Anchors, Guns and Strippers!!!!

[Lodesman]

Originally Posted by CaptainRivet

you don't want to have a weak link in your ankering system....

That's not what I said - I said you want a controlled mode of failure - otherwise the failure could occur where the result is catastrophic. Given the choice what would you prefer: (1) the anchor drags; (2) the rode parts; or (3) the bow rips off? Nothing is 100% bulletproof.

[Lodesman]

Originally Posted by CaptainRivet

fully agree. Additionally the big ships have a self positioning system means you set the location and all engines and bow/sterntrusters will keep it in position. Its also the way the resuce boats keep position to be able to operate a rescue mission or evacuation of a ship. they have massivly oversized engines and bow/sterntrusters or voith Schneider propellers to keep position in even the worst locations...
our cruising yachts don't have such systems.

No. Most big ships don't have dynamic-positioning systems or V-S drives - that's stuff for tugs, survey ships and such.

[CaptainRivet]

Originally Posted by Lodesman

That's not what I said - I said you want a controlled mode of failure - otherwise the failure could occur where the result is catastrophic. Given the choice what would you prefer: (1) the anchor drags; (2) the rode parts; or (3) the bow rips off? Nothing is 100% bulletproof.

nothing of the 3. if its that bad, a 2nd and even 3rd anker is deployed and share the load so one can drag but not all 3 and no rodes part or bow rips off.

Everything in that system need to be speced to the same max speced you can afford or the boat can withstand physically. Spec everthing to the weakest link, all obove is wasted money anyhow. Thats not 100% bulletproof but as close to it as possible.


And in this super extreme conditions there is no controlled mode of failure, everything is on the limit and you pray it holds.
Doesn't matter which fails, in this extreme conditions you end up on the shore if either fails anyhow, if its your planed weak link/mode of failure or not.

[Mike OReilly]

Originally Posted by Lodesman

I've done it in a destroyer, but not had a need in my own boat (yet). I do frequently have the motor ticking over enough to reduce the strain when shortening the cable for weighing.

As most of us do. But in this case you are taking up the rode as you move forward. It's a completely different dynamic when trying to find the right balance point in a situation of high, likely variable winds and waves. Trust me, it's not an easy task with your typical cruising boat.

Not saying it shouldn't be done -- I do it. But as I say, I view this as close to the final resort when dealing with a bad situation. The far better circumstance is to not get into that situation. A bigger anchor will almost always help avoid this kind of situation.

Originally Posted by Lodesman

I imagine my anchoring style is a lot more conservative than most - I put out a generous scope and situate so that more can be safely deployed (where possible). If I was anticipating gale force+ winds then I'd have all 300' of chain down and plan for plenty of dragging room. The force necessary to drag a Rocna 33 and 300' of chain in decent bottom conditions would probably be approaching, if not exceeding, the above-mentioned possible points of failure. A watch would be kept in such a situation, and I'd be running the motor once the beefy snubbers stretched by 30% or so. If the bottom is marginal (hard shale for example) then I honestly doubt another 20kg and a few more sq cm of frictional surface in the anchor will provide more security; I'd rather have the extra weight in additional chain, as I believe that gives you just as much deadweight with much more frictional surface area.

Anchor weight is largely a proxy for anchor area. While weight definitely helps with setting, it is the surface area and shape of the anchor which defines ultimate holding. So it's not so much the weight of the anchor, but the surface area it presents to the substrate. Clearly your best weight-to-holdingpower benefit comes in a bigger anchor, not more chain.

No doubt if you lay out enough chain you don't need an anchor at all, but I doubt the typical cruising boat can carry enough chain to come close to the holding power of an anchor.

[wsmurdoch]

Originally Posted by Mike OReilly

Have you ever tried to do this [motor forward to take the load off the anchor]? I have, in a very limited way. It is exceedingly hard to stay in the goldilocks zone of providing just enough power to relieve strain, but not too much power so as to produce yawing or otherwise increase shock loads as the boat moves forward, then falls back.

I certainly have done it, and would do it again, but I view this as getting close to the last option when faced with a deteriorating anchoring situation. Much better to be properly anchored in the first place. And this is best done with the largest anchor you can reasonably manage.

I too have tried to do this in a thunderstorm. It was blowing in the mid 40s with rain and higher gusts. The rain hurt. I could see nothing beyond the boat. I could not see the compass, chartplotter/GPS, nor the radar display. There were boats anchored nearby. The dingy floating on its painter behind my boat went airborne then landed upside down flooding the engine with seawater and spilling everything in the dinghy. From the cockpit it was impossible to judge the load on the chain or the orientation between the boat and anchor. In a brief period of less rain, I discovered that I was motoring forward with the tight anchor chain leading bit aft and off to one side. I was like a water skier running off to one side of the tow boat and almost passing the tow boat. I could have easily pulled my own anchor out but did not.

Bill

[Jim Cate]

I think the difference between ships and yachts employing engine power to augment anchor holding lies in their inertia. Ships are very massive and do not accelerate or decelerate rapidly. Thus as the wind and sea loads on the ship vary in gusts, the ship's response is very slow and this avoids the engine pushing the ship over the anchor in the lulls.

Small boats with large windage (like all of our cruising vessels) are relatively light and respond quite quickly to variations in wind strength and direction. This makes the task of relieving anchor loads with engine power far more difficult. I've never been able to do this with useful results myself.

It's one of those "sounds good when you say it fast" kinda things.

Jim

[Lodesman]

Originally Posted by Mike OReilly

Anchor weight is largely a proxy for anchor area. While weight definitely helps with setting, it is the surface area and shape of the anchor which defines ultimate holding. So it's not so much the weight of the anchor, but the surface area it presents to the substrate. Clearly your best weight-to-holdingpower benefit comes in a bigger anchor, not more chain.

That only helps if the anchor can dig in - if it's sitting on a hard bottom, then it only has a few more sq cm of contact area, and the extra 20 kg is largely useless being a microfraction of the weight of the boat it's holding. If you look at the Rocna website, they give the only reasons for upsizing is for deadweight on hard bottoms or where there will be a need to anchor at short scopes in marginal holding conditions - while there's some merit to the latter, the former is a fallacy.

[Mike OReilly]

Originally Posted by Jim Cate

I think the difference between ships and yachts employing engine power to augment anchor holding lies in their inertia. Ships are very massive and do not accelerate or decelerate rapidly. Thus as the wind and sea loads on the ship vary in gusts, the ship's response is very slow and this avoids the engine pushing the ship over the anchor in the lulls.

Small boats with large windage (like all of our cruising vessels) are relatively light and respond quite quickly to variations in wind strength and direction. This makes the task of relieving anchor loads with engine power far more difficult. I've never been able to do this with useful results myself.

It's one of those "sounds good when you say it fast" kinda things.

wsmurdoch

Jim, as usual your assessment sounds right to me. I just know it's a lot harder to accomplish successfully than people seem to realize. As you say, it sounds like a good idea, until you actually try it for real.

Originally Posted by Lodesman

That only helps if the anchor can dig in - if it's sitting on a hard bottom, then it only has a few more sq cm of contact area, and the extra 20 kg is largely useless being a microfraction of the weight of the boat it's holding. If you look at the Rocna website, they give the only reasons for upsizing is for deadweight on hard bottoms or where there will be a need to anchor at short scopes in marginal holding conditions - while there's some merit to the latter, the former is a fallacy.

Yes ... but no one is talking about this scenario. No anchor will hold based on weight with any real wind blowing. In light conditions most of us sit on the weight of our chain, but as soon as there's enough wind to start moving boats around much, then dead weight will quickly get dragged around, be it weight from a non-anchored anchor, or the chain.

This is why I specify that it's not just the set that is important, but being properly dug in. This is also why I think your "too big" comment has some validity (as I said).

But again, in the real world of actual anchoring, a heavy anchor will set easier than a lighter one (for a given design). And setting is the first essential stage to getting dug in. Even if you can't dig it in fully with your under-powered engine, a good set gives you a decent chance of getting dug in once the wind pipes up. And a bigger anchor will re-set on its own if it should come out.

Use the biggest anchor your crew and boat systems can reasonably manage. You will sleep better, and hopefully never have to discover why motoring to relieve strain is a last-ditch step.

[dfelsent]

Originally Posted by Beau.Vrolyk

Well, I guess that just shows how inaccurate the Pilot Charts are. I haven't ever sailed in your area so I took a look. They certainly show 30 knots to be common in wintertime. I doubt there are many cruisers there in the winter, but I don't know. It must be nice to cruise in a place with so few other sailors.



But even in December and January, they don't show a single observation of anything like a Force 9 blow. It's odd, the pilot charts for the areas I do sail in are pretty accurate except for small geographically local winds caused by venturi effects where no experienced person would ever anchor. We get Force 5 and 6 (up in Canada) but that's on the chart. Weird.

https://en.m.wikipedia.org/wiki/Williwaw
I’ve seen 50+ on the south coast of Newfoundland come up out of 15 or less. How did I judge that 50? The horizontal flying spray coming up off the surface of the flat water.
Occasional nasty summer thunderstorms this past summer in New England? Shore stations measured 70-80 for a few minutes. More than once. You can find videos on YouTube. Lucky me I only saw one of them personally.
I believe in using the big anchor every time. And In my experience the windlass will fail far less often than the wind will pipe up.

[noelex 77]

Originally Posted by Lodesman

Curious - there's been no comment/rebuttal to this. It's an interesting supposition - can an anchor be too big for the boat to be able to effectively set it? Not sure I really buy that argument, but would like to see what other more learned seadogs think?

Setting an oversized anchor is not an issue. You can look at the photos of my own oversized and other anchors here:

http://www.cruisersforum.com/forums/...26073-141.html

You can see that is very rare for my oversized Mantus not to be the best set anchor in the anchorage. Modern anchors, particularly the roll bar designs such as the Mantus and Rocna, set very rapidly and this helps them efficiently convert the setting force into digging into the substrate. Of course the setting force only provides a test equivalent to about 30 knots of wind for a sailboat. If the wind strengthens then the anchor will have to dig in deeper. This applies to both big and small anchors, but a small anchor will reach the limit earlier.

Originally Posted by Lodesman

I'm in the "bigger is not always better" camp; but for different reasons. In most systems, you want a controlled mode of failure - a weak link or relief valve. So the question is where do you want the anchor system to fail - you don't want the chain to fail, so it's sized appropriately; so if your huge anchor isn't going to budge, what's left to give? - your bitt? your cleats? the whole bow?

The biggest benefit to an oversized anchor is the ability to have sufficient holding power for poorer substrates and at shorter scopes. So in many circumstances the forces on the anchor rode and cleats will not be higher, rather the larger anchor will deliver a consistent hold in a greater range of situations. However, the anchor size recommended by manufacturers is often for only 30 knots of wind and a reasonable holding ground. Manufacturers such as Rocna recommend sizes for a slightly more realistic 50 knots, but if you occasionally anchor in stronger wind (as we do) then the size will need to be increased. Here you can expect higher loads on the chain and cleats. The chain is generally not a problem. Chain size recommendations have a generous safety factor so providing your chain is in good condition and you are using a recommended size, there is very little risk of ever breaking the chain. Cleats are another matter. Many full time cruising sailors reinforce their boat’s cleats and this is worth considering if you have any doubt about their strength. Damaging cleats is more common when tied up to a berth in strong wind rather than in an anchoring situation, so this needs to done to the stern cleats as much as the bow cleats. Extremely strong cleats are needed to use a drogue or occasionally in an emergency situation when being towed following a grounding. If you reinforce the cleats so that they are suitable for these potential loads, they will be way overkill for anchoring.

The anchor is invariably the weak link in the system so anything you can do to improve the anchor’s holding ability will make you more secure.

[noelex 77]

Originally Posted by dfelsent

How did I judge that 50? The horizontal flying spray coming up off the surface of the flat water.
Occasional nasty summer thunderstorms this past summer in New England? Shore stations measured 70-80 for a few minutes. More than once. You can find videos on YouTube. Lucky me I only saw one of them personally.
I believe in using the big anchor every time. And In my experience the windlass will fail far less often than the wind will pipe up.

If you do not have a serviceable wind indicator or are too scared to look at the reading , this is a good general tip for judging wind strength in an anchorage.

The “ white mist” that is engulfing this catamaran that was anchored next to us is not mist or fog but rather the spray that occurs when the wind strength has reached the stage that it is blowing the tops off the waves. This typically starts at around 50 knots in an anchorage.

[Izikalvo]

Originally Posted by Izikalvo

Good to see you are all alive and well.
Scubaseas, bigger is not always better, not with guns nor strippers and definitely not with anchors, read here:
https://vikinganchors.com/knowledge-...-always-better

Many opinions and lots of knowledge gathered by all of us over the years but almost no one here addressed the subject I made on top: it is less safe to use oversized new generation anchor.
There are many factors to consider while designing anchors, I will not waste your time mentioning all of them, after all, we all want to drop the anchor and sleep well (personally I never do but I am working on it), you can see here more
And if you still not convinced how about the price issue? why pay more for less?

[Mike OReilly]

Originally Posted by Izikalvo

Many opinions and lots of knowledge gathered by all of us over the years but almost no one here addressed the subject I made on top: it is less safe to use oversized new generation anchor.

There are many factors to consider while designing anchors, I will not waste your time mentioning all of them, after all, we all want to drop the anchor and sleep well (personally I never do but I am working on it), you can see here more

And if you still not convinced how about the price issue? why pay more for less?

Guess you didn't read the last few pages here. Most disagree with your assertion.

[noelex 77]

Some anchor companies like to recommend small anchors. The anchor buying public tend to assume when a smaller size is recommended, this must be because the anchor has exceptional performance. For boatbuilders, an anchor company that recommends small sizes is particularly beneficial. The boatbuilder can then supply a smaller anchor and importantly a smaller windlass, bow roller etc, which will add up to considerable savings and it looks nicer in the photos . High volume sales to large boatbuilders are dominated by companies that are prepared to recommend small anchor sizes.

I think this trend started with the Delta anchor, but Lewmar at least make it clear (providing that you read the fine print) that their recommended size is only suitable for quite modest wind strengths.

Izikalvo, I don’t think your anchor size recommendations are realistic.

Viking recomend a 8.2 kg (18.1 lb) steel anchor for a 15 m (49 foot) sailboat, and claim this will be fine up to 42 knots of wind.

In addition, the website points out “We measure our anchors holding power in a very conservative way, meaning, they will hold better than what shows on the charts.” “If you are not sure, go one size lower according to your boat size and weight, you will still have very good holding power”.

One size lower would be a 5.2 kg (11.5 lb) steel anchor for a 49 foot boat!

Unfortunately, those new to boating and anchoring will read these recommendations, and considering they have been made by the anchor manufacturer are likely to be persuaded by what in my view is very inappropriate advice.

[Lodesman]

Originally Posted by noelex 77

Cleats are another matter. Many full time cruising sailors reinforce their boat’s cleats and this is worth considering if you have any doubt about their strength. Damaging cleats is more common when tied up to a berth in strong wind rather than in an anchoring situation...

The anchor is invariably the weak link in the system so anything you can do to improve the anchor’s holding ability will make you more secure.

This is a very good point - but there is a practical limit to how much any cleat can be beefed up. How does one determine the safe holding limit of their cleat, even with a nice thick backing plate? Given the alleged holding strength of new-gen SHHP anchors, the weak link could very well be the fibreglass around the cleat.