[Public-list] Anchors

[Robert Kirk]

At 10:07 PM 10/9/05 -0400, George Dinwiddie wrote:
>[...]
>Funny, there doesn't seem to be much discussion of scope, however.  This 
>week I anchored a 5 boat raft (3 A30s and 2 bigger boats) in Baby Owl Cove 
>on one of those Danforth knockoffs that came with so many of the 
>A30s.  Even with only 6 feet of chain on that anchor, I felt perfectly 
>secure with a 7 to 1 scope.[...]

George... I agree with you that chain is not  important. Chain is really 
only for avoiding chafe on the bottom near the anchor which very useful for 
a permanent mooring buoy (at my marina, motion has even catastrophically 
chafed thru several chains on the bottom in less than 1 season) but 
unimportant in an overnight anchoring. (1) It adds no strength to the 
system - a chain is only as strong as its weakest link, like the line or 
shackle anyway, (2) you lose the stretchiness of whatever length of line it 
substitutes for, thus not helping any for shock load, and (3) the 
"flattening" of the anchor for horizontal pull due to the chain weight is 
meaningless. After all, the anchor only pulls loose when it is tight (!) 
and by that time the chain is off the bottom anyway. Even without any 
catenary, the angle with the bottom is only about 8 degrees. If the chain 
helps with that, it's trivial; a degree or two, maybe?, and (4) look at the 
weight you save in hoisting or bow storage.

So, my (our?) conclusion is that a rope only rode, with a good scope is 
perfectly ok for anchoring, even in heavy weather. I expect others may 
disagree.


Bob Kirk
Isobar #181







 1128958983.0