Fork or 'V' anchoring

[prr]

It's suggested that 'violent veering' in strong gusts is a primary cause of anchors dragging. Perhaps it may be of value to consider what factors predispose to this veering, and what could be done to mitigate it.

It is often suggested that having a 'cutaway forefoot' on an otherwise long keel-form encourages the bows to blow off, as the centre of pressure ( above water ) on the hull and rig is far ahead of the centre of ( underwater ) lateral resistance. 'Big couple', as POTUS might say. One possible solution is rigging a 'riding sail', which has been discussed here in the past.

There are many examples to be seen on Google Images.

Another approach might be consideration of anchoring by the stern.....


As for "From Reeds Seamanship 1890. 1st Mates exam FAQs... "You want to get under weigh; you are hove dead short, wind on the bow, there is a rock right aft; what would you do?" Anybody wish to answer??".......... One answer, in 1890, would seem to be 'clubhauling', and Captain Hayes' Manoeuvre used just that - but that's an unlikely manoeuvre in a AWB today. Could one adapt that principle for our use today?

The answer as written is.
Give her a broad sheer, back everything, and let her dredge.

Supposing there was no wind, tide dead ahead?
Give her a broad sheer, and let her dredge.

in fact ''giving her a sheer'' using rudder and small stay sails, is also the answer to yawing, but seems to require constant attention as the tide changes.
Could you not give an AWB a sheer by attaching a stout mooring line to the anchor cable outboard of the bow roller and leading it back to a bow cleat, then veer the cable until equal weight were in both. Or even all weight on the cleat, a broader sheer?

 

[Neeves]

To clarify and reiterate, again

We do not use, or would not use, a fork mooring if the winds are to be guaranteed 30 knots maximum.

Our forecast is a forecast and are not certainties. Our forecast cover quite large sea areas and cells can develop within the forecast area for which the forecaster cannot provide any detail. Having once had a forecast of 25 knots then had actual winds of 50 knots gusting 55 knots for 7 hours we are cautious. We also deploy, preferably from a dinghy and personally I'd rather be in a dinghy at 25 knots, not 50 knots. We have time on our hands, deploying a second anchor is simply not difficult. If people have forecasts that are offered with strong degrees of certainty then they might find this is not the case in other parts of the world (even 'first world countries').

I mention it again if you want to note the errors in Forecasts, or underestimates, maybe look at the history of the Fastnet or Sydney Hobart races - forecaster get it wrong and badly at times. I took part in a number of China Sea Races, as owner, and on one particular race we enjoyed unforecast conditions of 50 knots over for 48 hours.

There is no introduction of a fear factor - its real world.

As Thinwater mentions - he has different weather systems - catastrophic thunderstorms where winds go from 20 knots to 50 knots in 10 minutes - if you are settling in for a few days you plan accordingly as its a bit late to deploy a second anchor when the wind is already blowing 40 knots.

What is interesting are surprising number of people who use a 'V' or a fork and who suggest they deploy the second anchor when the winds are more benign.

I did some testing on short scope, in 3m of water - it was slightly less that 3:1. The snatch loads were 650kg (at the end of a yaw, or veer). the yaw angle was 75 degrees. I was not using a snubber and a 2m snubber is not a snubber to me. This load will unseat a Delta, CQR, Bruce and possibly NG anchors.

Anchors, most of them (if not all) will withstand a wind slowly veering as the wind change in small and is incremental. The seabed has time to 'give' but it takes time. Snatch load at 650kg tension and something has to give, either the anchor will rip out or the shank will bend (and I know the shank will bend AND can anchor pull out as I've tested anchors (and have rather a lot of bent shanks!). You may of course bend your bow roller.

Be careful of anchoring at short, low scope - it will work in deep water, but not in shallow water (though a good snubber might offer some comfort (but the snubber might fail - 650kg is well above WLL for a snubber of a size recommended).

If you don't believe any of this - take a step ladder to your local beach and place it at the waters edge, so that you have 5cm of water. Jump off the top of the ladder such that you land with your legs straight. Stand on that same spot and wiggle your feet, you will slowly sink in but with the jump, think of it as a snatch load, you will feel the jar right though your body and you will not sink into the seabed. Yes anchors shuffle round - but not at the point of a 650kg snatch load at short scope.

A 'V' allows each anchor to take the load/tension in a straight line so that neither is side loaded. The holding capacity of the anchors is not added together - each works largely independently - so both are taking, in turn, the full tension developed at 50 knots (though occasionally they will work together). So the idea that using 2 anchors is to increase hold and that the individual anchors are inadequate is nonsense, lacks understanding and is, for want of a better word, scaremongering.

If you reduce veering/yawing you will reduce the opportunity for the development of large snatch loads - and if you are using sensible snubbers (deck length) or bridle or you are using a mixed rode then the elasticity of the textile portion will 'cushion' the snatch loads. Many anchorages in storm conditions develop bullets of considerable intensity - setting 2 anchors to 'meet' these directions is prudent (and you cannot cover more than one direction with one anchor, obviously.

This will bore many - our snubbers are 2 arms, of a bridle. We can ow extend to about 30m. Normally they would be used at about 15m, deck length + enough to allow the 2 arms to join at a common chain hook. Because we secure the 'ends' on the transom we have minimal length forward of the bow. We run through the stanchion bases and use a turning block on the bow. You can do this on any monohull though you need to manage chafe where the snubber goes outboard. You can also double length by commencing the snubber at the bow cleat, running to the stern horn cleat, back to the bow and then outboard, through a fairlead. To allow them to be located permanantly and to ensure use of the horn cleats use a short dyneeme strop between snubber end and turning block (the dyneema will be thin as it only needs to be as strong as the snubber). By using the length of the deck you only need to have a metre or so forward of the bow - there is no need to fear that the hook will drag on the seabed. You can use a bridle, with this technique on a monohull, as thought the angle will be narrow it will help to reduce yawing.

We have every confidence in our ground tackle, 8kg alloy anchors (their steel equivalents would be 15kg - and we have the steel anchors, for Spade and Excel, sitting in my workshop gathering dust) and 6mm chain for a cat with the windage of a 45' Bav, and have used the ground tackle in varying conditions. Our anchors are a bit light to many - but meet Classification Society (Lloyds, ABS etc) for size.

Jonathan

 

[prr]

It seems a sailing vessel should be able to drag its anchor under sail, to carry out certain evolutions, but not be able to drag when snugged down at anchor,

 

[zoidberg]

It seems a sailing vessel should be able to drag its anchor under sail, to carry out certain evolutions, but not be able to drag when snugged down at anchor,

'Twas a standard practice in the days of working sail - when Saint Tom was a nipper - to lower a heavy anchor so that it touched and dragged on the seabed without 'setting', thereby slowing/halting progress. By this means one could back into a berth/alongside a quay by using the rudder as the tidestream flowed past AND by 'taking a sheer' using sheerlines onto the hove-short anchor cable to set the hull partly across the stream.... a form of 'ferry gliding'.

Impecunious young Frenchies were adept at using sweeps - an Ecole de Mer Glenans speciality - often still encountered close in to the Isles of Scilly.

As for 'Could you not give an AWB a sheer by attaching a stout mooring line to the anchor cable outboard of the bow roller and leading it back to a bow cleat, then veer the cable until equal weight were in both. Or even all weight on the cleat, a broader sheer?' - that's the essence of Captain Hayes' Manoeuvre, a modification of 'clubhauling' as I understand it. The point being, almost whatever handling problem we are confronted with, someone before us has faced the same - often many times - and developed a solution.

Knowing some of those allows us to adapt to our own circumstances, i.e. reversing a long sailboat into a tight short finger berth at Royal Clarence Marina, strong headwind and weak cross tide, dropping a looped warp onto a finger-cleat on the opposite, UPWIND side allowed us to manoeuvre back using engine and prop-walk, while the looped warp acting as a 'drudge' helped keep the bows from blowing off. Easy....

 

[zoidberg]

The trouble I have with riding sails is....... The riding sail need be tension further aft, than my bridge deck transom, and I have nothing load bearing on which to secure...... I have not thought of a solution, yet.

Do you carry sailboard rigs? One mounted right on each stern step? A short 'whisker pole' each side and some cordage?

Worth a trial?

 

[RupertW]

'Twas a standard practice in the days of working sail - when Saint Tom was a nipper - to lower a heavy anchor so that it touched and dragged on the seabed without 'setting', thereby slowing/halting progress. By this means one could back into a berth/alongside a quay by using the rudder as the tidestream flowed past AND by 'taking a sheer' using sheerlines onto the hove-short anchor cable to set the hull partly across the stream.... a form of 'ferry gliding'.

Impecunious young Frenchies were adept at using sweeps - an Ecole de Mer Glenans speciality - often still encountered close in to the Isles of Scilly.

As for 'Could you not give an AWB a sheer by attaching a stout mooring line to the anchor cable outboard of the bow roller and leading it back to a bow cleat, then veer the cable until equal weight were in both. Or even all weight on the cleat, a broader sheer?' - that's the essence of Captain Hayes' Manoeuvre, a modification of 'clubhauling' as I understand it. The point being, almost whatever handling problem we are confronted with, someone before us has faced the same - often many times - and developed a solution.

Knowing some of those allows us to adapt to our own circumstances, i.e. reversing a long sailboat into a tight short finger berth at Royal Clarence Marina, strong headwind and weak cross tide, dropping a looped warp onto a finger-cleat on the opposite, UPWIND side allowed us to manoeuvre back using engine and prop-walk, while the looped warp acting as a 'drudge' helped keep the bows from blowing off. Easy....

This is the closest to a solution I’ve found so far - I take the snubber outboard back to the middle cleat with a second line through the bow roller and adjust. This was the recommended solution for angling away from a side swell but it cut down veering a lot as the bow couldn’t go through the wind. Haven’t tried it in strong winds yet.

 

[Neeves]

Do you carry sailboard rigs? One mounted right on each stern step? A short 'whisker pole' each side and some cordage?

Worth a trial?

Not sure I entirely understand - but I could, possibly, mount two stern sprits (I bet they have name!) so as to extend the 'stern' or transoms (in the same way modern (bow)sprits (I understand) are secured with most of the pole inboard). I cannot believe tension need by that high, though I have read the sails need to be flat. So worth a try as I do, coincidentally, have 2 windsurfer rigs (looking for a new meaning in life, as they are both boardless).

Thank you!

Jonathan

 

[thinwater]

The increase in force depends on the degree of yawing and sometimes how the yaw is arrested. I did a bunch of tests by adjusting the balance on my boat so that yaw varied from <10 degrees, by steps, to 160 degrees (yes, I've seen boats yaw that badly).

At 90-110 degrees the force will be 1.5 to 1.7 times the fixed force. The range depends on the design and waves and was confirmed by measurement. Generally no hard jerks, but there is zero question that the increase is material.

Arresting depends on the rode type, water depth, and scope. In principle, the boat should be swinging in an arc described by the rode, not side-to-side. There should be no arresting per se at the end of a swing, only a gentle turn. It is not as the though the boat is beating to weather with no sails up. There is no slack in the rode, but some boat do generate enough lift from the keel to allow the rode tension to drop very low. At some point the force doubles as it gets sideways, AND when the catenary suddenly snaps out of the rode, there will be additional force. Sometimes this is triple the base wind force. It depends on the snubber, scope, shape of the underbody, and probably a few other variables. With rope it is much less; there is stretch, but not as much as the change in catenery and the snubbing is more gentle. The boat may swing a little farther (though in stronger winds chain makes no practical difference), but the force is less.

Drag at 20 knots? Yes, we're all being a bit dramatic and we know it. But at 60 knots doubling or tripling the force is dramatic.

Does the anchor wiggle? Obviously there are many variables. On one hand, the shank provides side resistance if well buried. In soft mud, any wiggle at all prevents soil from consolidating, liquefies the mud, and can reduce holding 50% or more. Maybe the anchor is not well-set. The best answer is to follow Nolex's lead and dive on your anchor more often. It is a great learning tool. Your boat, anchor, rode, and typical bottoms are probably different.

In the Chesapeake squall season the wind doesn't go from 20 to 50 knots in 10 minutes. More like 5 knots to 50 knots in 5 minutes. But you should see it coming. The concern is that often the bottom is mud so soft the water only gets thicker as the depth increases, and the depth sounder stops returning an echo. As for yawing, my boats have always been pretty quiet if properly rigged.

 

[noelex]

Our forecast is a forecast and are not certainties. Our forecast cover quite large sea areas and cells can develop within the forecast area for which the forecaster cannot provide any detail. Having once had a forecast of 25 knots then had actual winds of 50 knots gusting 55 knots for 7 hours we are cautious.

Jonathan, I fully agree about the forecast being very wrong occasionally. You seemed to be arguing the opposite earlier in thread, so I am pleased you have reported these instances.

However, your example of being caught out in a sudden 50 knots when only 25 is forecast that has happened to me (and worse!) illustrates one of the reasons why I feel that normally relying on a very small primary anchor and chain, but expecting to set two anchors in stronger wind is not a prudent strategy.

25 knots, if I understand correctly, is right on the border where you will always deploy two anchors, so it appears that you were fortunate that in the instance you describe you had elected to do this.

 

[Neeves]

Jonathan, I fully agree about the forecast being very wrong occasionally. You seemed to be arguing the opposite earlier in thread, so I am pleased you have reported these instances.

However, your example of being caught out in a sudden 50 knots when only 25 is forecast that has happened to me (and worse!) illustrates one of the reasons why I feel that normally relying on a very small primary anchor and chain, but expecting to set two anchors in stronger wind is not a prudent strategy.

25 knots, if I understand correctly, is right on the border where you will always deploy two anchors, so it appears that you were fortunate that in the instance you describe you had elected to do this.

We dislike being on a yawing yacht, I'm not doubting the effectiveness of the anchor. yawing seems to increase with windspeed so at 25/30 knots we think it is more comfortable to deploy 2 anchors at the 25/30 knot borderline - to stabilise the yacht. The anchors, as they effectively each take the full brunt of whatever wind we have experienced, have proved their mettle - its the mettle of the occupants that is at doubt (for some reason we think cruising should be a pleasure not a test of endurance - its the 21st Century and we have become used to the softer things in life) - not the anchors (similarly most yachts are quite seaworthy - but the occupants are more vulnerable, or delicate).

Call us wimps - I really don't care

But in case the message is not yet clear (clearly mentioned by other - so your point is aimed at more than ourselves) - the ground tackle, and specifically - anchors - are not in doubt and have proven themselves.

But this thread is not about anchor size - its about Fork or 'V' anchoring - which many practice. You are the only one being critical of our anchor size - which is not the basis of our using a 'V' - its about veering/yawing.

Jonathan

 

[prv]

'Twas a standard practice in the days of working sail - when Saint Tom was a nipper - to lower a heavy anchor so that it touched and dragged on the seabed without 'setting', thereby slowing/halting progress.

I believe they still do it when towing the china clay ships backwards past Fowey.

Pete

 

[geem]

We dislike being on a yawing yacht, I'm not doubting the effectiveness of the anchor. yawing seems to increase with windspeed so at 25/30 knots we think it is more comfortable to deploy 2 anchors at the 25/30 knot borderline - to stabilise the yacht. The anchors, as they effectively each take the full brunt of whatever wind we have experienced, have proved their mettle - its the mettle of the occupants that is at doubt (for some reason we think cruising should be a pleasure not a test of endurance - its the 21st Century and we have become used to the softer things in life) - not the anchors (similarly most yachts are quite seaworthy - but the occupants are more vulnerable, or delicate).

Call us wimps - I really don't care

But in case the message is not yet clear (clearly mentioned by other - so your point is aimed at more than ourselves) - the ground tackle, and specifically - anchors - are not in doubt and have proven themselves.

But this thread is not about anchor size - its about Fork or 'V' anchoring - which many practice. You are the only one being critical of our anchor size - which is not the basis of our using a 'V' - its about veering/yawing.

Jonathan

Is there any evidence that an oversized NG anchor is less likely to drag and better at setting than the anchor size recommended for a particular size and weight of boat by the anchor manufacturer? Our anchor is as recommended by the manufacturer. We are very happy with it and sleep well at night

 

[Neeves]

Is there any evidence that an oversized NG anchor is less likely to drag and better at setting than the anchor size recommended for a particular size and weight of boat by the anchor manufacturer? Our anchor is as recommended by the manufacturer. We are very happy with it and sleep well at night

There is gut feel, which obviously (for some) engenders better sleep.

I have seen not an iota of evidence to support the contention that an over size NG anchor offers any more security to one of the size recommended by the manufacturer. The exception is in mud where Fortress clearly show in their Chesapeake tests that some anchors are, totally, ineffective and or too small (but this is in very thin mud).

There is general agreement that NG anchors set more easily, and may reset more reliably - basically they are more used friendly - but this has nothing to do with size (though at very small sizes, 1-2kg - maybe they are not as good as a 15kg model - but this does not apply here as no-one would use a very small anchor as a primary on a yacht.

There was a belief that bigger anchors have more hold than smaller ones. Hold is a function of vessel size, not anchor size. If your yacht develops a tension of 400kg in the rode - that's the hold of your anchor, it will be identical whether the anchor is big or small. The bigger anchor will develop a higher ultimate hold - but your anchor may never, ever, develop that hold - something on the yacht will break first. Most 15kg NG anchors develop a hold of about 2t in decent sand - if you ever develop anywhere near a 2t tension in your rode - you should be seriously worried (and I suspect will have scared the pants off you!).

I hard seabeds - you need an anchor focused at hard seabeds - a bigger anchor will develop no more hold than a small one of the same design (excepting that ultimate hold will be higher).

There is also no evidence to support the idea that bigger anchors are better in 'marginal' seabeds. It does sound logical, heavier sounds better in weed - but possibly you would be better choosing an anchor with known performance improvement (like Fortress in thin mud) than buying a bigger anchor.

I had a look at size vs vessel length for a variety of anchors. Taking an average of CQR, Delta and Bruce as one set of data and an average of Supreme, Rocna and Excel then the weight of anchor vs vessel size was for each set of averages was almost identical. The exception was Spade who at larger sizes of vessels tend to recommend slightly smaller anchors than the other NGs. This is despite the brouhaha over anchor holding capacity. In effect the NG manufacturers have doubled safety factors, which is no bad thing. I did find it surprising as the weight to vessel length spread sheet for older anchors has been used for decades and is generally accepted by Classification Societies who allow, I think its, a 33% reduction in weight for NG over the older designs - for vessels in Survey (where people are paid or passengers pay).

Jonathan

 

[vyv_cox]

Is there any evidence that an oversized NG anchor is less likely to drag and better at setting than the anchor size recommended for a particular size and weight of boat by the anchor manufacturer? Our anchor is as recommended by the manufacturer. We are very happy with it and sleep well at night

I have seen the opposite situation. A very similar boat to ours with a Rocna a size larger than ours (20 kg? Ours is 16 kg) anchored near us. Although his initial set was OK it dragged on heavy pulling. Ours was OK, although it was not the easiest seabed for anchoring, mixed sand and weed. Maybe a one-off but it confirmed for me that our own is as good as it needs to be.

 

[NormanS]

Is there any evidence that an oversized NG anchor is less likely to drag and better at setting than the anchor size recommended for a particular size and weight of boat by the anchor manufacturer? Our anchor is as recommended by the manufacturer. We are very happy with it and sleep well at night

If you are going to rely on the size recommendations by the anchor manufacturer, you should be very careful of the wind strength quoted. I think I am correct in saying that some of these recommendations are for winds of up to 30knots. If you can guarantee never to be anchored in winds of more than 30knots, that's fine, but some of us have experienced rather more. Several times, we've had winds of 60knots or more. The worst was 74knots (measured at just above the wheelhouse roof).
Sorry, but I don't get this "small is beautiful" theory with anchors.

 

[KellysEye]

>Looks like a good product. What wind strengths did you fly it in?

We put it up at 25 knots on the premise that the wind could increase because it's easy to put up then, in strong winds it can be difficult. Height up the back stay won't stop it working but may reduce it's leverage also it is likely to need longer ties to the stanchions.

 

[Neeves]

When testing NG anchors many times with unlimited power they will set, 15kg in good holding, or develop ultimate hold at around 2t. In testing older designs in the same seabed, same time, same weight they will develop hold of around 1t. The tension is applied in a straight line pull.

Having dived on anchors and found that they 'twitch' fairly continuously when the chain lifts or the direction of tension changes and knowing that the US Navy concludes that anchor (or seabed movement) causes a reduction in holding capacity I am of the belief these figures are optimistic and this twitching may be the reason older designs have a greater propensity to drag. But the NG anchors have doubled safety factors and if we assume a worst case scenario? then the NG will still be good for 1t tension - and with reasonable scope and decent snubbers you will not have 1t tension in your rode on a 15kg anchor correctly sized for the yacht. Note that a 15kg anchor might be commonly paired with 8mm G30 chain which has a WLL of less than 1t (in fact 750kg). If you expect loads to be more than 1t I would be suggesting you look carefully at your bow roller and consider upgrading your chain - you then have compatible ground tackle for a bigger anchor - and most, if any, do not increase chain size when they upsize anchor.

I had a thread some months, maybe 12 months now, and no-one admitted to their NG anchor dragging and the replies included people using NG anchors of the size recommended, some with larger anchors (commonly 1 -2 sizes larger) and a very limited few, it might just have been me , with anchors slightly smaller then recommended.

Based on this summary I have seen no evidence to support oversizing - of NG anchors, using appropriate snubbers (which are not included when anchor makers make their recommendations) and using a realistic scope. I also see no evidence, ignoring gut feel as not being evidence, that a bigger anchor is better than a smaller one in difficult substrates (excepting thin mud - and in this case the design is at fault and you should be using a Fortress). There maybe other niche substrates where a bigger anchor might be better - but I have seen no evidence - so I'm not being dogmatic nor ruling out being able to add to thin mud as seabed where a larger anchor might be better.

I do have the fear that a significantly larger anchor, factorially larger, will be impossible to set deeply and will be more prone to twitching and simply lifting from the seabed. However this is gut feel and I have no evidence - its on my list to look at. Seabed shear strength increases with square of depth and the deep your anchor (and more chain buried) the less likely it is to twitch and break free.

We consider a well set anchor to be one where the anchor and some chain is buried - as buried chain reduces twitching (I have checked this) - and it is difficult for our auxiliary engines to develop the tension on oversized anchors to set them deeply (unless you own a MoBo).

Anchoring in a 'V' allows the anchor to be loaded in a straight line, allowing it to achieve maximum hold without significant changes in direction. The 'V' or fork also reduces yawing/veering and this will reduce twitching (and reduction in shear strength of the seabed at the anchor). Using a single oversized anchor means it is less likely to be set deeply, will be constantly subject to yawing and - gut feel - suggests it may not be the panacea suggested - it might be the panacea - but I have seen no evidence (and I cannot recommend upsizing).

If anyone has objective evidence that upsizing is advantageous - they have been keeping it a closely guarded secret.

Now shoot me down in flames - with evidence, other than gut feel - please.

If I were buying a cheap anchor and I suspect it might be cheap because corners had been cut and possibly its strength was questionable - I would buy a bigger anchor. This has nothing to do with hold - but simply strength, usually of the shank.

If I were in the market for a new anchor I would not buy one where comparative holding capacity data was not made available. I can think of 2 anchors where holding capacity comparisons have not been made available and I would not buy them - though I note others are less cautious.

Jonathan

 

[geem]

If you are going to rely on the size recommendations by the anchor manufacturer, you should be very careful of the wind strength quoted. I think I am correct in saying that some of these recommendations are for winds of up to 30knots. If you can guarantee never to be anchored in winds of more than 30knots, that's fine, but some of us have experienced rather more. Several times, we've had winds of 60knots or more. The worst was 74knots (measured at just above the wheelhouse roof).
Sorry, but I don't get this "small is beautiful" theory with anchors.

Our anchor size is as recommended by the manufacturer. We have been anchored in winds of 40kts a few times with no problems. I dont think you can simply say we have been anchored in 60kts or more and you need a larger anchor. What size swell did you have? Was it flat water? Were you using a snubber? In my experience if yo have waves involved its a game changer. If you are dipping the bow under the seas then a long snubber keeps the anchor set far better than without a snubber. In a recent squall here in the Bahamas, that is what happened. Our snubber was stretching over a metre.
Our anchor sets and disappears. We either dive on it or use our glass bottom boat to see it is set correcty. Once set it doesnt move.

 

[GHA]

I have seen the opposite situation. A very similar boat to ours with a Rocna a size larger than ours (20 kg? Ours is 16 kg) anchored near us. Although his initial set was OK it dragged on heavy pulling. Ours was OK, although it was not the easiest seabed for anchoring, mixed sand and weed. Maybe a one-off but it confirmed for me that our own is as good as it needs to be.

First time I used a new size up spade I had the same, very disappointing. Seemed to set ok but not great holding.
Re anchored to find a little piece of cloth on the tip.

Single instances are really not much good at showing anything..

 

[noelex]

Now shoot me down in flames - with evidence, other than gut feel - please.

Anchor threads can get a bit silly at times.

There are plenty of formal studies looking at the relationship between anchor size and an anchor’s ultimate holding ability.

Vryhof the largest maker of commercial anchors have done extensive studies and they have shown a simple and predictable relationship between ultimate holding capacity and weight:

UHC=0.92W.

In other words doubling the anchor weight increases the ultimate holding capacity by 1.84 times.

This research was done on large anchors. When we look at Professor Knox’s (of Knox anchor fame) excellent tests that included many different anchor sizes, his tests showed increasing the anchor size actually produced greater increases than the Vryhof model shows. Ultimately, he suggested a simple formula where an anchor’s ultimate holding ability is directly proportional to its weight so doubling the weight doubles the ultimate holding capacity, although his raw results suggest the gain was actually a little greater than this.

This is not rocket science, just common sense. Do we really need to be wasting time “proving” a bigger anchor has more ultimate holding ability than a smaller model?