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. |  |
| 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