Ground Tackle
Anchors
The type of anchor is dependent on the seabed where the vessel is used most frequently. Each type of anchor has a purpose and optimal holding scenario. If anchoring in sand and mud most of the time, a claw anchor may not be of much use. If anchoring on a rocky or weedy bottom, a fluke anchor is not going to be much help. No matter what anchor is preferred, wanted or needed, it still has to be the correct size for anchoring safely. Anchors for different seabed conditions:
*Fluke Anchors (Danforth, Lightweight) - Sandy or muddy bottoms.
*Plow Anchors (CQR, Delta) - Sand, mud, grass and gravel bottoms.
*Claw Anchors (Bruce) - Rock, weed and coral bottoms.
The plow anchor offers the greatest range of options for anchoring making it the most common anchor on cruising yachts.
Cruising yachts with planing hulls generally anchor less frequently or for shorter periods in calm conditions. These type of vessels tend to stay at marinas and make short day trips using a day anchor provided by the manufacturer for calmer weather. For active cruisers doing The Americas Great Loop, or multi-overnight outings, marinas are not always an option. Relying on the manufacturers undersized anchor can lead to dragging. In our case, Viatori came with a factory installed 35lb day anchor. It would hold us in place in calm water with little to no wind or current, but if there was a wind gusting, the anchor would drag.
To determine the correct size anchor use the following formula. The result will provide an anchor size considered a cruising/storm anchor for winds over 30 but under 50 knots.
Tons + Length + Beam = lbs.
Metric Tons + Loa(meters) + Beam(meters) = kg.
A method some use is to multiply the LOA by 1 or 1.5 to get an approximate anchor weight. This calculation is less reliable resulting in an undersized anchor for larger and heavier vessels.
For Viatori the formula, 23T + 47loa + 14beam, gives us an 84lb anchor. This weight is not influenced by the type of anchor as we would need an 84lb plow, claw or fluke. Anchors from Fortress and companies like them are much lighter in actual weight, but they are rated to the equivalent holding power of a steel anchor. In Fortress's case they designate it as such by the FX-## model number. For example, an FX-85 is equivalent to an 85lbs steel anchor but only weighs 47lbs.
The chart below is from Mantus Marine to use for comparison. We estimated the anchor size we need using the above formula to be 84lbs to anchor in winds between 30 to 50 knots. On the Mantus Marine chart they call it a cruising anchor and looking down to vessels 45-50 feet and under 50,000lbs, they recommend their 85lb anchor, reinforcing our calculations.
Mantus Anchor Sizing Chart
Chain
Along with a properly sized anchor is the chain. When determining what to use, not all chain is created equal. Getting the product with the proper working load limit (WLL) as specified in the American Boat and Yacht Council (ABYC) standards is is the best course of action. The WLL is typically 1/3 of the breaking strength of the chain. Using the properly rated chain will reduce the risk of failure when the chain is under load from wind and current. The majority of windlass gypsies, the gear that pulls the chain, require the use of short link chain and can usually handle 5/16 or 3/8 inch chain without changing the gypsy. Short link chain has consistent link size and is referred to as anchor chain.
Not all chain is intended for anchoring. Chain is graded by the tensile breaking strength. The most commonly used grades for anchoring are grade 30 (G3), grade 40 or 43 (G4) and grade 70 (G7). There is a company in Germany that is making anchor chain in grade 63 (G6) but it is a stainless steel only chain and limited companies distribute it. Anything above G7 (grades 80 and 100) are to stiff and usually not made in a short link. Most anchor chain is galvanized but stainless steel chain, like the G6, can be polished.
When buying chain, use a reputable source, even if it means paying a little more. Sourcing chain with cheaper prices is tempting, but sacrificing WLL is not ideal. Finding a good deal on galvanized chain can lead to disaster in a short period of time as it may not be hot dipped but sprayed. The two processes to galvanize, hot dip (HDG) and cold galvanizing are vastly different. HDG submerges steel into molten zinc that is around 800+ degrees Fahrenheit. This creates a metallurgical bond between the iron in the steel and the zinc which creates a more durable finish. Cold galvanizing uses a zinc rich paint to coat the steel. The zinc in the paint sacrifices itself to corrosion and has to be reapplied. HDG last longer with less failure. Cold galvanizing in salt water may fail quickly, sometimes within weeks as the zinc content in the paint can be inconsistent.
Windlass and Bow Roller Sizing
With anchor and chain selected let's make sure it can get pulled back onto the vessel. First is to make sure the bow roller is the proper size. Bow rollers that were installed with undersized anchors may not be able to handle a heavier anchor. There is no specific formula for this, but manufactures will state the maximum weight of anchor it will handle. The bow rollers function for launching the anchor is to keep the anchor away from the bow of the vessel to prevent damage. When retrieving the anchor, the bow roller guides the chain and anchor shank to keep it inline to the windlass, making the chain skipping out of the gypsy less likely.
The specification needed for a windlass is the pulling force. To determine the amount of pulling force needed, add the weight of the anchor, the weight all the chain and then multiply by 3.
(Anchor lbs. + (chain length x lbs. per foot)) x 3 = Pulling Force
For Viatori we have an 88lb anchor and 200 feet of 5/16 G4 at 1.1lb per foot. To get the total weight of the chain we multiply 200 x 1.1 for 220lbs. Add 88 and 220 for 308 and then multiply 308 x 3 for 924lbs of pulling force. If this is close to the manufactures specs, you may want to go up one size on the windlass to ensure that it will not be overloaded, overheat or reach lock up amperage.
When deciding on ground tackle, it is best to research all aspects, Anchor, Chain, Bow Roller and Windlass, to make sure the set up is as safe and efficient as possible.