Anchor sizing questions

[thinwater]

Originally Posted by overextendedfp

Exactly what boat do you have

See my signature and avitar.

[Steve Bedford]

I have watched this thread for a few days now and it certainly has gone as most anchor threads do. The initial post contributor is probably just as confused now as he/she was when the first post was sent. There is a huge amount of excellent information provided by some very very experienced folks.

We have heavy verses not so.
We have all chain verses not so.
We have one company and not another.
We have put the weight in the anchor and not the chain.

My two or three cents: Regardless of what you might read here or in other forums, there is no one perfect anchor. They all have their strengths and all have limitations. Try to determine what those limitations and strengths are and rate which are the most important to you in your typical anchoring situations. There are a few ways to uncover the strengths/weaknesses of various anchors and one would be real life experiences on forums such as this but do not rely solely on these forums. Often some posters like to justify their anchor choices in some exaggerated ways. You have to sort through all that.

I believe size does matter on just about any anchor but there is a practical limit. Go upsize to whatever you and your equipment can handle.

I believe some length of chain is important. Other than using a kellet, nothing like chain creates the catenary effect to help shock absorbsion and to better keep the anchor shank to seabed angle low. I personally prefer a long chain rode (150’) with nylon rode attached. However, I have a lot of my customers with the SuperMAX using far less chain with longer nylon rodes (and swear by it).

Determine the seabeds you typically anchor in and get a main bower that has superior setting and holding in those seabeds. Get a secondary anchor that has some strength characteristics in seabeds other than your main bower.

Good luck on your research and decision. The posts and suggestions here have been generally fantastic (yet possibly adding to your confusion). If would be happy to discuss more off list.

Steve Bedford

[kmacdonald]

Originally Posted by thinwater

There seems to be a lot of focus on the weight of the boat. With multihulls, like the OP, windage is more important, and a cat may have have as much anchor load as a mono 10 feet longer weighing 3 times as much.

There is also a tendency for cats to anchor in shallower water, and thus heavy chain is not very helpful (catenary requires deeper water to work it's magic) but long nylon bridles are (gotta rig one anyway).

The effect of yawing (sailing at anchor) is underappreciated by many. I've tested yaw reduction methods, but the most interesting lesson was the yawing just 25 degrees each side will double the load because the windage is that much greater at an angle. There can also be odd snubbing effects, related to the catenary snapping out of the rode, followed by slack, but they are very hard to model, since they are situation-specific. So what does doubling the load do to your anchor size calculation? A boat that yaws, vs. one that does not, will require TWICE the anchor size. How about them apples?


There are a LOT of things you can do to reduce the load. By all means get a big anchor, since it will hold only 1/2 or 1/3 if not used wisely... and we're all stupid once in a while.

With all-chain I like a long snubber.



With nylon rode, a Dyneema bridle can be better. Weird, but true.

That's exactly why anchoring from the stern in sheltered waters is best. No yawing.

[chowdan]

Originally Posted by Steve Bedford

I have watched this thread for a few days now and it certainly has gone as most anchor threads do. The initial post contributor is probably just as confused now as he/she was when the first post was sent. There is a huge amount of excellent information provided by some very very experienced folks.

We have heavy verses not so.
We have all chain verses not so.
We have one company and not another.
We have put the weight in the anchor and not the chain.

My two or three cents: Regardless of what you might read here or in other forums, there is no one perfect anchor. They all have their strengths and all have limitations. Try to determine what those limitations and strengths are and rate which are the most important to you in your typical anchoring situations. There are a few ways to uncover the strengths/weaknesses of various anchors and one would be real life experiences on forums such as this but do not rely solely on these forums. Often some posters like to justify their anchor choices in some exaggerated ways. You have to sort through all that.

I believe size does matter on just about any anchor but there is a practical limit. Go upsize to whatever you and your equipment can handle.

I believe some length of chain is important. Other than using a kellet, nothing like chain creates the catenary effect to help shock absorbsion and to better keep the anchor shank to seabed angle low. I personally prefer a long chain rode (150’) with nylon rode attached. However, I have a lot of my customers with the SuperMAX using far less chain with longer nylon rodes (and swear by it).

Determine the seabeds you typically anchor in and get a main bower that has superior setting and holding in those seabeds. Get a secondary anchor that has some strength characteristics in seabeds other than your main bower.

Good luck on your research and decision. The posts and suggestions here have been generally fantastic (yet possibly adding to your confusion). If would be happy to discuss more off list.

Steve Bedford

Steve,

Thanks for the post. It definitely has gone the way of most anchor threads. Not my intention, but alas I should have known as it typically always does. Definitely all the different perspectives people have makes it a hard choice to decide what to do. I do know that I believe in the new generation anchors over old.

Due to not having an endless deep pockets, I have changed my numbers a bit. I am thinking 100-150ft feet of 3/8" chain with 150-200ft of 3/4" 3 strand nylon rode.

I also will likely be going with a used Manson Supreme 60lb anchor as I will be able to get it for $400. I would prefer a new anchor, and when we go cruising full time, I'll likely replace it with something new and maybe an all chain rode.

One aspect I am buying the used anchor is to put the extra cash towards the windlass. I don't want a windlass that's going to be a giant POS. That being said, I can't afford to drop 5k on one.

[noelex 77]

Originally Posted by eyschulman

There is an obvious split in anchor size and weight philosophy. No one is stopping people from using as big an anchor as they like. If it makes a boater happy to know they have a storm anchor on the bow that is fine, but for people who ask the question and have no set bias I present the alterative. Use a good modern anchor of manufacturers recommended size one up is fine and keep the storm anchor in the bilge for the rare occasion when you think it will be needed.

Keeping a “storm” anchor in the bilge is a traditional technique. In fact, it was quite popular to have “storm” anchor in the bilge and both a “regular” anchor and a “lunch hook” on the bow. This range of sizes was used to reduce the workload when raising the anchor.

With the advent of modern powerful electric (or hydraulic) windlasses, the technique has largely been replaced with the view that the “storm” anchor does far more good on the seabed than in the bilge.

Most experienced cruisers have stories of unexpected storms at anchor and the routine use of the “storm” anchor has advantages in dealing with poor holding ground or at shorter scopes, even when anchoring in milder conditions.

The only significant drawback is a little extra bow weight, but the anchor is normally a small fraction of the total ground tackle weight, and the modest difference between a “regular” anchor and “storm” anchor is likely to have little impact on most cruising yachts so this is rarely a significant concern.

If you have an electric anchor winch, consider moving the “storm” anchor from the bilge to the bow.

Aviation has some sage sayings. The most useless things in the event of a problem are:
• Fuel on the ground
• Runway behind you
• Sky above you

For a boat at anchor I would suggest the following would be high on the “useless” list:
• A storm anchor in the bilge

[a64pilot]

When you size a windlass, go big with it too, cause you never know when you May need excess power.
Attached picture is a 40 kg Rocna, the steel cable I didn’t measure, but it was as big as my wrist.

[boom23]

Originally Posted by a64pilot

When you size a windlass, go big with it too, cause you never know when you May need excess power.
Attached picture is a 40 kg Rocna, the steel cable I didn’t measure, but it was as big as my wrist.Attachment 180023

I once lifted a coconut tree trunk... I was in a S. Pacific atoll and there were a lot of trees at the bottom from the previous cyclone season. I knew they were there but there was not much room to anchor somewhere else. It was fun unwrapping the anchor chain from it. It was VERY heavy.

Speaking of anchor sizing, I noticed that Manson Supreme website has a new anchor size calculator, which proposes heavier anchors than before. Just FYI.

https://www.mansonanchors.com/anchors/#anchorselector

According to it, my next boat (Amel 50) should have a 125 lbs / 56 kg Manson Supreme anchor. I many have under specced my Ultra anchor at 99 lbs / 45 kg... Now, my once thought as heavy anchor, seems light.

For my now-sold Lagoon 450, Manson now suggests the 125 lbs / 56 kg Manson Supreme anchor. When I was getting the boat ready, the recommendation was the 80 lbs / 36 kg Manson Supreme. Go figure... I never dragged though.

[chowdan]

Here's a few photos of my anchor locker.

The previous owner ripped out the original windlass as it was a custom built 90v system and he did not like the power requirement.

I am going to be getting a Maxwell RC 8-8 as I've found one for half the retail rate. I am unsure how I'll mount it, but am thinking it may have to be on the removable hatch portion. Which bring to question of securing that hatch down.Attachment 180117

[KeelMe]

https://www.petersmith.net.nz/boat-anchors/

Peter Smith and the Rocna knowledgebase have a wealth of information on anchors and anchor rode. None of it is specific to Rocna but it is the foundation Rocna was built on.


For the sake of full disclosure I use a Mantus not a Rocna.

[StuartWeibel]

All chain is convenient if you have the capacity for the weight, but provides you no more protection in a blow than any other rode of similar tensile strength. In a blow, your rode is a straight pipe... catenary contributes not at all. If anything, all-chain reduces the shock-absorbing capacity of the ground tackle... no stretch there other than whatever snubber you have, and it is the shock-loading of waves and wind that will yank you off your set.

See https://www.petersmith.net.nz/boat-anchors/catenary.php

Also, go to the effort of calculating your windage... it will guide you in selecting an appropriate anchor. See Obsessing About Anchor Rodes

good luck

[geoff3nebel]

Originally Posted by chowdan

Hey all,

I am in need of all new rode, chain, anchor, and unfortunately windlass.

That being said, I am trying to scope out what would be best for my boat. My boat is weighing in at roughly 16t according to documentation and the scales when I launched her.

I am thinking I should get the Rocna 73lb anchor as based on their chart the 55lb would be the correct size so going one size up for being able to handle any storms the PNW or anywhere we go will make us feel a bit more comfortable.

Is this anchor size over kill? Would I be wise just to go with the 55lb and spend the extra $300 on going with all chain? It wouldn't adjust the cost of the windlass all that much as I will need to find one that will still support a 3/8" chain.

Any advice or recommendations welcome. Trying to align all the eggs before pulling the trigger on a windlass :\

I would go for the 55lb anchor and as much chain as you can carry. Dropping the hook and laying out a minimum of four times the depth at HW of chain will attach you firmly to the sea bed. Unless I am in an anchorage with limited swinging room, I tend to let out all my chain - 60m of 10mm on a 20kg Lewmar holds my 41´ Westerly Oceanlord pretty firmly in UK and French waters

[Captmatt]

I would stick with the larger Rocna and all chain rode. You’ll be glad you did when the going gets tough! Just my two cents and experience.

[kmacdonald]

A good deal on a Manson Boss that might work for you: https://www.defender.com/product.jsp?path=-1&id=3279217

[CatNewBee]

All chain is always better, it is the friction and weight, that holds the boat, the anchor only holds the end of the chain....[emoji12]

the problem with rope is, the friction on the ground may chafe it through on some sharp corals or rocks...

[arsenelupiga]

large anchor seem to be promoted by uk based sailors. I can only think that this has something to do with tradition. I guess in olden days this may have worked.

Math however does not support that. Chain centenary is the most important. Forces may nearly straighten 30 m chain, but will not do this to 60 m chain. Nope, your cleat will go first. I carry 120 m of chain for these pesky nights when one chooses to anchor in 40m instead of risking trip in shallow anchorage.