Mooring redesign

[landonshaw]

I am about to put in a new mooring or at least refurbish the one I have. It is in 25 foot of salt water. I found that the shackles that held my boat to the chain had worn the chain down considerably. The mooring was 3.5 to 4 yrs old. Some of the links were extremely worn, at least half way. I have taken the boat off and am currently anchoring. We are in an area that is somewhat guarded, but one reason I am where I am is to gain the wind energy on my wind gen.
I had been thinking that the wearing was totally due to the metal against metal chafing. Was just talking to a friend and we were discussing the fact that I use stainless steel shackles to attach my rope to the galvanized chain. Could my problem be the dissimilar metal in contact with each other added to the salt water in a highly oxygenated environment?
Thoughts, similar experiences?

[Hydra]

I had a similar experience on my mooring: a stainless thimble caused corrosion on the swivel and it came apart when the nut freed itself.

Before that, I had tried a piece of chain for connecting the boat to this swivel. The links of this chain wore out very quickly where they rubbed against one another. I suspected it was caused by the large quantity of sand carried in the water.

Alain

[Kettlewell]

Yes, stainless speeds up corrosion, but also you get max corrosion at the top part of a mooring chain usually because that is where there is the most oxygen. I would use galvanized and replace more often. Another system, which I like, is to not have your mooring chain go all the way to a surface buoy. Instead you have a heavy bottom chain shackled to your heavy mooring painter, like in an anchor rode, with a light line that leads from the mooring painter up to the surface and a little float. To pick up the mooring you hook the little float and pull up the big mooring painter with the light line. When you are on the mooring it is just like being at anchor, but when you drop the mooring everything sinks to the bottom where it lasts much longer. Tripp's Boatyard in Massachusetts uses this system.

[landonshaw]

Nice idea Kittlewell. Thanks

[Hydra]

On my mooring, I had another system. The mooring block was connected to a very heavy chain, not long enough to reach the surface. A length of very thick rope connected this chain to the swivel under the buoy. This rope was kept almost vertical by the weight of the chain, so it was protected from being cut by a rogue propeller. It resisted to abrasion and corrosion better than chain and was lighter on the bow. It was feasible because the bottom is hard sand, not rock.

My boat stayed moored on this system for 6 years, 11 months per year.

Alain

[Kettlewell]

The only problem in use with the system I describe is that it takes a few extra seconds to pull up the big mooring painter from the bottom, which can add to the excitement when it is blowing. And then once in awhile, when you are away, some idiot will pick up your empty mooring and tie off with the little 5/16" line that goes to the float, not realizing there is a heavy mooring line further down. It is hard to believe, but I have seen people hang a 40-foot boat on that little line thinking that's the way it's done!

[sabray]

I'm thinking about a dyneema bridle with spliced eyes and stitched chafe gear at the chocks. Attached to a double braid larger line. Pipe insulation/ floatation slipped over the bridle lines. Not sure if I will attach this directly to the marina mooring chain or there large 3 braid eye splice with a thimble that goes through the buoy .
My older 2 line system that had one to the chain and one to the mooring eye had a bad habit of looping under the float Wrapping the pendant in a way that seemed like it could chafe the hell out of any line.

[Pelagic]

Personally I would stay away from rope, they get covered with barnacles and burrowing animal life so you never really know what is happening inside the braid.

This is how we do it at PGYC where we can have Typhoon conditions.

• Heavy low profile cement mooring block(s) that settle into the silt.
• Bolted to integral steel framework of block, heavy section of ship sized chain (length based on swing room) to act as a shock absorber.
• Then double your boats anchor size chain that goes thru a center tube floating buoy and finish with a big shackle.
• You can then shackle on a heavy bridle or single line with pick up float as desired.

I like the thru buoy chain system as it is easy to inspect the surface connection and there is no stress on the buoy.
SBS... Sur-Moor Mooring Buoys, Shackle Buoys, Tapered Buoys, Mooring Collars and Buoy Hardware by Taylor Made Products

Permanent mooring system should be inspected every year which we do by diving and gauging wear down.
Shackles are replaced as necessary, when the galvanizing wears off, we haul up anchor chain, chip down and coal tar links.

[Kettlewell]

Personally I would stay away from rope, they get covered with barnacles and burrowing animal life so you never really know what is happening inside the braid.

Easier and cheaper to replace the rope once a year or so. Believe it or not, letting the rope and chain drop to the bottom helps reduce the amount of growth on the line significantly. Yes, it does come up a bit muddy, but with less growth, barnacles, etc. The boatyard I mentioned that does this has a very good record with moorings surviving hurricanes. I believe they replace the rope part after every six-month boating season. And, since the chain lies on the bottom too (when not in use), it experiences less oxygenated water and less corrosion.

[landonshaw]

I dove the mooring and pulled all of the chain out to inspect. What I found was that the chain on the bottom was in great condition, clean form being sanded on the bottom. We were even able to unscrew the shackles. The chain at the surface was not as bad as I had thought. I only need to cut out about 5 feet, it is very worn. I am replacing the top chain with an additional 40 feet and then will inspect and cut off as I need too.