Choosing the right anchor.
There are a number of different anchor types available, which have different holding characteristics. The choice of type is mostly down to choosing one that suits the most likely type of bottom you will anchor to, or simply personal preference.
The second thing to consider, is what is the appropriate weight for your vessel.
Weight - starting point.
What weight of anchor do I require? 1.5kg per metre LOA is a starting point and not too bad a one, but only a guide. From there you need to adjust for varying factors - Increase the size if:
- You have a heavier boat than the average
- If you have lots of windage i.e. a big solid fly bridge, a ketch, etc
- You are a big wide boat
- You have a big blunt bow on your boat
- You are a nervous sleeper or are 'out to lunch' when you are asleep
- You have a lightweight rode behind the anchor
- You are planning extended coastal or offshore trips
- You boat is an area the weather changes fast
|BOAT SIZE||Anchor weight|
The above table is based on the 1.5kg / metre rule of thumb, not necessarily matching sizes of anchors available. For specific anchors, select the next weight up from this table.
Like an agricultural plough, CQR, Delta and Kobra II anchors drag when pulled hard enough, digging a furrow on the sea bed. Delta anchors are more effective, as they have a tip loading weight of around 28% of the anchor's weight, while a CQR has a tip loading of around 14% - the higher the tip loading, the more effective the anchor is at ploughing into the seabed. The CQR (Clyde Quick Release, not "secure") has the advantage over the Delta of being hinged, thereby allowing more movement when the tide turns, before pulling out and re-setting.
Flat anchors (Danforth):
Flat anchors performance is excellent in mud and sand, potentially the best of any anchor style. The downside is that outside of these bottoms, it does not perform at well. Therefore it is a mud/sand only anchor, which fortunately is what most seabeds are comprised of.
Claw / trefoil anchors:
This is basically the Bruce anchor. It sets and holds well in soft-to-medium bottoms, is said to hold on rock, but its long leading edge struggles to cut through weed. The flukes wings angle up which makes them differ from the Plough anchor where the fluke wings angle down. Claw types have difficulty penetrating weedy bottoms and grass. They offer a fairly low holding power to weight ratio and generally have to be over-sized to compete with other types. On the other hand they perform relatively well with low rode scopes and set fairly reliably.