Anchor sizing should always be interpreted as a guide only.
Many factors influence anchor size selection (e.g., the boat displacement and windage).
Also the chain size, weight and length is critical to anchor performance.
Finally the vessel usage should also be taken into account.
A vessel used for extended coastal and offshore cruising will have different demands
on the ground tackle than a vessel used only for fair weather day trips.
If in any doubt about anchor, the bigger anchor should be chosen.
In bad weather or motoring failure, it will be the only thing that can be relied on
to save the vessel and the crew.
The anchor-rode sizes given below assume winds up to force 7 for working anchors and force 9
for storm anchors, some protection from sea, fail holding ground and operation at an
adequate scope to assure full holding capacity of the anchor.
The anchor rode should have sufficient energy absorption capacity to minimize snatch
loading on the anchor and boat fittings.
If a nylon rope is used, it is recommended that chain of the diameter and minimum length
tabulated above be included between rope and anchor to resist chafing on the seabed.
Anchor System for 40-ft Yacht
For burying anchors of the "high holding power" type (Bow, CQR, Bruce, Danforth, ...), the rule of the thumb for the recommended anchor weight is:
Anchor_Weight [kg] = 2 * LOA [m]From this the following anchor system may be considered for a 40-ft yacht (40 ft = 12 m):
To handle these heavy anchors a large and powerful windlass (1500W) is required. Carrying around the weight of the windlass and two heavy anchors a the bow increases the yacht's pitching motion in a choppy sea. Anchors on small vessels are always a compromise and the additional weight at the bow may be reduced by stowing the anchor and rode at a more central position while sailing off-shore. In any case the storage for anchor and chain must be "roll-over secure"!
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