Wind Against Tide

[noelex 77]

Originally Posted by Tupaia

I disagree with the second statement. Fit an anchor that is sized for the boat. Oversized anchors may seem like a good idea. The heavier the better!! But, it can actually diminish the holding power, that is achieved by the bury not by the weight. A big oversized anchor that cannot be buried sufficiently because the vessel cannot set it will result in less holding than a smaller correctly sized anchor that can be set to a proper depth.

Every single study on anchor performance shows increasing the size of an anchor increases its maximum holding ability .

If you have a look at this thread and you will see that my considerably oversized anchor is generally the best set model in the anchorage:

https://www.cruisersforum.com/forums...26073-129.html

After over 4000 nights at anchor including 13 named storms (up to 81 knots) using an oversized Rocna or Mantus anchor I can attest that there are significant advantages. This is not just holding in extreme conditions, but the ability to safely use anchorages with poorer substrates and make use of shorter scopes when this is required.

Don’t fit an anchor larger than the boat can comfortably manage, but it is wrong to think a small anchor will perform as well as a larger model of the same design.

[Johan Leopard51]

From researching comparative tests, I’m leaning to Vulcan (the Rocna without roll bar which won’t fit on power cat setup) and the Blade. My decision will prob come down to which I can buy and get to Seychelles and after I have ensured what will fit Leopard and if need to change roller. Inventory in Seychelles is always a problem.

This site is useful even if Smith obv has bias, he does at least show that Blade is also very good. Elsewhere on site he has some interesting pieces about chain/rope and scope length. We presently are chain only so maybe I can overcome my issue with reef damage on long scope by changing to chain + rope. In 8m depth water, light weather, I can then do 25m chain but put out 25m rope for overnight/extended stay/change in weather.

https://www.petersmith.net.nz/boat-a...ce-testing.php

We are fair weather boaters in region that has no hurricanes. reading stories about anchoring in 50 knot conditions gives me chills. At Vulcan they say they size for length and mass and 50 knots and suggested a 40kg. I’m trying to find out what our OEM anchor was but think the swapped anchor we got saddled with is 27kg, so thinking of the Vulcan 33.

[Tupaia]

Originally Posted by noelex 77

Every single study on anchor performance shows increasing the size of an anchor increases its maximum holding ability .

If you have a look at this thread and you will see that my considerably oversized anchor is generally the best set model in the anchorage:

https://www.cruisersforum.com/forums...26073-129.html

After over 4000 nights at anchor including 13 named storms (up to 81 knots) using an oversized Rocna or Mantus anchor I can attest that there are significant advantages. This is not just holding in extreme conditions, but the ability to safely use anchorages with poorer substrates and make use of shorter scopes when this is required.

Don’t fit an anchor larger than the boat can comfortably manage, but it is wrong to think a small anchor will perform as well as a larger model of the same design.

Here are a couple of technical articles.


https://www.vikinganchors.com/data-c...-always-better


Oversize anchors – necessary? – Cox Engineering


Proper sizing is the way to go over-sizing may be more emotion than physics.

[noelex 77]

Originally Posted by Tupaia

Here are a couple of technical articles.
https://www.vikinganchors.com/data-c...-always-better

Viking anchors have moved the shank attachment close to the crown of the anchor. This makes fitting reasonable sized anchors impossible on most boats. The tip of the fluke will hit the bow.

Personally, I think this has unduly influenced their push to recommend very small anchors. For my own 49 foot sturdy cruising boat Viking recomend a 12.6 kg (less than 28 lb) steel anchor which I think is rather silly. I would not recommend you listen to this advice.

Originally Posted by Tupaia

Oversize anchors – necessary? – Cox Engineering

We have anchored next to Viv Cox and photographed his anchor. He is an excellent engineer, but I don’t agree with his personal anchor sizing philosophy.

Originally Posted by Tupaia

over-sizing may be more emotion than physics.

If you mean the happy emotion when your boat stays put, I have to agree .

[wholybee]

Originally Posted by Tupaia

I second the first statement, coral sand often has a hard crust that many anchor designs cannot penetrate and will therefore not bury properly. A Spade anchor has a very sharp point and is very effective at penetrating the crust.


I disagree with the second statement. Fit an anchor that is sized for the boat. Oversized anchors may seem like a good idea. The heavier the better!! But, it can actually diminish the holding power, that is achieved by the bury not by the weight. A big oversized anchor that cannot be buried sufficiently because the vessel cannot set it will result in less holding than a smaller correctly sized anchor that can be set to a proper depth.

When you really think about it, this doesn't make sense. Aside from the fact that you should use an engine to set an anchor, so even a small boat should be able to set an anchor that is oversized. But even without that. Say you have an anchor that is tremendously oversized for use in a hurricane. That hurricane comes, and your engine is broken so you can't set it at all. When the wind comes up and you start to drag, that huge anchor will set, while the smaller one will just plow and not hold.

I do believe that bow weight should be a consideration when choosing ground tackle. That means mostly to move weight from the chain to the anchor. Smaller chain, less of it with more rope, and a bigger anchor. A very heavy storm anchor can also be stored elsewhere down low in the center of the boat. But when given a choice of 2 anchors that will fit the bow, go for the bigger.

[smj]

Originally Posted by wholybee

When you really think about it, this doesn't make sense. Aside from the fact that you should use an engine to set an anchor, so even a small boat should be able to set an anchor that is oversized. But even without that. Say you have an anchor that is tremendously oversized for use in a hurricane. That hurricane comes, and your engine is broken so you can't set it at all. When the wind comes up and you start to drag, that huge anchor will set, while the smaller one will just plow and not hold.

I do believe that bow weight should be a consideration when choosing ground tackle. That means mostly to move weight from the chain to the anchor. Smaller chain, less of it with more rope, and a bigger anchor. A very heavy storm anchor can also be stored elsewhere down low in the center of the boat. But when given a choice of 2 anchors that will fit the bow, go for the bigger.

If your engine is big enough to set your sized anchor then you have peace of mind knowing it’s set. If the anchor is to big for the engine to set, then you have no peace of mind. I’d much rather be going through a storm knowing my anchor set in the bottom rather than hoping the anchor will set with the wind.

[Johan Leopard51]

Originally Posted by wholybee

I do believe that bow weight should be a consideration when choosing ground tackle. That means mostly to move weight from the chain to the anchor. Smaller chain, less of it with more rope, and

That website of the article I posted has an interesting piece about scope, chain, anchor, rope. We have 100m of 10mm chain, no rope (we would almost certainly never anchor in more than 15m depth as the nice spots are close to the island/reef/atoll). I have a big thing about the charter people that come along and (1) don’t seek out a sandy patch but drop anchor at a pretty spot = on coral in tropics (2) proceed to put out their formula 5 chain of 60m and overnight swing they destroy more than a football field of precious coral!

So I may try his suggestion of a good anchor, thinner and shorter but better quality chain to a length that will vary where you boat, and rope for the rest. In our case we anyway have 50m of idle chain lying in a pile below windlass, never used and if team is slack, is not cleaned and rinsed between trips, quietly eroding away.