22nd February 2023
Reading Time 20 Minutes
Before we start
Sumara is a long-keeled boat, 26 foot long, weighing about 5 tonnes. She tends to lie to the current, rather than the wind. The boat does not have a windlass. My final choice of anchor tackle needed to cope with fairly extreme anchorages in Arctic regions. Everything that follows relates solely to my experience with this type of boat. I have broken down the post into handy sections.
Sumara carries three anchors, a 15 kg Rocna bower anchor, an aluminium Fortress kedge anchor and a folding fisherman’s.
The Rocna Bower
Why a Rocna? Up until about 2008, I had been successfully using a genuine CQR anchor without experiencing any problems but there were loads of favourable reports about the “New Generation” anchors with “High Holding Power (HHP)” or even “Super High Holding Power (SHHP)”. HHP anchors must have 2x the holding power of the equivalent weight stockless anchor and SHHP need to exhibit 4x the holding power.
I was planning an expedition to Jan Mayen where I would need to anchor along the unprotected shore on the flanks of the Beerenberg volcano. Wind speeds of 150 knots with katabatic squalls have been recorded. I wanted a roughty-toughty anchor with good holding – not that I intended to hang around in those conditions.
It was the year 2008 or maybe 2009 and I had whittled down my choice to either the excellent Spade or the Rocna anchor. The Rocna felt more agricultural to me. The galvanising felt thick and the heavy welds looked like they would not give way.
My Rocna is the traditional style with the roll bar. I opted for a 15 kg version. Technically the 10 kg anchor was the correct choice but, because of the open anchorages that I would encounter, I decided to choose the next size up. There is a school of thought that choosing larger-than-recommended anchors is counter-productive, but the 15 kg anchor normally sets easily so it doesn’t appear to be a problem in my case. However, as years roll by, and my arms grow weaker, I feel a 10 kg would probably serve me best if I were to choose again..
The roll bar has been a source of criticism from some quarters. They say it can hold a ball of mud and prevent to anchor from digging in, and, in particular, from re-setting after a wind shift or tide change. They may be right. That said, if you do not have a windlass and need to haul up your anchor by hand, then you will find the roll bar a very useful grab handle for hauling the stonking lump up onto the deck.
On two occasions I have needed to reset the anchor, but it has never dragged once it has set. After about 15 years there is no rust.
I store it on chocks mounted on the deck. I had the fittings specially made by C&B Marine in Chichester. I originally had a very expensive stainless ball-lock quick release pin to secure the anchor through the special fitting but sadly one day, it did not release and we were forced to make embarrassing circles around the once peaceful anchorage whilst attacking the securing pin with hammers and hacksaws until we got the damn thing off. The gizmo was too clever by half. I now have a Wichard key pin shackle doing the same job and it is secured to the boat with a lanyard.
The Fortress Kedge
I chose an aluminium Fortress FX-11 Anchor to act as my kedge. I had become weight obsessed planning the Beerenberg Expedition and so aluminium had a great appeal. As I normally only deploy the kedge from my little Avon Redstart inflatable dinghy it would be very unhelpful having a heavy weight kedge anchor. The one I eventually chose was the Fortress FX-11 which weighs just 3.2 kg. It is recommended for yachts 8-10 m long.
I made a couple of wooden blocks with cleats on them for the storage solution. Its own warp can be used to secure the anchor and then it hangs alongside. There is a short length of chain then about 60 m of three strand nylon rope of about 14 mm diameter.
Don’t laugh, but I think this is a handy bit of kit. I use it most of all as a stern anchor when I am mooring bow-to onto a rock or suchlike. In these environments the seabed is generally so irregular that it is not possible to get an accurate idea of the depth. I just assemble the folding anchor and toss it over the stern with about 30 m of 16 mm Polyester Octoplait tied to it. I then motor slowly towards the rock to drop off the crew to secure the boat to the shore (or we lasso it). The anchor rode will tighten and the anchor will normally drag a bit but it still acts as a decent brake. Once the boat is tied off to the shore it will generally drop back away from the rock. If necessary, I will drop my anchor chum down the anchor rode to help pull the boat further away from the rock.
Obviously I don’t tie my lovely boat to rocks in windy weather, so this technique is for those tranquil nights in areas with little or no tide.
Anchor Rodes (Chain and Rope)
The chain we are using is 60 m of DIN 766 8 mm grade 70 galvanised which is about twice the strength of most anchor chains used by yachts. Standard anchor chain is normally grade 30 or 40. My chain was called Aqua 7 and I brought it in from Italy. I believe the company was taken over by MF Catenificio Frigerio who continue to manufacture it. It has a breaking strain of around 7,138 kgf and a manufacturer’s given WLL of 1,427 kgf. Due to the high strength of the chain, it is necessary to choose your connectors to the anchor very carefully to avoid introducing a weak point. Alternatively ask to have your chain made with an enlarged end link. If you are currently using 10 mm Grade 30 or 40, it would be possible to downsize the chain to this Grade 70 chain whilst maintaining virtually all the strength. This would give you a substantial weight saving or allow the use of a longer chain.
There are stainless steel anchor chains available which are grade 60. Beware of using standard 316 stainless steel which can rapidly corrode in the kind of warm salt water experienced in the Caribbean. Stainless chain is less liable to pile up in your locker and will generally come up mud free.
I choose 60 m because it allows enough chain to anchor in 20 m using my 12x the square root of the depth method. The bitter end of the chain is tied to a strong point down below with enough length of 14 mm nylon three strand rope to enable it to pull out through the “hawse pipe” allowing it to be cut with a knife if necessary, ideally with a recovery buoy attached.
Be warned that Grade 70 chain can not be re-galvanised unless by a specialist company. The metal can suffer from hydrogen embrittlement if galvanised incorrectly. Don’t try galvanising lifting chain!
The kedge rode is 14 mm three strand nylon. The rode came with the boat with an old Danforth anchor. If I were buying new I would probably choose polyester Octoplait. Indeed when I kedge from the little dinghy I do swap the rode for polyester Octoplait flaked down into a canvas deploy bag which is normally left on deck. That way the rope gradually falls out of the bag without any tangles while I am rowing away from the yacht with the anchor.
My small boat doesn’t have room for everything, so I use also my 16 mm polyester Octoplait for shore lines. Shore lines would ideally be floating polypropylene, but floating line is no good for anchoring. So I went for a line that sinks.
The theoretical internal width of the links of 8 mm DIN 766 chain is 9.6 mm but in reality they will generally take a 10 mm diameter shackle. Bolt type shackles are, in my opinion, the best type to use on anchors. A .75 t WLL Crosby shackle has a pin diameter of 9.7 mm which should fit through the end chain link. Crosby shackles have a 6 x safety factor indicating that the shackle would break at 4.5 tonne, well below the theoretical strength of the chain – 7,138 kgf (7.138 tonne)
I ended up using a Rud connector which has an oval hardened pin which fitted the 8 mm link perfectly. Of course, the body of the Rud connector would not get through the slot in the anchor shank but it did enable a large 1.5 t Crosby Bolt Type Shackle to be utilized. Sadly I can no longer find the Rud link on any websites but luckily Jimmy Green do sell a Grade 70 shackle that should serve the purpose. It has a MBL of 7,170kg which is perfect.
Scope and Technique
I normally pay out 12 times the square root of the depth. In tidal waters don’t forget to use the depth at high water, and always add your freeboard. Admittedly it means I can only anchor in 9 m or 16 m without my brain catching fire, but I can always make an educated guess – or use a calculator! I suspect it was my sailing friend Paul who came up with the clever technique. Using the rule means paying out 21 m of chain if you were anchoring in just 3 m depth (7 x depth) but if you were anchoring in 20 m it would mean paying out 54 m (2.7 x depth). It seems to work well for me.
Before anchoring I’ll have a look at the chart to see what the seabed is made from and if there are warnings of foul ground. If you have internet access, then Google Earth can sometimes throw some light on areas of the anchorage that are clear of weeds. If the anchor is liable to get caught on old chains or suchlike then I will use a tripping line (see below). If there are other yachts anchored, I will have a look to see how they are laying. Basically whoever gets there first has priority so it is up to the newcomer to keep clear of other boats. If there is no wind or current, it will be hard to judge where the yachts have dropped their anchors. It is probably best to try to ask the existing yachts, but they may not know. In which case you’ll have to guess and stay onboard until the boats have settled to a breeze.
If it is windy, some lightweight racing machines, or power boats with top hamper, may lie to the wind rather than the current. I like to anchor nearest to yachts with a similar underwater profile, although that can be guesswork with Spirit of Tradition yachts confusing the scene. I choose my spot trying to avoid weedy patches. I then stop the yacht, and as soon as it starts to drift back, I pay out the chain slowly. I do not flake the chain on the deck as it always seems to come out of the pipe without a hitch, and I don’t want to trash my deck.
I normally wear a pair of thermal fish handling gloves to give a good grip on the chain and to avoid tearing my hands on the coloured cable ties that I use to mark the chain (every 10 m in green and intermediate 5 m in red).
If the boat is drifting too slowly, then a little reverse gear is applied. I use a hand signal of backstroke for reverse, and front crawl for forward and point up for neutral. This method avoids waking up the entire anchorage, if there are other boats around.
Once the chain is laid neatly on the seabed, and definitely not in a big pile, I drop a chain link into the clever grooved stainless plate on the back on my massive 4×4 oak Sampson post. Why don’t all boats have Sampson posts? I then put my hand on the chain in front of the bow roller while some reverse gear is applied until the chain straightens right out. I can easily feel if the anchor is dragging or if it has set firmly. At the same time I will try to line up some features on the land to check that the boat is stationary against the transits.
If the weather forecast is calm, then the job is almost done. I wrap the chain around the Sampson post so it can’t jump out of the slot and I may secure the chain onto the bow roller with a sail tie. I then need to hoist the anchor ball and prepare the oil lamp for the night. If there is a bit of a blow due, or if I need to restrict my swinging circle, then I might use a snubber or chum or both. (see below). Once everything has settled down, I will take a few bearings of nearby features and write them into the log book. I might also set an anchor watch on the GPS. Phone apps are available but they may require your phone to be connected to power whilst the whole watch is taking place. Don’t be in a rush to leave your boat, have a cup of tea and make sure those transits aren’t moving and the bearings to the features remain the same. If you are in the Caribbean, why not grab your mask and snorkel and dive on the anchor to check it has set properly. It is a good idea to paint your anchor white if anchoring in clear waters.
Getting the anchor up is just a reverse process except this time the gloves are really helpful. I also make sure the Baby Blake lid is closed, just in case the chain decides to head that way! I may ask for a little bit of forward power to be applied while the bulk of the chain is being raised. The galvanised chain will normally pile up in the tray so it will need knocking over half way through. Stainless steel chain is less prone to this but ensure you buy the correct grade of steel if you go down that route. Once it gets really hard work, I pull on the chain and drop it into the grooved plate, and move myself back on the deck to get the boat into a rocking-horse motion. Waves will be your friend now. I then pull up another metre or so and repeat. The boat does most of the work and the anchor eventually breaks loose. The roll bar is a perfect grab rail to get the anchor back on deck. I then use a bucket of sea water and a stiff brush to clean off any mud.
I have never had the need to attempt tandem anchoring. There is a specific point on the Rocna to attach a second anchor. My preference has always been to escape from an anchorage if conditions are liable to become untenable. If forced, I would probably chain on my Fisherman’s anchor with about 10 m of chain and attempt to set both. It is essential that the length of chain between anchors is at least the depth of water (plus boat height) or, without a windlass, you wont be able to pull them up! By using the Fisherman’s it would leave the Fortress as a seperate back up should all else fail.
It is unlikely that I would anchor with two separately laid anchors, but if I did I would ensure the included angle was below 90 degrees and most definitely not over 120 degrees which would increase the force on the anchors and be totally counter-productive.
I have attempted to reduce the rolling by using various methods mainly involving buckets but without much success. Because Sumara is so low in the water, rolling isn’t too much of an issue, so I just accept it.
Chums (Angels, Kellets Etc)
This is very controversial, but I am still a believer in carrying a “chum”. My first one was made from old lead dive weights on a galvanised eye bolt and it looked pretty tatty. It also had sharp corners so it wasn’t very user friendly. To improve things, I went to my local engineering shop (remember those days?) and asked them to make a 15 kg one from solid bronze. When I phoned to get the price they said “You won’t want to go ahead, the price of bronze keeps going up and up” to which I replied “Well, why wouldn’t I want to go ahead!” So now I own a beautiful solid bronze chum with a Davey and Co galvanised chain shackle.
I agree that a chum is unlikely to significantly improve the catenary angle on the anchor chain in anything other than moderate conditions. The main reason I deploy a chum down my anchor cable, other than as a precious metal investment, is to act as a dampener. Even this theory is often sneered at, but I still believe in angels! I give my possibly dodgy reasons below.
But before we get into my dampening effect reasoning, there are other uses for the chum which are less controversial. It will definitely drastically reduce your turning circle in a tight anchorage so long as it isn’t blowing old boots. In theory it can also prevent your keel getting tangled in the chain, not that I have ever encountered that scenario. Furthermore, it can be used on mooring warps when you are moored to a wall in a tidal harbour. It will keep the boat snugly alongside at high water, rather than drifting out away from the wall. It can also be launched down a stern anchor rode to pull you away from the shore. I suppose it would make a handy sinker for a storm drogue too.
So now for my reasons why I still think the chum works as a dampener. Be aware that I have a small long-keeled yacht and a comparatively heavy chum. If you have a big fin-keeled yacht with no forefoot and a comparatively light chum, then my argument might not work.
In the world of lifting, when you sling a load on two slings the general rule is to try to keep the included angle at 90 degrees or less. It is easy to see a 90 degree angle. If you are lifting 15 kg then the force on each sling with a 90 degree included angle will be 10.5 kgf. Once the included angle rises to the maximum permitted lifting angle of 120 degrees then the force on EACH sling will equal 15 kgf. However, should you incorrectly rig your slings with an included angle of 171 degrees then the force on each sling would increase to 90 kgf on each sling, thus converting your easy-to-lift 15 kg bronze chum into a formidable effective weight. As the chain begins to straighten out the force multiplies more.
You can find a calculator for the force multiplier here. To simplify things, let’s assume that when the chain is drum-tight the angles either side of the chum will be zero. If we ignore that the chain is sloping downwards and just say that our 15 kg chum is halfway along the chain.
When the angle between the chum and the chain is 14 degrees, then the force on the chain will have doubled to over 30 kgf. Now as the wind pushes the boat back more and the angle reduces the following will happen:
- at 10 degrees the chum will exert 43 kgf
- at 5 degrees the chum will exert 85 kgf
- at 2 degrees the chum will exert 214 kgf (=2,107.3 N as in diagram above)
- at 1 degree the chum will exert 429 kgf
So what does this all mean?
Firstly we need to try to work out what forces might be involved during strong winds. The table below from ABYC gives an idea.
Cox Engineering’s website recommends using Professor John Knox’s equation to calculate the force on an anchor rode: Force (in kg force) = (1/500) x (LOA in metres squared) x (wind speed in knots squared). Using this equation the force on Sumara’s rode in 50 kn would only equal 320 kgf rather than well over 400 kgf using the table above.
To my simple mind, my 15 kg chum will be exerting over 400 kgf before the chain goes drum tight. My yacht is a smidgen over 25 ft so, according to the worst case table above, in a 42 kn wind, which is the top end of a force 8 gale, the theoretical load on the chain could be 444 kgf (980 pounds). Just enough to straighten the chain BUT I haven’t included anything for the weight of the chain. I’m no expert on these calculations, but I reckon that a 60 m chain (with 55 m deployed) weighing 1.4 kg per metre with a 1 m sag will exert about 528 kgf, rising to 1,056 kgf with a 500 mm droop. This doesn’t allow for the fact it is in seawater which is beyond my brain to calculate.
From these simple sums for simple sailors I would, possibly incorrectly, conclude that a 15 kg chum hung about halfway down a 55 m anchor chain would actually have a considerable dampening effect in winds up to at least a full gale. I may be wrong, and I often am, so I would be very happy for someone to tell me why I am wrong. Please fire ahead in the comments. I can’t really lose, if I am wrong, my chum will look splendid polished up sitting on my mantel piece as a relic from the past. Or I can visit my local scrap metal merchant and see what it is worth!
I realise there are other reasons why my chum should be sitting on the mantlepiece. One strong argument against deploying a chum is whether you can swiftly get rid of the beast if you need to make a quick exit from the anchorage. Another argument being why have all that extra weight, when a nylon snubber can do the trick just as well?
So will my lovely chum remain lying in my bilge ready for action or polished sitting on the mantlepiece?
My current snubber is made from about 4 m of 12 mm nylon three strand but it is way too short to comply with the latest trend. It is also quite old, so its due for replacement.
It seems we should be aiming for a stretch of about 1.35 m when the rope is at 20% of its breaking load (653 kgf)
12 mm Liros three strand nylon (polyamide) has a given breaking load of 3,265 kgf and a working stretch of between 16% and 27% at 30% of the BL which equals 979 kgf. As we are not loading the rope to 30% of BL, let’s use the lower stretch figure of 16%. I just can’t be bothered, or capable, of making the proper calculation. So here goes:
If my new snubber is 8.5 m long and subjected to 653 kgf (20% of breaking load) it would probably stretch about 1.36 m. I really do not want to handle a rope any longer than 8.5 m and most of the time I’ll snub it off much shorter but at least it will be there to do its thing when it is needed.
I use the Wichard Chain Hook with a plunger to attach the snubber. I found ordinary chain hooks just kept falling off during deployment. A rolling hitch would work just as well.
If the ground is foul, or uncertain, I normally use an anchor trip line. It is a light line attached to the head of the anchor blade. The other end is buoyed, normally with a fender. Obviously the line needs to be as deep as the water where the anchor is set.
In very tidal areas the buoy can be held over the anchor by using a snatch block clipped to the bottom of the fender. A longer trip line can then be passed through the block with a weight attached. This will hold the fender in position in any state of tide. I occasionally resort to writing “DO NOT MOOR” on it, just in case!
I do have a preference to using a paraffin light hung in the fore triangle. It provides a distinctive glow which is unlikely to get confused with shore lights or stars. A full tank will run for about 25 hours. All the cooking on Sumara uses paraffin so I always have plenty on board. I have also used it as a back up navigation light when my electrics failed crossing the Atlantic, non-compliant but better than nothing.
Having said that I prefer a paraffin light, if I am off for a long walk ashore, and not sure what time I will be back, then I will resort to flicking the switch to light up my all round Lopo LED Light at the top of the mast to add to the constellation of stars.
Blimey that was a long post!