Those of you who attended Cruising Helmsman’s Captain’s Deck in Manly (Qld) last November, will have already been introduced to the Boomerang.
Two people from that event were even lucky enough to become owners of the device. For those that could not attend the presentation here is a very small part of what you missed.
Anchoring or more precisely for this article, the rode, throws up a number of issues that are sometimes insufficiently common to encourage any commercial company to develop a product. Most have a variety of personal solutions, often developed to meet very niche problems, but we have had a look at one common problem and offer one answer.
The answer is not particularly original, we have borrowed extensively, but we think the answer simple and the technology, such that it is, well within the grasp of any reader of CH.
What's the problem
A common problem for cruisers occurs when lifting the anchor, arriving at the bow roller ‘upside’ down (or back to front).
This not a life threatening issue but the extra snatch loads as the anchor hits the bow roller and then falls over to the correct attitude can do nothing for the integrity or lifespan of the windlass nor its shaft. Plus it can potentially cause damage to anything in the way as the anchor self rights.
Why the anchor arrives upside down has a whole range of mechanisms too many to elaborate here. Many windlass makers (for example Muir and Maxwell) both recommend use of a swivel. Strangely, people with swivels still complain their anchors arrive upside down, often 50 per cent of the time.
We are not keen on swivels in the first place as they do not appear to be the quick fix as suggested, but decent swivels can empty your wallet very quickly.
Another quick fix is manually realigning the anchor before it hits the bow roller, less easy if the anchor is heavy, chiropractic fees can be high!
Current fixes available
There are few commercial products in the market place.
Ultra recently introduced a rather tasteful swivel/self righting device, the ‘Ultra flip' swivel. We are not keen, to operate it you extend the shank and hence its lever length, which is not part of the accreditation when it achieved super high holding power certification with ABS.
Rocna had aspirations and had plans for a device called a ‘roller righter’ but we have never seen one and assume it was put on the backburner.
An Italian company, Osculati, market a device called an ‘anchor connector’, though it is made in China and has no numerical specification. Coincidentally, we met the Chinese producer (they make a whole range of stainless marine fittings) and they are aware of the issues and plan to have all of the load bearing components certificated.
Kong have an enviable reputation for its stainless barrel swivels but the price can make your eyes water and it has no ‘self righting’ features.
Simpler, cheaper and adequate conventional swivels are available from Peerless and Campbell, to name but two reputable suppliers.
Finally we know of one individual who simply bent some 3/8th” stainless rod and welded rings to each end. A good solution if you are a good welder.
What we did
We took all of this on board and set ourselves the task of building something that worked. It is simple to make and, hopefully, foolproof!
The result is the Boomerang, it comes from Oz, it looks the part and it ensures your anchor comes back the right way up!
We designed it round a Grade L (G30), eight millimetre (5/16th inch) chain with a 10mm pin rated shackle and the appropriate-sized anchor. Once finished and tested we then made drawings for a version for both 10mm and 12mm/13mm chain from 10mm steel and ensured that the 8mm chain version made from 8mm steel would be acceptable for a 6mm chain.
Please note that the loads on a six millimetre chain would be low and the Boomerang may well be unnecessary.
Care needs to be taken as we have found some metric 8mm chain, which should have a 10mm inner diameter, actually will not take a 10mm pin shackle. But anyone with this problem will already have cursed and found a solution.
One answer, that we have not tested, is to squeeze the end link in a vice to ‘open’ it out, sufficient for the pin.
We made prototypes of the Boomerang in MDF, then plywood and eventually high tensile steel, Bisplate 80 (ASTM 514A).
Why the overkill? The design is simple and anyone with an angle grinder and decent bench drill can make one. The steel is easy to work and erring on the side of caution in terms of strength, by a factor of two times, seemed prudent.
Advantageously, Bisalloy had given us some pieces of steel for precisely this sort of development, so we could not look a gift horse in the mouth!
We made a number of steel prototypes to play around with the balance of dimensions and the result is provided on the accompanying drawings. We developed files so the 6mm/8mm and the 10mm/12mm versions could be cut on a laser cutter.
The final version has been galvanised, we Armorgalv-coated our pieces as it is kinder to HT steels and works a treat.
Seven are currently in use without issues, they do what they are meant to do. We have checked and the Boomerangs have no negative impact on anchor performance. In fact when we went to take underwater images the anchor was so well buried it had taken the chain and Boomerang below and into the seabed.
Put it together
Installation is easy. You need to ensure the chain from the gypsy/wildcat has no twists.
The Boomerang is attached with a rated bow shackle, with the shackle's bow through the Boomerang, to the rode. You need a length of chain between Boomerang and anchor, same size as the existing chain and this is again connected to the Boomerang with the pin through the short piece of chain and then yet another bow shackle with the bow through the slot in the anchor shank.
We have found nine links, it must be an odd number, between anchor and Boomerang works well. Our nine links are 5/16th” Peerless Armorgalv G80.
When you have completed the installation the link attached to the anchor shackle should be a vertical link, in line with the vertical of the anchor shank. Each shackle should be also joined to a vertical link, the Boomerang should be vertical and the the vertical link of the rode attached to the Boomerang shackle should be in line with vertical links in the rode. So no twists as it enters the gypsy. All the shackles should be horizontal.
What could possibly go wrong
There are obvious downsides.
If you have a grooved bow roller you need to ensure the Boomerang does not lock in the groove or it will not rotate. If this is an issue use slightly thinner or slightly thicker plate.
Secondly, you need three rated bow shackles all of which need to be moused.
The big restriction is you need a reasonable gap when the anchor is housed on the bow roller between the shank slot and the gypsy of about 500mm minimum. You can reduce the overall length of both the short chain and the Boomerang and it still works but becomes a bit more abrupt; though you can massage this by stopping the windlass for a few seconds as the Boomerang self rights the anchor.
One of our original Boomerangs was only 100mm long, instead of 280mm of the final version and one installation only uses five links not nine. These variants work but the ‘righting’ moment leaves the anchor swinging just as it hits the bow roller.
We strongly urge against use of mild steel and we equally strongly recommend against buying a Boomerang which is not made from ASTM 514A (or something close). It is almost definitely overkill but it is the same way we urge use of rated shackles that have a strength at least greater than that of the chain. We make the same strong recommendation for
the Boomerang.
In Australia the Boomerang has commercial interest, not because it is a direct profit earner but because it makes for happy customers. Anchor Right have some models in stock.
CH is not interested in any commercial development, our motivation is similar: happy yachtsmen; hence this information is freely shared.
Variations from Boomerang to Bananas
We were not entirely comfortable with the need for three shackles and an offshoot of the Boomerang is the Banana Split.
This has an identical shape and dimensions to the Boomerang but is made from 2x5mm plates of the same high tensile steel. Each plate has opposing slots which form opposing hooks, like a Highfield lever, to take each end of the chain: the main rode and short length attached to the anchor.
There are 2x5mm diameter x 10mm long bolts securing the two halves, which have no load bearing function. We did not quite get the slots correct and had need to lock one slot off, against the remote chance the chain might slip ‘up’ the slot, with a clevis pin.
Each piece was galvanised, Armorgalv.
The fear was that the assembly would simply unravel like a chain of paper clips and we tested to just over two ton without any distortion. This is 20% higher than the proof test for our 8mm chain (Grade L G30), We did not test higher, we only had one test piece.
We have been using the Banana Split with confidence for three months.
More recently we have been offered some 2.5mm and 3.0mm HT steel plate: 700MPa Optima700, which is about the same as the Bisplate 80 we had been using; plus a 950MPa Optima950 product by SSAB from its Ruukki plant in Finland. This thickness of sheet is simply not made here in Australia, the minimum for Bisplate being 5mm.
We intend to retire the first Banana Split and replace it with one made from three pieces of 950MPa steel. One unit we will then test to destruction, the other we will subject to long term field testing.
We may lock the hooks to each other with a HT steel pin through the hook tip in the same way many HT lifting products are secured.
The Banana Split is not something for home manufacture, the dimensions to accommodate the chain are very critical.
Once we are comfortable with the design we will look at providing drawings for a cross section of chains.
Take a bow
And finally bows; another common complaint is that the pin of bow shackles and even the shackle itself, catches on the bow roller.
Basically, bow rollers are too narrow, a small component in the modern marine industry’s quest to cut costs. One solution is to use stainless shackles with recessed pins (though the strength is not much different to the chain). The other is to cut off the gal shackle pin head. This, however, makes it difficult to secure and release, though you can cut a slot for flat screw driver.
The late Alain Poireaud, inventor in 1996 of the Spade and thus a father of modern anchor design, promoted the use of stainless steel rigging toggles, which happen to be low profile. We have been trialling rigging toggles but find they are the wrong shape and not strong enough. The opportunity to move forward technically with the availability of thin high tensile steel, from SSAB, maybe provides a more flexible route.
It is very early days but the stainless version is illustrated using sex nuts with galvanised high tensile male inserts.
We will report in the future.
High tensile steel in the marine industry
Rocna brought HT steels to everyone’s attention when they used Bisalloy 80 for its anchor shank.
Manson followed using the same steel in its Supreme and subsequently the Boss. Anchor Right used Bisalloy 80 in its Excel and have completed the development work to use HT steel in its SARCA, recently it has reported to be using Bisalloy 400. Finally the Knox anchor, UK, uses a Corus/Tata HT steel of 900 MPa.
The other big application for HT steels is in the fins of performance racing yacht keels. The fin is ground to shape, leaving a stub at the top and bottom to bolt on the bulb and bolt the keel to the hull or, more commonly, a swing mechanism inside.
HT steels coated with Armorgalv provide a good substrate for powder coating, offering opportunity to use HT steels that do not look 'agricultural’.
Chain plates offer a possible application, lower weight and higher strength than the more commonly used stainless. Application is hardly large but possibly greater than most of us realise.
Finally, ‘sheet’ and ‘plate’ have an almost technical meaning in the steel industry, Sheet is used for product less than 5mm or 6mm (1/4”) thick and plate refers to product of sizes thicker.
