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Old 03-30-2017, 11:54 AM   #1
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Small boats: less chain, bigger anchor

I thought I would start a new thread here for those of us with smaller and/or lighter weight boats, regarding our ground tackle.

Quote:
Interesting article from the rocna guy.

Catenary & Scope In Anchor Rode: Anchor Systems For Small Boats
- from TF user what barnacles, posting in the thread "A new use for your bow eye"

Quote:
it is a widespread myth that all boats should carry as much chain as possible....

In fact, we shall see that catenary rarely offers much benefit which is truly worthwhile, and any unnecessary extra weight of the chain is often far better invested in other elements of the anchoring system....

The conclusion is that “all chain” is not particularly desirable in terms of performance, and a considerable amount of weight may be saved without detrimentally affecting the anchor....

Taking a few kilograms of weight out of the chain and putting it into the anchor results in a significant increase in holding power.
- Peter Smith, from linked article above


This article was very illuminating for me, since we will soon have delivery of our new boat, which is 36' in length with a 10'6" beam and rather lightweight (6,000 lbs unloaded & b4 engines). The author points out that he is talking about boats in the 10m range, so this may be also applicable to folks who own the Camano Troll, the Albin 28-32' and the Prairie 29 style of boats.

After reading ALL of the threads on anchors and anchoring (whew!), this article clarified for me that we should be going with a heavier anchor and a short length of chain. Our first trip in the TT35 will be half the Loop, from St. Petersburg, FL to Cleveland, OH. We plan to utilize anchorages as much as possible.

Before I discuss this with Hubby Dan, any thoughts? Flame suit on.
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Old 03-30-2017, 12:43 PM   #2
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I spent most of my time on sailboats, anchoring boats from 24-40, all much lighter weight than my 31,000lbs trawler.

On the sailboats we always used a combination rode. Chain followed by nylon three strand. Having enough rode out is critical as that article explains (which has been discussed in the past). Getting a long enough rode in a lighter boat is a lot easier with a combination rode. The idea of the chain was to add some weight for catenary, but also to provide chafe protection for the nylon rode on the bottom.

On my 40' sailboat we have 90' of chain, 200' of nylon three strand, and a 45# CQR. On my 43' trawler I have 300' of all chain and have upgraded to a 65# anchor. On our smaller sailboats we had proportionately less chain and more nylon three strand but always carried 300' total.

In short, what you are proposing makes a lot of sense and is what many of us have been doing for years.
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Old 03-30-2017, 12:51 PM   #3
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Far be it from me, to cut short what is sure to be a lively debate, but its going to come down to your boat, your anchor, and your circumstances. There will be no universal law that works for grass, mud, rocks and sand, in gales and calms, with and without diurnal tidal changes, rivers and oceans, and high and low windage boats.

Bigger anchor is better than smaller anchor.
More rode is better than less

I'm sure by the end of your journey, you'll have complete knowledge of your ground tackles abilities, and your boats requirements.
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Old 03-30-2017, 01:23 PM   #4
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I like a bigger anchor to a point. It would seem to me that you could run 1/4" chain and carry 135' for about 100 pounds of weight. 200' looks to weigh around 147 pounds. These are both examples of G4 chain. My guess is that 99% of the time you will use less than 150'. So, I would go with 200' of G4 1/4" and add 200' of nylon to the end. You'll probably never use the nylon, but you will sleep better knowing it's there.

Now can we start arguing about which anchor?

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Old 03-30-2017, 01:30 PM   #5
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Why not just go with 20' of chain, a good sized anchor, then all nylon. No need for a snubber or bridle as the nylon provides lots of shock apsorbtion. Isn't Eric using something like that on his?
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Old 03-30-2017, 01:50 PM   #6
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Maybe a better way to do this is to list out several options from almost no chain to all chain with the associated weights for the entire road including the anchor. Then say the lightest is the minimum. From there, if I add 50 pounds I get this; if I add 100 pounds I get this, etc. To me, you're pondering the additional weights, not the weight itself as you have to have at least the minimum.

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Old 03-30-2017, 02:04 PM   #7
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Was'nt going to say anything but since I see my name .....

I only use 3' of chain Dave. But it's 3/8" (that's really oversized for a 30' boat) and it's there to help hold the end of the shank down. I may up it to 5'.
I also have a 50' 9/16" nylon line inbetween the 5/8" Brait and the 3/8" chain. The 9/16" line is to throw away when it's been dragged across the bottom too many times.
The heavy chain should hold down the shank. I saw quite a few vids from Steve (Panope) whereas the anchors rotated fwd plunging the shank end into the seabed. This was almost shocking to see as I had assumed the opposite. So w the anchor giving strong help, the short chain should finish the job and give the anchor plenty of help. As long as my setting is dependable and consistant no more chain should be necessary. I usually use my modified 18lb XYZ or my highly modified 15lb Manson Supreme. The XYZ uaually sets in an upright position and the Supreme sets on it's side.
Both anchors have excellent short scope performance.
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Old 03-30-2017, 02:11 PM   #8
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Thanks Eric,

Yeah, I had always used more chain than your 3', but I don't know that I had a very good reason for it. For lighter boats, I like a combination rode. Easier use and cheaper to replace. You can buy premade combo rodes exceedingly cheap.
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Old 03-30-2017, 02:26 PM   #9
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It has been posted countless times before...

All chain is for convenience of windlass retrieval as much as anything...not many chain users dispute that in storm conditions, things get complicated for any ground tackle.

Proper use of snubbers pretty much makes an all chain rode partially a combo rode.

99 percent of the time none of it matters, what matters is the skipper getting AN anchor set, AND using enough scope to hold for current and forecast conditions.

What some swear by has been poison for others.....and their laptop physics disproven by others.
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Old 03-30-2017, 02:37 PM   #10
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Can I ask a question for the all chain guys ? Doesn't the catenary act as a shock absorber so you don't need a snubber ? I would think that unless the pull on the boat was so much that the rode was a straight line which would only happen in an extreme situation.....is a snubber necessary ?
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Old 03-30-2017, 03:03 PM   #11
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I think about three things:

1. Anchor Setting. Some anchor guru (can't find it, now) has written that a general design principal of anchors is that if the pull on the shank is less than 10 degrees from horizontal, the anchor will tend to dig in, and at more than 10 degrees, the anchor will tend to dislodge. How to get below 10 degrees? Two ways. One is rode length. With a 6:1 ratio, the angle is more than 10 degrees; at a 7:1 ratio, the angle is less than 10 degrees. I suppose that is where the magic 7:1 comes from. The other is rode weight. With a heavy rode (chain, or a kellet), the rode will lay on the bottom, keeping the pull horizontal. That is, until the wind gets up and straightens the chain out; then you need the magic 7:1 again. (Many will say they use 5:1 nylon all the time; maybe the 10 degrees is conservative; I don't know. Also, in deep anchorages, less scope seems to be required for reasons I do not understand.). But no matter how big the anchor, if the pull is dislodging it; not good. A big anchor, set, obviously provides more holding than a small version of the same anchor

2. Shock absorber. The catenary of the chain, or chain laying on the bottom, acts as a shock absorber. So does a nylon rode, but again, only until the wind gets up and straightens out the chain or pulls the stretch out of the nylon.

3. Chafe. Nylon will stay off the bottom if there's any breeze, but if the wind dies, or reverses, or the current reverses, the nylon will also drag across the bottom, potentially encountering something sharp.
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Old 03-30-2017, 03:45 PM   #12
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Quote:
Originally Posted by Benthic2 View Post
Can I ask a question for the all chain guys ? Doesn't the catenary act as a shock absorber so you don't need a snubber ? I would think that unless the pull on the boat was so much that the rode was a straight line which would only happen in an extreme situation.....is a snubber necessary ?
Depends on length and weight. Assume a 45' boat weighing 40,000 pounds anchored in 20' of water with 3/8" chain. With 500' of chain out (scope 25:1), you probably can't straighten the chain out, so there is less shock. I'm sitting in low 20 knot winds on 7:1 scope, and without the snubber there would be a lot of hard jerks. When the wind gusts 25 knots, the chain (90'), is straight.

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Old 03-30-2017, 03:51 PM   #13
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wow....I would have thought it would take more wind to straighten the chain...thanks for giving me some real world insight.
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Old 03-30-2017, 05:30 PM   #14
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I can't say how much wind is required to straighten out the chain in any given situation, but can definitely attest to Ted's observations above. It does not take as much wind as you might think.
I have 400' of 3/8" chain on my 34,000 lb. boat, and I can tell you, the chain is often straight, and without a snubber there is a fair bit of jerking going on.
I almost always use a snubber!

Regarding the original question, I do like all chain rode, but have been quite happy with combination on lighter vessels. As stated, it sometimes comes down to the windlass. If you have one, all chain works nicely. If you are without a windlass, I can tell you from personal experience that hand-hauling say 350' of chain and then manhandling a sixty pound anchor aboard gets 'old' real fast!
........ been doing that for thirty years, and from now on I will have a windlass, thank you very much!
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Old 03-30-2017, 06:45 PM   #15
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There is nothing unique about a small, light boat in terms of what anchor it needs vs a big, heavy trawler.

If that big, trawler needs an 80 lb anchor to hold its 60,000 lbs of weight and 200 sf frontal area, then an 8,000 lb trawler with 120 sf of frontal area will need proportionally less.

I can't tell you how much less. I don't think that the physics is good enough to calculate it accurately as anchor holding is a very dynamic proposition, but I do know that weight and frontal area are the two main parameters.

All of the things that are also important for anchoring the big, heavy trawler are also important for the light, small trawler: height above water line of anchoring point, snubber, catenary, etc.

And finally an anchor that works well for the big, heavy trawler like the Rocna, Spade or Manson Supreme will also be a good anchor for the light, small trawler, just smaller.

The principles are all the same.

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Old 03-30-2017, 06:52 PM   #16
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Don't know this as fact but I'm quite sure the all chain system has more catenary that most of the time isn't needed.

And more importantly the chain weight near the anchor vastly promotes setting.

A third advantage is a much reduced swing circle. I've seen many fish boats w very heavy chain and anchor stay right where they anchored the night before in the morning. Wonderful advantage in tight anchorages typical of Canada and SE Alaska.

Also having 50 to 100' of chain is nice as it is super easy to attach a bridal and stop swinging (sailing).

As I've said for years rode weight is best applied to the anchor for highest holding power.
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Old 03-30-2017, 07:07 PM   #17
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People make anchoring much harder than it is, like single engine no thruster docking, practice makes perfect.

That includes changing things in your inventory as you work through the issues.

But in all reality, buy a decent anchor at least 50 pounds unless you are a Danforth type fan...put some or all chain on it and learn how to pick decent anchorages, learn to set it and learn how to monitor it.

Sure if you have a small or large boat size accordingly, but my 50 pound guesstimate is based on something heavy enough to penetrate most bottoms.

It isn't all that hard and those that try and make it harder...are just playing with their own little hobby.
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Old 03-30-2017, 07:46 PM   #18
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My boat is 30 feet and heavy, I have an aluminum fortress anchor which is not heavy,50 feet of chain, 110 feet of rope. One day in our favorite bay we anchored during the afternoon of a nice warm summer day, then in the middle of the night I have been woke up by the sound of the wind, no number but quite strong, I went out to store the wooden table on the deck and saw that the boat was really rocking on the wind, turning around the anchor. But it never moved an inch.
I know there is a great debate around anchor and everything related but the bottom is making a great difference I think. In this bay we were anchored it is a muddy clay bottom, very solid with a huge grip. In another bay I know, where the bottom is just round gravel I wouldn't spend the night...
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Old 03-30-2017, 07:55 PM   #19
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Please be aware: I was given 25' of 3/8" chain. I had a 25 pound plow and could NOT get it to set. I believe the chain was too heavy causing anchor to plop over on its side. Switched back to my all chain 1/4" G4 and all was well.

I had added the 3/8" between my 1/4" and the anchor. Plow versus Danforth style incidentally.
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Old 03-30-2017, 08:00 PM   #20
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I believe Fortress warns against too much or too heavy chain and long scope that deters setting in some situations like soft mud.
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