Anchor design and misnomers

[estarzinger]

^^

Cotemar, I honestly think most of us get that. But I at least don't think it is all that useful in understanding anchor performance.

The more important questions:

- which ones dig in deeper/faster in penetrable bottoms
- which ones can be constructed to have greatest surface area, while still having the other desirable traits
- which ones set better in hard but still penetrable bottoms
- which ones set best and hold most reliabily in non- penetrable bottoms

The "pushing dirt to the sides" vs "pushing dirt to the middle" aspect really does not answer any of these more important questions. And there may well be complex non-obvious trade-offs, just for example the convex shape may have a lower coefficient of friction, which on a simple examination would seem to reduce holding power, but may in fact increase its ability to penetrate deeply and thus actually increase holding power.

[transmitterdan]

Originally Posted by Factor

Been down this path before Evans - its not a Delta copy, if it were then it would have a HHP rating like the Delta, rather than the SHHP rating that it actually has. I have seen both side by side, hell I have owned both on the same boat, the difference is quite marked when you see them up close and side by side.

The rating differences is not an answer to the question. Since you have seen the physical differences side by side then please describe them to those of us not in a position to see the Sarca. A plus would be an explanation or theory as to why those physical differences should be expected to result in better performance.

[downunder]

Originally Posted by Cotemar

Anchor evolution

Convex plow, problem bend is up which cuts the seabed and pushes it to the sides.

Flat Fluke, holds the seabed on the face of the fluke.

Concave fluke concentrates and holds the seabed on the face of the fluke.

Evans,

This is a good example of the plough discussion you comment on.
I expect we need a new SARCA Excel thread started with a heap of photos showing the differences between the Delta/Excel.

All we know is that actual users believe they act quite differently and do not act as a plough as suggested by some. I have not used one but as a prospective purchaser of an anchor value any useful contribution.

As a farmer I certainly would not want an anchor that ploughs the seabed. I want one that buries and holds to its maximum in various seabeds.

Cheers

[Marqus]

Originally Posted by estarzinger

And there may well be complex non-obvious trade-offs, just for example the convex shape may have a lower coefficient of friction, which on a simple examination would seem to reduce holding power, but may in fact increase its ability to penetrate deeply and thus actually increase holding power.

This single sentence raises the level of the discussion by orders of magnitude.

Cotemar's diagrams may be taken to imply that the "weight" of the soil/clay/stuff scooped up by the anchor surface is what delivers the anchor's performance, whereas it may be more strongly related to factors mentioned in the above post (in addition to scooping). The latter factors are obviously going to vary based on the type of seabed involved, which would make mathematical modeling in anchor design such an incredibly challenging task.

So I think "gut feel" and intuition when comparing anchors visually cannot really be relied on. Could be like saying "that shape of aircraft wing will fly faster than this one, based on looks".

You would imagine well-capitalized anchor manufacturers to analyze and model geometries (time consuming and expensive), before adding a great deal of experimentation and empirical data to the mix before releasing a new model to compete in the market.

Don't think they'll want to make all their data public.

Can part-timers like most of us on the forum obtain/produce even a fraction of the data the manufacturers deal with? I'm pessimistic.

I'm not offering a solution, and enjoy reading these forum contributions as much as anyone, but some of the posts tend to underestimate the complexity of the physics, as the quoted post so strongly suggests. And too much underestimation will not lead us to a useful place.

[Factor]

As I understand it Cotemar, that is the whole idea of the spine as you call it, it is designed to separate, penetrate, if you look at the excel it has a single plane fluke, when you watch the video presenting the Excel you will see how it forces the substrate over the rear rather than plow it to the sides

In the concave anchor environmental destruction video it is clear as well. Whereas the Delta has a plow shear, the Excels toe is turned down and is accompanied with cutting edges all round to further aid setting in hard clays, weed, and other various substrates. I think the underside is also interesting , it has a bulbous shape which I am told aids in pivoting/turning in tide changes or wind.

But honestly these are questions for the manufacturer, what I know is that the excel sets better and holds longer than the Delta, by far. I dont have to justify it to Evan or you, I had to justify to me before I spent the money and after.

It was worth every cent.

Again though I will say that I have no commercial involvement with SARCA. Just a happy owner and user. I dont give a toss if you like/don't like the Excel, couldn't care any less. I do object to justifications by people using misnomers and I do simply want a place where I can talk with other users of Excels to learn from them the good and bad experiences.

[Dockhead]

Originally Posted by Marqus

This single sentence raises the level of the discussion by orders of magnitude.

Cotemar's diagrams may be taken to imply that the "weight" of the soil/clay/stuff scooped up by the anchor surface is what delivers the anchor's performance, whereas it may be more strongly related to factors mentioned in the above post (in addition to scooping). The latter factors are obviously going to vary based on the type of seabed involved, which would make mathematical modeling in anchor design such an incredibly challenging task.

So I think "gut feel" and intuition when comparing anchors visually cannot really be relied on. Could be like saying "that shape of aircraft wing will fly faster than this one, based on looks".

You would imagine well-capitalized anchor manufacturers to analyze and model geometries (time consuming and expensive), before adding a great deal of experimentation and empirical data to the mix before releasing a new model to compete in the market.

Don't think they'll want to make all their data public.

Can part-timers like most of us on the forum obtain/produce even a fraction of the data the manufacturers deal with? I'm pessimistic.

I'm not offering a solution, and enjoy reading these forum contributions as much as anyone, but some of the posts tend to underestimate the complexity of the physics, as the quoted post so strongly suggests. And too much underestimation will not lead us to a useful place.

Marcus and Estarzinger have both raised the level of the discussion unrecognizably (especially for an anchor thread!). It's great to see that it is actually possible, after all, to say something intelligent about anchors. Who would have thought!

[noelex 77]

Originally Posted by Marqus

Could be like saying "that shape of aircraft wing will fly faster than this one, based on looks".
.

Someone with a reasonable knowledge of aerodynamics could do just that.

I think in a similar way we can intelligent comments about the performance of anchors based on their geometry. This is easier to do when the design is extension of an existing design rather than a radical new concept (like say the Hyrobubble).

There are a number of anchors that have a fixed convex design blade. The Delta and Kobra are very popular designs in Europe. These two anchors share many common characteristics.

In a similar way the concave roll bar anchors Rocna, Manson supreme, and Mantus also show similar performance.

We can evaluate the anchors further looking at weight distribution tip sharpness, blade area etc.

A good aircraft (or yacht) designer can predict the performance of their creation very accurately before its ever left the drawing board. We are not at at that level of sophistication when evaluating anchors, but I believe we can come to some useful predictions.
Once an aircraft is constructed its speed, climb rate, fuel consumption etc can be accurately measured. Evaluating anchor performance is far less precise, so concentration on those designs contain favourable characteristics for further evaluation is especially helpful.

This does not mean that all convex anchor will perform the same. Sharper and more complex tip profiles, better weight distribution, tweaks in the geometry can all achieve worthwhile improvements and produce class leading performance.

But I am skeptical that they can elevate themselves above the limitations of their class that are governed by the fundamental geometry.

Time will tell.

[Kettlewell]

I dont have to justify it to Evan or you, I had to justify to me before I spent the money and after.

So, how did you justify the performance of an Excel before you spent money on it? I'm not trying to be snide, just wondering what evidence and facts you had that prompted you to write that. For myself, I find it hard to determine what is the best anchor for me based on the claims, counterclaims, flawed published anchoring tests, and just the looks of an anchor.

[Factor]

Fair question Kettlewell. I spoke at length with the designer, watched the videos, spoke to the independent testing agency, spoke to lots of owners and current users, spoke to a few former work colleagues in various Water police establishments - and well you get the idea.

All of which convinced me it was probably worth a shot.

The big key was that the manufacturer said to me if you don't like it - give it back, no problem.

So I tried it - liked it - a lot and I am not giving it back.

And unlike some other people, I don't say its the only good anchor out there, I am sure that Manson Supreme and the rest are quite good. But I want a convex burying anchor for a number of reasons.

I didn't dive my anchor on the weekend, I walked it, when the tide was out it was in knee deep water, it was buried, and there was little evidence of furrowing. I walked a number of other anchors and with out exception the CQR types were all barely in the sand. There were a couple of roll bar types that were in - but I wouldn't call them buried. But that may have been slack technique as much as design etc.

[Jimbo485]

So who has a Boss? Any comments, positive or negative?

[denverd0n]

I majored in physics at university and, personally, have very little interest in the physics of anchor design. What I am interested in are real world results. What sort of experiences are actual people having using the particular anchors in a variety of different anchorages? That's all that really matters in the end.

[Kettlewell]

Fair question Kettlewell. I spoke at length with the designer, watched the videos, spoke to the independent testing agency, spoke to lots of owners and current users, spoke to a few former work colleagues in various Water police establishments - and well you get the idea.

I think that's more than most of us do, so kudos on your hard work, but you have to admit it is still not a scientific method. For myself, I have tried a few different anchors numerous times in the same harbor that I know intimately, and I have observed others using many other types of anchors in the same harbor, and my conclusion is that given decent holding and a reasonable-sized anchor that it mostly comes down to technique up through gale force. A properly set anchor and a decent amount of scope and you're good to go with any modern anchor. It is very rare that most of us get to test the outer limits of an anchor's holding power, so things like ease of setting and handling are more important 90+% of the time.

The one place modern anchor designers have improved things greatly is realizing that a very sharp and weighted point can make a huge difference in hard bottoms and weeds, extending the versatility of the main anchor. I sometimes wonder if you could take almost any old fluke design and put a sharp enough point on it to start penetration and you're good to go for the most part. Though the new-gen anchors also have designs that orient the anchor more quickly to get that point started into the bottom. That's how the Fortress anchor beats out the Danforth, despite having nearly identical dimensions--sharp blades start deep penetration faster.

So I wouldn't be surprised if the sharp-pointed Excel beats out the similar looking Delta. And look how the Bruce aficionados point out how the originals have much sharper flukes than the knock offs. And, we have read how some CQR users believe in sharpening the point with a file.

[Cotemar]

Here is an illustration of how the problem bend on a Convex plow anchor not only
cuts the seabed and pushes it to the sides, but it also loses projected surface area

Flat Fluke, holds the seabed on the face of the fluke and has the most surface area.
This is why Fortress with its sharp tip flukes, once set in a straight one direction pull, cannot be beat.

Concave fluke, concentrates and holds the seabed on the face of the fluke, but also loses projected surface area.
It loses less projected surface area than a Convex plow anchor, because its bend angles are smaller

[Liam Wald]

Anchors that I have owned since 1980;
Danforth Standard
Danforth HT
Fortress
CQR
Bruce
Delta
Rocna

Anchors that have dragged after set;
Bruce.

Current anchors on board;
Rocna (primary)
Delta
Fortress

[Anonymous7500]

I spent some time on the Anchor Right website reading about there tests and watching the videos. The problem that I have with the test is that the rode is always at an infinity-to-one scope. If the most widely used scope is 5:1, why aren't the anchors tested using this scope?

The testing apparatus doesn't need to be complicated. The TATS tool is going in the right direction though. However, they seem to use the infinity-to-one scope. Of course, they don't say what scope they used for the test. The TATS connection point looks to be about 3' off of the ground. Unless they are using a 15' rode the test doesn't reflect real world conditions. The test stand only needs a connection point for the anchor 5' above the ground and the pull point with a force scale slightly lower on the opposite side. There doesn't need to be an operator chair. Putting a human in that position is irresponsible at the very least.

The SARCA Excel does appear to be a modified whatever. But, who cares? It seems that they have made significant improvements over the design that they modified. The outermost part of the blades appear to be in the same plane on both sides while the plow portion is at a much leaner angle. There is also a two stage angle from the point back along the center-line which presents the tip in a downward posture. The back edge is flares back down, minimizing the plow affect.

One last thing, SARCA does not do themselves any favors with the pictures that they post of their product. It is too easy to develop a 3D part that can be rotated in the web browser to not have one. The shiny surfaces of the part and angle that the pictures are taken make it difficult to accurately determine the geometry