How much rope does it take to anchor a boat?
Most boats no matter size shape or style will follow the same basic principles of anchoring. No matter what type of anchor is being used the same rules will almost always apply.
In this post we will run through the different considerations you might make when deciding what type of anchor line (rope) to get and how much of it.
The first decision to be made will be what type of rope to use.
When customers come into the shop looking for anchor line we always recommend a 3 Strand Polyester Rope.
3 Strand Polyester has several important properties making it an ideal anchor rope.
Whether wet or dry (below and above water) it is extremely high strength. The rope although it doesn’t feel very heavy, is a sinking rope which is important for anchoring. Highly resistant to chemicals, salt water and abrasion you do not need to worry about your rope wearing out.
Polyester ropes also have very good stretch. 3 Strand Polyester can stretch up to 10% allowing the rope to absorb the shock of the boat pulling on the anchor. This will reduce the load being placed on deck fitting and decrease the chances of gear damage. For those who put a thimble on the end of their anchor line, 3 Strand is also straightforward to splice.
There are other options for ropes on the market such as 8 Plait Nylon or Polyester which have similar properties to the above. You can also use weighted anchor lines. For some bigger boats or boats anchoring in more challenging conditions all chain anchor lines are used. Although these are much higher in strength a windlass is required and they are substantially heavier and more expensive. If you are looking for an all chain anchor line using a calibrated chain is essential.
All anchor lines should have about chain connecting them to the anchor. This chain adds to the holding strength of the anchor on the ground. It also prevents the end of the anchor from lifting. Heavier boats such as yachts should have approximately 5 meters of chain and smaller or lighter boats 2 - 3 meters of chain will do. This is of course dependent on the situation. We can offer advice tailored to your specific needs.
The rope diameter used should reflect the size of your boat. It is important to know the breaking and working load of the rope.
What Length of Rope
As a very basic rule the anchor rode or anchor line (chain and rope combined) should be at a very minimum 3 times as long as the depth of the water. We would recommend using a 5:1 Ratio however. That is to say for every meter of water depth you would have 5 meters of line.
The amount of rope used is very dependant on the situation. Based on the situations you find yourself in it will guide you on how much rope you will need to get.
The area you are using your boat or planning on using your boat will have a big impact on the length of rope required. The water depth you will be anchoring in is important. Dublin Bay and the shoreline along the east coast doesn’t get to much more than 25 Meters Depth. In water much deeper than this, the quantity of rope required becomes impractical and you should be looking for more shallow water to anchor your boat.
Tide plays an important role in anchoring and the amount of rope required. The depth of water should be measured not on what depth is below the boat at the time of anchoring but on what the max depth will be while anchored. It is important to research the tides to know what depth you will encounter.
In calm conditions with little wind and calm seas using 5 meters of rope for every meter of water is more than sufficient. As you encounter rougher conditions using more rope should be considered. The more rope you have will increase how much it can stretch. As mentioned above, the rope stretching will absorb shock making it less hard wearing on deck fittings but more importantly it will be more comfortable for those on board.
Increasing the length of line also reduces the angle between the boat and your anchor on the seabed. This will reduce the chances of your anchor being lifted by the rope and increases the holding power to prevent dragging.
If you plan on anchoring regularly in rough conditions you should carry a longer length of rope onboard.
An important consideration for how much line you lay out should be your surroundings. Increased line length will increase your swing circle. The area you could drift to depending on wind direction and tidal flows. Your anchor line ratio should take into account any obstructions or other boats around you. In certain situations a secondary anchor and anchor line can be used off the stern of the boat to hold it in a specific position.
Help is on hand
If you have any further questions the team of experts here in Viking Marine will be more than happy to offer advice based on your specific needs.
Ian O'Meara has decades of sailing experience from racing to cruising. He has also been involved in chandlery for over 25 Years. When it comes to anchors and rope Ian has a wealth of experience which he has passed on to the team in store in Viking Marine.