If you are replacing a well worn anchor windlass, or upgrading from a manual windlass to an electric windlass there are many points that must be considered. It is a good time to review your whole ground tackle anchor arrangement, and your boat anchor techniques. Windlass manufacturers offer a range of useful tools and guides to help you make the right choices for your particular boat and circumstances.
The first criteria is all about your sailboat. That means length and displacement. Then we look at the anchor type being proposed, so many to choose from. Plow anchors, Delta anchors. Kedge anchors, CQR anchors and a few more as well. Then we come to the anchor rode. This can be all rope, or a combination of rope and chain, or an all chain rode. Then we have to factor in the total length and weight of the chosen anchor rode. Then we need to consider the actual anchor weight.
Finally all these factors including anchor and rode choices have to calculate for your specific boat size and the displacement. The minimum anchor winch capacity is derived from the following formula after working out the chain weight or chain/rope weight from the table for your vessel size.
The x3 factor covers windage, tidal current and a safety margin.
Windlass Capacity = (Anchor Weight + Chain Weight) x 3
Most manufacturers have useful charts to assist in selecting the right unit, and many prudently add in a safety margin of 15- 25%. Always over engineer in your decision making.
Having calculated the windlass capacity for your particular boat then comes the choice of either a horizontal or vertical windlass. This is directly related to the available space for installation and the boat anchor chain fall. Vertical electrical boat anchor windlasses have the motor located below the deck, and horizontal ones everything is above deck. Vertical units take up less space on deck, although they can impinge on below decks space. What is the fall you might ask? The fall is where the chain “falls” directly below the windlass as it hails in, directly into the chain locker. This fall is entirely gravity based. Considerations are that there is enough space for all the chain to cleanly fall and pile up. If it piles up too quickly or unevenly there is no tension on the chain a sit falls down as you haul in and you get a jammed windlass. I know this all too well on one boat, absolute pain. Ensuring that an anchor rode comes in off the bow fairlead at the right angle is important to avoid fouling and jamming. This is critical in horizontal windlasses and also very important on vertical windlasses as well. So make sure you calculate chain lead in angles properly before you bolt the new windlass down. Even replacements have different footprints and geometry.
Important fact to consider. An anchor windlass is not designed to take the entire load applied through the anchor rode when riding to anchor. This is especially important in large swells or heavy conditions. You can easily damage the windlass gearbox with heavy shock loads that get applied.
As a safety precaution always transfer the load to a bollard or load bearing point using a rope snubber or use the chain stopper. Also it is worth checking how solid a base the windlass is mounted on, I was horrified to see how much stressing the foredeck suffered on one of my boats and ended up heavily reinforcing the foredeck area.
Also use a good swivel between anchor and chain, so that the anchor rolls and comes neatly into the stem-head fitting. One thing I look at with every boat is signs of stressing on the deck area under a windlass, if its stressed or fatigued the chances are the anchor windlass has sustained some hard stress too, so regularly inspect every part of the anchor system. More about the anchor windlass to come and also lots to learn about anchor handling.