Anchor sizing questions

[zboss]

Originally Posted by kmacdonald

Fair enough. What's your specific formula for anchor size so we can plug in our numbers and have it spit out the perfect size anchor?

Well that is my point... I don't think its just the weight. Look at the Rocna anchors... the Rocna "Classic" and the new Vulcan. The new vulcan weighs the same but exceeds the fluke size of the original Rocna. I would believe that the Vulcan would have a higher holding capacity than the original Rocna once dug in....

So that means that you could use the Vulcan (44 pound version and up) to avoid going up in weight while enjoying a higher holding capacity.

This is just my opinion here based on a very unscientific method - I have no way of proving this to be true.

[thinwater]

Originally Posted by Ecos

The mfg has no idea what it will be like in the real world. You can't test for a 2 am squall. Bigger is better.

Hmmm...


Rocna was invented by a sailor.


Mantus was invented by a sailor.


Spade was invented by a sailor.


I'm sure I could find more examples.



All three where very active in the companies for quite a while and I'll bet all three experienced a few mid-night squalls.


So where did this assumption come from? It doesn't seem to match the facts.



(Obviously safety margins, bottoms, and sailor skill come into play when sizing. I won't join that fight.)

[Mike OReilly]

Originally Posted by kmacdonald

Fair enough. What's your specific formula for anchor size so we can plug in our numbers and have it spit out the perfect size anchor?

I’ve stated it many times:

I boil all this down to a simple recommendation: for your bower anchor, get the largest new-gen anchor you and your boat’s system can reasonably manage. Use as much chain as your boat can manage without compromising other factors.

[Jim Cate]

Seems to me that anchor manufacturers have some conflicts of interest in their sizing charts. On one hand, they want the anchor to work for the buyer, and recommending a larger size improves the likelihood of success. But, larger anchors cost more, so buyers are reluctant to upsize if they can avoid it And if a competitor recommends a smaller, less expensive anchor for the boat, off goes the customer to that cheaper alternative. A quandary faced by all anchor makers...

And I kinda suspect that this sort of marketing is why one sees so many really inadequately sized Deltas on new boats, for as I recall their sizing charts promote such practice and boat mfgs are always looking at means of lowering costs of delivered vessels.

If one looks into the fine print, I believe that most anchor's sizing charts mention some set of operational criteria for the sizing... things like "good for 30 knots" or "for storm conditions, go one size larger"... that sort of caveat, not likely to be read and understood by all buyers. None that I've seen are couched in the terms that a long range cruiser would use... "good up to full storm conditions", or "usable in unprotected anchorages up to 50 knots" or sumpin like that. Until I see such words, I'll stick to thinking that for serious cruising one should likely exceed the sizing charts ideas by a decent margin.

Jim

[Souzag818]

Hey Jim and Ann- I value your opinion, and most of the time I completely agree with your comments. You're one of a handful of people here that are doing it full time and I respect that. I've got a Spade S100 and have never been happier or felt more secure and safe whenever I've used it. It's held my boat in 30 knots, with 100' of chain and about 30 of nylon rode let out, and I had another 220' of line I could have let out, but didn't need to. My question is what do you have for an anchor? I'm not planning on giving up my Spade, I'm just curious.

[ranger58sb]

Originally Posted by thinwater

Rocna was invented by a sailor.

Mantus was invented by a sailor.

Spade was invented by a sailor.

I think (but don't know for sure) the SuperMAX was invented by a guy into commercial anchoring of some sort.

Steve Bedford could likely correct me if I've remembered incorrectly...

-Chris

[jkleins]

Originally Posted by Jim Cate

Seems to me that anchor manufacturers have some conflicts of interest in their sizing charts. On one hand, they want the anchor to work for the buyer, and recommending a larger size improves the likelihood of success. But, larger anchors cost more, so buyers are reluctant to upsize if they can avoid it And if a competitor recommends a smaller, less expensive anchor for the boat, off goes the customer to that cheaper alternative. A quandary faced by all anchor makers...

And I kinda suspect that this sort of marketing is why one sees so many really inadequately sized Deltas on new boats, for as I recall their sizing charts promote such practice and boat mfgs are always looking at means of lowering costs of delivered vessels.

If one looks into the fine print, I believe that most anchor's sizing charts mention some set of operational criteria for the sizing... things like "good for 30 knots" or "for storm conditions, go one size larger"... that sort of caveat, not likely to be read and understood by all buyers. None that I've seen are couched in the terms that a long range cruiser would use... "good up to full storm conditions", or "usable in unprotected anchorages up to 50 knots" or sumpin like that. Until I see such words, I'll stick to thinking that for serious cruising one should likely exceed the sizing charts ideas by a decent margin.

Jim

“Unlike other manufacturers, our anchor sizing recommendations are intended to provide an anchor adequate for use in most all conditions. We base our calculations on 50 knots of wind, associated surge, and poor holding bottoms. For more on our philosophy and rationale, please consult our Knowledge Base article on our sizing recommendations.”

This is from Rocna’s sizing chart. It does seem like they are trying.

Jim

[model 10]

Originally Posted by thinwater

Hmmm...
So where did this assumption come from? It doesn't seem to match the facts.
(Obviously safety margins, bottoms, and sailor skill come into play when sizing. I won't join that fight.)

You have to consider those things in the real world.

[thinwater]

Let's say you are building a 40' boat from scratch, so it is on you. Blank sheet of paper, no "biggest you can handle" advice because you can handle whatever you put in the roller and windlass for. This is close to what the OP asked, since he is replacing the anchor, rode, and windlass. Replacing the roller too is nothing.

For example, my last boat could have fit anything from 25 pounds (what it came with, which was too small) to 200 pounds (new roller and windlass, but there was room). 34-foot catamaran. How would you chose? No "biggest I can handle" cop out, since I was fully willing to change the roller.

Yes, weight counts. But put a number on it. For a 40' mono I'd probably suggest 50-60# if traveling far, combined with enough high strength chain meeting ABYC Table 1. One size smaller, about 45 pounds, if cruising locally.



Now you.

----

Second thought. I'm not in love with one-size-fits-all solutions. I'm betting out tool boxes don't support that thinking. Many of the sailors on this thread will never see coral and really don't care about it. That will account for more than 70% of US sailors I'm guessing. Chain has other advantages--catenary and smooth windlass operation-- but chafe resistance is going to ring hollow for these guys. Just sayin'.

[Allied39]

LOl, asking sailors about anchoring, too funny!!

Bottom type, how much windage does your boat have (huge factor), scope out, all chain, anchor type, riding sail.....are all variables to be considered.

OK, In my experience, less than some but not insignificant I have found that it's best to be on all chain. I find that the anchor is not as important as having all chain.

However, I always say that any idiot can make a boat move, keeping it in the one place is whats hard.

I sat the last two huricanes to hit Jacksonville Fl out on my boat in the St Johns river, no issue , no problem. And that was on a 35 CQR .

I use a CQR, but I am not going to say thats the best anchor. I have seen a 70lb rocna drag across a big bay in honduras 3 times. There is no such thing as the "RIGHT" anchor. Anybody who makes that statement is delusional. To make the statement "the right anchor for my situation".....well, thats perfectly reasonable.

So, my last statement is : First is as little windage as possible, then as much chain as possible and lastly any good anchor thats a bit heavier than recomended.

PS; I did'nt like the 70lb rocna, solely because it was too heavy to hand set (dig through) sea grass. But once again if you are not the type of fellow to hand set, that would be of absolutely no concern.

Have a great day,
Ralph

[model 10]

Maybe then it's a matter of experience. I would think everybody who has done some serious cruising knows that things don't always work as planned. I have made all kinds of mistakes when anchoring and need all the help I can get.

[Allied39]

Thats smack on! the reason you get so many different opinions is we all have had so many different experieinces.

A mistake is when you did'nt learn from the last time something did'nt go right and did it again. The first time something doesnt go right is where we get experience.

Personally I prefer to learn from not only from my own experiences but others as well.

How many times I have looked and said "hmm, that doesnt look good"....enquired as to what happened and vowed never to do the same.....well, I would say countless.

Good luck!

[Delfin]

Originally Posted by thinwater

Let's say you are building a 40' boat from scratch, so it is on you. Blank sheet of paper, no "biggest you can handle" advice because you can handle whatever you put in the roller and windlass for. This is close to what the OP asked, since he is replacing the anchor, rode, and windlass. Replacing the roller too is nothing.

For example, my last boat could have fit anything from 25 pounds (what it came with, which was too small) to 200 pounds (new roller and windlass, but there was room). 34-foot catamaran. How would you chose? No "biggest I can handle" cop out, since I was fully willing to change the roller.

Yes, weight counts. But put a number on it. For a 40' mono I'd probably suggest 50-60# if traveling far, combined with enough high strength chain meeting ABYC Table 1. One size smaller, about 45 pounds, if cruising locally.



Now you.

----

Second thought. I'm not in love with one-size-fits-all solutions. I'm betting out tool boxes don't support that thinking. Many of the sailors on this thread will never see coral and really don't care about it. That will account for more than 70% of US sailors I'm guessing. Chain has other advantages--catenary and smooth windlass operation-- but chafe resistance is going to ring hollow for these guys. Just sayin'.

If weight is irrelevant to the thought exercise I think the "number" is somewhere around 80# for most new gen anchors to have a hook that will penetrate most bottoms. Gravity is reality, and surface area on new gen anchors, or any anchor for that matter, doesn't go up proportionally to the mass with the same external design. The greater the mass, the more likely the anchor will penetrate and dive into the bottom, all other factors being equal. All other factors are never equal, however, so there is a balance between compactness and weight if you are talking about the ability to penetrate. If two anchors weigh the same, but one is designed for maximum holding power once buried and another is designed to bury itself more easily by having a more compact surface area, which anchor is best will depend on the particular bottom conditions. If muddy, the former. If compacted sand and shell, the latter will be better. In my experience, 80# is sufficient mass to dig in well in most conditions. We carry a 176# Ultra that is relatively compact, but which has a disproportionate amount of the total mass in the toe. I like this design because while you can increase holding power by increasing surface area (once dug in), you can also increase it by designing a diving anchor that just keeps digging deeper the more you pull on it. Spade, Ultra, Excel - all these are designed with this in mind. Rocna, Manson, Mantus depend on a sharp toe that digs in really easily, but the trade off is a hook with a roll bar that inhibits digging in a bit. That said, once you get over 80#, the hook is going to bury itself up to the limits of the design because gravity really does work.

[JDWS]

Originally Posted by jkleins

“Unlike other manufacturers, our anchor sizing recommendations are intended to provide an anchor adequate for use in most all conditions. We base our calculations on 50 knots of wind, associated surge, and poor holding bottoms. For more on our philosophy and rationale, please consult our Knowledge Base article on our sizing recommendations.”

This is from Rocna’s sizing chart. It does seem like they are trying.

Jim

Jim (and Jim) have good points. Going by manufacturer’s recommendation still doesn’t tell you much without the fine print. Our boat came to us with a 10kg claw that met that mfg’s recommendation. Rocna’s recommendation for the same boat was 15kg, which now hangs on our bow. I both sized up and met the mfg recommendation with the same hook because the companies size differently, as Jim points out. My wife now sleeps well at night, and I only poke my head up a couple times, depending on the weather

What I haven’t finished yet is setting up the rest of the ground tackle. For now, we are still swinging off of the original nylon rode plus 35 ft of 5/16 chain. In the PNW, being choosy about weather, abundant well-protected coves, and good mud holding this is working for now, but before moving onto the boat for the 2019 season, I want to upgrade. My current thinking, based on a lot of reading and chatting with other sailors (and our own overnight-to-2 wk cruises in the area) is 30 meters of 5/16 backed my nylon, and move the existing rode plus the 10kg claw to the stern. We plan to stay in the region for the next couple of years, but may also jump to the sea of Cortez at some point.

Any thoughts?

[kmacdonald]

JDWS, 1/4" G40 would be fine for your boat. A 10 kg Rocna would be OK also.

Good info here: Rocna sizing recommendations (Rocna Knowledge Base)