Anchors, Guns and Strippers!!!!

[Lost Horizons]

Originally Posted by Dockhead

I have been using Spade anchors of different sizes since the late 90's, starting with I believe 30 pounder and ending up with a 100 pounder, with a couple of sizes in between. The difference in bottom-penetratrating power between the small ones and the big ones is very striking, immediately noticeable. Even in relatively good bottoms the big ones go in noticeably better.

This is a very interesting data point. It would be great if it could be experimentally reproduced by an unbiased testing facility such as Practical Sailor. It does contradict my own experience, for I have not noticed any difference in setting performance of three different sizes of the same design (Bruce clone), although they were on three different boats that I had in succession over years, so I cannot make conclusive claims. I also wonder why anchor manufacturers are silent on non-linear anchor performance that you describe. It seems to have a great marketing value if the above were true. Unless smaller anchors generate bigger profit margins, which seems to be counterintuitive.

[Dockhead]

Originally Posted by Lost Horizons

This is a very interesting data point. It would be great if it could be experimentally reproduced by an unbiased testing facility such as Practical Sailor. It does contradict my own experience, for I have not noticed any difference in setting performance of three different sizes of the same design (Bruce clone), although they were on three different boats that I had in succession over years, so I cannot make conclusive claims. I also wonder why anchor manufacturers are silent on non-linear anchor performance that you describe. It seems to have a great marketing value if the above were true. Unless smaller anchors generate bigger profit margins, which seems to be counterintuitive.

Yes, testing would be very interesting. I can't prove anything and don't even have a good theory for why this is true, but I do know that I have heard similar reports from very experienced off-grid cruisers, and Dashew writes about this very thing, but this doesn't really prove anything conclusively.


To really understand what is going on here, and whether or not this is really true, I think you are right and we would need to have testing.


The very good work by Alain Fraysse does NOT indeed assume any disproportionate holding based on size, but this is an ASSUMPTION so maybe he's not really saying anything for or against this idea. Also he is talking about holding power and not setting ability.


Tuning an Anchor Rode

[Dockhead]

Originally Posted by Lost Horizons

. . . As for the density, it is the same for the different sizes of the anchors of the same design. If the latter was not true, smaller boats equipped with smaller anchors would have hard time setting them, which is not true.. . ..

Well, but note Post 137 above:

Originally Posted by GRIT

That's interesting. I just looked at spade anchor sizes and noticed the same thing. The spade s100 weighs 44 lbs, and the 200 weighs 120 lbs. Though it only has twice the area, it's nearly three times the weight!

Another data point.

Paul.

[GRIT]

Originally Posted by Lost Horizons View Post
. . . As for the density, it is the same for the different sizes of the anchors of the same design. If the latter was not true, smaller boats equipped with smaller anchors would have hard time setting them, which is not true.. . ..

Conversely, it would mean that heavier anchors work better, which many think is true.
The evidence shows that weight and size does not increase in parallel.

Paul.

[rslifkin]

Heavier anchors aren't more dense, as weight goes up in correlation with volume of metal. However, as you increase weight and volume, you end up increasing weight faster than you increase external surface area. And I think that's the key here.

[Lodesman]

Originally Posted by Dockhead

A couple of different boats. But including different sizes in the same boat. It's very noticeable.


One data point, but based on a lot of experience.

I'll trust your perception, but that still falls in the 'anecdotal' category and lacks the rigour of a controlled test.
Found an actual test that notes specifically that "larger anchors require a longer distance to embed" - granted the test defined 'fully embedded' as that point where ultimate holding capacity was achieved. It makes sense that the longer the shovel, the longer it takes to dig it in. It does not actually rate the initial penetration rate. It tends to support Viking's claim that an anchor can be too big.

at the bottom in the PBO verdict: http://www.spade-anchor.com/IMG/pdf/...BOAT_OWNER.pdf

[Lodesman]

Originally Posted by Dockhead

For the same reason probably I find the Spade anchors to work somewhat better than other "new gen" anchors -- the point of the Spade is full of lead, so the anchor is quite dense, plus with no roll bar there is less resistance to diving down (the thin roll bar on the Mantus is probably a similar advantage). I had a 55kg (121 pound) Rocna for a while on this boat; it was less dense and had a somewhat less sharp point, and was noticeably harder to set than my current 100 pound Spade, despite the extra size.

.

I think the point of the Spade's ballast isn't to add weight - it's to put the centre of balance at the point - the geometry of the shank would then tend to tip the anchor up onto its point when the rode is pulled. The roll bar on the Rocna only keeps the anchor from dragging inverted - it rolls it onto its side - which positions the point at a fairly shallow angle of incidence to the seabed.

[Izikalvo]

Originally Posted by rslifkin

Heavier anchors aren't more dense, as weight goes up in correlation with volume of metal. However, as you increase weight and volume, you end up increasing weight faster than you increase external surface area. And I think that's the key here.

Also, as harder and denser as the steel is used, its weight gets heavier.
Meaning that the steel used by the manufacturer also contributes to the general weight of the product, in this case, anchor, see here.

[noelex 77]

Originally Posted by Lodesman

"larger anchors require a longer distance to embed" - granted the test defined 'fully embedded' as that point where ultimate holding capacity was achieved. It makes sense that the longer the shovel, the longer it takes to dig it in. It does not actually rate the initial penetration rate. It tends to support Viking's claim that an anchor can be too big.

The suggestion that large anchors are going to take a long time to set and therefore are unsuitable is not correct. Take a look at my anchor photos and judge for yourself.

http://www.cruisersforum.com/forums/...26073-141.html

Below is one example. The marks in the sand show where the anchor has landed so it is easy to estimate the distance taken to set.

The red arrow shows the most rearward position where the anchor landed. The green arrow shows the point where the anchor had rotated around to the correct direction and had started to dig in. You can see the final position and estimate the setting distance. If you look at all my anchor photos you will see that this example is not cherrypicked for its exceptional rapid setting, rather if anything most of the time my Mantus anchor set more rapidly than this.

This is 57kg Mantus anchor, which is larger than most sailboats fit. It is also oversized (this was fitted to my previous 47 foot yacht). Much of the credit must go to to the Mantus anchor which is a design that sets incredibly rapidly. For a comparison a slow setting design such as a typical convex plow anchor will take many times longer to set no matter what the size.

If you look at my anchor photos there are examples of many different designs and sizes. While many cruising boats oversize their anchors, this is not universally true. I cannot think of single anchorage where any anchor from any boat set more rapidly than my large and oversized example. Most were longer, often much longer.

In short these photos show it is fallacy that a large anchor will take longer to set. The setting distance is far more dependent on the anchor design.

[wsmurdoch]

Originally Posted by Izikalvo

Also, as harder and denser as the steel is used, its weight gets heavier.
Meaning that the steel used by the manufacturer also contributes to the general weight of the product, in this case, anchor, see here.

https://amesweb.info/Materials/Density_of_Steel.aspx
Except for the tungsten and molybdenum tool steels, they all look about the same to me. (Both tungsten and molybdenum are quite dense at 19.3 and 10.3 g/cc.) What steel were you thinking of?

Bill

[Dockhead]

Originally Posted by Lodesman

I think the point of the Spade's ballast isn't to add weight - it's to put the centre of balance at the point - the geometry of the shank would then tend to tip the anchor up onto its point when the rode is pulled. The roll bar on the Rocna only keeps the anchor from dragging inverted - it rolls it onto its side - which positions the point at a fairly shallow angle of incidence to the seabed.

Yes, this is of course absolutely correct. That is the big advantage of the Spade, that it doesn't need a roll bar to land on its point. Another benefit is that the anchor is much easier to handle as it naturally points correctly so comes into the roller correctly.


But a side benefit is that the whole anchor is denser so should penetrate better and sink down better in mud.


Downside is it's much more expensive to build this way.

[rslifkin]

An oversize anchor will likely be easier to set (although if the bottom is really good it might not matter much, as any anchor will start to dig easily). Design will be the biggest impact on how much distance it takes to set once it starts to bite the bottom. But on a bad bottom (weeds, dense gravel, etc.), the heavier anchor should sink through the crap more easily, meaning it will go from sliding across the crappy bottom to starting to dig in more easily (even though the big and small versions of the same will set similarly once they start to dig).

However, there is a point where given a big enough anchor, you'd have trouble getting it dug in well, which could end up causing a holding problem if you get a wind or current reversal before it gets loaded enough to dig in further. However, unless you have a particularly underpowered boat, you probably can't fit a big enough anchor for this to become a real problem.

Personally, I've found that light weight for their size anchors, such as a Fortress, hold well, but can be a little more tricky to set. The Fortress has a ton of holding power, especially for how light it is. But because it's light weight, in some bottoms you have to be a bit careful and gentle setting it, otherwise you end up just dragging it across the bottom without it really digging in. Once it starts to dig, then you can load it up a bit more to dig it in deeper.

[Mike OReilly]

I've always like the reports and look of Spade . But I like the price tag less .

Does anyone have a sense of how the Rocna Vulcan stacks up against the Spade?

[rslifkin]

Originally Posted by Mike OReilly

I've always like the reports and look of Spade . But I like the price tag less .

Does anyone have a sense of how the Rocna Vulcan stacks up against the Spade?

I don't have a comparison to the Spade, but I'll have a 33kg / 73lb Vulcan going on the bow this spring. Judging by how similar the design is and the good reports I've seen online (from the limited number of people that have used them), the Vulcan should perform well. And the Vulcan price tag only had me thinking it's a bit pricey, while the price tag on the equivalent size Spade left me doing this:

[Dockhead]

Originally Posted by Mike OReilly

I've always like the reports and look of Spade . But I like the price tag less .

Does anyone have a sense of how the Rocna Vulcan stacks up against the Spade?

I like the Spade and have used Spades for decades but I'm not selling them. In my experience all the new generation anchors work well. I've never used the Mantus but have heard consistently stellar reports about them.