Tech: The wonder of winches

I love winches. When I got Arriba it came with 5 manual winches, which might have seemed adequate in the eyes of the designer; but not to me! Arriba now sports 7, including my pride and joy, an Andersen 40ST compact electric winch.

If you sail anything bigger than a dinghy, you almost certainly rely on winches to get work done on your boat. And the bigger your vessel or the lazier the sailor, the greater the need.

Strictly speaking, what we have on modern yachts are not winches but capstans. The technical definition of a winch is a winding device that stores its cable (or rope) on its drum. Anyway, we’ll stick with “winch” since that is the prevailing term.

Although winches starting appearing on large yachts in the 1930s, they didn't become very common on smaller yachts until after World War II. Modern Bermudan sloop rig yacht designs, i.e., large fore-and-aft sails, undoubtedly owe some of their popularity to the advent of the modern winch. Instead of numerous small sails, as you would find on the tall ships of yesteryear, we can now use powerful winches to manage a couple of big sails.

The first thing to understand about a winch is mechanical advantage. The mechanical advantage of any machine, albeit a lever, a wheel and axle or a winch, is the output force divided by the input force. Winches generate mechanical advantage in two ways, firstly from the internal gear ratio (G) and secondly from the ratio of the handle length (L) to the drum radius (R). The product of both is referred to as the power ratio, i.e., P = G · (L / R).

For example, an Andersen 40ST winch, which like many modern winches has 2 speeds, has the following ratios:

Gear ratio (G)
Power ratio (P)
1st speed
1.3
8.5
2nd speed
6.0
39.5

Note that Andersen, like many winch manufacturers, uses the power ratio (rounded up) for the winch name. The power ratio must be always quoted for a given handle length (L), which is typically for a standard 250mm (10”) handle. Incidentally, the drum radius (R) for the 40ST is 38mm. I’ll leave it as a homework exercise for the reader to calculate the above power ratios from the gear ratios.

The second thing to understand is that the pull of the winch (expressed in kg or lbs) is simply the power ratio multiplied by the pull applied to the handle (expressed in the same units). For example, a power ratio of 39.5 means the winch can pull 395kg (870lbs) when applying 10kg (22lbs) of pull to the handle, assuming of course that the winch is 100% efficient. In reality, the efficiency is reduced by friction losses, which is another reason to clean your winches regularly.

A corollary is that the easiest way to get more pull out of a winch is to simply use a longer handle. For example, going from a 10” handle to a 12” gives you 20% more power. It's that or eating more Wheaties for breakfast.

I only recently added a seventh winch. Arriba's gennaker is a big, powerful sail, and I found it almost impossible to furl without a winch. The trouble was I also needed a winch to keep it partially sheeted in while furling. Problem solved with the addition of another winch.
Arriba's starboard winches exposed.
One cautionary note about electric winches. Having an electric winch really is a godsend, especially when single-handed or short-handed. It's like having another crew member, except one who never complains when you tell them to grind harder :-) If you’re not careful though, your electric mate will wreak havoc, in the blink of an eye. You can't blame them; they don't know their own strength. I once destroyed a perfectly good halyard by not paying attention, with my fat thumb pressed to the electric winch control.
Arriba's electric winch - right at the helm
So always watch what you are winching (halyard, sheet, sail, etc.) so that you don’t damage anything or anyone. Be especially careful when using a winch to furl a headsail, since it is very easy to damage the furler or furling line.

Finally, there's the tedious subject of maintenance. Winch manufacturers sell service kits for their winches and publish detailed instructions. It's typically recommended that you take apart your winches, clean them, check for worn parts and lubricate them every couple of years - even more if you sail a lot.

Be kind to your winches and they will give you years of faithful service. 

OVER.

PS For the sake of completeness I should also include Arriba's windlass, a Muir VR1250.