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Anchor & Dock Page
Facts about Anchors
| Anchor cable between the boat and
the anchor on the bottom forms a curve called a catenary. Ideally the catenary is such
that the bottom angle is zero and the curve is sufficient to absorb shock loadings from
wind and waves. Two things effect the catenary. The length of cable paid out relative to
the depth of water, this is called the scope (normally about five times the depth of
water) and the proportion of chain in the cable. It is good for the entire anchor cable to
be chain especially in rocky or coral areas but sometimes the weight of the chain can be
prohibitive, such as in racing sailboats or high performance planing powerboats. Certainly
the bottom section of the anchor cable should be chain so as to reduce the wear of the
cable dragging over the bottom as the boat moves around in the wind and also to maximise
the catenary. |
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| The two most popular
high holding power anchors are the Danforth or sand type, and the CQR or plough type. The
sand type gives very good holding power for its weight and is easy to stow. Its
disadvantage is that it does not penetrate through weeded bottoms well, and its
performance is very sensitive to zero bottom angles so more cable needs to be paid out on
average, the plough type gives good holding on most types of bottom but is slightly
heavier than the equivalent sand type and is more cumbersome to stow. |
Anchor Tackle Selection Guide
The following table is our recommended table for anchor
tackle. Care should be taken when using this table as boats with more windage or
displacement may require heavier tackle in rough conditions. The rope diameters and cable
lengths are taken from the Victorian Marine Board Regulations for boats of a given length
in metres. We have given approximate equivalents for boat length in feet for those that
still work that way. The Victorian Marine Board only advise 2.5m minimum of chain. For
those boats over 6m in length that may find themselves wanting to anchor in rough
conditions we recommend the Australian Yachting Federation (AYF) regulation for 10m of
chain. We have chosen anchor and chain sizes from or suppliers as appropriate. Variations
between our recommendation and the AYF regulations are annotated at the bottom of the
table. The galvanised chain should have shackles of one size greater (e.g 8mm chain should
have 10mm shackles). Shackle pins should be wired in with monel wire to prevent pins
working loose. We sell this wire in 3m lengths.
Length of Boat |
Anchor Type
ref size (weight) |
Minimum
Chain Dia / Length |
Cable
Length Min. (m) |
Silver
Rope Dia (mm) |
Nylon
Rope Dia (mm) |
| Sand |
Plough |
| Up to 10ft |
Up to 3m |
4 (2kg) |
9 (4kg) |
6mm 2.5m |
45m |
10 |
8 |
| 10 - 13ft |
3 - 4m |
6 (2.7kg) |
9 (4kg) |
6mm 2.5m |
45m |
10 |
8 |
| Up to 16ft |
Up to 5m |
8 (3.9kg) |
9 (4kg) |
6mm 2.5m |
45m |
10 |
8 |
| 16 - 20ft |
5 - 6m |
13 (6kg) |
15 (7kg) |
6mm 2.5m |
50m |
12 |
10 |
| 20 - 26ft |
Up to 8m |
16 (7.5kg) |
15 (7kg) |
8mm 10m |
50m |
12 |
10 |
| 26 - 29ft |
8 - 9m |
22 (11kg) |
25 (11kg) |
10mm 10m |
55m |
20 |
16 |
| 29 - 32ft |
9 - 10m |
27 (13kg) |
30 (13kg) |
10mm 10m |
55m |
20 |
16 |
| 32 - 36ft |
10 - 11m |
35 (16kg) |
45 (20kg) |
10mm 10m |
55m |
20 |
16 |
| 36 - 40ft |
Up to 12m |
45 (21kg) |
52 (24kg) |
10mm 10m |
55m |
20 |
16 |
Australian Yachting Federation Variations
| Boat
Length |
Sand |
Plough |
| Up to 8m |
13 (7.5kg) |
15 (7kg) |
| 8 - 9m |
22 (11kg) |
20 (9kg) |
| 9 - 10m |
22 (11kg) |
27 (11kg) |
| 10 - 11m |
22 (11kg) |
27 (11kg) |
| Up to 12m |
40 * |
35 (15kg) |
* This size is currently unavailable and next available
size is 45 (weighing 20.5kg)
Mooring Lines
| MOORING
APPLICATION |
NORMAL
RECOMMENDATION |
UPGRADE |
| Anchor Cable |
Polyester Staple |
Nylon |
| Dock Lines |
Polyester Staple |
Nylon |
Polyester Staple (Silver
Rope) - 3 strand for easy splicing. No strength loss when wet. Low stretch, good
abrasion and UV resistance. Floats in salt water. White only.
| Diameter (mm) |
6 |
8 |
10 |
12 |
14 |
16 |
18 |
20 |
24 |
| Nominal Break Load (kg) |
760 |
1420 |
2360 |
3200 |
3930 |
5090 |
7100 |
7770 |
11210 |
Nylon - 3 strand
for easy splicing. Easily stretched which makes it particularly good at handling shock
loads in mooring applications. White only.
| Diameter (mm) |
6 |
8 |
10 |
12 |
14 |
16 |
18 |
20 |
24 |
| Nominal Break Load (kg) |
860 |
1540 |
2400 |
3560 |
4850 |
5520 |
6900 |
8630 |
12400 |
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