To swivel or not to swivel, that is the question!

[Neeves]

Norman,

Size does not matter its quality that counts.

But you raise an important issue. On some modern yachts designers have squeezed the location of the windlass so far forward (in order to increase the forepeak dimensions (even though you cannot use the extra space) that there is simply no space between the anchor shackle and windlass, when the anchor is housed. there I thus no room for a 'whatever'. Nothing new here - as Boathook confirms. If you are making your own 'whatever' you can vary the dimensions from those I quote and I have made a short boomerang - that works well. You still need links between boomerang and anchor and there is a proliferation of shackles - but a short boomerang works. You can also cut back on the links between boomerang and anchor, even 1 link will work.

Modern windlass are exceptionally quick. We find that if the anchor is going to arrive inverted then the Boomerang does what is intended and self rights the anchor. But this is quite a violent encounter and the anchor can still be widely gyrating when it actually hits the bow roller. We tend to stop the windlass when the boomerang hits the bow roller - everything then slows down, restart, the anchor self rights - but a bit more sedately.

My favourite steel maker, Bisalloy not only gave me a lump of plate (delivered on a pallet) but also some small bits and pieces from which I made ..... later or I'll introduce e some drift.

The long boomerang is as the dimensions in the article - the short one was restricted by the length of steel that Bisalloy gave me


This illustrates a point I tried to make - as the anchor sets the shank end and toe bury together - you can see here the shackle has buried and the chain is about to be driven into the seabed (or it would do were we to drive it in - power set). But the Boomerang is sitting 'vertical' and if made and sized correctly has a cross section smaller than the chain - and actually enhances anchor performance. The Boomerang is the same as in the photo above. As background - we were drying out over night and not wanting to float away we had laid 3 anchors - one off the bow and one, with dyneema rodes, of each transom.






This is one of Her Majesty's vessels and they, being experts in the field, have no need to frequent Forum nor read learned yachting journals and have not learnt the means to self right an anchor (and it would be a waste of time to try to point out the error of their ways).

This is the result:



Just check next time you see one of 'our' new aircraft carriers - if the anchor is housed correctly then maybe tucked away unseen is a monster Boomerang - maybe proving - it is never too late to learn.



However I would not want to discourage anyone from making their own Boomerang, nor even discourage anyone from making a 'whatever'. I hope I have illustrated there is room for personalisation and they could make great conversation pieces.

Jonathan

 

[NormanS]

Jonathan, I'm not going to write an essay about this ?, but my bent link just has the bend roughly in the middle. I notice that yours has the "bend" offset towards one end. What's the theory there? Which end is fitted nearest the anchor, and why?

 

[Daverw]

This is what I had made from Neeves info


had it laser cut from these guys, cost me about £30 including steel
Metal Fabrication in the UK | Instant Quotes Online | Fractory

i had the 3D CAD file drawn by office at work and it’s all done remotely via upload to their site, took 10 days.

just to add the above is as it came back to me, nothing needed doing, I did polish it to make it shiny and file the slot to help the crosby link as I had it made from 8mm 316l plate, most of the cost was setting up and item costs dropped significantly for additional numbers.

 

[Neeves]

Jonathan, I'm not going to write an essay about this ?, but my bent link just has the bend roughly in the middle. I notice that yours has the "bend" offset towards one end. What's the theory there? Which end is fitted nearest the anchor, and why?

You do not need much of a 'lever' to have the anchor rotate. So the arm that is forcing the anchor to self right can be quite short. Windlass retrieval, or ours is, very quick so you need a long arm that remains on the bow roller whilst the short arm is doing its work.

The short arm is nearest the anchor. So the long arm is in the roller itself, the Boomerang is unbalanced, because the weight is acting on the short arm, the weight of the anchor rotates the boomerang so that the short arm is hanging down (recall the long arm is still in the bow roller). Once the short arm is hanging down the anchor has been righted. This all happens in seconds.

I made a little video but the speed of the windlass was so fast you could not actually see what was happening. I could have slowed the film (too clever for me) and I simply retrieved by hand - then it all happened in slow motion.

The angle is 45 degrees. The slots are of a size to allow the correctly sized (think strength) shackle eye to be inserted. None of the dimensions are smaller than the link - so for a 10mm chain link the dimensions round the slot are always at least 10mm and the plate should be 10mm plate. If you do this you could use a mild steel as the steel will be 10mm square at its thinnest and the link is 10mm diameter. I'm putting my name to what I design so I go for belt and braces and the device is much stronger than necessary - but perfectly safe.

The trouble with swivels is that they do not actually self right the anchor. They need manual intervention to turn the anchor round, say using a broom handle. If you are single handed or your bow cluttered this is not an ideal scenario. The boomerang will self right automatically, its stronger than the chain, when set it buries and offers some extra resistance to veering (as the Boomerang offers a vertical plate in the sand) and when buried is thiner than the chain and offers less resistance to burial.

The only issue, if you make from steel - is how to galvanise or you could simply paint and refresh. Or make from Duplex stainless. If you used 316 it will still be overstrngth, your decision to use a material of lower strength than Duplex, you could use a slightly thicker plate - just make sure that the shackles fit and can rotate and do not lock up.

Bow of shackle in the slo, pin through chain.

If you are a member of a yacht club - get a group of you together and make a batch that happened here in Oz, 20 or 30 were made. I don't recall but it was quite cheap. Or buy mail order from Viking, I think they are also quite cheap (I don't get any financial benefit - I'm just pleased to get my ego stroked .

Finally PM Daverw - he made his - he'll give you the background and the cutting file (which may need to be modified for your chain).


As you mentioned Norman - this is what PBO, the magazine and this section of the forum is all about.

I did make one from 7075 aluminium, in my quest for lightweight - it snapped like glass - don't bother with that route.

There is or was a fear that the Boomerang would jamb in a slotted roller - this does not seem to happen - or no-one has complained.

When laser cut (or whatever) they look quite professional - many of mine if you look carefully are obviously hand made. You could make with a decent bench drill, for the shackle holes, an angle grinder and a decent grinding wheel + ma file to reem out the shackle hole.


If you make and you are having yours laser cut - post here on PBO - you may find some like minded people and having a batch galvanised would be so much easier. (One offs are impossible to galvanise - though a slab of beer is a good persuader).


And in addition to Daverw - if you need help PM - me.

Jonathan

 

[NormanS]

Mine was made in half an hour, using a short length of half inch round bar (bent in the vice) and two links of half inch chain. That is for 10mm chain. I used a hacksaw to cut out a half inch gap in the end of each link, put the round bar into the gaps, and welded them up. Someone along the road who fabricates farm gates added it to their galvanising load. Nothing high tech about it, but my wife, who normally does all the anchor management, tells me it's wonderful. She has enough sense to slow the windlass as the link approaches the bow roller. ?

 

[Neeves]

Mine was made in half an hour, using a short length of half inch round bar (bent in the vice) and two links of half inch chain. That is for 10mm chain. I used a hacksaw to cut out a half inch gap in the end of each link, put the round bar into the gaps, and welded them up. Someone along the road who fabricates farm gates added it to their galvanising load. Nothing high tech about it, but my wife, who normally does all the anchor management, tells me it's wonderful. She has enough sense to slow the windlass as the link approaches the bow roller. ?

I imagine that if I had had different raw materials lying about and was a competent welder I would have developed something different to what is , possibly, known as the Boomerang. But with a plate of Bis80 looking for a home - to me, though I was initially unaware, the outcome was obvious. I similarly based my bridle plate on the same Bis80 though have stepped outside the obvious and also have some made from 2205 Duplex stainless and 7075 aluminium.

This the Boomerang we use regularly, with weight saving slots . BIS 80 and Armorgalv coated. The end links on the chain, attached to the Boomerang are Omega links - tested and found to be stronger than the chain. The end slots were produced to allow application of the Omega links.



Omega links come in a variety of forms, but commonly G80 or G100 strength. These are just 2 of the designs. The long or pear Omega has an oval clevis pin. The clevis pins are secured with hammer in locking pins.




And our bridle plate cut from 2205 Duplex with 316 x 2 part threaded LFRs, 10mm dynamic climbing rope and 6mm HT Armorgalv coated chain.





We mark our chain with yellow paint, for depth/length. We have also painted the 1m section prior to the boomerang solid yellow and have marked the bitter end with a 3m sold section (3m because the chan runs under the deck). The paint is not really as effective as desired as it is quickly abraded off the external parts of the link - but enough stays on the inner surfaces of the links to be noticed.

We too know when the end (of the chain) is nigh and when the anchor will come up correctly over the bow roller.

Jonathan

 

[differentroads]

If you do look at Neeves banana link I have one spare for 8mm chain as I had two laser cut from 316 stainless earlier this year or can send you the 3D CAD file and any laser cutting company will cut one complete with slots etc

Can I take you up on the offer of the cad file? I want to get a couple made up in spain in the coming months. I'll pm you my email address if thats ok

 

[Daverw]

Can I take you up on the offer of the cad file? I want to get a couple made up in spain in the coming months. I'll pm you my email address if thats ok

No problem sending it to you, PM your direct email,
Dave

 

[Neeves]

The slots are sized to take an appropriately sized shackle eye for the chain (bow through slot) with the clevis pin being the largest that will fit the chain. The metal work round the slot is sized to be the same as the diameter of the chain, and as its a square section and steel chosen to be stronger than the chain then the 'smallest' metal work is stronger than the chain. If you use oversized chain this would be really belt and braces. Obviously if you choose stainless - you don't need to worry about galvanising. You don't need to go overboard with shackle quality - the shackles cannot be side loaded. All our shackles are Crosby 209a (a 3/8th" shackle has a WLL of 2t) as then any shackles we have can be used for the anchor shackle - they are all the same, you cannot make a mistake.

If you are tight for space between housed anchor on bow roller and windlass you can reduce the number of links between boomerang and anchor, but you need an odd number, so 1,3,5 etc, more is actually better - but few have that luxury.

If you are retrieving from the helm and cannot actually see the bow roller you will know when the Boomerang arrivers at the roller as it rattles or clatters differently to the chain. Stop retrieving as soon as the noise changes and you should find that the anchor is sitting correctly on the roller - read to be lashed down. If you don't stop immediately its the same as not stopping when you retreive without a bow roller - ramming the anchor tight on the bow roller is not really recommended - strains the bolts holding the windlass secure, might damage the reinforcing and cannot do much good to the windlass.

If you have plenty of room between windlass and bow roller then you can lash the anchor. maybe using a chain hook, to a toe rail bow cleat or amidships, foredeck cleat to secure it on passage and use the same strop and hook as your back up to your snubber (in case your snubber fails).

Our bow roller is catamaran specific but:

The green, dyneema, rope and hook secures the anchor on passage (attached to a strong point). The chain between anchor (on right, off photo) and windlass is slack - no tension on windlass. The 'U' channel which is structural (holds bridge deck to cross beam between bows) has a slot and flanges for the bow roller (also to right off photo) but the 'U' beam also had extra holes in it and we have used 2 of them to hold a pin that passes through a shackle. Because we are using small high tensile chain we need enlarged links at the ends of the chain, we are using galvanised Omega links, again see above, but we have also used hammerlocks with success.



The device at the bottom of the photo is our bridle plate, see previous post above, - the slot accepts the chain, the 2 stainless LFRs are for each arm of the bridle. The smaller hole at the top of the plate allows us to secure the bridle to the cage of the furler when on passage

We have had lecture circuits in Oz and have used the Boomerang as prizes for competitions and they make gifts if you carry a spare for other yacht owners who have offered help beyond normal.


Jonathan

 

[noelex]

So what do people think, should I just have the chain connected to the anchor with a shackle as per my current setup, or should I allow more movement from chain to anchor -

which may also make a weak point in the system?

Using a good quality shackle is a simple and reliable KISS approach.

Swivels and anchor straighteners can be satisfactory, but there is a real risk of binding leading to an unfair pull and increased resistance to anchor burying.

Personally, I am not a fan of anchor straighteners. The complicated set of joints and associated components introduce the risk of binding and fouling in circumstances where the direction of pull reverses. The resulting unfair pull is a significant concern. As well, there is extra hardware that can reduce the anchor bury. This is particularly a concern with the flat plate models, as if they turn horizontal it significantly interferes with the anchor performance. Look at the photo in post #29.

I would suggest starting with a simple, high quality, but inexpensive connection such as the Crosby 209A shackle.

 

[Boathook]

Using a good quality shackle is a simple and reliable KISS approach.

Swivels and anchor straighteners can be satisfactory, but there is a real risk of binding leading to an unfair pull and increased resistance to anchor burying.

Personally, I am not a fan of anchor straighteners. The complicated set of joints and associated components introduce the risk of binding and fouling in circumstances where the direction of pull reverses. The resulting unfair pull is a significant concern. As well, there is extra hardware that can reduce the anchor bury. This is particularly a concern with the flat plate models, as if they turn horizontal it significantly interferes with the anchor performance. Look at the photo in post #29.

I would suggest starting with a simple, high quality, but inexpensive connection such as the Crosby 209A shackle.

In Neeves picture in post 29 the plate is lying over as there is no tension in the chain. If you look at the picture in post 26 you see that the plate is correctly aligned as there is tension in the chain.
If I had room I would have a boomerang and I don't even have room for a swivel having tried a kong one.

 

[NormanS]

Using a good quality shackle is a simple and reliable KISS approach.

Swivels and anchor straighteners can be satisfactory, but there is a real risk of binding leading to an unfair pull and increased resistance to anchor burying.

Personally, I am not a fan of anchor straighteners. The complicated set of joints and associated components introduce the risk of binding and fouling in circumstances where the direction of pull reverses. The resulting unfair pull is a significant concern. As well, there is extra hardware that can reduce the anchor bury. This is particularly a concern with the flat plate models, as if they turn horizontal it significantly interferes with the anchor performance. Look at the photo in post #29.

I would suggest starting with a simple, high quality, but inexpensive connection such as the Crosby 209A shackle.

The "complicated set of joints and associated components" is precisely two shackles. Is that really too complicated for you? Since my bent link is a short piece of half inch round bar, it will cut into mud easier than the chain.

 

[Neeves]

The cross section of the vertical Boomerang is less than the cross section of the chain - consequently the Boomerang will enhance anchor burial. This is a picture of a Boomerang correctly attached and under tension. It lies vertically.

The picture below - Bruce market devices called Boosters. They fit into the chain link (of large chain) and act like mini flukes. They have found that the mini flukes enhance chain burial and improve anchor performance. I don't make this up


I tried this by attaching a mini fluke either side of a Boomerang, see below., the same boomerang as above. If my boosters had worked the angle of the Boomerang would have changed and the angle of the buried chain, to the right and the Boomerang would have been 'tipped down' (I was ignoring the obvious defect - how would all this fit on a bow roller). The little mini flukes I attached made no discernible difference - but note that the boomerang is buried vertically. I do have other images of 'vertical buried boomerangs.

I have a friend who worked for the US Navy researching anchor design and application and who consulted to both Bruce and oil rig companies. He has used the Bruce Boosters and con firms they do work. Most of the companies at the forefront of commercial anchor developments, US and UK Navy, Bruce, Vryhof are able to attach sensors to their anchors and can determine hold, depth of set etc. It beats taking pictures of anchors and not interpreting the pictures correctly



If you take say 0.5m of chain and 0.5 m of chain plus boomerang there are more 'connections' in the all chain length (they are called links) the Boomerang if made correctly is 2-3 times the strength of the chain, it has been tested and the shackles will also be stronger than the chain.

The idea that the rode detracts from anchor performance is correct and some swivels are very large. This swivel might, or might not be, a marvel of engineering but it is huge, compared to a skinny Boomerang, or even a simple shackle. The Swivel is made to fit a specific size of chain, the chain being used. Consider which will enhance anchor performance (on the assumption that burying chain is good? - and I might be wrong,)


Using much heavier chain than is recommended is the most common problem (and is just another reason to use HT chain of a smaller size). The rode is buried by the anchor, as the anchor buries it pulls the rode into the seabed, you can see in the pictures above that the chain is buried. One specific anchor, Mantus, sets very shallow, the fluke is commonly at only 16 degrees to the seabed surface) and can really struggle to bury chain. If you measure most buried anchors their fluke addresses the seabed at 30 degrees and, everything else being equal, will bury twice as much chain as a Mantus. Now a 16 degree fluke angle to the seabed might be good - but no other anchor maker uses 16 degrees (they all use plus or minus 30) and an explanation has not been forthcoming. For those with an interest and an ability to access this link - its all explained here.

An Inquiry into Anchor Angles - Practical Sailor

Burying chain is advantageous - it reduces veering by a small amount (and buried chain means your anchor is well set). The Boomerang as it sits vertically and has 'surface area' means it increases resistance to veering. Its like a little vertical fluke (in the same way your anchor shank resists veering - also a vertical fluke - and the deeper the shank is buried the more resistance.

This is also why we now have thin shanks made from HT steel, and in the extreme tapered shanks, Vulcan. The beefy shank of the original CQR was a deterrent to the anchor setting.

I try to keep pushing design, often with no success (my idea of copying Bruce was a miserable failure). But I try them first - some manufacturers seem to think its a good idea to have the customer base try their ideas and or the manufacturer has no idea of the issues involved.

Take care, stay safe and

all the best for 2022.

Jonathan.

 

[Neeves]

There is no doubt, at all, that if your anchor is retrieved 'correct way round' every time - then do not use anything like a swivel or Boomerang. You are better keeping it simple and attach your anchor to the chain with a decent moused shackle, the Crosby G209a are the easiest to find but Yoke in Taiwan make some comparable shackles (but might be difficult to source). I have also found a couple made in China - but they are more difficult to source than Yoke. If you are in the US then Peerless and Campbell both make decent shackles, equivalent to those from Crosby.

Anchors are hydro dynamic and, depends on the anchor, they align themselves to water flow, right way round if you are going forward or backward as you retreive your anchor. As you don't know how you will be ,moving when you retreive you have a 50:50 chance of your anchor being aligned the wrong way. If you are anchored and suffer from continual direction changes at anchor either wind or tide, or both then your chain will be twisted - and the swivel will not allow this twists to twist out - swivels as a 'bearing' are useless, they don't work under tension to much friction and they don't work if simply lying on the seabed (no tension ).

The best way to remove twists in the chain is to retreive the anchor until it is hanging vertically and simply let torque and gravity remove the twists - but again you might not be able to sit waiting for the chain to untwist - there may be other priorities. Also torque will not remove all the twists and even 0ne twist in the chain will have your anchor being back to front at the bow roller. You can also wait till the anchor is just at the bow roller and if you have a swivel (or no swivel) you can poke the anchor round, with a broom handle) to suit - but again this may not be convenient.

This is an article of why not to use a swivel - if you can access. Nothing new here - just a neat summary.

Anchor Swivels: Caution Required - Practical Sailor

I did some tests on swivels 'working' and they need a twist every 1.5m and be in tension (but not too much tension) to have sufficient torque to work.

How Well Do Swivels Reduce Twist? - Practical Sailor

The 2 articles underline the background to the development of the Boomerang - there had to be a better way. NormanS gave me the confidence to make my own, Oscalutti, Normans and others the fundamentals (Bisalloy had given me the steel and I don't weld) - the rest was patience and try, try and try again. I have tried 7075 aluminium alloy - no yield and I do have duplex stainless copies that work well.

Jonathan

 

[noelex]

The "complicated set of joints and associated components" is precisely two shackles. Is that really too complicated for you? Since my bent link is a short piece of half inch round bar, it will cut into mud easier than the chain.

It is important to check the two shackles cannot bind or jam on the holes/slots on the anchor or the two ends of the anchor straightener.

When the anchor is first dropped the chain often does not lay out perfectly straight (as the photo illustrates) and when force is applied there is a danger of the connections binding or jamming and creating an asymmetric force on the anchor that can significantly reduce the anchor performance. This can also occur when there is a large change in direction of pull.

https://imgur.com/gCNgLkk

Binding can occur even with a single shackle, but the risk increases as the hardware and number of connections increase.
The best solution is to pull the chain from different directions on dry land and see if there is any tendency for binding to occur.

 

[Neeves]

It is important to check the two shackles cannot bind or jam on the holes/slots on the anchor or the two ends of the anchor straightener.

When the anchor is first dropped the chain often does not lay out perfectly straight (as the photo illustrates) and when force is applied there is a danger of the connections binding or jamming and creating an asymmetric force on the anchor that can significantly reduce the anchor performance. This can also occur when there is a large change in direction of pull.

https://imgur.com/gCNgLkk

Binding can occur even with a single shackle, but the risk increases as the hardware and number of connections increase.
The best solution is to pull the chain from different directions on dry land and see if there is any tendency for binding to occur.

The slots for the drawing of the Boomerang are sized to ensure that if you use the appropriately bow sized shackle - it should not bind.

It might be useful Noelex if you actually tried a Boomerang. You can buy one from Viking Anchor they offer fairly rapid mail order and I believe hold stock of their portfolio, anchors, Boomerangs and Bridle Plates, in Belgium - you can then take pictures of faults you find, or fabricate, and your comments would then be more useful (than guessing). I, for one, would be pleased to read critical comment based on usage as I could then introduce improvements to the current design. Knowing your skill and enthusiasm for underwater photography I am sure if you had actually tried any or all of these devices that if you had images showing faults - we would see them being posted. The absence of images is - telling.


Jonathan