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Old 11-03-2012, 06:16   #16
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Re: Rocna Vs Spade

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When experiencing winds in excess of 60 knots while at anchor, the only thing that matters is weight, the more the better. According to most cruisers, the Bruce is not worth buying, but it is my preferred connection to dry land.
I'm not meaning to open an anchor debate, but the only thing that matters in anchoring is friction with the bottom. With enough chain, you wouldn't even need an anchor. Weight is meaningless, other than higher weight anchors generally have more surface area to provide friction than lower weight anchors (and that a minimum amount of weight is necessary to allow the anchor to get to the bottom in a position to set).

If an oversized Bruce is the anchor that works for you, then it is the correct anchor for you.

Mark
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Old 11-03-2012, 06:49   #17
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Re: Rocna Vs Spade

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Originally Posted by colemj View Post
I'm not meaning to open an anchor debate, but the only thing that matters in anchoring is friction with the bottom. With enough chain, you wouldn't even need an anchor. Weight is meaningless, other than higher weight anchors generally have more surface area to provide friction than lower weight anchors (and that a minimum amount of weight is necessary to allow the anchor to get to the bottom in a position to set).

If an oversized Bruce is the anchor that works for you, then it is the correct anchor for you.

Mark
Not true. Sorry to say. With a lot of tension the whole rode/chain lifts of the ground and the only piece that holds the boat is the anchor itself.

Of course, with no wind or current or very little the statement "enough chain, you wouldn't even need an " is correct.
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Old 11-03-2012, 07:26   #18
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Re: Rocna Vs Spade

I think mark was using the term "friction" loosely. "grab, holding, resistance" could be applicable too. The effect is the same.

BTW, whoever posted above that Spade has a sharper point than Rocna is wrong. Rocna or especially Manson Supreme are sharper and will set more easily in a hard-packed bottom or weeds. But in a soft mud bottom I suspect anchors with hoops don't set as deep due to the hoop providing resistance.
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Old 11-03-2012, 07:32   #19
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Re: Rocna Vs Spade

Actually, my statement is true - if not absurd for the sake of making the point. With enough chain, it would never be lifted - ever - that's the whole point of "with enough chain".

But the point I was trying to make is the one about friction being the actual workhorse and not weight. Of course nobody can carry around enough chain to forego an anchor. So, as you correctly note, the anchor is used to hold the boat. And the anchor relies on friction with the bottom and not weight to do that.

Putting aside the material strength for a moment, a properly set plastic anchor will hold just as well as the identical properly set steel anchor. The friction is doing the work, not the weight. Of course, material strength does matter in usability, so anchors aren't made of plastic. But material, and thus weight, does not matter in holding ability once set.

If one relied solely on anchor weight, one would be in the same position as relying solely on chain. In other words, it isn't practical to carry around that much weight. Even most moorings rely on friction and not pure weight.

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Old 11-03-2012, 07:57   #20
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Re: Rocna Vs Spade

You are right that weight doesn't matter for an anchor to hold and that it is actually the friction holding the boat, but in order to keep your anchor in one piece you need enough thickness of the material to meet that requirement. The larger the anchor (= more friction) the thicker the blades need to be to overcome the bending moments that are applied to these blades, ergo: the more weight the better. In practice, i did some experiments, 1 kg of anchor gives roughly the same amount of friction as 18 kg of chain.

Miracle anchors do not exist, there is only so much force that a certain amount of ground can hold, do you need more holding power, than you need to "grab" more ground with your anchor, and that can only be achieved with size (= weight) normally the sunny and warm cruising routes have very good holding ground and generally 40 knots of wind (outside hurricane season) is considered to be very much. On higher latitudes how ever, you will experience much higher wind speeds and very often poor holding grounds. That was the main reason for my statement of anchor size, it totally depends on which area of the world you are sailing.

The anchors that are called "the best" are usually anchors that dig in faster, they do not have higher holding power in poor anchor grounds so be careful with believing what the sales person tells you.
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Old 11-03-2012, 08:03   #21
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Even more unscientific I dropped a 27 kg Manson off the bow while at dock. The damn thing sunk in the mud and set. It was a bear getting it to come out with the tag line I attached in case I dropped it. Dohhhh. I' dug the 30 kg cqr out of the stern locker and added to my lawn ornaments sitting next to my 70 lb Luke and a really old 30 lb fishermens anchor. And a 40 lb danforth. Nowbim modernized with a Manson a Bruce that is a great anchor an a fortress. Anyone interested in a cqr in the Annapolis area give me a shout.
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Old 11-03-2012, 08:51   #22
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Re: Rocna Vs Spade

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Originally Posted by colemj View Post
I'm not meaning to open an anchor debate, but the only thing that matters in anchoring is friction with the bottom. With enough chain, you wouldn't even need an anchor. Weight is meaningless, other than higher weight anchors generally have more surface area to provide friction than lower weight anchors (and that a minimum amount of weight is necessary to allow the anchor to get to the bottom in a position to set).

If an oversized Bruce is the anchor that works for you, then it is the correct anchor for you.

Mark
" Weight is meaningless" is an over-simplification. Weight also assists penetration (setting) which is why I sold the aluminum Spade to you

I found that anchor didn't penetrate hard-packed bottoms well, although once set its a great anchor.
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Old 11-03-2012, 10:15   #23
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Re: Rocna Vs Spade

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Originally Posted by colemj View Post
Actually, my statement is true - if not absurd for the sake of making the point. With enough chain, it would never be lifted - ever - that's the whole point of "with enough chain".

Mark
True --I dont even have an anchor , but I have 18 miles of chain!
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Old 11-03-2012, 16:48   #24
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Re: Rocna Vs Spade

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" Weight is meaningless" is an over-simplification. Weight also assists penetration (setting) which is why I sold the aluminum Spade to you

I found that anchor didn't penetrate hard-packed bottoms well, although once set its a great anchor.
That Spade has been a perfect secondary anchor for us! Stores well, easy to carry about in a dinghy and doesn't crush my fingers like the Fortress does. Fortunately, we don't need to use it much - which is about the best thing you can hope for a secondary anchor (or, more accurately, a primary anchor)!

I did mention that a minimum of weight was necessary for setting and meant for my discussion of the meaningless of weight to be around the holding abilities of set anchors.

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Old 11-03-2012, 17:44   #25
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Re: Rocna Vs Spade

I understood that Mark and agreed with everything you wrote. There were times I regretted selling that anchor, as it would be a good secondary or backup.
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Old 11-03-2012, 17:57   #26
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Re: Rocna Vs Spade

I was looking at both sites, and it seems the Rocna has a higher surface area to the Spade... I think the Manson is about the same as the Rocna for size.
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Old 12-03-2012, 16:45   #27
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Re: Rocna Vs Spade

well i was warned anchor questions would provoke some pretty firm opinions!

I guess its what helps you sleep soundly at night so fair enough too.

thanks again for all the replies

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