+xI agree totally that the myth about chain providing a "spring" should be bust.
No realistic chain provides useful shock absorbing in over 40 knots wind. Two of our experiences support this.
We anchored in the Alligator River in the Carolinas in our former boat, a 40 foot 14 ton vessel We set a 60 lb CQR on 180 feet of 7/16" chain in 10 feet water. After allowing for bow roller height, that is 15:1 scope.
The wind was reported at over 60 knots by a nearby airport. We had some shelter from waves but little from wind. Waves were only about 3 ft high
The chain was secured to a large cleat (secured by two 1/2" bolts through the deck to a solid backing plate) by a couple of feet of 1/2" nylon.
The chain was bar taught, and after a couple of hours the rope snapped, half way along its length, with no chafe involved.
Breaking load of the rope was about 8,000 lbs, the chain about 20,000 lbs.
The boat was delivering sledgehammer blows to the anchor, which dragged about 100 yards through the thick mud. When the wind dropped we had a heck of a job getting the CQR up, and found it and the first 10 feet or so of chain nicely polished.
"Oceanography and Seamanship" by William Van Dorn has an excellent analysis of the mathematics of anchor rodes that shows that the ideal rods has half its length chain and half rope.
A few years later we sat through hurricane David, 1979 in St Martin. Cat 4 as I recall.
Fortunately, I had read Van Dorn's book, and applied his mathematics to our boat to select the anchor rode.
They eye of David went over us, so we had wind from two directions. Nobody local could measure the wind speed.
We had same CQR but with 90 feet chain and 90 feet 3/4" nylon on the inboard end. We barely moved, and the boat did not bang and clang.
These anecdotes support Dick's myth busting.
Of course chain is necessary on the bottom to avoid chafe on rocks, but there is no advantage in heavy chain.
Hi Neil,
Good to hear from you.
Thanks for the field report: always the best data in our marine world. And your support that chain should be bought with regard to strength and not to weight.
And yet, at least once a year or more, in the popular magazines, one sees the usual diagram of a boat at anchor with a nice arc from bow to anchor lauding the benefits of chain catenary.
I wonder whether the author has ever been at anchor in a gale: sort of like going below a boat in a boat show, finding no handholds, and wondering whether the naval architect has ever been off-shore in a sailboat.
I am surprised that your ½ inch snubber gave way: ½ inch nylon should not have parted in the way you described. It is usually incredible strong tough stuff.
I would suggest that I would have veered more than a couple of feet of the ½ inch nylon snubber. A couple of feet gives some stretch and would protect chain and windlass, but so short a snubber would be subject to continual impressive shock loads in the conditions you describe. I am no expert, but I read about loaded up nylon getting hot and weakened, but I have always supposed that to be where it gets compressed going around a chock or something. There are also some nylon manufacturers who use dis-continuous strands (something to check at purchase and a good reason to buy from well-respected manufacturers who can answer the question). Where one strand ends and a new strand begins is a weak spot which can appear when the line gets stretched (little puffs of nylon revealing a break). A longer snubber eases the shock loads considerably and the boat might lie better. (I write this for others to read as I realize that you may not need -generally- a snubber with your present ground tackle set up.)
And I think the hybrid system you describe is one that is under-appreciated and should be a viable consideration for many boats with the caveats you mention. It is an especially decent solution for boats that anchor shallow most of the time (they will usually be on all chain with the nylon as snubber). And for those where weight is very important (catamarans). And for those that like chain but are sometimes required to anchor deep, 150 feet of chain followed by 300 feet of nylon allows anchoring safely 100+ feet and is far less weighty and easier to handle than 300 feet of chain or more.
BTW, are you still using a CQR?
After Hurricane Bob, weathered in Onset, Mass, we needed 6 hours to get our 3 anchors up.
My best, Dick Stevenson, s/v Alchemy