Bob,  On bottoms of rock or coral an anchor can hold only by hooking
on to a projection or getting a fluke between two rocks or into a hole
or crevice. The kedge type of anchor is best suited to this condition.
Other types, notably the Bruce and CQR, will also work but somewhat
less effectively. In this situation holding power is limited only by
the structural strength of the anchor, the rode, and the associated
deck fittings. When anchoring in rocks or coral a buoyed trip line
should always be secured to the crown of the anchor and used for
raising it. In the Hawaiian Islands scuba divers and fishermen use a
device known as a "Japanese rock anchor" for short term anchoring on
the coral reefs. This is a simple hook with a stock welded across it
at the balance point, both fabricated from concrete reinforcing bar.
A length of bamboo lashed to the stock provides sufficient buoyancy
to insure the anchor landing hook down on the coral. Small inexpensive
buoyant line is used without chain. The idea is to keep cost to a
minimum so that, if necessary, the line may be cut and the anchor
abandoned with no great loss. Anchoring on rocky or coral bottoms
should be avoided whenever possible.
     Kelp grows on rocks that do not dry at low tide. There will be
foul bottom under it should the anchor find a way down through the
kelp. In moderate winds an anchor may hold to the kelp alone.
Anchoring on kelp is to be avoided. When necessary to do so a trip
line should be used to assist in disengaging the anchor from the kelp
or underlying rocks.
     If possible, boats anchoring in rocks or coral should have chain
rodes to minimize the chafing danger. Failing that, much chain should
lead from the nylon rode to the anchor.
     A kedge anchor, with its stock in place, may be stowed with its
flukes flat on deck in chocks, the upper end of its shank resting on
the bulwark and the stock standing vertically outboard of the rail
alongside of a lifeline stanchion or shroud to which it is lashed. As
the shackle is then outboard of the rail the rode may remain attached
so that the anchor is ready for immediate use.            --- Bob ---
--- WILDMAIL!/WC v4.12 
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