March 2, 2012

Managing surge with docklines and snubbers


Totem's parking spot in the Brisbane river comes with lots of current and regular rolling from the wake of passing ferries. Both of these are quite unfriendly to docklines. Poor Totem springs back and forth in her slip, and snaps so hard against the docklines that it honestly hurts me a little inside. We clocked the motion at almost 4 knots (and then learned that our neighbors recorded 6 kts)! The jerking back and forth is tough on lines and tough on the boat- we badly need to absorb the shock.

Jamie wrote about docklines and dealing with these conditions in some detail for this month's issue of 48° North. At the time he was writing the article, we were working through our options. Our assumption was we'd switch to nylon 3-strand line (it's stretchier, unlike the old genoa sheets we have masquerading as docklines) and put on a snubber.

Standard snubber setup
When we bought Totem, there were already two snubbers on board. They were the conventional garden variety snubbers you see around marinas that look like this one pictured. I scanned enough reviews to gather that people love them as much as they hate them. The material matters: some suffer from UV degradation and don't last. They do a nice job of acting like a big hung of bungee integrated to your docklines.

We used snubbers like this while we were in a marina on Bainbridge Island. In hindsight, that must have looked pretty funny. There's not much surge to speak of in little Eagle Harbor! But they were already on the lines- possibly stemming from the prior owner's time at a marina in Hawaii.

One of them was still buried in our transom garage "somewhere"; the other had gone bloop to a watery end many moons ago. You kind of need two for a functional system. We might not find a quality snubber here- friend Toast said the snubbers they saw in Auckland were terribly UV-degraded.

Many people use smaller line to minimize the jerking. It's got more spring to absorb the shock than larger, heavier line. You can put a bigger, badder line on in addition as a backup- but using underspec'd docklines just strikes me as a questionable option.

We have dock neighbors that employ a seriously robust looking setup. It made me wonder if the simple snubber was really enough- check out that monster spring!

Docklines in Brisbane

We wondered if the chain was really smart (seems like a link could get weakened from bending around the cleat under load), but our friend Jason on the cat EA knew otherwise. He's a rigger at West Marine and has replaced busted docklines for a lot of the boats that rock in the swells at the dock in San Francisco. The default solution there is to chain an old tire to the dock cleat, then tie your docklines to the tire.

So...what to do? Buy a snubber? Go for a whole new system? In the end, we defaulted to a choice that has proven to be brilliant on a few levels. Totem has a few spare fenders on board which can't be inflated thanks to a defective pin fitting. They're quality UV resistant construction and have just enough give in them. There's a handy loop at each end to secure to our lines. So now, we've found a use for something that was "broken" and kept a bunch of plastic out of the landfill in the process. And- it WORKS.

Docklines in Brisbane

It looks a little silly, sure. However, several weeks later I can confidently say they work exceptionally well. I no longer feel the need to pat a bulkhead and apologize to our boat when she moves with the surge. But about those docklines...

UPDATE: this did not have long term success. The fender bungee did work exceptionally well, right up until it didn't. The extreme surge in the slip ultimately broke the fender, but it did take a few months. Given less extreme conditions, it would probably have been sufficient and a great way to re-purpose something that was otherwise headed for the garbage. Instead, we just used stretchy lines for the remaining handful of months we spent in Brissie.

4 comments:

  1. Like the idea and we will have to give it a try. While in Kona, the surge actually busted one of our bow chocks. Not good!

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  2. Wow, what a great idea! We don't have any type of snubber yet, but we do have some fenders that can't be inflated ... thanks!

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