Rocking / Rolling Dock at Pier 39 in SF

[Farlander]

I was recently a guest at the Pier 39 marina in San Francisco. While the location is great, the docks themselves are very rolly. I think I would have been calmer at anchor. A phone call to the marina reveals the staff there have a very 'that's just how it is' attitude with everyone convinced that the tidal surge is what causes the rolling. I studied the problem briefly and came to my own conclusion, and now I'm looking for input to support or counter this theory.

What I witnessed was glassy flat water, and the docks swaying back and forth + up and down approximately one foot in either direction. I saw many boats tied up suspended by the four corners in the middle of the slip - not tied tight to either finger. One offender at the beginning of my row, a derelict looking sailboat, was loosely tied and had scooter tires on all the dock lines acting as shock absorbers. What I witnessed was the slightest breeze would start to move the vessel, which would then start pulling on the dock lines, and the extra bounce from the scooter tire stretch caused the boat and the whole dock to start rocking like crazy.

I suggested the marina encourage or require their guests to tie up tightly to the leeward fingers, and get rid of the added rebound caused by all the scooter tire shock absorbers, and they scoffed at me.

Who has experience with rolly marinas and can attest to the cause being tidal surge related or maybe actually being caused by wind and poorly secured vessels?

Thanks in advance,

[gamayun]

It's tidal surge as well as the wakes from the ferries. Everyone uses the tires as snubbers or else their dock lines break on a regular basis. I've seen marina personnel there chasing down wayward boats because they often break loose. Go to other docks on the city front and you'll feel the same effects but their configuration is more open so the energy doesn't bounce back and forth like it does at Pier 39 with the nearly enclosed breakwater. I don't have (and never looked for) the data to back that up, but I'd bet that's your answer if you look into it further. Wind alone can't set up cavitations that cycle through like that.

[Mystic38]

my apologies if this sounds rude to you, but they were right to scoff at you.

Originally Posted by Farlander

I suggested the marina encourage or require their guests to tie up tightly to the leeward fingers, and get rid of the added rebound caused by all the scooter tire shock absorbers, and they scoffed at me.

Its unclear why you believe you are an expert in this area, but tying up tight to docks is simply a way to dramatically increase wear and stress on all parts of the setup... the docks do not move..and the boats do.. its how it works.

what you propose would simply make everything worse as it is the fact that boats are more loosely tied, and some use shock/snubbers that allow the boats to respond to water conditions while mitigating any forces on the dock..

[svHyLyte]

Originally Posted by Mystic38

...tying up tight to docks is simply a way to dramatically increase wear and stress on all parts of the setup... the docks do not move..and the boats do.. its how it works.

Ah... While I agree that mooring lines should not be unduly tight, nor lack snubbers--and for Pier 39 big snubbers--the docks at Pier 39 are floating and move ALOT, with our without a boat moored to them. With a 6' average tide, virtually all of the dockage in the Bay Area is floating. Surge and wakes are a fact of life in the locale but particularly at the City Front.

FWIW...

[Nicholson58]

We have found in some areas that the surge is almost invisible but that water below the surface is scooting around. If your keel is perpendicular to the movement you will roll a lot. Especially true if you tie up tight. If the period of the movement matches the natural frequency of your boat’s roll it can get large. We had this happen in a Lake Michigan marina nearly a mile up river from the lake. Conditions on the lake were driving big stuff into the channel. We were pitching +/- 15 degrees with no visible water movement and glossy. Once we slacked lines and de-coupled the boat from the rigid docks the roll nearly disappeared.

I know it’s just a fresh water puddle but this is that harbor entrance with waves occasionally topping the 52 foot light.

[GordMay]

Greetings and welcome aboard the CF, Farlander.

[jonarck]

Whatever you do, watch where you walk (ex-SFer)...

[jonarck]

Seriously, Emery Cove Marina, on the East Bay, is a great Marina.

[rmesfo]

Yep, that is the way it is at Pier 39. Great location but you need to be able to put up with the rolls. Not bad at night after the ferries stop. Busy place. I it makes anyone feel any better the private docks on the other side have the same problem, just a little less with the ferry traffic.

[sail sfbay]

I docked my sailboat there a month ago for a couple of nights. Will not do that again due to the constant surge and risk of hull damage. South Beach, Municipal or Golden Gate Yacht Club Marinas are better options to avoid it.

[geoleo]

Originally Posted by Farlander

I was recently a guest at the Pier 39 marina in San Francisco. While the location is great, the docks themselves are very rolly. I think I would have been calmer at anchor. A phone call to the marina reveals the staff there have a very 'that's just how it is' attitude with everyone convinced that the tidal surge is what causes the rolling. I studied the problem briefly and came to my own conclusion, and now I'm looking for input to support or counter this theory.

What I witnessed was glassy flat water, and the docks swaying back and forth + up and down approximately one foot in either direction. I saw many boats tied up suspended by the four corners in the middle of the slip - not tied tight to either finger. One offender at the beginning of my row, a derelict looking sailboat, was loosely tied and had scooter tires on all the dock lines acting as shock absorbers. What I witnessed was the slightest breeze would start to move the vessel, which would then start pulling on the dock lines, and the extra bounce from the scooter tire stretch caused the boat and the whole dock to start rocking like crazy.

I suggested the marina encourage or require their guests to tie up tightly to the leeward fingers, and get rid of the added rebound caused by all the scooter tire shock absorbers, and they scoffed at me.

Who has experience with rolly marinas and can attest to the cause being tidal surge related or maybe actually being caused by wind and poorly secured vessels?

Thanks in advance,

Life can have some challenges. Especially in SF.