Vanish has performed extremely well for us over the past 2 years. During our trip home, we left a job list which was primarily composed of routine maintenance for Mike to carry out. In addition to these maintenance jobs we had two larger jobs on our "wish list". These were to change out our anchor chain and to replace four guest toilets. Whilst we have anchored in a lot of different conditions and have never dragged anchor, Maynard has not been entirely comfortable with the amount of chain we have carried. With regard to the anchor chain, we carry 70 meters (230 ft) of ½" high tensile G4 galvanised anchor chain with 30 meters (100 ft) of 1" nylon rode. At times this has proved to be inadequate in some of the deeper depths that we encountered in Panama and will encounter in our future travels. Occasionally this particular chain would become very stiff and would form a high pyramid in the anchor locker which always had the potential of jamming the windlass. Because of this piling up, we have restricted ourselves to using 50 meters or less of chain which we acknowledge is sometimes marginal. This always made us slightly nervous as the anchor system wasn't entirely bullet-proof and we often felt we did not have enough chain in any sort of problematic weather. This 70 meters of chain weighs over 270 kg (600 lb). Given the occasional pyramid issue and the weight, Maynard was reluctant to add any more G4 chain to an already heavy bow locker.
After considerable research, we have ordered 100 meters (330 ft) of 3/8" Cromax DUPLEX (318LN stainless) chain. This is highly specialiased (eg. $$$$ expensive) chain made in Bad Edorf, Germany by Ketten Waelder. This chain weighs 40% less than ½" G4 high tensile chain and has a similar breaking strength but costs four times as much. Unlike other chain, it can actually stay submerged in salt water with no negative side effects. It has the slippery shiny quality of stainless steel with superior strength of high tensile galvanised chain and will not form a pyramid. We've had to conduct a lot of research to find proper fittings that are a size that will fit this relatively small chain yet will still have an adequate breaking strength. After much research, we found acceptable shackles made by a company called Titan in Canada. We now have a chain system which is slightly weaker than the bollards we attach the snubbing line to, which holds the chain. We've given this a lot of thought but feel that the effort and expense to put this together will give us comfort at some of the undoubtedly windy and deep water anchorages we may visit.
For our engineering readers the following are specific numbers we used to design our primary ground tackle. Standard ½" anchor chain has a breaking strength of 15,000 lb and ½" high tensile anchor chain has a breaking strength of 26,000 lb. The cost per foot for standard chain is around $7.50 per foot and high tensile galvanised chain is around $10 per foot. Stainless steel 316L ½"- has a breaking strength of 25,000 lb. chain and costs around $16 per foot. Cromax ½" 318LN stainless has a breaking strength of nearly 38,000 lb which is way more than what is required for Vanish. All of these varieties of ½" chain weigh approximately 2.6 lb per foot. It turns out that we could downsize our chain two sizes to 3/8" using Cromax chain and we still achieve a breaking strength of 22,000 lb which is slightly less than the load rating of the bollards which our snubbing lines are attached to. 3/8" Cromax chain weight is 1.5 lb per foot which is over a 43% reduction in weight from a standard ½" chain.
To calculate the load required for our chain, we derived the wind profile from our stability report and published charts and have determined that a 40kn wind exerts approximately 5,500 lb of force on Vanish and a 60kn wind exerts a force of 11,000 lb. 90kn would exert a force of 22,000 lb. In the extremely unlikely case that we experience winds of 60 kn or more, first of all Vicki would be choppered off the boat (just joking), and we would probably use the engines to relieve some of the force on the gear. We would also deploy a least 30 meters of 1" nylon rode which will greatly reduce any shock loads by at least 30 - 50%. We will be using Titan shackles which have a breaking strength of 22,000 lb to attach to our 180 lb Lewmar CQR anchor. For the time being, we are going to keep the 120 lb Rocna anchor attached to 40 meters of high tensile standard ½" chain with 100 meters of 1" nylon rode. Incidentally, the 1" nylon rode has a breaking strength of approximately 30,000 lb. Lastly, we discussed the affect of having lighter chain on the catenary of the ground tackle. Due to the relatively high weight of Vanish and its twin keel configuration shearing is minimal and catenary effect is eliminated in any wind over 25 knots.
Shipping this chain has been a tricky operation as it had to be air freighted from Germany to the USA, bonded in the States then transited while still in bond to the Bahamas and cleared as a replacement part for a "foreign vessel in transit". Lots of paperwork and phone calls. We have the best situation for unloading our old chain and replacing it with the new Cromax as Vanish's bow is just feet from an unused parking lot. It was incredibly easy to take off the old chain and replace it with the new as you can see from the above photo. We look forward to testing our new chain and reporting our findings. Any questions or comments are appreciated and if anyone wants more specific information on the DUPLEX chain go to their website www.swi-tec.us If anyone is still reading this, our next blog will be the story of the changeover of our toilets. Woohoo!! Don't despair ladies, we'll get to the fun things soon enough.
We will be leaving the Bahamas soon, as hurricane season is approaching once again.
(Go to Photo Gallery for more photos.)