Anchor Surface Area Comparison - Manson Supreme vs CQR

[Dockhead]

Originally Posted by craigsmith

. . . concave flukes . . . are quite superior to flat flukes which in turn are superior to convex plows.

Do you have some technical evidence of this? Why would this be the case? Has anyone done any real objective research?

[Fortress]

Surface area is certainly a key component to anchor performance, as the larger the surface area, the greater the resistance the anchor will have to breaking free from a sea bottom.

Another key component is the anchor's ability to bury deeper into a sea bottom, because as anyone can easily imagine, the deeper the anchor buries into a sea bottom and the more weight from the sea bottom that is on top of the anchor, the greater the resistance will be to the anchor breaking free, once again.

This is why we precision machine the two large flukes and taper the shank of our anchors to be sharp, so that the Fortress is more like a razor blade cutting into a sea bottom vs. a dull knife. This sharpness allows for faster setting and deeper burying, resulting in greater holding power, particularly in any form of a clay, mud, or sand bottom.

Admittedly, a complaint that we might hear from our customers is getting the anchor back out after a heavy blow. Sometimes these complaints come in the form of jokes, i.e. the anchor was stuck on the core of the earth, it pulled up dinosaur bones or fossils, or a Chinese gardener, etc.

As a further example, on Monday we received a call from an 87' US Coast Guard vessel in Texas who have been using our 47 lb FX-85 as their primary anchor. The "coastie" told us that they hung on the anchor for 3 days since the seas were too rough to go out on their patrols. When it came time to break the anchor free, they couldn't and so they had to cut it loose.

If they had they used some form of a buoy or trip line, that might not have occurred, but that is a topic for another day. Maybe it was stuck in a large camp of mermaids, who knows.

Regards,
Brian

[Fortress]

Originally Posted by Dockhead

Do you have some technical evidence of this? Why would this be the case? Has anyone done any real objective research?

I can provide test results from Australia, France, Germany, Italy, and Sweden which will certainly present real objective research, as you wish, and I have already sent this info to one of the post readers.

If there are others who want to read it, then just send me a private message with your e-mail address and I will fire away.

Regards,
Brian

[Blue Crab]

Originally Posted by S/V Alchemy

When Maine gets bored, Practical Sailor gets nervous. The guy's a one-man Consuming Sailor Reports.

That's a compliment, by the way.

Classic. I feel exactly the same way. How about the exposition last year where he was measuring the drag on something in the water...I can't even remember what but I'm laughing out loud right now and I can't even recall what he was testing! But it was damn sure thorough.

Thanks MaineSail.

[craigsmith]

Originally Posted by Dockhead

Do you have some technical evidence of this? Why would this be the case? Has anyone done any real objective research?

Yes, for the same reason a parachute is concave, and yes.

A good place to start if you're genuinely interested would be Alain Poiraud's book The Complete Anchoring Handbook, as much as it's a bit of an infomercial for Spade, and the Blackwell's Happy Hooking; both explain nicely how a concave fluke is demonstrable superior than the alternatives.

[S/V Alchemy]

Originally Posted by tgzzzz

Classic. I feel exactly the same way. How about the exposition last year where he was measuring the drag on something in the water...I can't even remember what but I'm laughing out loud right now and I can't even recall what he was testing! But it was damn sure thorough.

Thanks MaineSail.

You have no idea. Reading his opus on the joys of butyl tape in the far, far larger topic of cutting holes and sealing F/G decks...it's like taking a course at Youglassit University.

This is my favourite, though. Finally, anchors and crimping, together under the same subject heading: Marine Wire Termination Photo Gallery by Compass Marine at pbase.com

[Dockhead]

Originally Posted by craigsmith

Yes, for the same reason a parachute is concave, and yes.

A good place to start if you're genuinely interested would be Alain Poiraud's book The Complete Anchoring Handbook, as much as it's a bit of an infomercial for Spade, and the Blackwell's Happy Hooking; both explain nicely how a concave fluke is demonstrable superior than the alternatives.

There's nothing more technical in either of these books than "yes, for the same reason a parachute is concave".

Enquiring minds really want to know. This is a problem of soil mechanics and there are solid scientific and engineering approaches to how anchors hold. Have they simply never been used in relation to boat anchors? I really can hardly believe it.

[Maine Sail]

Originally Posted by S/V Alchemy

You have no idea. Reading his opus on the joys of butyl tape in the far, far larger topic of cutting holes and sealing F/G decks...it's like taking a course at Youglassit University.

This is my favourite, though. Finally, anchors and crimping, together under the same subject heading: Marine Wire Termination Photo Gallery by Compass Marine at pbase.com

Aw c'mon that's old. I've gone one better and invested in a digital strain gauge..

For crimps....

http://www.youtube.com/watch?v=pXYgcE4zemE

& anchoring / mooring stuff too. This is 17-18 knots capturing "peak" loads on a 36 footer. I like my toys..!

http://www.youtube.com/watch?v=y2oRFt5cX_0

P.S. If anyone out there wants to "donate" the software so I can connect this strain gauge to my laptop to measure and graph real world scenarios I'd be more than happy to accept it!! Maybe an anchor manufacturer is willing to put their money where there mouth is for some truly independent and unbiased testing..???

[Kettlewell]

No, I'm afraid many anchors if not most have been designed by clever backyard engineers, so the technical data behind the designs is often lacking. That's not to say they haven't come up with some pretty clever stuff that works!

One thing that perpetually annoys me is that the actual loads an anchor is required to resist are only vaguely known. The usual ABYC chart of anchor loads is based purely on theory as far as I can tell, and is suspected by several authorities to be way too high. Bob Smith and I believe Don Dodds did some actual on-the-water measurements of the loads put on an anchor line on various boats under various conditions, and the loads were drastically less than the ABYC charts. I have long suspected this to be true based on some of my own observations. The main one being that I can physically pull in the line even in near gale conditions (a bit) and I don't believe I am capable of generating thousands of pounds of force. The ABYC load for a boat like mine in 15 knots of wind is something like 300 lbs, and that just seems way out of whack because I routinely pull in the anchor by hand in that much wind.

In any case, I think many things about anchors and anchoring are based on seat-of-the pants engineering.

[Lancerbye]

Well we have anchors and crimp connectors in this thread. Now if we can sneak in guns vs no guns, batteries and cats vs monos all other threads could be closed. lol

[Maine Sail]

Originally Posted by Kettlewell

The ABYC load for a boat like mine in 15 knots of wind is something like 300 lbs, and that just seems way out of whack because I routinely pull in the anchor by hand in that much wind.

Conservative yes, but maybe not totally out of whack, look at the video above for a 36 footer. 17-19 knots and seeing 209+ pounds... Fetch & waves also add into this equation and in the above video there is maybe 8"-10" max of wind ripple/wave. If you're exposed the snatch loads could be rather high for the peaks which could potentially un-set a poor holding anchor. The ABYC numbers are very conservative but I'd still want an anchor that could do a conservative "worst case"...

[Kettlewell]

Maine Sail, do you have loads from higher wind speeds? The loads that Bob Smith measured seem to indicate that things get further out of whack at higher speeds. Nice to see some real data. Of course that still indicates that you could be anchored with a 5-lb. Danforth on 3/16 nylon in that much wind if you wanted to be. It's too bad that the ABYC tables that everybody bases everything on are not based on any actual measurements. Of course different boats are very different. For example, I used to have a small cat that pulled much harder than much longer monohulls.

[Maine Sail]

Originally Posted by Kettlewell

Maine Sail, do you have loads from higher wind speeds? The loads that Bob Smith measured seem to indicate that things get further out of whack at higher speeds. Nice to see some real data. Of course that still indicates that you could be anchored with a 5-lb. Danforth on 3/16 nylon in that much wind if you wanted to be. It's too bad that the ABYC tables that everybody bases everything on are not based on any actual measurements. Of course different boats are very different. For example, I used to have a small cat that pulled much harder than much longer monohulls.

I do have higher wind speeds but not on video and nothing over 35 yet. Only got the strain gauge at the end of last summer. Ordered it with battery power to leave it overnight in storms but when you do peak hold it resets when the load gets about 30% less than peak so you need to be there watching it with a video cam. This is why I need the software so I can plot it over time.

If there is one thing I learned it's that rode forces are not stable at all. They cycle up and down, even at 35 knots, and the peaks can be much higher than the averages. Mooring loads cycle even more due to the lifting of the massive bottom chain.

The ABYC data is very conservative but accounts for more than just wind. Alain Fraysse has written an interesting piece on it here: Forces


Of course as the wind and waves build the shock loads can certainly become quite a bit..

I doubt even "Worlds Strongest Man" competitors could hold the boat in these conditions...



This is 5/8" or heavier mooring chain pulled near bar tight..



Considering I have dragged properly sized and up-sized anchors in 50 knots or less, while they continued to remain set but pulling through the bottom, I think I'll stick with one with high holding power and won't drop down to a 5Lb. Danforth...

I have read Don Dodd's work and it does not mesh up with my own strain gauges measurements on my own 36 footer. I think he wrote a very pretty white paper but having seen numerous draggins over many, many years, with properly sized anchors, I suspect there was something missing in his analysis? Don't knwo what but his gauge on a 36 slop does not mesh up with my measurements. Mine do not meet the ABYC data but are beyond the loads Dodd's reported..

[Kettlewell]

MaineSail, I'm not arguing that the loads don't get big and those conditions are dramatic. Just that we really don't know what the loads are because nobody seems to have measured them. So people are building anchors and anchor systems to be able to handle so much loading, which is just conjecture. Seems like an odd way to go about doing things.

I do believe that the developers of the Danforth anchor actually were engineers and did do a lot of testing. Robert Danforth Ogg frequently refers to "thousands of tests" in the little booklets he wrote, which are still quite good to read.

By the way, here's a fun experiment that can be rather hilarious. Next time you're securely anchored up someplace take your dinghy anchor if it's a Danforth. In my case I have the smallest real Danforth, which I believe is around 5 pounds total weight. Tie some light line to the anchor (skip the chain) and take it out in the dinghy, or just hurl it to windward if the water is fairly shallow. Set the anchor and ride to it perfectly securely while your main anchor rode just lays slack. Sure, some of the load is being taken off by the weight and drag of the chain on your main line, but you will be amazed by how much wind your little dink anchor can take.

[SA/USA]

Yes surface area is very important when you are speaking of holding power. The weight of an anchor is also important for penatration power. That is why the Spade anchor has 50% of the total weight of the anchor in the tip of the anchor. The Spade therefore digs in instantly and the holding power of the anchor comes from its concave surface area.