah...it was THAT bad). Three guys came off the yacht and started cinching down on the dock lines, trying to make them as tight as possible, then went back aboard. I thought: "guys...you are not going to win that battle!" Five minutes later...BANG...BANG...the lines started snapping (and they were good sized lines!). The guys came back out and started untying the Yacht. I thought "Good, they are going to take her out of here". They did, and proceeded to turn her around and tie her up in the same spot (Presumably so the new side would match the beaten up side? She HAD a lovely Navy blue hull BTW!). Seems like a classic case of more money then sense.
In any case, how do you deal with surge? Put her in bondage, or let her dance?
 
#3 ·
Was the power boat moving around so the bow would face the surge? That's a good idea.

I guess, I'm an "everything in moderation" kind of guy. In those conditions, I don't want the lines so tight that a jumped fender has no chance of slipping back in, nor do I want so much slack that the lines are getting too much momentum when snapping on their cleat. Also don't want so much on the bow and stern that the surge can lift the topsides above the bottom of the fenders.

If conditions are bad on a floating dock, my preferred method is to secure the fenders directly to the dock in a way that they can't jump. All of our fenders are the type that the line passes through, so they could be hung horizontally, when desired.
 
#10 · (Edited)
Was the power boat moving around so the bow would face the surge? That's a good idea.
That is probably what they were thinking, as it's the only reasonable explanation. However, this surge was off the beam, and I don't see boat direction making much difference in this case. It actually seemed like the only reason they realized there was a problem was because their Martini's were spilling inside the yacht!
They were using those orange ball fenders, which were getting tossed up on the dock, which was apparently why they cinched the boat down. At that point the tension on the lines was completely vertical. Had it not been a commercial dock, I think they would have pulled the cleats out of the dock if the lines hadn't snapped first.
What is the theory behind of those ball fenders? I've always thought they would be prone to exactly this problem. I see them on commercial boats, so I know they must have some use. They seemed too small for this boat anyway.
 
#7 ·
I cinch her down tight in the direction of the surge (for and aft in my case) to prevent movement, we get a lot of tidal surge which stretches and cuts lines very quickly if left unchecked. I also use heavy chafe guards at all the turning points.

We survived the Japan tsunami surge using this method. In fact, it just occurred to me I haven't had to replace lines since before the tsunami.
 
#8 ·
When I was on a floating dock I'd double up lines before a storm. My normal 1/2" lines, then my 5/8" storm lines tied with a little slack. As the 1/2" lines started to stretch the 5/8" lines would start taking the load. Seemed to work well and prevented that sharp jerking motion.

I also doubled up my fenders at different heights, so if one popped up above the dock the other would still be in place.
 
#9 ·
I get surges all the time...really
I am tied up on a comercial dock, 25' under me, on average, so when the swell is running, she prances...
The water literally moves along the dock about 6' back and forth. The only workable solution for me are long, stretchy spring lines. I dont mind the boat moving, a few feet at the most, but if you let her pick up speed, she will ripp the lines and take the dock with her. So, the idea is to dampen the motion, without presenting anything hard to oppose it. Spring lines do it best... and vertically hung fenders, allowing the boat to roll.
 
#12 ·
L124C, Where was this guest dock? Was it the public dock at the Ferry Building? I've heard a lot of nasty things about it. So much, that MrsB prefers to use South Beach's guest dock and walk to the farmer's market.
 
#13 ·
To tie up to a public dock I use large fenders, spring line and snubber on both bow and sturn line. This seems to work well for me.
 
#14 ·
I tie my boat up so that the lines are just loose enough to prevent them from being stretched, but tight enough so that there's not much obvious slack. This allows the boat to move a bit, but without building much momentum before the lines one one side or the other begin to take up some strain and start to stretch. I also keep the spring lines a bit tighter than the bow and stern lines. That way the longest lines (i.e., the spring lines) are the ones taking most of the load, so their greater length can absorb more of the "shock" loads. Since my slip has fingers on both sides, I can keep the boat from contacting either side, and use fenders more ore less as a last "line of defense"
 
#16 ·
A couple of things that, based on what I see at most docks, a lot of people don't seem to know. (1) A dock line that's held up fine for weeks during settled weather, can chafe through in a very short time when exposed to rapid movements. Especially where there is any kind of turn or riding over even a smooth edge. (2) Nylon dock lines have a lot of stretch, especially three-strand but not as much with double-braid. The longer the line, the more shock loading it will absorb. Spring lines should be as long as possible, and no lines should go directly from the cleat at a 90 degree angle to another cleat below it.

The fact that the crew of the large yacht above didn't know this shows their inexperience.
 
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