On Sat, 03 Jun 2006 16:31:46 GMT, Courtney Thomas wrote:



Courtney Thomas wrote:

I want to install a fixed mooring this summer and see that for example
mushroom anchors are expensive.

The environment is... Atlantic salt water, in a fairly well protected
cove, with 6' tides, in about 10-15' of water, virtually no traffic and
a spit serving as immediate breakwater.

Alternative suggestions to a mushroom would be appreciated.

Courtney


My understanding is that concrete loses a lot of it's 'weight' in water,
whereas steel/iron do not and given the recent hurricane rash I'd prefer
all I can reasonably get. Plus I'm not in an area catering to such
services as installing moorings, for example.

Gratefully,
Courtney

correct on the "losing it's weight" in water ...

sal****er is 64 lbs per cu ft (displaces 64 lbs per cu ft)

per my pocket ref on material weights (any typos are mine)

cast iron 450 lb/cu ft

portland cement 100 lb/cu ft
mortar cement 135 lb/cu ft
gravel concrete 150 lb/cu ft
limestone w/Portland concrete 148 lb/cu ft

marble 160 lb/cu ft

so, water will displace 64 lbs of an item, so cast iron has a bottom
weight in salt water of 386 lbs per cu/ft

the different cement mixes are 36 to 86 lbs per cu ft when in the
water

I've seen both cement and marble slab moorings in this area ... in
blocks (not formed to dig) and while they tend to sink in over time
depending on bottom composition. I've also seen them move to shore
during a storm.

I personally wouldn't use a block without adding a mushroom to the
works ... the block would prevent the mushroom from lifting, the
mushroom would keep the block from moving.

note: I am not a ground tackle expert ... I have used the weight
formulas to determine lift bag requirements or drums to perform uw
lifts and recovery.


- Ed

--
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