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Old 29-10-2018, 21:44   #1
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Anchor sizing questions

Hey all,

I am in need of all new rode, chain, anchor, and unfortunately windlass.

That being said, I am trying to scope out what would be best for my boat. My boat is weighing in at roughly 16t according to documentation and the scales when I launched her.

I am thinking I should get the Rocna 73lb anchor as based on their chart the 55lb would be the correct size so going one size up for being able to handle any storms the PNW or anywhere we go will make us feel a bit more comfortable.

Is this anchor size over kill? Would I be wise just to go with the 55lb and spend the extra $300 on going with all chain? It wouldn't adjust the cost of the windlass all that much as I will need to find one that will still support a 3/8" chain.

Any advice or recommendations welcome. Trying to align all the eggs before pulling the trigger on a windlass :\
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Old 29-10-2018, 23:12   #2
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Re: Anchor sizing questions

You are better off putting the weight in the anchor and not the chain.
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Old 29-10-2018, 23:44   #3
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Re: Anchor sizing questions

Oh boy, this is a loaded question. You are bound to get a bunch of answers.

It really depends on your individual boat's characteristics. For instance, one with more windage requires more anchor in storm conditions. A cat won't like an all chain rode due to the weight in the bow, etc. It also depends on how much you anchor, and why you anchor - lunch hooks, occasional overnights, or cruising..

A good rule of thumb is to look at the anchors used on commerical fishing boats in your area. Those guys rely on their gear heavily, and need to be able to trust it.

If it were me, I'd go with the biggest you can fit (the bigger anchor you list seems about right) and all chain rode. This is if you can take the weight in the bow.

This is for multiple reasons. I've heard way too many times it is not the anchor that holds you, but the chain, and there is some truth to that - at least in moderate conditions. The chain acts as a shock absorber for the anchor, and ideally the anchor will see next to no load. During a gale or better, the chain still will provide some buffer in the gusts, but there the anchor weight is critical, and you don't want an undersized one then.

My personal experience - my 37' 7 ton cat (prout snowgoose) with low to moderate windage is rigged for fulltime cruising and living on the anchor. I carry a genuine Wasi 25kg (55 pound) anchor with 100' of 5/8" chain and 150' of nylon 3-strand behind the chain. We have never drug it, including this summer with 2 days straight of 40-50 knot steady winds at anchor (in a 70' deep anchorage anchored at 3:1 scope too..)

Another item to consider is that I always try to anchor on all-chain but it can be difficult to find shallow enough anchorages to do so here in SE Alaska. The main reason for this is because it is a pain to retrieve the nylon as it will slip a bit in the combination gypsy, where the chain just comes up, no problem. If I could take the weight in the bow, I would switch to 250' of all chain.

Again, just my experiences. YMMV.
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Old 30-10-2018, 03:30   #4
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Re: Anchor sizing questions

My experience is that the heavier chain makes a big difference. I have seen that on a friend's Lagoon 440 (12 ton+ cat with high windage) switching from 12mm to 10mm chain. But then a good anchor also makes a huge difference, quite obvious when that same boat then went from 25kg Delta to 25kg Spade.


IMO the most important factor is that the chain pulls the anchor horizontally. The weight of the chain acts pretty much like the length to depth ratio. So a heavier chain will allow you e.g. to have 3:1 instead of 4:1. Very useful for me in some crowded mediterranean anchorage. An oversized anchor would not really help here. But what works for me may not work for you.


FWIW, after more than two years full time with 75m of 12mm chain and a 25kg Delta, I have just purchased a 30kg Spade. That because on a few occasions the delta would not settle properly in some algae/sand grounds.
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Old 30-10-2018, 03:55   #5
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Re: Anchor sizing questions

i have rocna 25kg four years and never dragged, excluding grass. No need for largest possible in my opinion. Extra weight gives you not enough extra odds of holding to warrant extra mess. Was in up to 60 kn gusts and 45-55kn steady.

However there were 2 times i was very happy not to have the largest possible anchor as I had to pull it up 2x by hands. Both times anchor winch failed.
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Old 30-10-2018, 04:09   #6
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Re: Anchor sizing questions

I am replacing the 25kg Lewmar Delta by a 85lbs / 39kg Mantus on our Lagoon 400, will fit it next spring. Will also extend the 60m chain to 80m.

The Delta is OK at calm conditions, but in stormy weather does not hold very well. I hope the Mantus performs much better (relying on the reviews). I'll keep the Lewmar Delta as a third (spare) anchor, my second is a Danforth with 5m chain and 60m rope as stern anchor when needed.
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Old 30-10-2018, 04:10   #7
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Re: Anchor sizing questions

If you are worried about the extra 300 don't buy a rocna buy a delta , and use the extra money to oversize chain and anchor .
Rocna is a good anchor but is not the best and it's overly over priced.
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Old 30-10-2018, 06:30   #8
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Re: Anchor sizing questions

Quote:
Originally Posted by chowdan View Post
I am thinking I should get the Rocna 73lb anchor as based on their chart the 55lb would be the correct size so going one size up for being able to handle any storms the PNW or anywhere we go will make us feel a bit more comfortable.

Is this anchor size over kill? Would I be wise just to go with the 55lb and spend the extra $300 on going with all chain?

Even the 55-lb model seems like a lot to me, for a 16T boat. Really that's what the Rocna tables suggest?

Anyway, were it me... I'd take two approaches, simultaneously... ignoring over-all cost (within reason) because a good ground tackle system is fairly important.

1) Determine what weight you want to be able to lift manually, should the windlass crap out.

2) Shop all modern anchors -- Rocna, Mantus, Manson, Anchor Right (Sarca, etc.), Ultra, SuperMAX, Spade, whatever else Ive forgotten -- for a combination of suitability to your expected holding grounds, weight (including your manual-lift factor), mounting/launching capability, etc.

Then I'd go with an all-chain rode unless your area is signficantly muddy, like it is here on the Chesapeake (cleaning mud from chain is a pain). Note that the weight of the chain will slightly affect the dead lift weight of you anchor for the last several feet, but that could be the case no matter which rode style you adopt.

-Chris
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Old 30-10-2018, 08:33   #9
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Re: Anchor sizing questions

I’m maybe a 14 ton boat fully loaded as a guess.
I have two Rocna’s on the bow, a 25 kg and a 40 kg. 40 was bought as a storm anchor, but decided why not always use it?
I have drug the 40 in not real severe conditions, improperly set, most anything can drag.

I like having an oversized anchor, I think it has come in handy at times, but my boat doesn’t seem to notice the weight, and my windlass can handle it.
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Old 30-10-2018, 09:01   #10
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Re: Anchor sizing questions

I’d go with the biggest spade-style anchor your boat and crew can reasonably* manage. Since you are installing a windlass, then I would install the largest one your boat can reasonably accommodate. This will then define the rode and anchor working sizes.

My boat is 15 tons, 37 feet (36’ 9” to be exact). Fairly low windage. I’ve used a 25 kg (55#) Rocna as my bower for many years now. I use 3/8” all-chain, and have a manual windlass. Sat through three day gales and have never dragged once set. If I were buying a new anchor today I would go at least one size larger; mainly b/c I know me and my windlass can handle it.

*By “reasonable” I mean just that … something that doesn’t unduly compromise sailing characteristics, and that can be operated without extreme effort by the crew. A bower anchor should be easily deployed and retrieved. If it is not, then it is too big, or you need a different windlass.
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Old 30-10-2018, 09:52   #11
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Re: Anchor sizing questions

Why NEW GEN Anchors are Better:

Anchors & TEST Results of New Generation Anchors EXCELLENT & Important

Anchor System Sizing Tables (Reply #6) & Why Swivels are a bad idea Ground Tackle & Anchor System Sizing TABLES & Swivels

Steve’s Anchoring 101

The Rocna. All 20kg of it with 100ft of chain. The rest of the world can debate all they like. When I pull into a place like Bodega Bay at midnight and the fog is so thick I can't see the jetty 50 feet away to make an entrance, I drop my hook in the rolling ocean swells with the surf crashing (Foster says it's like staying in a cheap Best Western beside the highway), and I sleep. And in the morning I have a windlass to pull the beast up and I wouldn't trade it for anything. (I also wouldn't add more chain - this works perfectly in 25 to 30 feet of water - you let all the chain out and you tie off nylon at the preferred scope and don't bother with snubbers and chain hooks and all that stuff...)


Your boat, your choice.


Good luck.
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Old 30-10-2018, 11:17   #12
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Re: Anchor sizing questions

Anchor loads vary primarily with physical dimensions of the boat and amount of rigging and other windage with displacement affecting loads a distant 3rd.

What are the basic dimensions of you boat and do you have a photo?
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Old 30-10-2018, 11:39   #13
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Re: Anchor sizing questions

Quote:
Originally Posted by Excalibur5 View Post
Oh boy, this is a loaded question. You are bound to get a bunch of answers.

It really depends on your individual boat's characteristics. For instance, one with more windage requires more anchor in storm conditions. A cat won't like an all chain rode due to the weight in the bow, etc. It also depends on how much you anchor, and why you anchor - lunch hooks, occasional overnights, or cruising..

A good rule of thumb is to look at the anchors used on commerical fishing boats in your area. Those guys rely on their gear heavily, and need to be able to trust it.

If it were me, I'd go with the biggest you can fit (the bigger anchor you list seems about right) and all chain rode. This is if you can take the weight in the bow.

This is for multiple reasons. I've heard way too many times it is not the anchor that holds you, but the chain, and there is some truth to that - at least in moderate conditions. The chain acts as a shock absorber for the anchor, and ideally the anchor will see next to no load. During a gale or better, the chain still will provide some buffer in the gusts, but there the anchor weight is critical, and you don't want an undersized one then.

My personal experience - my 37' 7 ton cat (prout snowgoose) with low to moderate windage is rigged for fulltime cruising and living on the anchor. I carry a genuine Wasi 25kg (55 pound) anchor with 100' of 5/8" chain and 150' of nylon 3-strand behind the chain. We have never drug it, including this summer with 2 days straight of 40-50 knot steady winds at anchor (in a 70' deep anchorage anchored at 3:1 scope too..)

Another item to consider is that I always try to anchor on all-chain but it can be difficult to find shallow enough anchorages to do so here in SE Alaska. The main reason for this is because it is a pain to retrieve the nylon as it will slip a bit in the combination gypsy, where the chain just comes up, no problem. If I could take the weight in the bow, I would switch to 250' of all chain.

Again, just my experiences. YMMV.


Holy cow! 37’, 7 ton cat with 5/8” chain! Must be a helluva windlass.
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Old 30-10-2018, 11:53   #14
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Re: Anchor sizing questions

I think posters on anchor threads should be required to include the number of nights they have spent at anchor. After 5,000 nights on the hook, I'd go with the bigger Rocna and all 5/16 HT chain.
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Old 30-10-2018, 11:57   #15
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Re: Anchor sizing questions

I cruise PNW sail and power 35-50 foot boats. If you use Ronka or Spade type 73lb is heavy and more like a storm unit. Weight of anchor is not as important in modern deep diggers as set-reset and general holding ability. Light smaller aluminum anchors such as Al Spade and fortress may out hold and in general out perform a big Ronka. I would think a 55lb Ronka with at least 60Ft of chain and 400ft rode or all chain to 300ft would be fine for PNW. If you use the storm size and all chain you may be adding a lot of un needed stress to retrieval.
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