Anchor sizing questions

[Mike OReilly]

Would be interesting to correlate long-term anchorers with anchor size. Would require perhaps a three-step survey. I don’t think CF’s polling system can manage that, but it’s not a hard survey.

[boom23]

Eyschulman,

Keeping every other variable the same, there is no way to convince me, or most everyone I think, that anchor size does not make a difference... Yes, the newer generation anchors are better than the older generation ones. They have to be.

MANY factors affect anchor performance, like boat weight, freeboard, windage, hull type, chain length and weight, bottom type, swell/wave height and direction, etc. Anchor manufacturers cannot account for all of that when they spec their anchors. They average. It is up to the captain to decide what he is comfortable with and for what conditions.

I prefer to have the odds on my side.

[Delfin]

Originally Posted by ranger42c

Yep, been there, done that.

Our windlass does indeed have a way to lift our anchor "manually" -- except it doesn't work all that great. The final lift in that situation is really "manually". (And we don't have other winches, not having all of those sailboat things. )

Given that windlasses can be repaired or replaced... maybe that manual lift only has to happen once before the fix happens... and maybe lifting 75- or 100-lbs (or whatever) once can be acceptable...

But if you can't lift it, you may just have an issue that shopping could have addressed. My suggestion wasn't to go "light" -- just manually liftable. That could be 200-lbs for OP, for all I know...

-Chris

Just one opinion but...

You'll appreciate a heavy anchor every time you drop the hook and a lighter anchor once in a thousand times you have to raise it by hand. To prepare for that eventuality, we carry a come-along, which has potentially other uses than bringing an 80kg anchor and 150' of 1/2" chain on board.

[Delfin]

Originally Posted by eyschulman

The multiple anchor tests over the last decade have all made it clear anchor weight and size are not the critical factor in holding setting and resetting performance. The heavy oversized anchor crowd ignores science and is very old school. You want anchor security(never 100%) use a good all around deep digging anchor sized as manufacturer recommends pick a good spot to set it and set it well with a adequate scope. Chain will help particularly with abrasion resistance and better catenary angle. If you like to hobby horse use a heavy monster anchor and lots of chain. For those who think there is no retrieval issues with extra heavy gear maybe they have not been doing this long enough. Have you ever had a windless fail? Yes I have. Where I have boated in PNW-East Coast and VI there are lots of well protected anchorages and its the skippers job to pick one right for the conditions. There is little need to get beat up unless we are talking extreme weather which for most is rare and even there multiple lighter deep digging gear still has more holding power and the weak point is at the boat chafe and weak fittings. If you still need more security get an oversized aluminum spade or fortress and stow it below, they come apart..

Given the law of gravity, I'm sure you would agree that two anchors of exactly the same design but different weights dropped onto the same bottom will favor the heavier of the two in terms of holding power. But I am with you completely that an anchor that can dig deeper by design is preferable to one that cannot, all else being equal. Which may be why the Excel/Spade/Ultra design type seem to do so well.

[kmacdonald]

Your back will appreciate the smallest anchor to get the job done in 99% of the anchoring scenarios. It will never complain that you didn't drop the biggest anchor that will fit the bow. It won't keep you up at night in pain from the previous anchor retrieval. Go light and trust the new generation anchors, they're not your daddies anchor.

[Kenomac]

Buy a Spade or Ultra anchor according to the size chart.

[seadago]

With new generation anchor designs, a next-size-up from what the manufacturer recommends for your boat LOA and tonnage would be a good safe choice. The "biggest you can carry" (as has been suggested above) is excessive and unnecessary, and it will break your back if you ever have to bring it up by hand. Rode is up to your preferences. I don't particularly like all-chain rodes. Yes, chain ads to holding power, but only while the chain is lying on the bottom. Chain hanging in mid water only ads dead weight to your bow. Also, chain has very little elasticity. A cause of anchors unseating is the jerking on the chain caused by short period waves. Braided nylon cable for the longer section of the rode is a better option IMO. You can carry more of it with less weight overall. If you feel you need to improve your catenary, ad a weight to your chain a few yards before the link to the cable. This chinks your catenary curve, achieving the same effect.

[ranger58sb]

Originally Posted by Delfin

Just one opinion but...

You'll appreciate a heavy anchor every time you drop the hook and a lighter anchor once in a thousand times you have to raise it by hand. To prepare for that eventuality, we carry a come-along, which has potentially other uses than bringing an 80kg anchor and 150' of 1/2" chain on board.

Sure, fair enough, but there's that Boy Scout "be prepared" thing.

I do like heavier over lighter. I wonder, though. if perhaps the words "heavy" and "light" are relative for some and more absolute for others during this discussion.

Actually our anchor is in the neighborhood of 50- to 55-lbs, easily sufficient for our particular boat and I can also lift it manually... The next size up is 80-lbs I think; not sure I could lift that (maybe could) but it won't fit on our pulpit anyway.

A come-along is a good idea, thanks.

-Chris

[jkleins]

Rocna does size their anchors pretty conservatively compared to some manufacturers. They calculate for 50 knots and wave action (which is tropical storm strength) so if you at the bottom of the scale you might feel better then if you are at the top. I went up a size for our Vulcan because we were in the middle of the size recommendations and we could fit the bigger. I would probably feel fine with the smaller but this one works great so I don’t try to second guess.

Jim

[sailorboy1]

Originally Posted by chowdan

Is this anchor size over kill?

the only overkill in anchor size is when it doesn't fit on the bow

while chain weight does improve an anchoring "system" chain very very very rarely breaks and if you have all chain already I would put the extra weight into the anchor, which not only is heavier it has a greater surface area for holding

[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. My method is to keep high holding power aluminum secondary anchors(Spade and Fortress) in the bilge and set a second anchor with short chain and mainly braided rode from my dinghy when needed. Cruising most of summers for last 20 years in PNW only set second anchor a few times. While live aboard gunk holing on East Coast back in the 70s and 80s similar experience. Back then my heavy Bruce with heavy all chain rode did tend to drag in the common afternoon thunder storms. I doubt my present deep digging much lighter modern anchor would do that.

[overextendedfp]

the mantus anchor beats all the the competition hands down

[thinwater]

Originally Posted by Mike OReilly

Completely agree, on both counts.

I’m not sure which "multiple anchor tests” eyschulman is referring to. All the ones I’ve seen are as you’ve described noelex.

Size definitely matters with regard to anchor. But design, proper rode, and most importantly anchor technique, are the MOST important factors. Good technique can compensate for an undersized, or poorly designed anchor. And conversely, poor technique can make the biggest and best anchor useless.

I like that. In testing I've been held by a 2-pound anchor fine sand up to a 400-pound load (34-foot cat in a good breeze) and dragged a 35-pound anchor on hard pan in 5-8 knots, with a rode tension of 50 pounds.



(I often intentionally anchored with undersize anchors so I could observe how a properly sized anchor might behave in a storm, with yawing and surging, as opposed to simple pull tests. Just a small part of the research, but educational.)

[overextendedfp]

Exactly what boat do you have

[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.