Upgrading to a Smaller Anchor

[rslifkin]

Originally Posted by kmacdonald

It seems a lot of people are using oversized anchors to compensate for poor holding anchorages. A little more care in selecting an anchorage might be the better choice.

This all depends on your cruising area. If you're cruising in an area with plenty of choices with good holding and room to deploy long scope, and especially if it's an area you're familiar with, you can get away with a lot less. In those cases, you can pick the good holding spots and put out plenty of scope and hold fine.

But having bigger gear means you've got more options. You can anchor in a worse bottom before holding power becomes inadequate. This could be due to no better bottom available, or you didn't know how bad it was, or it was just the better spot to be for other reasons. You also gain the option of being able to use less scope and throw away some of your holding power that way when swing room is a problem. Throwing away 30% of the holding power from an oversized anchor can easily leave you with still having enough.

[wingssail]

I love this quote:

Originally Posted by thinwater

...a rock climber that wants safety does not get a larger rope, he buys a good rope and inspects it often. It is strong enough. The difference is in how he uses it.

On the other hand....

Originally Posted by Gerrit Coetzee

For the difference between 15kg and 10kg, you wish to put at risk your safety, and the safety of other vessels around you?

We twice ended on reefs because of an undersized anchor.

Well, then, don't use an undersized anchor, and possibly work on your anchoring technique. In 34 years on this boat, anchoring in all kinds of situations and places, using a properly sized anchor (44lb) for our 43' boat, we have never dragged onto shore or shallow water.

Going lighter on a boat as your motivation to reduce safety is same as dropping food and water rations for the sake of weight gain.

His motivation is not to reduce safety.

A proper anchor at 5kg more does not seem that important, until you find your vessel on a reef or any other spot at night.

This, is of course true: 5lbs increase for a properly sized anchor is reasonable. And even 5lbs increase more than is actually needed isn't too bad either. But if having your boat light is important then one looks at avoiding those 5lb increases everywhere on the boat. It all adds up. I doubt if you, or many cruisers, pay any mind to weight on a boat, but some people do, and I don't see any reason to disparage him as a danger to others because we wants his boat light. He has not admitted to poor anchoring technique causing him to twice drag onto reefs.

It is not about penny wise and pound foolish, it is weight 'wise' and pound foolish.

Post like this make me worry as to sea savviness.

Posts like yours make me worry about closed mindedness.

[thinwater]

Increasing the size of an anchor by 20% increases holding by about 20% in most bottoms other than weed. You can argue that if you like, but the test results from many, many sources say otherwise. I've tested multiple sizes of the same anchor numerous times.


Change bottoms and holding capacity can vary 80-90%. Variations of +/- 30% from one pull to the next 10 feet apart are common in testing.


In the example of the rock climber I gave, what matters is not the size of the rope or the strength of the rock anchor, but how the anchor was placed. A 4500-pound anchor can pop right out if placed poorly, pulled in the wrong way, or if the rock is rotten. Same thing.



Just sayin'.

[Mike OReilly]

It seems to me that all this is a very simple calculation. IF you only anchor in known areas with known conditions, then you can target your gear to those exact conditions. In this case it makes little sense to go larger than needed.

If you are a cruiser (who anchors out), you have far less control over the conditions in which you must put down the hook. Here it makes sense to maximize your anchor system so as to give the widest range of holding possibilities. This is why I say get the largest 'new gen' anchor and largest amount of chain your crew and boat can reasonably manage.

This doesn't mean get the largest anchor available -- it's clearly possible to go too big. Every boat has limits, otherwise we'd all carry 10-ton moorings as anchors. Each boat and crew's maximum may be different, but that's where a little experience comes in. Learning what you and your boat can manage is part of the skills development for any cruiser.

But Thin's point about technique is one that often goes under-emphasized in these threads. Learning how to anchor properly is more important than the type or size of anchor. Some anchors are better than others, and some styles are better in certain conditions vs others. But without good technique, no amount or type of pointy metal will hold our boats once the wind and seas whip up.

[Cheechako]

Another consideration is : Your current anchor may have been a choice based on weight availability in the first place. I know on my 47 foot Passport, buying a new Delta I was left with a choice of 55# or 88#... (they hadn't added the 70# yet back then) I tried the 88# and returned it. Too big to use on my roller etc.
In a modern anchor, I probably would have opted for the 55# range anyway to start with.

SO I suppose "sizing down" description fits that scenario.

BTW, in a 70+ mph storm cell my 55# pulled out... but it wasn't an anchor failure, it was a bottom failure... the anchorage was clay and when I pulled that anchor up it was a big ball of clay... nearly as big as a medicine ball! ... You couldnt even see the anchor except for the shank sticking out. ... no anchor slippage.

[Mike OReilly]

That's the other thing about this discussion; weight is really just a proxy for holding power. Heavier anchors will have more ultimate holding capacity. But you can only accurately compare weights within the same anchor family: Rocna to Rocna, CQR to CQR, etc.

Making cross-comparisons between different types of anchors is highly problematic, and not really very useful. Design matters, so it is certainly possible to have a smaller anchor of one design with the the same holding power as a larger one of a different design. And of course, different anchors perform better, or worse, in different conditions. One may excel in certain substrates, but suck in others.

All this means it's hard to make simple weight comparisons between anchor types, let alone between radically different designs (fluke vs plow vs scoop vs claw vs...).

[Stu Jackson]

Ach, I was wrong, not a troll.


Should have been posted on the New Joke thread.


Thanks for the grins & giggles, kmac.

[kmacdonald]

Originally Posted by Stu Jackson

Ach, I was wrong, not a troll.


Should have been posted on the New Joke thread.


Thanks for the grins & giggles, kmac.

Stu, dont you have an undersized Rocna? I bet it holds just fine.

[kmacdonald]

Originally Posted by Cynara

If the new anchor is better than the old you would be defeating the purpose of the new anchor. What would be your actual savings.

Weight and easier anchor retrieval.

[thinwater]

Originally Posted by Cheechako

... BTW, in a 70+ mph storm cell my 55# pulled out... but it wasn't an anchor failure, it was a bottom failure... the anchorage was clay and when I pulled that anchor up it was a big ball of clay... nearly as big as a medicine ball! ... You couldn't even see the anchor except for the shank sticking out. ... no anchor slippage.

I would have loved to see that. Interesting soil mechanics. Very cohesive.


BTW, what was the scope? And was there any trash/sticks on the ball? It sounds like something cause the anchor to lift.

[Stu Jackson]

Originally Posted by kmacdonald

Stu, don't you have an undersized Rocna? I bet it holds just fine.

Nope, it's NOT undersized. It's sized properly FOR MY USE. In my oft-linked Anchor System Sizing Tables https://c34.org/bbs/index.php/topic,4990.0.html, I wrote: "...I used the 40 foot boat at 42 knots, which is partway between 42 and 60 knots for the 35 foot boat."

Others, with my same boat, use a Rocna 15 because they get afternoon & night time thunderstorms, one got a 20 because he was sailing both way up the BC coast and to Mexico.

And, yes, it holds just fine , thanks, here in the Gulf & San Juan Islands. If I went further afield, I'd have to resize.


For those who don't know me, I don't have a windlass, sail in protected waters and anchorages, and haul by hand. R10, 1/4" chain, 50 feet, oversized 5/8" rode because 1/2" wasn't available the day we left SF for the second time on our trip to BC (long rode wrap story).

[kmacdonald]

Yep, a Rocna 10 is two sizes smaller than Rocna recommends. Glad you got the one for YOUR own needs.

[mitiempo]

Originally Posted by kmacdonald

Yep, a Rocna 10 is two sizes smaller than Rocna recommends. Glad you got the one for YOUR own needs.

One size too small, not 2 sizes.

[Stu Jackson]

Originally Posted by mitiempo

One size too small, not 2 sizes.

This^^^ Thnx Brian.


But too small for what? I used the Rocna charts that came in the packing with the anchor that stated the pounds of pull or whatever the right term is, and, per my link, sized my SYSTEM accordingly.


Oh well, since kmac started this thread as a goof and many took it seriously, I figured I'd be goofy and tell my story.


Thanks to Frank Sinatra, I did it MY WAY.


Damn engineer that I am, I used Calder's tables. Helpful stuff, that...

[thinwater]

Originally Posted by Stu Jackson

Nope, it's NOT undersized. It's sized properly FOR MY USE. In my oft-linked Anchor System Sizing Tables https://c34.org/bbs/index.php/topic,4990.0.html, I wrote: "...I used the 40 foot boat at 42 knots, which is partway between 42 and 60 knots for the 35 foot boat."

Others, with my same boat, use a Rocna 15 because they get afternoon & night time thunderstorms, one got a 20 because he was sailing both way up the BC coast and to Mexico.

And, yes, it holds just fine , thanks, here in the Gulf & San Juan Islands. If I went further afield, I'd have to resize.


For those who don't know me, I don't have a windlass, sail in protected waters and anchorages, and haul by hand. R10, 1/4" chain, 50 feet, oversized 5/8" rode because 1/2" wasn't available the day we left SF for the second time on our trip to BC (long rode wrap story).

In fact, back in the day, 20-25 pounds for a 34-foot boat would have been considered normal, with lesser performing anchor. I would be comfortable with Stu's set-up around the Chesapeake Bay, no problem.



I cruised a 34-foot catamaran (a lot more windage) with a 25-pound Delta for a while, though eventually I went to a 35-pound Manson, which is equivalent, considering his is a mono.


And I can understand going up a size too. The problem on the Chesapeake, for example, is some really poor holding mud locations and powerful thunderstorms.