Anchoring "fun"

[vyv_cox]

Two anchors in line gives greater holding power but you do have the swinging issue. Cheers, Andrew

I have been trying to organise testing of this one, which I strongly doubt. In no area of engineering that I know of does doubling up the holding result in distributing the load evenly on both parts. Screw threads for example, where 90% of the load is taken on the first thread and most of the rest on the second. High pressure gas seals, which have been a large part of my work for many years, do nothing like what the compressor industry think, but again almost all the pressure is taken on the first ring pair. Some packings have 12 ring pairs, all the others just sitting there with no pressure acting upon them.

So for tandem anchors, I shall not be surprised to find that either one or the other does nothing while the other does everything. I will be amazed if there is any sharing of the load between them. With anchors laid at 90 degrees of course there is no doubt: the load alternates between the two, never pulling both at once.

 

[J Neeves]

Vyv,

I would go along with what you say - worse, or as well, the further away anchor probably sits in the disturbed seabed made by the first anchor so its holding (if it takes much load will be reduced) - unless the rode between first and second is long.

In any event tandem, or in line, anchors can only be considered for small anchors as the second anchor will need to be retrieved by hand, or a very inconvenient purchase system.

Setting 2 anchors on 2 rides seems simpler and be more effective (though unless you have 2 windlass - you will still need to retrieve by hand, which is why alloy seems a good option for the second anchor).

Jonathan

 

[vyv_cox]

Setting 2 anchors on 2 rides seems simpler and be more effective (though unless you have 2 windlass - you will still need to retrieve by hand, which is why alloy seems a good option for the second anchor).

Jonathan

Yes, we use this method quite often (although not this year in the strange, nearly windless conditions that have prevailed in the Cyclades, usually blasted by the meltemi throughout the summer). I generally recover the kedge from the dinghy, hauling in on the anchorplait until immediately above the Fortress and short chain. It takes energetic heaving to break out the anchor after a good windy session but lifting the lightweight anchor is relatively easy.

 

[CaptainBob]

Yes, we use this method quite often (although not this year in the strange, nearly windless conditions that have prevailed in the Cyclades, usually blasted by the meltemi throughout the summer). I generally recover the kedge from the dinghy, hauling in on the anchorplait until immediately above the Fortress and short chain. It takes energetic heaving to break out the anchor after a good windy session but lifting the lightweight anchor is relatively easy.

Why not let out additional scope on the bower anchor while pulling in the kedge, until you are over the kedge. Then pull in the bower. Especially if both are off the bow as you can then use the windlass for both, separately.

You're then not letting loose the boat at one end while not even being aboard to take the helm should you need to.

 

[vyv_cox]

Why not let out additional scope on the bower anchor while pulling in the kedge, until you are over the kedge. Then pull in the bower. Especially if both are off the bow as you can then use the windlass for both, separately.

You're then not letting loose the boat at one end while not even being aboard to take the helm should you need to.

I'm describing recovering the kedge when laid at 90 degrees to the bower, rather than as a stern anchor, so the boat is only attached at one end. I agree, I could haul the boat up the kedge line and break it out from there and have done so once or twice but using the dinghy seems an easier option.

I am not singlehanding and Jill is perfectly capable of handling the boat should the need arise.

We changed our windlass for one with a capstan last year, mainly for handling lazy lines, but it would be equally good at hauling in the kedge, so may try that sometime.

 

[TradewindSailor]

I have tried tandem anchors in Opua NZ. The ground is silt and although deep, it is not very good holding. A friend had a 30 tonne displacement ketch that had a tendency to drag through the anchorage. Once it started dragging it quickly went downwind and never recovered.

The initial set up was a 120lb CQR (South African Copy) and he had 5:1 down in 10m. Depending on where it was anchored in Opua, it would go walkabout in as little as 25kts or so.

I thought we would try tandem anchors : one 35lb? Danforth in front of the 120 lb CQR bower .... Initially it wouldn't set. So we cleared the anchor and put it down carefully again and let the anchors settle for about half an hour before pulling back hard. This time it worked ... we didn't move. However, when the current reversed, the CQR plowed through the Danforth and the yacht dragged .... I spent about 45 min untangling the mess before we used two rodes at 90 deg to each other and transverse to the current and that worked.

I eventually talked him into buying a 120lb Manson Supreme and sell one of the 120lb CQR copies. The Manson Supreme is virtually identical to a Rocna in looks. Anyway it set quickly and held better than the CQR, so much better that we thought we had found a solution ..... until it went walkabout again.

I had used a 45lb Seadog Claw on my Catana 40 without problems for 4 or 5 years, apart from one time when a coral rock fouled the anchor. However in Opua in 45 knots my catamaran dragged slowly.

So I anchored with a Fortress FX37 and a Danforth type anchor ..... each on 70' legs before being attached to a single riser ... Bahamian moor? This worked extremely well, even in 60+ knots in the Opua mud.

I sold the 45lb claw and bought a 65lb Manson Supreme. My Catana has a 5 tonne design displacement and low profile. It is still my bower anchor. It sets fast and holds in most conditions on 5:1 approx scope. BUT it has failed a few times in the Opua silt and in clay-silt in the rivers in NSW and QLD .... OZ. When I am in dodgy holding conditions now I set the Fortress FX 37 on a separate short (70'-90') rode transverse to the Manson Supreme that in on my all chain rode. The benefit of this set up, in reversing current conditions, is that I can un-knit the rodes easily from the fore deck.

I always set the main anchor first and set it, and then launch the Fortress from the bow when in position. I used more rode on the main to provide the slack. I then set and prove the Fortress. Finally I adjust the rode lengths so they pull equally up and down current. Sure there are times when only one rode is working, but it doesn't matter. If one anchor does drag, the other will allow it to set. I have NEVER had the anchors foul themselves in this set up. I can retrieve both anchors over the bow using my capstan/gypsy windlass .... Lofrans Tigress.

This is my way of anchoring. It is not the only way, but it works for me in the places I have anchored.

The Manson Supreme and the Fortress FX 37 are considered large for my Catana 40 .... but they do allow me to sleep well at night. The Fortess has NEVER failed, but I only use it as a secondary. The Manson Supreme has failed .... but when it does it has resulted in a slow drag; rather than the lying abeam, uncontrolled downwind flight of virtually free dragging. I still rate the Manson Supreme as an excellent anchor for anything where it can't plow ... Mud, clay, and silt .... and light coral sand ..... this is the rightful territory of the Fortress NOT the Manson Supreme.

 

[J Neeves]

If the Fortress has never failed but the Supreme has failed - why not use the Fortress as the primary anchor. I suspect an obvious answer, such as - the Fortress does not fit in the bow roller assembly - but to use an anchor that fails in preference to one that has never failed deserves some sort of comment?

But an FX 37 on a 40' Catana, a 'monster', the 25kg Supreme, not exceptional (we use a 15kg Excel on a 38' cat (with an FX 23, or 15kg Spade or 9kg alloy Excel).

I do not think it displacement but windage that is critical - and a 40' Catana (with no disrespect) has considerable windage.

But mud - Fortress has been publishing some interesting results.

Jonathan

 

[jdc]

...In no area of engineering that I know of does doubling up the holding result in distributing the load evenly on both parts. Screw threads for example, where 90% of the load is taken on the first thread and most of the rest on the second...

So for tandem anchors, I shall not be surprised to find that either one or the other does nothing while the other does everything. I will be amazed if there is any sharing of the load between them. With anchors laid at 90 degrees of course there is no doubt: the load alternates between the two, never pulling both at once.

Can plastic flow not help distribute loads? Didn't Kipling write a prose/poem about it wrt rivets?

Back to anchoring: while I'm sure you're right in 99% of cases could there be one exception in the case of an unknown and mixed substrate? We recently found ourselves anchoring on unknown bottom type (in uncharted water too) but which we believe to be large weed-covered stones interspersed with patches of very soft silt.

The main anchor (a Delta) would appear to set, but sometimes gave up suddenly - not very surprising given the nature of the bottom but hardly conducive to peace of mind when hiking ashore!

What to try? We did two things on different occasions (so no control experiment possible):

1. A Bahaminan moor of the kedge (a Fortress) laid out one way and the main the other, with the rope rode of the Fortress passing through a big bow shackle about 5m down the main anchor's chain and hauled tight.
2. A tandem of the 25kg Delta with a 60lb fisherman's.

#1 was when we expected the wind to change by 180 degrees while we were away from the boat, and #2 when we expected the wind to increase considerably during the night but not change direction. No tide in either case.

I freely admit we couldn't compare the tandem to a 50kg single anchor, which might well have been better. Nor could we actually perform a break-out test anyway so I really don't know what would have been the optimum approach.

 

[TradewindSailor]

If the Fortress has never failed but the Supreme has failed - why not use the Fortress as the primary anchor. I suspect an obvious answer, such as - the Fortress does not fit in the bow roller assembly - but to use an anchor that fails in preference to one that has never failed deserves some sort of comment?

But an FX 37 on a 40' Catana, a 'monster', the 25kg Supreme, not exceptional (we use a 15kg Excel on a 38' cat (with an FX 23, or 15kg Spade or 9kg alloy Excel).

I do not think it displacement but windage that is critical - and a 40' Catana (with no disrespect) has considerable windage.

But mud - Fortress has been publishing some interesting results.

Jonathan

I would never use a Fortress or a Danforth alone because if the pull is reversed it may not reset under load .... that is why it is always used with a second anchor.

The Manson Supreme is a reliable anchor in the correct bottom conditions. As I spend a lot of my time in either good sand anchorages or in rock/coral areas the Manson is a better choice as a single anchor than the Fortress. BUT I wouldn't be without the Fortress for its holding abilities in areas where the Manson's is iffy like in silt.

Anchor sizing ..... I like to use oversize anchors ..... the Fortress FX37 is rated for 46-51' boats, the Manson Supreme 60lb for 45-55'. My Catana 40 is a 1988 version ..... the low profile Lock Crowther 40, 5 tonne displacement ..... looks a little like the older Outremers .... so it has a lot less windage than the modern Catanas.

 

[Storyline]

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We changed our windlass for one with a capstan last year, mainly for handling lazy lines, but it would be equally good at hauling in the kedge, so may try that sometime.

Laid a V shape using our backup CQR just for fun (and practice) last year and successfully used the capstan on our vertical windlass to retrieve the CQR which had a short length of chain but mainly 3 strand nylon. Very useful to be able to use the capstan independentantly of the gypsy (in fact it would be near useless if it could not be !). There is a sort of 'big ship' feel when using the powered capstan.

 

[J Neeves]

Storyline and Vyv,

Just out of interest - what sort of windlass are each of you using.

Jonathan

 

[vyv_cox]

Maxwell, 8 mm gypsy. Checking up which model on internet would take me about an hour on this gprs link, so suffice to say it is the latest model but the previous one was the older version. I sold that and the buyer tells me he is delighted with its speed and power by comparison with the Italian one that it replaced.

When YM tested windlasses last year(?) the Maxwell performed best but came second due to its price. I certainly don't regret spending a bit extra. I was attracted to the Muir but it was a lot more expensive at the time, exchange rate? However it didn't do all that well in the YM tests so no regrets.

 

[Andrew G]

Vyv, re your post #41 - how about a connection with steel plates with through-bolts in shear? One uses the cross section area of all the bolts (not just one) to calculate shear loadings (on the assumption that the plates yield until the shear force on each bolt has evened out). Sea-bed is a little more plastic than (hardened) steel bolts and nuts . . .

I am suggesting that in-line has "greater holding" than two in a V, but am not necessarily promoting it - I agree that I have not seen tests, and would like to (but as you know it is hard to get statistical significance).
With two anchors in-line at least the far one will be fully bedded in (and with a zero angle to the sea-bed) and so will the near one if the scope is right - this may not be the case with a V setting as they tend to "walk" as the load alternates. This is on the proviso that the far one was properly set before the near one (hard to do) and that there is sufficient chain between them (eg 10 to 15m) to avoid the furrow problem that Jonathan points out.

• Two in tandem requires you to set it up before you anchor (or pull it all up and re-anchor), whereas a second in a V can be added if the wind kicks in by motoring up to the first anchor then across to the second position (or use a dinghy);
• In a V, both anchors and rodes should be the same/similar to minimise "walking" (this is a problem for me as my second anchor only has 25m of chain then rope. I have had one nasty experience where the rope rode on the second anchor was causing her to sail far too much up a narrow gutter - 50+kts on the nose with strong surge up the stern - we gave up and ran under storm jib the 40nm back to harbour we had just left arriving at 02:00);
• Both have problems with tide changes but when I've used them tide was not an issue (compared to the wind);
• In tandem can be a pain to put down and pull up but my windlass has a capstan so it is easier, but as a single hander you are drifting while you sort it all out . . . A V is dead easy, lay/retrieve one then the other.

So what do I do? If it looks dodgy and everything else is equal I put down two in tandem, otherwise add a second in a V when needed. Cheers, Andrew

 

[Andrew G]

Jonathan - I'm sure you were going to ask, Maxwell Liberty RC1700, 700kg of pull at 19m per minute, with its own Optima AGM up the bow. Sits nicely on the bow of a 34' boat but absolutely no disincentive to pull it all up and try again if you are not happy with holding/lie.
(And takes me up the mast in just under 1 minute - and please don't start, I know, I know . . .)


Cheers, Andrew

 

[J Neeves]

Maxwell, 8 mm gypsy. Checking up which model on internet would take me about an hour on this gprs link, so suffice to say it is the latest model but the previous one was the older version. I sold that and the buyer tells me he is delighted with its speed and power by comparison with the Italian one that it replaced.

When YM tested windlasses last year(?) the Maxwell performed best but came second due to its price. I certainly don't regret spending a bit extra. I was attracted to the Muir but it was a lot more expensive at the time, exchange rate? However it didn't do all that well in the YM tests so no regrets.

Thanks Vyv,

I knew you had had a Maxwell previously and just wondered.

We have been using a Muir Atlantic, for 12 years, and no problems. I suspect we might have passed its use by date (though no evidence of such) - but thought, as it was topical - I'd ask.

Sorry for thread drift.

Jonathan

 

[J Neeves]

Jonathan - I'm sure you were going to ask, Maxwell Liberty RC1700, 700kg of pull at 19m per minute, with its own Optima AGM up the bow. Sits nicely on the bow of a 34' boat but absolutely no disincentive to pull it all up and try again if you are not happy with holding/lie.
(And takes me up the mast in just under 1 minute - and please don't start, I know, I know . . .)


Cheers, Andrew

Vyv mentioned the same thing - they are so quick!

Edit, Having a cat our windlass is just in front of the mast (and thus just in front of the saloon) so all our batteries sit basically just behind and under the mast (so short cable runs). The chain is stored just in front of the mast. But our bow roller is half way between mast and cross beam (under the tramp) - and would be a nightmare to attach a second anchor in tandem. Hence a preference for a 'V'. Someone will suggest this is all unnecessary - just use a bigger anchor in the first place - but my preference remains to carry extra anchors (big locker under mast) - all of which are 'primary' sized and are more than adequate 95% or 99% of the time.

Jonathan

 

[vyv_cox]

I am suggesting that in-line has "greater holding" than two in a V, but am not necessarily promoting it - I agree that I have not seen tests, and would like to (but as you know it is hard to get statistical significance).
With two anchors in-line at least the far one will be fully bedded in (and with a zero angle to the sea-bed) and so will the near one if the scope is right - this may not be the case with a V setting as they tend to "walk" as the load fluctuates.

I find it very difficult to believe that two anchors connected by chain ( not considering where the chain is attached to the inner anchor, a whole separate topic) can have anything like the rigidity of your fishplate analogy. Seems more likely to me that when the load comes on they both set. One inevitably sets more strongly than the other and the weaker of the two does very little. Where the chain for the outer anchor is attached to the shank of the inner, which I have seen promoted as the 'correct' way to do it, I suspect the effect to be even more pronounced. As soon as the stronger setting outer anchor drags slightly the inner one might well tend to rotate rather than contributing to hold. In reality I don't think anybody knows but it would be interesting to find out, which I hope to do.

 

[J Neeves]

I am of the belief that an ability of an anchor to dive, or the depth to which it dives, is eventually restricted by the resistance of the chain to being pulled into the seabed. In a tandem pattern the anchor nearest to the yacht (inner anchor) will have 2 chains, both restricting its ability to dive. The interconnecting chain will, moreover, upset the balance of the inner anchor (wherever the chain is attached).

Consequently the inner anchor will not set as well as it would do (and will have lower holding capacity) compared to it being used alone.

I appreciate that anchor makers often provide holes in the shank which it is sometimes suggested they are primarily to use in a tandem situation (the other hole being to allow retrieval backwards). I have never, ever, seen an anchor maker demonstrating the use of their anchor in a tandem pattern - which raises the question, have they ever tested it?

A further problem I see with tandem anchors is - how do you know both anchors are set? You can set one anchor (and as you only use it when the chips are to be down you will set it properly - engines in high reverse). So having set one anchor immovably (as if it still moves under engine power its too small to start with) - how on earth do you set the second such that you know it is not lying on its side, caught a beer can in the toe (or in Studland - impailed a hippo)? A solution might be set one anchor hard, move toward the set anchor (so that the interconnecting chain is slack) and set the second - both set, how do you know where the interconnecting chain is?

edit

If the inner anchor is small is there a chance the inner anchor is actually 'lifted' between the outer anchor and yacht - much to test here Vyv!

end edit

You might gather my preference is for a 'V' anchor pattern - but am more than happy to receive a better education

Jonathan

 

[Storyline]

Storyline and Vyv,

Just out of interest - what sort of windlass are each of you using.

Jonathan

Lewmar V3 with 3/8" gypsy. Decided on this model because of ease of installation (and service if needed). The capstan, gypsy and gearing is installed first and then the (separate) motor is attached horizontally. There is a choice of 3 or 4 positions revolving around the centre point (see illustration below). You have to have fairly strong forearms to lift the motor into position whilst leaning forward, I used a piece of wood as a lever to help share the weight.

View attachment 45397

Have heard some criticism that it is slow but we have not found that to be a problem, certainly when retrieving the anchor we like to take our time and let the boat settle onto the direction of the chain as sometimes she has swung with the tide/sea or land breezes. Not sure how the power (1000w) stacks up against others but if the Rocna really buries deeply we slowly drive over it to release it anyway.

 

[noelex]

Lewmar V3 with 3/8" gypsy. Decided on this model because of ease of installation (and service if needed). The capstan, gypsy and gearing is installed first and then the (separate) motor is attached horizontally. There is a choice of 3 or 4 positions revolving around the centre point (see illustration below).

I think this is pretty standard on a lot of models.
Sounds easy, but the reality of lying cramped in the anchor locker holding a heavy motor above delicate bits of your anatomy while attaching the bolts with your other hand is less appealing in reality

Have heard some criticism that it is slow but we have not found that to be a problem, certainly when retrieving the anchor we like to take our time and let the boat settle onto the direction of the chain as sometimes she has swung with the tide/sea or land breezes.

I think slow is good. The windlass has a tough job of converting a reasonably small motor into a lot of pulling power. If comparing different windlass models with the same same sized motor and gearbox type, a slower retrieval rate fills me with a bit more confidence that the speciations are not exaggerated.