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Old 03-04-2015, 01:10 PM   #13
Marin
Scraping Paint
 
City: -
Join Date: Oct 2007
Posts: 13,745
Where boat weight or displacement plays a roll is when the boat is at anchor in a windy, wave-filled anchorage. The boat will have removed some or most of the catenary from the chain and as it surges up and down it will subject all the components Sunchaser listed to an increased strain.

At the private island where we have property we used buoys owned by other island association members when we went down there. One in particular was always available. Supposedly it was dove on and checked every year, and we had no problems with it even on windy, wavy days.

A few years ago we were down there and friends with a 36' lobsterboat joined us and rafted to us. That afternoon the wind came up and closely spaced waves about 3' came marching across the fetch and into the bay. This was no big deal, we'd been on this buoy in worse. But now instead of 30,000 pounds of boat we had over 45,000 pounds of boat on the buoy.

Within an hour there was a loud bang and our raft was adrift. Our friends started their engine and powered us out of the shallow water we'd drifted into. Once clear we pulled the buoy up on deck to see what had happened. The chain that connected the buoy to the concrete block anchor was now about six feet long. It ended with an undamaged link so we could only assume the link attached to it had broken.

Which proved to be the case when the buoy's owner had a diver replace the chain.

The owner has a 25' fishing boat and the buoy chan was sized for it. So we were probably putting it to the test with our own boat on rough days as it was. When our friends added the weight of their boat it proved to be too much.

We still use the buoys today if conditions are forecast to be calm or minimal. But if there's a chance the wind's going to pick up we anchor. The anchoring is very good there, it's just less effort to use a buoy.
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