Originally Posted by drewzn
I am renting a mooring this season and when I was last on the boat, I noticed the chain must be too short for the mooring. The mooring ball is submerged at high tide. It got to where the entire ball was just under the surface of the water. I know this should be fixed, but is this something I should immediately be concerned about?
Most likely suffering "chain twist" very common with our tides and swings especially on moorings without top swivels. It is town ordinance in Falmouth and top swivels are now required.. Chain twist results in short scope and in a worst case can result in the un-setting of a mooring. You should have a "swivel" below the ball that in most cases will prevent this but sometimes they don't. You'll need to disconnect and have your mooring guy "un-twist" it.
Also keep in mind this last week we have had very high tides. Here in Casco Bay about 3 feet above normal... I am assuming your ball is sized right for the chain...
The town of Falmouth mandates top swivels be used but some installers still disobey the law and do not use them.
"Each mooring must have one (1) top swivel; all swivels and shackles must be to the appropriate size diameter."
As the boat swings around the mooring, with wind
and tide shifts, the chain twists & twists and as a result, it shortens. This chain can shorten so much that the ball gets sucked under water.
Short scope with minimal ability to retain caternary, especially in a storm, can literally lift
the mushroom or granite block out of the bottom and the boat can begin to drag through the mooring field. It also makes shock loading of the hardware
more likely with little to no caternary present. If the Apprentice Shop does not use swivels go to Hamilton, buy a LARGE one, I use 1" for a 36' boat, and hand it to them and pay them to install it...
While swivels are and can be a high wear item they can also easily be over-sized to compensate for wear. We use a 1" swivel on our own moorings and regularly get 4-5 years out of them. They have always out lasted our 3/4" top chain.
They are also available in 1 1/4" and 1 1/2" for larger vessels. Hamilton Marine
sells them in these sizes. Are they expensive in that size, sure, but a LOT less than the hull
deductible for my vessel. My 1" swivel costs about $100.00 far less than totaling my boat..