Friday, June 20, 2014

Why has my mooring moved?

"Why has my mooring moved?" is one of the most common questions we receive from new mooring owners. In 99% of all cases the short answer is "it hasn't."

On some situations a mooring will move. If it is undersized, improperly set, or there is a very bad storm it might get dragged across the ocean floor. But in most cases it is the mooring ball, and not the mooring itself, that has shifted. 

The position of a  mooring ball can vary greatly depending on wind, tide, current, and whether or not there is a boat on the mooring. The image below shows 4 different possible positions of a mooring ball in relation to the actual anchor. 

In all 4 examples the chain is the same length (minus slight artistic variations). 

A. represents a mooring that has all the chain piled up close to the mushroom, with no wind current or boat affecting the mooring. This is the only situation that will result in the ball accurately marking the location of the anchor. This is incredibly rare.

B. represents a mooring that has been stretched out but does not currently have any wind, tide, or boat forces being applied. This is the ideal "at rest" example. The chain has been stretched out but only the minimum amount of chain is being lifted out of the mud.

C. represents a mooring that is completely stretched out and being pulled on hard by wind, current, a boat, or a combination of all three. This is an undesirable situation because the chain is lifted out of the mud which leaves it susceptible to corrosion and reduces the mooring's holding power.

D. represents is the same example as C. only it is at low tide.

The moral of this story is that a mooring ball does not usually accurately mark the location of the anchor. It will move in a large circle depending on wind, current, tides, and boat weight. The greater the forces applied, the greater the movement will be. 

Wednesday, June 4, 2014

Mooring Recovery Attempt

We will dive for lost equipment, but prefer to avoid it. The visibility is terrible to start, then add a little disruption to the mud and you have blackout conditions in no time flat. We tend to say if you can't throw an anchor overboard and have it land on the lost mooring, I'm not going to be able to find it. And finding it is only the first challenge. Retrieval can be just as difficult.

This video shows well all the best things about diving on a lost mooring. 

On Monday we were performing a routine mooring inspection. We were supposed to pick it up, clean the growth off the lines and then put it back down. It was a relatively new mooring so we did not expect to have to perform any work on it. 

We hooked onto the mooring's halters and started winding it up on the net reel. Right off we knew something was not right, it had tightened up much too quickly. With the scope tight and the barge directly over the mooring we dropped our own anchor in the water. Dropping an anchor serves three purposes.

1. Once we have picked the mooring up and inspected it, it will be much easier to put it back in the same spot. 

2. If we have to do any repairs on the mooring, the anchor will hold us in place while we work.

3. If the line parts, we will have a better chance of finding the lost mooring. Theoretically, we should be within a few yards of the missing mooring. 

It was a good thing we were following our standard operating procedures on Monday, because shortly after dropping our anchor in the water, the mooring line parted. I donned my dive gear and hopped in the water with a marker line. I descended to about 35 ft and was thrilled when I saw that the mooring was visible from the anchor. Don't you just love when a plan works the way it is supposed to? We were very lucky our anchor was in the right spot, because the visibility was poor (less than 5 ft) and I didn't have enough air to do a full search (I had not planned on diving that day and I had two tanks on the boat, each with less than 1000 psi). 

I opted to skip the marker line and head back to the surface for a lifting line. Back on the bottom I tied a bowline into a link of chain. 

Once I was aboard the barge, David began to pull on the lifting line. Just when I thought we were in the clear, the lifting line parted. I cursed loudly, put my gear back on, and entered the water. We parted two more lines trying to pick up that mooring before we gave up for the day. We have a plan to proceed but this is an excellent example of how even if we know where the mooring is, bringing it to the surface can be difficult.