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Old 09-28-2014, 01:58 PM   #541
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Setting and penetrating are quite different things Marin. One is dependent on the other of course.
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Old 09-28-2014, 02:05 PM   #542
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Setting and penetrating are quite different things Marin. One is dependent on the other of course.
You said the rollbar doesn't help with penetration. That's exactly what it's there for. Review the video as you clearly don't understand how the rollbar anchor works and what the job of the rollbar is. It's to force the fluke to PENETRATE the bottom. Once it has penetrated the bottom, the shape of the fluke and and geometry of the anchor then turn it which makes the anchor SET.

It's a very simple and brilliant design which I understood the moment I saw the demo of how it works, and it's why we bought one.
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Old 09-28-2014, 02:07 PM   #543
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I can only hope my anchor penetrates to the point where the roll bar clogs every time.
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Old 09-28-2014, 02:54 PM   #544
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Originally Posted by Marin View Post

The issue of convex vs. concave is purely physics or geometry or whatever science it is. A concave survace concentrates material--- be it mud, air, or dirt in a ditch-- by forcing it toward the center of the suface. In the case of an anchor, a concave fluke surface will concentrate the bottom material toward the center of the fluke, which will increase the fluke's resistance to the direction of pull. It's why the concave surface of a shovel picks up and holds more dirt than the convex side.

A convex surface sheds material.

Without regard to cleanliness...

I wonder if a concave design eventually collects enough weight toward the back of the fluke such that the tip no longer points downward... so the direction of pull becomes more or less horizontal from that point on?

Whereas a convex surface maybe never collects enough weight toward the back so that the tip always still points downward... and the direction of pull continues to dig deeper?

Not arguing, simply thinking (typing) out loud, as it were.

The Delta design is a convex flute, and our experience with it was generally positive. In soupy mud, I think I remember the whole shank showed evidence of having been buried... suggesting it at least keep digging further downward until we finally gave it a rest.

That was the time we did drag, during a raft-up when I had about 10 sailboats on our 35-lb Delta... Don't know overall weight, but we were a 14K-lb 34' powerboat, the shortest sailboat was about 25,' and most were in the neighborhood of 34-38'. Tidal current and a light breeze interrupted our happy hour for a bit, but one of the sailors came to the rescue... with a bigger/heavier CQR. The guys who came back in the dinghy from setting the replacement were pretty much all covered in muck. Yuck! Glad they offered to solve the issue, so I didn't have to go out there

In any case, I didn't fault the anchor; I think we just overloaded it beyond it's size/weight capabilities. And I always appreciated the "no moving parts" design.

Seems to me the Sarca Excel anchor looks similar to a Delta?

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Old 09-28-2014, 03:22 PM   #545
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Fortress or Danforth can NOT lay on their side... and ... there is NO upside down. Flukes did and dig. Fortress' additionally capable 45 deg. shank to fluke angle should make mud bottom setting even better, overall.

Jus sayen!
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Old 09-28-2014, 06:08 PM   #546
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Quote:
Originally Posted by Marin View Post
Peter-- The quote I included in my post was from Djbangi in his post 501, not psneeld.
Ah, apologies, I missed that one. Sounded like a misremembered version of psn's. Actually his, as I quoted, is nearer the truth, I think you would agree..?
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Old 09-28-2014, 06:49 PM   #547
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If the roll bar contributed to setting, after the anchor had been righted, then Peter Bruce who invented the roll bar would have used it himself. If the roll bar aided penetration and setting every anchor would have one. Take the roll bar off a Mantus, arrange that its on the seabed correct way up (it will not self right without the roll bar) and it sets more deeply and with a greater hold. I've tried it and Mantus said so (and they ought to know).

The roll bar resists penetration - its a hindrance and is about 10% of the surface area of the fluke (depends on the roll bar - some are smaller) edit - all anchor makers reduce anything that retards penetration - which is why we have thin shanks, why Fortress chamfer their shanks, why the Danforth HT and XYZ came with wire traces etc.

What a load of rubbish some people suggest
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Old 09-28-2014, 07:45 PM   #548
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So there you have it. "Remove the RB and achieve better penetration" the RB is like a starter on an engine. Once the engine's started it's just excess weight. Kick start motorcycles were great. MUCH smaller battery and no starter motor.

An anchor that uses weight for orientation (like a Delta or Spade) dosn't pay the RB drag penalty. Funny thing though that the Supreme and Rocna outperform the Delta and Spade. So obviously the RB ain't all bad.

Art the stock causes drag just like the roll bar.

There's no engine that's 100% efficient and there's no anchor that can hold a boat, set, pitch down advantageously, break out when asked ect ect. But we can do better than a RB anchor. But I think the best anchor will not excel in any one category but achieve excellent results more of the time in all categories. A Navy anchor would do that except that holding power would probably be lacking. How much it would lack is unknown among most or all of us. But then if one overlooked weight (as many here do re chain) the perfect anchor is already here.

The Mantus has a bigger RB than the Rocna or Supreme and if it performs as well (or better) that would be another indication that my interference drag theory playing a big role in holding power is correct.
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Old 09-28-2014, 08:21 PM   #549
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Quote:
Originally Posted by Marin

The issue of convex vs. concave is purely physics or geometry or whatever science it is. A concave survace concentrates material--- be it mud, air, or dirt in a ditch-- by forcing it toward the center of the suface. In the case of an anchor, a concave fluke surface will concentrate the bottom material toward the center of the fluke, which will increase the fluke's resistance to the direction of pull. It's why the concave surface of a shovel picks up and holds more dirt than the convex side.

A convex surface sheds material.

Rex Wrote:

Yes well I am not going to convince you but there is no harm with facts, concave –shovel is for removal of substrate, cuts in –cuts out and retains, add a roll bar, you now have a sausage maker, so well compressed it then becomes a resistance for hold, not lock up, no further depth.


A well designed shallow convex cuts in--- compressors, compression builds with depth, depth is encouraged with further load, plowing is not a result of convex, “ plowing is simply a result of directional concave sheers” we do not have plow sheers.


Marin we are not comparing substrate to air—water—air craft, we are talking substrate where speed has a minor effect as compared to how the above reacts.


Ranger42C Wrote:

Seems to me the Sarca Excel anchor looks similar to a Delta?


Rex Wrote:
The Excel is based on the same principle as the Super Sarca, convex body – turn down toe –cutting edges all round-- A single plain flukes that does not plow, whilst they look similar to the Delta they are two very different breeds, more importantly the Excel now over five years is building a remarkable reputation, I say remarkable as it has been a short time since its release, not just in holding power, but as an improved anchor design for many substrate types.


But you are right ranger42C they do look very similar unless you know what to look for.


HopCAR:

Sorry I cannot deliver you free anchors, if I did you would have to ban psneeld, seems all too difficult to some so we will carry on regardless supplying anchors direct at your distributors cost to offset freight, it may seem odd to operate this way, then again customers are so passionate about anchor technology there seems to be no length with some as to how far they are prepared to go, then again the landed cost with our discount works out pretty good for most.


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Old 09-28-2014, 08:59 PM   #550
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Whatever Smith said for marketing purposes to flog his product, the utility of the roll bar on a Rocna or a Mantus or a Supreme is because without it, the anchor is useless as it as likely to glide along the bottom upside down as in the attitude that will dig in. The Sarca Excel and Ultra achieve their results without a roll bar through a drooping tip and a lot of weight in the tip. When I lay my Ultra on the dock, it immediately flops into the optimum penetration position. It is completely unstable in any other position and I assume the Excel would be as well. Had I a Rocna without a roll bar, it would be perfectly stable upside down. As Rex notes, the disadvantage of the roll bar is that it prevents the anchor from penetrating as deeply as it would otherwise, and can load up to the point where the tip of the anchor rotates upwards, losing all holding power. The Super Sarca seems to avoid this both with its convex design that moves material to the sides, not concentrating it to pile up against the roll bar, but also by making the roll bar so thin it presents little resistance to digging in.

As a practical matter, the roll bar also adds resistance to dragging even if it prevents digging in as deeply, but this disadvantage likely disappears in high wind loads. Other digging anchors, like the Fortress will dig in so deeply under such conditions that they may be very hard to retrieve, which might be inconvenient but hardly could be said to be a disadvantage to an anchor if staying put is the primary objective.

Like everything else in engineering, there are trade offs in anchor design. To assert that roll bar anchors are some kind of pinnacle of anchor design is silly, since they are good in some ways, deficit in others and IMO ultimately the deficiencies outweigh the advantages, at least in a world where better all around anchors are readily available.
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Old 09-28-2014, 08:59 PM   #551
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If the roll bar has air or flotation it could serve two purposes. #1 keep the anchor from dragging upside down or on its side. The air could also cause the point to tilt down and help with setting
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Old 09-28-2014, 09:12 PM   #552
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Quote:
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Sorry I cannot deliver you free anchors, if I did you would have to ban psneeld, seems all too difficult to some so we will carry on regardless supplying anchors direct at your distributors cost to offset freight, it may seem odd to operate this way, then again customers are so passionate about anchor technology there seems to be no length with some as to how far they are prepared to go, then again the landed cost with our discount works out pretty good for most.Regards Rex.
Discount?

May I inquire for whom?

PS: That is a really long sentence.
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Old 09-28-2014, 09:43 PM   #553
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eyschulman,
Ever heard of the anchor called "Hydro Bubble"?

Now and then they delivered great performances.

They relied on a plastic air chamber high on the anchor to keep it right side up. The opposite of weight in the tip of a fluke. But I'm not shocked at their failure as all other anchors use weight as a positive force. Would be hard for an anchor to set w an air chamber lifting it up.
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Old 09-28-2014, 09:43 PM   #554
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Quote:
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The issue of convex vs. concave is purely physics or geometry or whatever science it is. A concave survace concentrates material--- be it mud, air, or dirt in a ditch-- by forcing it toward the center of the suface. In the case of an anchor, a concave fluke surface will concentrate the bottom material toward the center of the fluke, which will increase the fluke's resistance to the direction of pull. It's why the concave surface of a shovel picks up and holds more dirt than the convex side.

A convex surface sheds material.
One thing occurs to me that I have not heard considered, but I may have missed it here or in a different thread.

It seems reasonable that the deeper the anchor gets, the more compact the substrate will be, and therefor the better the holding. Between a concave and convex shape, might the convex shape while being set and shedding material, be able to dig deeper? Could that be an advantage?
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Old 09-28-2014, 09:53 PM   #555
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While I have not had the intestinal fortitude to read every post in this thread, a few overall themes emerge to me (when I say "boat" I mean the boat and its ground tackle system) :

• Most of the participants don't anchor out very much, so anchoring is still some sort of voodoo rite to them. Or, they only anchor in one kind of bottom. Or, both.

• People do not observe how their boat actually interacts with the water and weather, as evidenced by those who do not understand how current shifts work on their boat, or how the wind shifts direction and affects their boat.

• The lack of distinguishing between an anchor grabbing and an anchor setting. The universal desire to plop the anchor into the water and just have it grab with no further work.

In my opinion, the above issues cause the over, and, again in my opinion, ultimately virtually useless, analysis of the design of that hunk of metal at the very end of the boat, a phenomena the anchor marketers exploit to their advantage, several thousand years after man began anchoring water craft.
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Old 09-28-2014, 09:56 PM   #556
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Post 555 is right on!
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Old 09-28-2014, 10:01 PM   #557
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Quote by Great Laker:
Originally Posted by Marin
The issue of convex vs. concave is purely physics or geometry or whatever science it is. A concave survace concentrates material--- be it mud, air, or dirt in a ditch-- by forcing it toward the center of the suface. In the case of an anchor, a concave fluke surface will concentrate the bottom material toward the center of the fluke, which will increase the fluke's resistance to the direction of pull. It's why the concave surface of a shovel picks up and holds more dirt than the convex side.

A convex surface sheds material.


One thing occurs to me that I have not heard considered, but I may have missed it here or in a different thread.

It seems reasonable that the deeper the anchor gets, the more compact the substrate will be, and therefor the better the holding. Between a concave and convex shape, might the convex shape while being set and shedding material, be able to dig deeper? Could that be an advantage?



Rex Wrote:
Well it has worked a treat for us over twenty two years, remember convex without directional outward sheers is not a plow, deeper penetration favors the Excel over the Super Sarca as it has no roll bar, then again the Super Sarca has a greater holding area so depth is not so crucial.
Regards.

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Old 09-28-2014, 10:13 PM   #558
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One thing occurs to me that I have not heard considered, but I may have missed it here or in a different thread.

It seems reasonable that the deeper the anchor gets, the more compact the substrate will be, and therefor the better the holding. Between a concave and convex shape, might the convex shape while being set and shedding material, be able to dig deeper? Could that be an advantage?
Yes.
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Old 09-28-2014, 10:39 PM   #559
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Rex, I wish I was in a position to be your US distributor. I think your anchors would sell.

I think it would be a no brainer for Imtra Corporation. They already import Muir Windlasses from Oz, have the warehouse facilities and are already established as a distributor in the USA.
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Old 09-28-2014, 10:52 PM   #560
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Yes hopCAR you are right they do sell well over their, thanks very much for the contact I will look into it in the furture as we supply Muirs for over seas customers such as Imtra.

You are a good bunch blokes on the TF, thanks for your concern and contact.

Regards Rex.
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