I swore that I would never get involved with an anchoring thread again, but I'm weak in my resolve...
Seems that we mostly agree that:
1. In extreme conditions one can remove the catenary from both chain and composite rodes,
2. That excessive weight in the bow has bad effects on sailing performance, but in different degrees for different boat designs.
3. That some means of reducing shock loading to anchor and deck hardware
4. That for a given total weight, adding weight to the anchor increases ultimate holding power more than adding weight to the rode, and that some anchor designs hold better than others.
5. That many anchorages
do not allow the use of large (7-10:1) scope
ratios due to crowding or other size limitations.
6. That many anchorages
have bottom features that can abrade or cut rope rodes, and that they may be unavoidable in practice.
Possibly I have missed some points of agreement, but these will do for now.
I add some personal observations, garnered from 25 years of continual cruising with ~90% of that time spent at anchor (as opposed to on moorings or in marinas).
1. I have personal knowledge of 4 boats whose rope rode parted due to chafe, and this parting lead to the loss of 2 of them. In one case the chafe was due to the nylon becoming wrapped around the boat's own keel
in a wind against tide situation.
2. I have personal knowledge of 2 boats whose chain parted, resulting in the loss of the boats. One of these involved chain purchased second-hand from a Mexican fisherman who had condemned the chain due to excessive rust (WTF?). The other was a 72 foot ferro
brigantine that was anchored on 1/2 inch chain with no snubber... during cyclone Lisa at Raoul Island in the Kermadecs.
3. In the cruising grounds that we have enjoyed (Pacific Ocean, Tasman, Southern Ocean) the all-chain rodes far, far outnumber the composite rodes once one gets away from day-sailor radius of yachting centers. Thus, the populations that lead to the above losses were heavily skewed towards chain.
4. That in less than extreme conditions, having chain lying on the bottom does reduce the magnitude of sailing about one's anchor.
5. That having an excessively stretchy rode or snubber causes "slingshotting" forward in lulls in the wind, allowing the boat to fall off beam-to-wind in the next puff.
6. That some hull
designs bear the additional weight forwards better than others. For instance, boats with long overhangs and lots of rocker in the hull
more than ones with short or no overhangs and flatter hull profiles, and suffer greater detriments from added weight in the ends. As it happens, we made just such a design change between Insatiable I, an older IOR one-tonner and Insatiable II, a more modern hull shape with a dinghy-like profile and virtually no overhangs. The difference in pitching is remarkable... and both boats carry lots of 10 mm chain all the way forwards.
From all the above, I draw the following conclusions:
1. The security
of all-chain coupled with snubbers of appropriate elasticity and length is better than a composite rode of equal strength. The ultimate holding power is essentially equal if similar anchors are used.
2. That all-chain rode is better adapted to the realities of modern cruising which entails crowded anchorages.
3. That for me the decrement in theoretical performance at sea is well offset by the advantages that chain offers. For others, whose boats may not bear the weight as well, the offset may not exist.
Finally, to answer the query about what gear
is appropriate for South Pacific
anchoring with a 35 foot boat: Insatiable I was 36' and about 10 tonnes heavy ship weight. We used a 44 lb Bruce on 275 feet of10 mm chain. We had a long 16mm nylon rode spliced to its end, but in 17 years and 86,000 miles (Mexico and South Pacific) we never needed the extra length. I hope that this data will help your decisions.