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Old 08-11-2018, 04:08   #1
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Aluminium anchor as main

Going in where angels fear to tread, another anchor question...

But I have read a lot of the anchor threads over the last few years and not arrived at my mind made up. Relative beginner so appreciate the perspective of the community's experience.

Completing a refit of a 45' open bridgedeck Shuttleworth, 45' X 28' beam, 14,000 lbs. My user case, to call it something, is cruising long hops two to four weeks at a time, accepting lack of comfort and willing to trade comforts for weight management.

And here is my dilemma. I inherited a 35' CQR on the front cross beam, electric windlass, 100' of chain, all stored nicely in the right place under the mid cross beam. Limited experience of anchoring out, but already a very mixed bag of difficulties to set, but once set held well so far. So want to go new generation.

Rocna looks great, Spade as well, I can work out size, but being weight conscious I am tempted by the aluminium Spade. I have read that there are issues with the shank bending, I get the wisdom of having a heavy anchor for ease of setting, I gather that Spade people do not recommend aluminium for main, but my understanding suggests that, once set, the shape and geometry determines holding power rather than the weight.

And as the anchor will live on front beam, less weight is desirable, and my use will be less on the hook and more on passage than some, maybe.

I appreciate that the prevailing views around here tends towards as heavy as possible, as much chain as possible, but posting within Multihull Hull Sailboats I am curious if you have gone thru the same deliberations and arrived at conclusions that would help me make my mind up, steel or aluminium?

Cheers,

Dan
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Old 08-11-2018, 04:31   #2
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Re: Aluminium anchor as main

I had an aluminum Spade as a primary on a small boat, and it was amazing. If you get a size that has decent surface area, I'd have no concerns. However, I'd be inclined to at LEAST 35# anything smaller won't have the surface area you need.
What would be better, IMO, is a 45# steel Spade. You have a lot of boat for a 35# hook of any sort!
The way people bend Spade shafts, is by getting the tip caught under a rock and using violence to remove it. Better to dive it, if possible.
Some people unship the anchor and stow it below when on passages, so as to remove the weight from up forrard. I've done this as well, and it's not such a huge pain.
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Old 08-11-2018, 04:47   #3
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Re: Aluminium anchor as main

The steel Spade is an excellent anchor. The aluminium Spade is a good anchor, but it has significantly worse performance in firm and weedy substrates.

I would suggest that unless weight is critical, for example for a secondary anchor that may need to be deployed by hand or via the tender, or in the case where the boat has no electrical anchor winch, then I would choose the steel Spade (or Mantus or Rocna).

The difference in weight is not great. For example, a S140 weighs 30kg. An A140 weighs 15 kg. Anchoring gear is critical and that 15kg is “well spent” even when weight is important on a vessel such as yours.

However, everything on a yacht is a compromise so you need to make that judgment for yourself. If you do want a general purpose primary anchor and you need to select a very lightweight model, the aluminium Spade is by far the best choice in my opinion.
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Old 08-11-2018, 10:54   #4
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Re: Aluminium anchor as main

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I had an aluminum Spade as a primary on a small boat, and it was amazing. If you get a size that has decent surface area, I'd have no concerns. However, I'd be inclined to at LEAST 35# anything smaller won't have the surface area you need.
What would be better, IMO, is a 45# steel Spade. You have a lot of boat for a 35# hook of any sort!
The way people bend Spade shafts, is by getting the tip caught under a rock and using violence to remove it. Better to dive it, if possible.
Some people unship the anchor and stow it below when on passages, so as to remove the weight from up forrard. I've done this as well, and it's not such a huge pain.
Thanks, that's exactly what I was hoping for. The option of removing the anchor and stowing hadn't occurred to me! Duh
Keeping the weight down is an imperative on my boat I feel, and becomes an obsession. Or the road to bloat is a few pounds here and there. But hard to manage - junk accumulates
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Old 08-11-2018, 10:56   #5
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Re: Aluminium anchor as main

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Originally Posted by noelex 77 View Post
The steel Spade is an excellent anchor. The aluminium Spade is a good anchor, but it has significantly worse performance in firm and weedy substrates.

I would suggest that unless weight is critical, for example for a secondary anchor that may need to be deployed by hand or via the tender, or in the case where the boat has no electrical anchor winch, then I would choose the steel Spade (or Mantus or Rocna).

The difference in weight is not great. For example, a S140 weighs 30kg. An A140 weighs 15 kg. Anchoring gear is critical and that 15kg is “well spent” even when weight is important on a vessel such as yours.

However, everything on a yacht is a compromise so you need to make that judgment for yourself. If you do want a general purpose primary anchor and you need to select a very lightweight model, the aluminium Spade is by far the best choice in my opinion.
Yeah, it's hard and your point is well made that weight saving on anchor might not be the best choice
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Old 08-11-2018, 12:46   #6
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Re: Aluminium anchor as main

Had the same headace a few years back. Ended up with a steel spade S140. Alu version is lighter, but its not a HUGE margin, and the anchor is critical in my view. Its fearly easy to take the Spade apart, only one big bolt that holds it together. Easy to stow when parted if you want to get it off the bow. You are probably on top of it already, but you CAN save some weight on the chain by going down a size or two, but a higher spec chain.
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Old 08-11-2018, 12:55   #7
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Re: Aluminium anchor as main

Any anchor itself is a compromise, because you anchor with varied bottoms and you can't carry them all. Every one I've owned has been improved markedly by all chain rode. Heavy, but it absorbs shock better than you would think, and does a much better job of keeping the anchor on the bottom than my nylon rodes did.
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Old 08-11-2018, 13:57   #8
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Re: Aluminium anchor as main

With the displacement and windage would want at least the fluke area of a 45# steel anchor. Aluminum with equivalent fluke area would be an opton to trim some weight off but may not set well in some bottoms.
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Old 08-11-2018, 14:07   #9
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Re: Aluminium anchor as main

Something I think often gets overlooked in anchor debates and test is where you will be anchoring and thus predominant bottom types. For example, a danforth style anchor is great for the Gulf of Mexico, but nearly useless for rocky/weedy areas. NewGen anchors set in a wide variety of conditions.

Your location shows up as UK. I assume thats mostly where you will be anchoring? Mostly rocky bottom?
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Old 08-11-2018, 14:08   #10
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Re: Aluminium anchor as main

I'm occasionally accused of favoring light anchoring rigs, specifically for multihulls. Very light.


That said, I still favor steel for the primary. There's nothing like a sharp toe on a steel anchor for cutting through a hard bottom or weeds. To save weight, I favor high strength chain on the main rode and very little chain on the secondary anchor. The secondary anchor will be a Fortress, which is ridiculously light for the holding power.


Another option is a mixed rode for the primary. Up size the rope--it will STILL be much lighter than chain. Safer than too light an anchor, and LOTs of weight to be saved. At the very least, carry no more than 150 feet of chain. The rest can be rope.



You'll save more weight by careful choice of chain, secondary, and rode, than by skimping too much on the primary.
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Old 08-11-2018, 14:13   #11
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Re: Aluminium anchor as main

I certainly wouldnt go all chain, though I think 25 metres would be about the lower end, and am not interested in making the chain heavy, any weight you have in an anchor system is best spent in the anchor. The catenary effect of 8 or 10 mm chain is virtually non existent. and follow that chain up with 50-75 metres of good quality octo or 16 mm nylon. I would consider the 20 kilo Sarca Excel, or maybe the 15 kilo Aluminium Sarca (which is a larger size). and the 7 kilo Fortress FX23. (cause you should have a second anchor, indeed in this part of the world you are lawfully required to do so.)
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Old 08-11-2018, 15:27   #12
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Re: Aluminium anchor as main

We have a similar size and displacement boat. I recently went from a 20 kg anchor to a 30 kg.

There's no noticeable difference in sailing. Only in how secure we are at anchor.

There are better areas to look for weight savings than in your ground tackle.

And as has been said, on long passages you can stow the anchor in a more central location.
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Old 08-11-2018, 15:30   #13
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Re: Aluminium anchor as main

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I certainly wouldnt go all chain, though I think 25 metres would be about the lower end, and am not interested in making the chain heavy, any weight you have in an anchor system is best spent in the anchor. The catenary effect of 8 or 10 mm chain is virtually non existent. and follow that chain up with 50-75 metres of good quality octo or 16 mm nylon. I would consider the 20 kilo Sarca Excel, or maybe the 15 kilo Aluminium Sarca (which is a larger size). and the 7 kilo Fortress FX23. (cause you should have a second anchor, indeed in this part of the world you are lawfully required to do so.)

For "School's Out" 45' 6 tonne boat, Rex at anchor right recommended the 30 kg excel.
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Old 08-11-2018, 15:54   #14
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Re: Aluminium anchor as main

I defer to that recommendation in that case.
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Old 08-11-2018, 16:37   #15
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Re: Aluminium anchor as main

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I certainly wouldnt go all chain, though I think 25 metres would be about the lower end, and am not interested in making the chain heavy, any weight you have in an anchor system is best spent in the anchor. The catenary effect of 8 or 10 mm chain is virtually non existent. and follow that chain up with 50-75 metres of good quality octo or 16 mm nylon. I would consider the 20 kilo Sarca Excel, or maybe the 15 kilo Aluminium Sarca (which is a larger size). and the 7 kilo Fortress FX23. (cause you should have a second anchor, indeed in this part of the world you are lawfully required to do so.)
I have always been taught (with nothing to back it up) that the effect of chain is to reduce the angle of pull on the anchor. I remember seeing a youtube vid where some guy was anchored in South Georgia in a gale with over 100 knot winds and the chain was tight, but I was in a 50 knot line squall and my chain was not tight. My set up is 150 feet of chain and 125 feet of nylon.

I have never seen test data on the catenary effect but would be interested in seeing it.

I mostly in the places like the Florida Keys/Bahamas where I anchor in less than 20 feet of water. Can only recall anchoring in more than 30 feet once and that was in the Gulf and I had to be 10 miles off shore. As a rule I am using all chain due to the depth.


Any advice welcome
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