Boat Anchor Size Chart
So, what size anchor do I need for my boat? Take a look at our chart above, and you’ll find a helpful guide by matching your boat’s length to a recommended anchor size. Alongside our anchor size chart, here are some steps to follow for determining the anchor size your boat needs:
Anchor Types For Expected Bottom Conditions:
Lets take a look at a few different types of anchors and the ground conditions they are commonly suited for:
|Anchor Type||Why This is Best|
|Danforth||The design of the two large triangular flukes joined to the stock enables the flukes to position themselves to the sea bottom at an angle for maximum holding power.||
|Plow||When deployed, it first lands on its side and then rights itself while it, like the name indicates, plows into the seafloor.||
|Mushroom||The silt from the bottom builds up over the anchor, resulting in extreme holding power.||
|Grapnel||Holding power comes from hooking onto another object.
Although not the most reliable, it can create immense holding power. This can also make retrieving the anchor difficult.
How Much Anchor Chain And Rope Do I Need
The generally accepted guide for the length of your anchor rode An Anchor Rode encompasses Chain, Rope and the all the shackles and connectors is 8 metres of rode for every metre of depth you will be anchoring in. This is referred to as the scope, in this case 8:1.
This works for the middle range of anchorage depths but starts to look a little out of kilter as you approach either end of the scale e.g.
- 8:1 in 3 meters of water equates to 24 metres total rode length which is possibly not a satisfactory anchoring solution in anything but benign weather
- 8:1 in 5 metres of water equates to 40 metres total rode length which may be adequate for Inshore and Coastal hopping
- 8:1 in 20 metres of water would be 160 metres of total anchor rode which would seem a little bit over the top !
However, Scope 8:1 for 10 metres of depth = 80 metres total chain and warp and this makes a good benchmark starting point for your final decision.For long distance Offshore and Ocean cruising you may want to consider increasing the scope to 10:1 on all chain or even 12:1 on a chain/rope combination. This particularly applies to anchorages around some Pacific islands.
Budget and weight carried forward in the bow are the natural restraints on your final decision regarding the total length of chain and warp.
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Select Your Anchor Chain And Compatible Anchor Rope Size
|Yacht Length Overall|
N.B. This table is a guide with columns based on:
- Top Quality LIROS Rope
- Jimmy Green experience and customer feedback
- Top Quality Grade 40 Anchor Chain
Which Anchor Is Right For My Boat
As a long-time boater, theres a lot of gear that I bring aboard my pontoon boat. From coolers to paper towels, I usually keep a small stockpile of necessities stored away all summer long for easy access.
The more I hit the water, the more I learned about whats valuable to keep with you at all times and what can leave the boat after each use. Things like extra flip flops for last-minute pit stops and sunglasses in case a friend forgot theirs became a norm.
If youre new to boating, I recommend making a long list of boat accessories before you jump on board. Doing this can save a lot of hassle when youre in the middle of the lake and you run out of sunscreen or need an extra anchor on a windy day.
Speaking of anchors, that is one item that never leaves my boat, even through winter storage. I live on a sandy bottom lake and we throw anchor nearly every time we venture out for the day. This is one of the most important pieces of boat gear you can have, but do you know which type is right for you?
Im going to explain some of the more popular anchor types and how to choose the best one for your situation. You might be surprised that theres more to consider in an anchor other than weight.
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Use Two Anchors Of Different Styles
Most boating experts agree that, for greatest anchoring security, you should carry two anchors of different styles, one each of the Danforth style and the plow/scoop variety. The type of bottommud, grass, sand or rockwill dictate different choices of anchors, as will the size and windage of the boat, the wind conditions and the sea state. Some anchoring situations also call for more than one anchor to be used simultaneously.
You sometimes need to set two anchors in a crowded anchorage, with anchors at the bow and stern of the boat to limit its ability to swing. Two anchors set from the bow at a 60° angle are another good way to improve security against swinging and dragging, and they allow you to shorten the rodes and use less scope. In heavy weather conditions, where one anchor may not have enough holding power, setting a second anchor may be critical to staying put. Remember that as the wind speed doubles the force on the boat increases by four times.
What Are The Typical Bottom Conditions
Anchors need to develop enough resistance in the seabed to withstand the environmental forces on the boatthe wind and the waves. An anchors ability to develop resistance is entirely dependent on its ability to engage and penetrate the seabed. In all of our anchor tests, there always seems to be one undeniable conclusion: the selection of a suitable bottom for anchoring is a much more critical factor than the design of the anchor. So how do you choose the right anchor design? You must take expected bottom conditions into account. Here are some potential options, based on the seabed:
Sand: Fine-grained sand is relatively easy for anchors to penetrate and offers consistently high holding power and repeatable results. Most anchors will hold the greatest tension in hard sand. Pivoting-fluke anchors and non-hinged scoop anchors are the best types in sand. The Rocna performed excellently in our anchor tests in sand.
Rocky bottoms: Holding power is most dependent on where you happen to drop the hook, rather than the type of anchor. Plow-shaped or grapnel-type anchors, with high structural strength to sustain the high point-loads, generally work the best. These anchors include the Claw, CQR, Delta, Rocna and Supreme.
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The Rocna Sizing Chart
|Some content referred to in this section is located at the main Rocna Anchors website. To avoid duplication, this content is not repeated here.|
Our sizing chart is a simple two-dimensional table, with vessel lengths down the left and displacement ranges in metric tonnes along each row . To choose the correctly sized Rocna, the vessel’s length selects the correct row, along which is found the appropriate displacement range . The resulting column then provides the recommended Rocna model.
Our chart is intended for monohulls. In general, an anchor for a multihull should be up to 50% larger than that for a monohull of the same LOA. Commonly this means going to the next higher recommendation , depending on how close the vessel is to the upper limit of a particular size range.
Vessels larger and/or heavier than covered by the Rocna chart
Those with boats for which the Rocna 110 is too small will find that our sizing chart does not extend to a large enough range. For more on sizing anchors for these vessels, please refer to classification requirements below.
How To Choose An Anchor
Does your boat have an anchor? If so, is it of sufficient size and strength to hold your boat in place? Believe it or not, many boat owners decide on which anchor to buy based on convenience and storage space.
A visit to your boat dealer will prove there is more to choosing an anchor than how handily it stores in the boat, though. Anchors come in a variety of shapes and sizes, just like the boats they anchor. The reason why there are so many choices comes down to the weather, type of boat and size, as well as the bottom conditions where the anchor will be used.
Dont be the guy who digs out the anchor from the storage compartment, tosses it overboard and discovers that its too small to hold the boat during an afternoon swim. Visit your nearest Bass Pro Shops/Cabelas Boating Center to find the right anchor for your boat. Before you go, read these tips to get started making the best choice.
WeightBigger is better when choosing anchor weight. You wont need as much for holding the boat in a quiet cove, but you will need much more weight for an emergency situation in the wind. You can also carry two anchors of differing weights. A smaller lunch hook is adequate for short anchorages in calm water when you will be keeping watch on the anchor. Youll also want to have a larger working anchor for overnight trips or when going ashore in gusty winds. Using two differing anchor styles can also be beneficial, especially with high-profile boats like pontoons.
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What Is The Best Way To Retrieve An Anchor
Retrieving an Anchor
Sizing For Equitable Holding Performance
The Rocna out-performs all other anchor types in most real world scenarios. This includes straight-line pull performance. A benefit of this is that when specifying an anchor to handle any given force, a Rocna may be smaller than another type. Conversely, another type will need to be larger in order to offer comparable holding power.
The actual differences depend obviously on the anchor type, the seabed, and the scope of the rode.
Nb.: Such sole consideration of resistance for a straight line pull ignores the fact that in the real world, most failures and draggings occur in different scenarios. Under this false assumption, it may be concluded that a certain size anchor of another type could replace a Rocna but this would likely be incorrect for general purpose use, as the Rocna will better handle the combination of actualities thrown at it in the real world, and it could take a still larger alternative anchor to provide equitable performance.
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Manufacturer Recommendations And Bottom Conditions:
If you find it difficult to determine the perfect anchor, you should always refer to the anchor manufacturers recommendations and specs before buying.
Its also a terrific idea to consider more than one anchor, the main one at the bow and a smaller one to set the stern.
Its also important to note, if youre unfamiliar with the ground conditions in the area you are boating in, it will be important to do a little research and map out the area before settling on one anchor or another.
The Rationale Behind Our Sizing
Peter, the Rocna designer, comes from a background of world cruising, and we tend to consider gear inadequate if it is not suitable for extreme environments. By this we mean the anchoring scenarios found in high latitudes northern Europe, Greenland, southern New Zealand, Patagonia, Antarctica, et cetera.
Our sizing is conservative, intended to provide an anchor adequate for use in all conditions most boaters would ever endure. We base our calculations on 50 knots wind, associated surge, and soft moderate holding bottoms into which it is assumed the anchor has set. Adequate scope is assumed. This is far in excess of most manufacturers.
Windage and resulting forces is judged based on typical vessel profiles according to LOA and displacement.
Note that tidal flow generally does not generate a hugely significant amount of force and in most areas can be all but disregarded. On a typical 10m yacht, it takes a 6 knot current to generate about as much force as a 20 knot breeze on the same boat.
Naturally there are many variables involved, and in many situations an adequately sized Rocna will easily handle far worse winds than 50 knots. There are others where even a Rocna will not hold well. However, our aim is to consider a realistic poor case scenario as the basis for our recommendations.
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Does The Boat Type Influence The Anchor I Choose
Before we move to the recommended anchors I want to quickly cover one last thing.
At this point you might be wondering if the type of boat that you have will influence the anchor you choose.
The answer in most cases is no. 23 feet boats are considered small boats, so there is a limit to how much weight they can carry. So if you have a 23 feet pontoon, or a bass boat, or a skiff, or a ski boat, you shouldnt worry too much about the weight of your boat. Most anchors that you will find on the market will suit you just fine.
Things get more complicated when we get to bigger boats, if we were talking about a 30 foot boat, or even a 27 foot boat things might be a little different, but right now its not the case.
Jon Boat Anchor System
As I have already discussed many boaters will have 2 anchors on their Jon boat a back or side anchor in addition to a front anchor to hold the boat in place and also reduce swaying.
There are very cheap anchor sets that include a small grapnel anchor and a pole anchor for bow and stern, like this one, though if you want to mount the pole you will need to buy a mounting bracket separately.
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Choosing The Right Anchor
The type of bottommud, grass, sand or rockwill dictate different choices of anchors, as will the size and windage of the boat, the wind conditions and the sea state.
There are a number of brands and styles of anchors on the market. They all have different strengths and weaknesses, and new ones are being developed all of the time. So, how is anyone supposed to know which to carry and deploy? We take a look at some new anchors and some old favorites.
Every boat should have not only the right sized anchor for the boat, but also the right anchor for the bottom conditions encountered.
Picture the situation where an anchor is needed. Obviously, we need anchors that hold, but in what conditions? Cruisers may want anchors good on a variety of sea floor types that are very secure in extreme wind and sea conditions, while fishermen anchoring repeatedly in a location with one bottom type, sand for instance, may choose a different style.
One thing is certain: anchors that dont set quickly, on relatively short scope, in a situation where the boat may be out of control are not to be trusted. And it is this trust factor that an anchor will hold in adverse conditions, on a lee shore, even when the boat swings and the set is reversed that should help boaters decide which is best.
Choosing The Right Anchor For Your Boat
A number of variables affect anchoring. In choosing the Anchor for your vessel, give consideration to the following: Type, Displacement, draught and windage of vessel tidal conditions type of sea floor wind strength.
Suggested sizes in this website considered for average boats under average conditions with a minimum of 1.5 Boat lengths of appropriate sized chain fitted in addition to the AnchorRope. Final selection should be based on personal experience. If in doubt select one size larger.
Not all anchors perform in the same Way. The Sarca Anchor has the highest holding power followed by the traditional Plow anchor with the lowest holding power coming from the budget priced Sand anchor .
Finally, don”t skimp on the amount of anchor rope you use. At least 5 times the water depth should be deployed and doubling that will also double the holding power. Therefore anchoring in 10m of water requires a 50m minimum AnchorRope.
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