Anchor Size: Multihull v. Monohull

[boatman61]

Originally Posted by Gone2long

I do not mean that as a joke or an insult.

What I am wondering is, do you think that there would be any way to stay anchored I such a storm? I assume that the only safe thing one could do is to head for a mooring in a harbor where one could tie up to a sturdy pontoon. Unfortunately, that may be impossible where I will be sailing in the next few months, and such storms are known to frequent that region on occasion.

Your thoughts?

G2l

Do NOT rely on pontoons/moorings to keep you safe..
When I was delivering the ex America's Cup boat Azzura 2 from Denmark to Holland for shipping to the US we pulled into Cuxhaven after transiting the Kiel Canal.. we tied up on the end pontoon as it was the only one that could take our 64ft LOA... across the pontoon from us was the Cuxhaven Lifeboat.. almost the same length..
Anyway.. the North Sea threw one of its Autumn fits and blew 50+kts onshore which was no biggie.. however.. tied in with a Spring tide it generated a big tidal surge the broke the chains holding the pontoons to the posts..
They broke so fast that I had to cut all my shorelines to avoid serious trouble yet still dinged the stern as the sea's swung the pontoon into us as we got away..
The advantage of YOUR gear is you know its condition and strengths and weaknesses.. what someone else has laid is an unknown.
I used to service mooring in Poole back when and you would be amazed by the effect 12 months off sand rubbing back and forth can be.. mind.. Poole Harbour is an exception as it has twice as many High tides as elsewhere along the S coast..
A good anchor and All chain is the only way I will go.. weight can be counter balanced fairly easily and my boat and my life are worth a LOT MORE than a measly 1/4 to 1/2kt gain in speed.. that's day sailor tactic's.. not serious cruising.
As for the Bruce and weed in the Med.. I've spent many years sailing round there.. and weed there is.. but in these weed beds.. for example Alcudia.. there are patches of clean sand to drop your hook..
Follow good anchoring practices and one should have no problems.. just charge in and drop.. well.. its your boat..

[Gone2long]

Originally Posted by TrentePieds

What we call a "Bruce" is indeed a miniature version of the anchor Peter Bruce designed for use by oil rigs in the North Sea way back in the 60's. I don't know what the gizmo in the pic is, but it ain't a "Bruce" :-)

I knew Bruce slightly through a hengeneer-type friend in Vancouver and had a conversation with him about why his device was so "exotic". Among the things he told me was that it was specifically designed for the sandy ground that you find in the North Sea, and that these anchors (at a coupla tons apiece) were laid out in bridles from each corner of the rigs then in use, each leg of the bridles having three anchors in tandem. Therefore there would be no question of the pull on the shanks changing direction. He also told me that "surface roughness" of the anchor casting in relation to the anchor's dimensions had an effect on it's holding power.

Other posters have made significant comments: 1) the hook itself is only one part of the "system". 2) Total weight of gear on the bottom (hook or no hook) is of the utmost importance and 3) anchors have to be selected for the specific combination of holding ground, wind and wave that obtains at the time of anchoring. I thot that was a very timely reminder. There really isn't such a thing as a universally "best" anchor. I think it's possible to select an anchor that works best for you in most of the places you "normally" go, in the conditions you "normally" go there. But universally "best"? Well, if you expect the impossible, you WILL be disappointed :-)!

TrentePieds came with a 35lb Bruce for a bower with 40 feet of 5/16" chain and 200 feet of 1/2" nylon and a 7 lb Fortress with 150 feet of 1/2" nylon, but no chain for, a "stern" anchor. I added a 250 foot "shot" of 1/2" nylon to deploy when, and if, needed. For what we do, that is adequate.

The notion that and anchor should be "lightweight" (a "selling point" for the Fortress) misses the whole point, in my opinion. If you are a kayaker, then okay. But for a yacht? No! What's needed is LOTSA weight on the bottom and as long a scope as circumstances and you gear will permit. And, if it blows, a scrupulous anchor watch!

TrentePieds

Thanks for a great summary. You folks have generously supplied a wealth of knowledge that would have taken me years to learn on my own. I will copy your post, Tom's and a number of others and keep them close, as a handy reference to use when making future anchoring decisions.

Best to all,

G2L

[TrentePieds]

"Yes, I understand. However, like one of the other posters above, I AM the windlass, and I am not a young man anymore. Pulling up even 50 or 60 feet of chain over a rocky/coral bottom is pretty taxing, so we really do need to go as light as is reasonable."

Forgive me if I'm chewing the cabbage twice, or in any other way being redundant, but no G2L, if your physical strength is declining [mine is too:-)!], the compensation is NOT to lighten your tackle, since ultimately it is weight of tackle that will keep you safe, but the installation of a capstan/windlass with sufficient oomph to do what you yourself can no longer do.

I have a silly little Vetus capstan. So far it's never wanted to tell me what it wants to be when it grows up. I ignore it, and allus do what I've allus done - just plain old pulley-hauley. It helps to keep me in shape. If I begin to wimp out I take a turn on an Andersen #12 sheet winch and let MyBeloved tail it while I crank. By the time the chain/rope splice reaches the winch there is no more chain out than I can still pick up in one hand. But why do that when I have a capstan?

Well, baby capstans (vertical axis drum) are useless because you cannot trust the little pawl-jobby that's meant to do the tailing for you. And you cannot tail the beast yourself because to do that you have to exert a horizontal pull four inches off the deck so you cannot get your back into it. Baby windlasses (horizontal axis drum) are MUCH better because you can stand on your feet to tail so you can give significant assistance to an innately inadequate electric motor.

So there are decisions and compromises to be made. Just don't compromise your ship's safety by going too light on your ground tackle!

TrentePieds

[tomfl]

Originally Posted by boatman61

SNIP

A good anchor and All chain is the only way I will go.. weight can be counter balanced

SNIP

I agree about the weight issue, good ground tackle is more important than extra cases of beer.

One reason I have rope at the end of my chain is because of the added shock absorption. Once I have let out all the chain I tend not to worry about sharp rocks/whatever damaging the rope. I also have only let out enough chain to get to the rope when the wind is really blowing and I worry about needing the extra shock absorption due to bobbing waves. I am torn between keeping a bridle in high winds and heavy seas and getting it off before the conditions are too bad to to allow me to get the bridle off.

If the truth be known I am still trying to learn more about heavy weather anchoring.

[UNCIVILIZED]

Originally Posted by roland stockham

You are right to think that ground tackle for a multi does not work the same as a mono. Basically a traditional mono with plenty of keel area should lay relatively stable pointing into wind and not yaw aroud.

For the OP: The Vast majority of monohulls out there are decidedly prone to sailing at anchor. Many violently so, when a proper system of abating such hasn't been worked out for the boat. As is often the case/norm, in say, charter fleets.
Fin keeler's are notorious for such behavior. But it's far from being confined to them alone (in the realm of monohulls).

[Ribbit]

Originally Posted by kas_1611

As a convert from a Delta to the Rocna Vulcan I can vouch for the performance of the Vulcan. Sets extremely quickly, normally in less than an anchor length, and will hold you secure in normal conditions on 3:1 quite happily.

Other similar new generation anchors such as the Rollbar Rocna, Mantus, Manson Supreme are also good options to look at. For my boat at the size of anchor I was looking at the Rocna and Mantus would not fit on the roller but then I was looking at 30kg+ anchors. Compare that to the 16kg Delta I had originally! We plumped for the 33kg Vulcan based on the theory that the bow anchor should be a storm anchor capable of holding us in 60kts.

Hope that helps

Keiron

Encouraging to hear your Vulcan is working out well.

Severe storm conditions was my yardstick, as I intend to be travelling around quite a bit, and I was sweating cobs about getting a good setup for ground tackle, for a 32ft monohull.

So the final result after sweating it out on a thread about getting to grips with anchor and chain size overlaps, to acquire peace of mind, was a Maxwell RC8-8 windlass (so I can lift the tackle up), 275ft of 5/16" HT chain, and a 20kg Vulcan on the end of it, for the main anchor. The info that was produced on that thread for me to digest, was absolutely superb, and the contributors deserve high praise imho.

For the money, to me anyway, good ground tackle is very cheap insurance.

[Ribbit]

Originally Posted by tomfl

I agree about the weight issue, good ground tackle is more important than extra cases of beer.

One reason I have rope at the end of my chain is because of the added shock absorption. Once I have let out all the chain I tend not to worry about sharp rocks/whatever damaging the rope. I also have only let out enough chain to get to the rope when the wind is really blowing and I worry about needing the extra shock absorption due to bobbing waves. I am torn between keeping a bridle in high winds and heavy seas and getting it off before the conditions are too bad to to allow me to get the bridle off.

If the truth be known I am still trying to learn more about heavy weather anchoring.

Chain hooks are cheap:

Chain Hooks - Stainless - Stoppers & Snubbers - Anchoring & Docking - Downwind Marine

If struggling to get it off, cut the rope (have a sharp knife handy).

[admiralslater]

We have an Outremer 45 and replaced the 55 delta with a spade 120. Their guide said to move up one size for a multhull. It sets vert quickly ,so far I am happy. BTW I use a "improved soft shackel" to attach the bridal it comes up through the roller well

[thinwater]

Originally Posted by TrentePieds

What we call a "Bruce" is indeed a miniature version of the anchor Peter Bruce designed for use by oil rigs in the North Sea way back in the 60's. I don't know what the gizmo in the pic is, but it ain't a "Bruce" :-)

Bruce for cruisers and Bruce for oil rigs are different.

Bruce Anchors

[thinwater]

Originally Posted by tomfl

I would point out there are multiple types of snubbers. I was talking about the rubber ones you basically wrap some line around. My bridle is composed of two length of line both attached to a single chain hook so if one side breaks there is still one side intact.

Please take this politely. I've done the testing using load cells.

A rubber snubber of that sort only allows the line to extend ~ 0.5-1 foot or so, about the amount is shortened by wrapping. Thus, it can only absorb 8" shocks. This may be just fine for docklines, where there is sometimes little room to work with.

However for an anchoring snubber, this is effectively a waste of time and space. an additional 3-5 feet of nylon would do more. When anchored, to truly absorb the snatch loads from waves you need either a boat-length of nylon or chain cataneray from 30' of water, or a combination. However, I have seen the instrumented testing, and a bit of rubber is not effective in real storm conditions.

[Ribbit]

I might be wrong, but doesn't nylon lost its stretch ability if it exceeds a roughly 20% stretch limit? I wouldn't want that happening in a storm.

So I was thinking of going with maybe a 35ft snubber of 7/8" nylon, and having the slack in the chain accommodating less than 7ft stretch (20% of 35 ft) - say 5ft or 6ft? The shock absorbing effect should smooth out the chain being straightened, and the spring back on the down side of the wave should keep things happening smoothly, with no loss of stretch ability in the snubber.

I 'think' the shock absorbing characteristics of 7/8" nylon, should provide some healthy leeway. If it does prove to be way too stiff in normal use, I can drop the size down, and keep the 7/8" for Oh Sh!7 times.