A sailboat equipped with two good anchors, properly deployed, can hold on a solid seabed in 30, 40, or 60 knots of wind... What makes for a good anchorage in bad weather, what kind of seabed should you look for, and what techniques should you use?
On a sailboat at anchor, it is the chain lying on the seabed that "holds" the boat. The anchor itself only serves to hold the assembly in place when there is tension.
On a sandy bottom, anchors hold well. Often, it is the waves that cause anchors to break loose by creating a vertical motion in the boat.
Therefore, if the anchorage is well-protected from waves, the seabed is sandy, and there is enough room to swing on the full length of the chain (without the risk of being driven onto the shore, an obstacle, or another boat), you can consider spending a windy night there.
First, you must find the right spot.
The goal is to find a location sheltered from the prevailing winds and, above all, the associated waves. You can access wave forecasts for several days on the Ifremer MARC website.
It is also always good to have enough water under the keelbehind in case the anchor drags ! Also, keep in mind that the wind might shift…. So, you need plenty of space!
Once you’ve found the best bay, it’s worthidentifying the seabed. In France, we are lucky to have access to Shom’s online sedimentology data, here is an example : The cove of Bénodet: sand is in yellow, rock is in red. It’s definitely worth shifting your position a bit to be over sand, which will hold much better!
Keep in mind that seabeds covered in seaweed have very poor holding power, so they should be avoided. Especially since your anchor can sometimes cause irreparable damage to the ecosystem. This is a great opportunity to discover an app: DONIA which maps posidonia seagrass locations in the Mediterranean. Plus, the basic account is free, so why not use it?
That’s it, we’ve found the spot! Phew!
The stronger the wind, the more scope you need. If you can let out all your chain, along with a good length of anchor line, do it. The line, secured to a cleat, acts as a shock absorber. This polyester rope, which is (slightly) elastic, will significantly increase the holding power of your anchor. In high winds, it is essential to let out as much as possible. By the way, don't forget to attach the other end inside the anchor locker!
Be wary of the idea of taking a mooring line ashore when it's really blowing.
Wind shifts are frequent, and suddenly exposing your sailboat broadside to a strong wind is a very unpleasant experience, especially since anchors hold very poorly when pulled from the side.
In a nutshell, the strategy is to anchor with plenty of scope, securely, on good holding ground, and with lots of room.
