How big is too big?

[Don C L]

I always thought in terms of holding power, not weight. Look at the Fortresses, according to the charts anyway, they can hold a tremendous amount compared to weight. When I see a huge, heavy CQR now I tend to think the folks need to re-think how anchors hold... It's one reason I am Danforth holdout, dinosaur, myself... hard to beat the holding power/weight ratio. My 4 ton boat has a 20H and I'd bet good money the mooring bit would rip out before the anchor drags, or breaks.

[Snowpetrel]

Originally Posted by Panope

Snow, does your formula work for ever larger boats and ships?

Steve

It works reasonably well up to super tankers size.

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[Don C L]

Originally Posted by Snowpetrel

Simple rule of thumb (boat length×boat length in ft)/weight of anchor in lbs should be somewhere between 20 to 30. The dashews 83 footer has a 240lb anchor for a relatively poor ratio of 28.7. I have always sat around 25. Beth and Evans had about 20 with a Bruce anchor. A rocna 40 would give you about 16.4, far to low.

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This is a very curious formulation... hmmm, forgive my skepticism...... waterline or length over the deck? Now my 29 footer with my 20H yields 42.05, a very bad result by your calculation, but if I use waterline length of 22' I get 24.2, dramatically better, no? (I may be having the same brain fart but is not lower better?) But still I can set the anchor well without any backing down (pulling against a stern anchor) and I am pertty darn sure my boat will not pull that anchor out, in this millennium anyway.

[Snowpetrel]

Originally Posted by Don C L

This is a very curious formulation... hmmm, forgive my skepticism...... waterline or length over the deck? Now my 29 footer with my 20H yields 42.05, a very bad result by your calculation, but if I use waterline length of 22' I get 24.2, dramatically better, no? (I may be having the same brain fart but is not lower better?) But still I can set the anchor well without any backing down (pulling against a stern anchor) and I am pertty darn sure my boat will not pull that anchor out, in this millennium anyway.

Hi Don, no you have the numbers right, but like all these sorts of things the numbers become subjective. I think its easier to keep things general and standardised, and let the user decide how much they want to juggle things. I use LOD. I ignore bowsprits. But some boats are high windage for their size and others are low windage so you just edge to a lower number for a higher windage boat, and vice versa.

I take it you are using a danforth, and your typical holding is good. If so that would explain why it works well for you. I would have thought a 20lb danforth is a touch small for a 29 footer but it obvously works fine for you in your area in your typical conditions. Do you rate it as a storm anchor? That's what the 20-30 number is for, with a next gen anchor.

Obviously anchors like the fortress don't fit so neatly into these numbers. Its easy enough to aproximate the equivalent steel anchor weight. Nor do low holding power anchors like a fisherman's or stockless. But again you can easily make allowances.

The basic concept seems to scale well even up to big ships. From memory HMS victory has a anchor ratio of 5, a very low number indeed, but she has extremely high windage, a very low holding power anchor, all rope warp and no engine to get her out of trouble so I think it makes sense for them to go very big. Most ships seem around 30 or so, but for they are low windage shapes that sit nicely at anchor and this compensates for the low holding of the stockless anchors that they use.

A few anchor handling tugs I checked had low numbers around 15, but they are fwd wheelhouse and high freeboard so generate relatively high anchor loads and they often tow or are involved in salvage so need extra heavy gear, and again the anchors are low holding power.

I have all the calcs somewhere on a spreadsheet back home. Might dig it out again.



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[Snowpetrel]

http://www.cruisersforum.com/forums/...ter-99104.html

There is a huge thread here about anchor sizing.

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[Jim Cate]

All the arguments about "too big" seem to ignore that when really cruising, one sometimes must anchor in unknown areas, and that sometimes those places have poor bottoms, crowded conditions, poor protection and other adverse factors. It is then that having an anchor that is vastly oversized may save your bacon... those times when you can not use good practice in anchoring.

This post will likely get the knee jerk response that " you should move to a better place" or some such. My observation is that these posters seldom anchor at all, and hardly ever in a strange place with no local alternatives. Ann and I surely have been in some anchorages that were less than ideal, and for which there were no accessible "better places", and we've been glad to have a big anchor and heavy chain.

For the OP, if the 40 kg anchor fits and you can afford it, why the hell not have it? (Even if the 30 kg one would likely work.) The extra 10 kg on the bow will not have any perceptible influence on your sailing performance no matter w hat the pundits claim!

Jim

[Snowpetrel]

Jim, it's a 38 footer. That's like you guys fitting a 125lb anchor. By the same metrics your 65lb anchor is a tiddler in comparison to your windage.

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[noelex 77]

As others have already said, I think the best rule is to fit the biggest anchor you can reasonably manage.

Most people focus just on holding power: "Will I drag with this anchor", forgetting that a larger anchor gives you much better versatility. You can make use of many anchorages that otherwise would not be suitable, or not suitable for overnight anchoring. This may be because of poor holding, limited protection or limited room that restricts scope. There are many other situations where the reserve anchoring ability can make your life much easier.

For example, with a temporary wind change where the anchorage becomes exposed. Removing the fear of dragging and staying, can be a nicer option than plugging on hours to reach the nearest protected spot. Or if someone anchors too close, on occasions shortening scope is more practical than moving. There are many other examples.

This does not mean that you can be irresponsible with a bigger anchor. There are still judgment calls about what is safe and what is not, but the extra reserve ability opens up options that would not otherwise be feasible.

People seem immensely concerned about a small amount of extra anchor weight. Curiously, if you talk about carrying more spare parts or other items, no one mentions weight. Our sewing machine weighs 50 lbs ! I suspect for most cruising boats a decent tidy out of the V-berth could save as much as going up a size in anchor.

Extra anchor weight, providing it can be comfortably managed, is perhaps the most valuable addition pound for pound that you can make to a cruising boat.

[ranger58sb]

Originally Posted by a64pilot

Is having too much anchor like having too much money, I've heard its possible, but have yet to understand it.

For the main anchor... I draw the line at an anchor that's too heavy to lift manually (including the weight of the final bit of deadweight chain) -- routinely, over the course of remaining days in one of our typical cruises -- should our windlass fail near the beginning of the trip.


That would also influence my buying decision if I wanted a storm anchor, not permanently mounted but routinely available, that's seriously larger but near the same weight limit... and assuming efficacy in the expected holding grounds. The Fortress line is the only candidate I can think of just now.


The weight limit is a variable number; a younger, stronger me could lift more... way back when.

-Chris

[a64pilot]

A lot to try to answer, yes I did consider the Mantus, hard. I like that it is US made, and that it can be taken apart, and I really. Like their swivel so I assume they are an up and coming company, but I have no experience with one, and have yet to see one in person, and I got a good price on the Rocna.
As far as not being able to pick it up, well I guess then if we hold to that, then we can never get a big boat?

I read the report on Jedi, and I believe he was tied into and had everything out, yes the Bruce may be what saved the boat, but there was a lot of other stuff that was holding too, I believe he used every means at his disposal to keep the boat in place, I assume they failed one at a time during the worst part of the storm, and that the Bruce alone may not have saved her?


I thought hard about a Fortress, I. Really did. It seemed logical to be able to disassemble a huge anchor and store it for hopefully ever. But one thing kept nagging me, if they hold so well, how come I never see one on the bow? I may not be aboard in a major storm, I may be ashore and maintain need something that can shuffle around and reset itself, to me that means one of the new generation anchors

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[ranger58sb]

Originally Posted by a64pilot

As far as not being able to pick it up, well I guess then if we hold to that, then we can never get a big boat?

I dunno about that. If you can dead lift 50-60 lbs now (or whatever), then a big-a$$ Fortress could be well within your lift limits. Assuming it'd work in your expected holding grounds...

FX-80 = 47 lbs, FX-125 = 69 lbs. Awkward, for mounting on your current boat (or ours), but they store nicely and could make a decent storm anchor if you really needed one.

I probably have significantly more windage than you -- can't take a reef in our flybridge -- so that's the kind of approach I'd probably take if necessary. Our hurricane plan doesn't include anchoring out, though, so haven't yet decided to "need" a bigger Fortress storm anchor than the one we already have.

And for anything less than a hurricane our mounted 50-lb SuperMAX is our storm anchor. Might factually fair OK in a hurricane, for that matter....

-Chris

[Mike OReilly]

I think a storm anchor is different than a bower. I want my bower to hold through say normal x 3 conditions. For me that's up to around 65 knots. My Rocna 25 (55#) has been tested in over 50+ knots and has done fine. I might go another size up if buying again, but no more ... not for the bower.

As I and others have said, a bower should be one your normal anchoring system can handle, and that includes the crew. Go with the biggest one your systems can reasonably manage without heroic effort. Save that level for actual storm sets with actual storm anchors.

More important than anchor size is proper anchor technique. Anchors don't hold on weight, the hold based on quality of set, choice of location and proper rode.

Size matters, but it's how you use it that really counts [emoji6]


Why go fast, when you can go slow

[sck5]

Rocna recommends 7/16 chain for an anchor that size. Are you going to have a swivel on it? What can that take?

FWIW I have had a Rocna for years. On my 33 a Rocna 20 never once dragged or presented a problem of any kind in 6 years of cruising to the Caribbean and back via the Bahamas, Bermuda, and most of the East Coast. Why put a massively oversized anchor on the boat in honor of 100mph winds (or whatever you are planning for) when a smaller anchor will hold just as well - that is, it will hold until the chain snaps or the deck fittings explode.

To each his own I say. Bigger is always better but go ahead and try to lift an anchor that size and carry it anywhere. You might reconsider. Seems like massive overkill to me and I am someone who believes in overkill.

[DumnMad]

My blunt tipped Bruse copy was useless. Size/weight is only useful if it helps the anchor to dig in welli. In soft soil the resistance is in proportion to the cone pull-out resistance which is roughly proportional to cube of the depth. Anchoring technique plus anchor design are therefore both key to acheiving a good result.
In hard soil a sharp point and plenty of weight bearing on the tip would be more important than weight that does not load onto the tip.

[ontherocks83]

Can't we all just chip and and buy 3 small derelict boats, leave them in hurricane alley, put 3 different size or types of anchor and let the results speak for them selves. I'm in for $100+ if someone wants to head it up