How heavy is too heavy?

[basssears]

16000# pilothouse (so plenty of windage) and we sleep well with 45# Mantis and 100' 5/16" chain and the rest rope rode.

Some (most?) manufacturers have paper templates you can print and cut out to test fit on your roller.

Be sure to pay attention to all the little connection points... no point in good holding modern anchor and a bunch f nice high strength chain held together by a shackle that is going to fail in 15knots of breeze.

[thinwater]

Originally Posted by noelex 77

The point I was making is that the shank does not adopt the same angle as the chain. As you can see in this example.

This does not mean the holding power at short scopes is the same as longer scopes. From memory the scope in this case was about 3:1. As you point out the holding power of most anchor designs is typically around 40% at this sort of scope, in average anchoring depths and substrates.

Agreed. I will tell you, however, the drop-off in soft mud is more rapid (aside from being far worse to begin with).

Chain buried with the anchor can also makes a difference, though the photographed anchor is not deeply set.

[noelex 77]

Yes, the loss of holding power as the scope is reduced is quite variable depending on the substrate, design of anchor, depth of water etc.

40% at 3:1 is quoted by a number of manufacturers, but it is only a very rough ball park figure to give users some idea.

In practice, when observing anchors underwater it is obvious that as the scope is reduced most anchor designs reach a point where they refuse to set at all. At this scope the holding will be very poor and the boat risks dragging in very light wind. The scope where this occurs varies considerably with different designs of anchor.

It is important to realise that while I am talking about scope, what is important is not the numerical scope number but the angle of pulł of the rode relative to the seabed. Many factors effect the angle of pull. So for example if you anchor on a downward sloping seabed you might feel you have used a nice 5:1 scope, but the effective scope may be 3:1 or less.

So even if you have a policy of always anchoring at reasonable scopes, your anchor's performance at a high rode angle can be important.

[jmac9365]

Mantus anchor....check out tests on youtube,feels like your hooked to a semi truck

[UNCIVILIZED]

Originally Posted by jmac9365

Mantus anchor....check out tests on youtube,feels like your hooked to a semi truck

Hooked the boat to an 18-wheeler once. Next thing I knew we were in Cleveland. Which was a bit of a problem, given that before I hit my bunk we were in Maryland. Great SOG though

[hamburking]

Originally Posted by Arrandir

I have seen that most boats in the same size (32 feet, 7 ton) have 15 kg anchors.

I used a 15kg bruce on a Hunter 35.5 and never had any trouble (plenty of big winds too).

I used a 10kg bruce on my Pearson 30 (heavy boat). Again, lots of wind, no trouble.

IMHO, a 15kg bruce is already overkill on your boat. If you really want to be sure, get a 20kg bruce, or better yet, a 15kg ROCNA. But IMHO, 20kg is plenty of overkill. You don't mention a windlass or chain. These are factors (and money) too. A 15kg anchor with 20 feet of chain is managable by a healthy adult, and you will be rewarded with big guns (biceps). A good bow roller and chain locker are important too.

[Arrandir]

Thanks for all the replies.
I will sail around the world, I must therefor be ready for most bottoms and windconditions.
I have 50 m 8 mm chain and will buy a Cobra 2. I hadn't heard about it until recently, but Cobra gets good reviews, at least compared to anchors for the same price.
The reason why I wanted to have a heavy anchor is to avoid situations when I'm not sure if it will hold, but don't hesitate enough to use another anchor in a crowded anchorage. I will feel safe often enough with 20 kg.

[ranger58sb]

Originally Posted by Arrandir

I have 50 m 8 mm chain and will buy a Cobra 2. I hadn't heard about it until recently, but Cobra gets good reviews, at least compared to anchors for the same price.

I know sailors are usually on the more-frugal side...

But in my mind, and FWIW, price and anchor selection have no place in the same sentence. A good anchor will save the boat: priceless.

Can't see paying extra for anchor bling unless there's a purpose (e.g., stainless, in some cases), but I can see paying whatever it's going to take to save the boat.

To the original question, I draw the line at an anchor weight -- plus the remaining deployed chain bits of the rode (~1-lb/ft) -- that I couldn't manually lift if our electric windlass were to crap out.

A secondary consideration would be about pulpit/roller and winch capacity, but all of that on our current boat already exceeds what I can lift manually anyway.

-Chris

[Spade Anchor]

Originally Posted by thinwater

Show us the data, because I very seriously doubt that is true. In fact, Spade has been reported by many sailors to be somewhat weak at short scope.

Show us the data. A graph of holding capacity vs. scope from an independent source. What you are saying is not true of any data set on any anchor I have reviewed. Otherwise, I read this as hype. If I am wrong, I apologize, but it defies soil mechanics.

Practical Boat Owner Data:
http://www.stfeurope.com/pdf/Practic...Owner-2002.PDF


Video proof:

https://www.youtube.com/watch?v=tqNzSrfG_8A

Real World Testimonals:
http://www.spade-anchor.com/IMG/pdf/...STIMONIALS.pdf

More Real World Testimonals:
https://www.morganscloud.com/2015/03...-right-anchor/

Competitions Data:
Catenary & Scope In Anchor Rode: Anchor Systems For Small Boats

Please provide sources for replies.
Thank YOU

[Gung Ho]

Much good advice has been given but nobody has mentioned the surface area of anchors which dictates their holding power in any given seabed and that has little to do with their weight, probably more to do with their strength/design.
The second thing no one has mentioned is the fact that if the shank is caused to rise more than 8 degrees off the sea bed from its set position then the anchor WILL pull out. Again its weight has not much to do with this phenomenon but much more to do with the size and length of chain attached to it; heavy chain short scope,or lighter chain longer scope again depending on the holding on the sea bed and surface area of the anchor.
My advice would be to choose one of the very modern anchors with big surface area, quick setting ability and go with the manufacturers recommendations for size/length of boat. After that it is up to you how much weight of what size chain you weigh the front of the boat down with and what size/ power of windlass you need to match the ensuing weight of tackle you have just chosen.
I have a 32ft boat with a Lewmar 1000 windlass, 8mm chain attached to a 10kg Spade anchor which I think is undersized according to the manufacturer. It is second hand from a 28ft boat but it has not let me down yet. Do not spend money needlessly. If the anchorage gets "too" rough you should not be there! Cater well for the average and avoid the exceptional!Good luck.http://www.cruisersforum.com/forums/...lies/peace.gif

[Steve Bedford]

"Much good advice has been given but nobody has mentioned the surface area of anchors which dictates their holding power in any given seabed and that has little to do with their weight, probably more to do with their strength/design.
The second thing no one has mentioned is the fact that if the shank is caused to rise more than 8 degrees off the sea bed from its set position then the anchor WILL pull out. Again its weight has not much to do with this phenomenon but much more to do with the size and length of chain attached to it; heavy chain short scope,or lighter chain longer scope again depending on the holding on the sea bed and surface area of the anchor."

Excellent points. The Super MAX anchor has the largest fluke area of comparable anchor sizes in the industry and, because of its concave shape, provided maximum holding resistance when properly set.

The leverage lifting upward on the rode attachment point on the shank can be tremendous. There are ways that folks can reduce that leverage and better keep the shank/rode attachment point on the seabed.

There are lots of experts in this list about anchoring and most still like to learn new theories and techniques. I would recommend the book authored by Rudy and Jill Sechez titled, Anchoring, A Ground Tackler's Apprentice. Basics and Beyond. It is an excellent easy read and a valuable resource. I have no affiliation with this book, just respect the opinions and experience of the authors.

Steve

[noelex 77]

Originally Posted by Gung Ho

The second thing no one has mentioned is the fact that if the shank is caused to rise more than 8 degrees off the sea bed from its set position then the anchor WILL pull out.

Welcome to the forum Gung Ho.

That is an interesting theory. Could you please explain the reasoning behind the 8° value?

If we can define the shank angle where an anchor will lose all grip, I am not sure the information helps. Anchors have a remarkable ability to keep the shank down despite a steeply angled chain exerting a significant upward pull. So it is hard to know what the anchor shank value is without diving down and checking.

One thing we can say, is that the shank angle to the seabed cannot be above 8° if the scope is over 7:1, providing the seabed is flat. Anchors can still drag at scopes greater than 7:1. Therefore, we can say that anchors can drag when the shank angle is less than 8°.

[Steve Bedford]

"One thing we can say, is that the shank angle to the seabed cannot be above 8° if the scope is over 7:1, providing the seabed is flat. Anchors can still drag at scopes greater than 7:1."

This will probably start another thread!
Correct about the angle at 7:1 and correct that anchors can drag with scopes greater than 7:1. The question and debate will be under what conditions might this occur? There are many factors contributing to this: Improper or incomplete setting of the anchor, anchor type not matched to the seabed substrate, anchor too small for the load, as mentioned unlevel seabed sloping downward toward the vessel, seabed impediment prohibiting shank from positioning on the seabed, and Mother Nature's severe weather conditions.

I am sure there are other factors. Dragging when one feels the set is good is why many boaters feel more secure with heavier anchors or concave or flat flukes or larger flukes, or anchors that can adjust to different seabeds or longer scopes (or combinations of any of these listed). Some anchors may perform much better than others under different circumstances and conditions.

Steve

[thinwater]

Originally Posted by Spade Anchor

Practical Boat Owner Data:
http://www.stfeurope.com/pdf/Practic...Owner-2002.PDF


Video proof:

Real World Testimonals:
http://www.spade-anchor.com/IMG/pdf/...STIMONIALS.pdf

More Real World Testimonals:
https://www.morganscloud.com/2015/03...-right-anchor/

Competitions Data:
Catenary & Scope In Anchor Rode: Anchor Systems For Small Boats

Please provide sources for replies.
Thank YOU

Oh come on. That is a politician's answer.

You said "The Spade anchor will perform at 100% holding power at a 3:1 scope." Even your data does NOT say that.

---

Per the reports you attached: The spade held 70% at 3:1 scope. The curves used to estimate this were way to straight for comfort; anchor data is NOT that clean, unless the soil was unrealistically clean. Realistically, including soft mud, trash in the mud, and soil liquification effects, 50% is a better estimate, and even that requires an optimum set.

Also, note that Danforth did better (85%) than Spade, and Fortress has been tested at about the same value.

I never said or implied that the Spade was not an excellent anchor. I believe that it is. I said don't exaggerate. 50-70% will be enough most of the time.

[double u]

huge-4-the-boat has always served us well, I have only one little caveat:
do NOT be lulled into complacency by the biggy thinking "it can never drag!": under the "right" conditions & bad holding even a far-too-big-for-the-boat anchor will drag