Chain caught

[noelex 77]

Our anchor chain managed to wrap itself (in fact I think it managed to to invent a new knot ) around this debris. It was an old steel rudder and rudder shaft from a commercial boat.

This is the third time in less than month that our anchor chain has been caught by debris or rocks.

There are a couple of lessons from these, and previous incidents we have experienced.

1. If you have a good anchor that sets quickly you are much more likely to catch the chain rather than the anchor when debris is present.

2. You need to be careful with rope rode lying on the bottom. The edges of this rudder were very sharp. I managed to cut myself in couple of places freeing it. Rope rode would have been cut through in a short period of time.

3. A powerful anchor windlass is a real asset. The rudder would have weighed well over 100kg (220lb) and being able to raise it to surface made the job much easier.

4. Cruising people are great. In previous incident when our chain was wrapped several times around rock, it was freed by a Danish guy who showed up from an adjacent boat and free dived to unwrap the chain even before we had a chance to get into the water.

[GreenWave]

Thanks for sharing. I will add that one can tie another line to chain and then take that to a winch in some cases to help with hoisting it all out of the water.

[thinwater]

Originally Posted by noelex 77

...2. You need to be careful with rope rode lying on the bottom. The edges of this rudder were very sharp. I managed to cut myself in couple of places freeing it. Rope rode would have been cut through in a short period of time....

I agree about rope vs. chain in general, but the is a slight misconception here, which explains why people can successfully use rope.


Rope does NOT sit on the bottom unless there is absolutely zero wind. As soon as there is any tension the rope picks off the bottom, which is why we consider there is zero catenary. I checked this with a catenary calculator.

• For the rope to lay on the bottom (50' with 10:1 scope, 7/16-inch rope) there can be only 1.2 ounce tension.
• For the rope to virtually straight (6" sag) there can be only 1 pound tension.

The reason, of course, is that nylon is virtually weightless in water. As a result, within 8 feet of the end of the chain the rope is likely more than a foot off the bottom, depending on scope. The chain may stay on the bottom in very, very light winds, but the first few feet will lift in just a few knots. But the rope will all lift. And possibly wrap around the keel, but that is a different discussion.

[noelex 77]

Originally Posted by thinwater

Rope does NOT sit on the bottom unless there is absolutely zero wind.

That is a good point, although I would also include wind reversals.

However, both the rocks and the the rudder stock were sticking several feet above the seabed so I suspect it would still have been caught with rope. The other problem with rope rode is that it moves around more than chain, sweeping a larger area and increasing the chance of encountering debris.

I understand that if cruising in a lightweight boat some rope rode is sometimes the only sensible choice, but be aware there are plenty of sharp objects, both rocks and unfortunately human rubbish that are lurking on the seabed.

[donradcliffe]

Originally Posted by thinwater

I agree about rope vs. chain in general, but the is a slight misconception here, which explains why people can successfully use rope.


Rope does NOT sit on the bottom unless there is absolutely zero wind. As soon as there is any tension the rope picks off the bottom, which is why we consider there is zero catenary. I checked this with a catenary calculator.

• For the rope to lay on the bottom (50' with 10:1 scope, 7/16-inch rope) there can be only 1.2 ounce tension.
• For the rope to virtually straight (6" sag) there can be only 1 pound tension.

The reason, of course, is that nylon is virtually weightless in water. As a result, within 8 feet of the end of the chain the rope is likely more than a foot off the bottom, depending on scope. The chain may stay on the bottom in very, very light winds, but the first few feet will lift in just a few knots. But the rope will all lift. And possibly wrap around the keel, but that is a different discussion.

Nice theory, but its not reality. The tropics are littered with coral bommies, which stick up from the bottom. I had a rope rode 2/3 severed after anchoring one night in the lee of Pitcairn.