About Sailboat Winches Selection

Sailboat winches, whether the plain top or the  self tailing variety, you need to consider a few factors when selecting them. As outlined elsewhere there are many multiple deck winches available. The more common self tailing winches on most offshore yachts are used on everything from mainsheet trimming, job and genoa control and halyards. In many cases with halyards as I have had on some of my boats, I have a clutch located before the winch and also cleats located to hold free ends.

Sailboat Winches Selection

There are basics to consider and its always a prudent decision to review your specific boat sail plan and running rigging configuration. The boat running rigging must be able to cope with the loads to be imposed but you need to quantify what they are. When the wind exerts a force on the sail the running rigging holding those sails, such as sheets, must be capable of withstanding it. It is one thing to be cruising along with a comparatively even load applied but that changes when a larger gust hits them. This imposes a shock loading on the sail, standing rigging and running rigging sheets and the winch.

Sailboat Winches Selection

So now we have to look at the numbers and answer some questions.

Question 1. What will be the exerted force on the sails

Question 2. How is the exerted force transmitted to the boats running rigging?

Question 3. How strong does the running rigging need to be?

The basic and simple formula for calculating the force of wind imposed on a sail is as follows:

Wind Pressure per Square Foot = (0.00256) x (Wind Speed in mph) squared

Note the wind speed is squared which means that as wind speed increases the forces applied to the sail increases at a significantly higher rate. On a large mainsail or even a large genoa this can be quite considerable. So if you double the wind speed you end up with the wind pressure being quadrupled. This applied force gets transferred to the sail clew and the sheets and other running rigging. This also impacts on the loading on every block and also winch that is part of that running rigging. It is good to know that most winch manufacturers make this exercise comparatively easy by providing online calculators to facilitate sizing of sheet load, and Harken has valuable resources for this for headsails and mainsheets.

Sailboat Winches Selection and Genoa’s

A headsail or genoa sheet needs to be able to accommodate the full load of the clew as in many cases the single sheet is usually routed via a traveler or genoa lead car and then to the deck winch. It is important to consider this when also reviewing deck winches. Like most I have had genoa traveler car systems to facilitate alteration and adjustment of sheet angles to improve sail shape efficiency, and this applies to hanked on and furling headsails where partial furling requires adjustment.

The genoa car size is also determined by the sail area and sheet load.  Harken has some great information and resources in calculating this. They also include information on block loading and angles of deflection. The loading experienced by a block is a combination of the line load passing through that block along with a block loading factor. This is then determined by the angle at which the block turns that sheet. So when considering winch selection and positioning look at this often overlooked factor. Again reducing system friction is important to sheeting efficiency so best to over specify a genoa car and choose a ball bearing system. Even when cruising, sea states and wind conditions alter and sometimes rapidly and often as many of you know, require fast adjustment and trimming to maintain optimum sail shape and keep the boat moving forward.  

Sailboat Winches Selection and Mainsheets

Unlike a genoa and jib, the mainsheet comprises a purchase system. This multiplies the purchase capability and spreads the load ultimately reducing main sheet loadings. Many of the same principles apply and these include main sail area, whether you have end boom or mid boom sheeting systems. Also whether you have low beam supported tracks or unsupported high beam arrangement.  There are many opinions on mainsheet handling and several arrangements in use. Traveler systems are many and there are some very efficient configurations to choose from. I am one who opted in the past to having a dedicated self tailing deck winch for mainsheet trimming along with cleats and clutches. There are some great resources on line about sailboat winches and how to select them and do the math when planning a winch for this function.

Sailboat Winches Selection Factors

When wind exerts a force onto the sail, the sail results by moving. The sheet function is to resist any movement and maintain the sail position. These applied wind forces are shared between the tack, head and clew of the sail. As the sail is secured it exerts a force which helps drive the vessel forward. The sailboat winches also bear these loads. Although these are sailing basics they can be repeated.  In practical terms the luff is maintained by the tack and the head, which pull to resist sail deformation. Luff tension is applied by the halyard pulling on the sail head. Both the leech and foot are both maintained in tension by the sail clew. When you adjust the genoa or jib sheeting angle it consequentially shifts the location of where the applied force is. Move it forward the sheet acts like a leech, move the car aft and it acts more on the foot. It is important to note that there will also be small sheeting angle changes to your deck winch.  Deck winches really don’t ever need winches to operate. If they cause issues its generally because something is failing, usually lack of maintenance and where swivel bearings are seizing sue to salt or dried out or the sail halyard is too tight or a halyard twist is occurring at the top swivel. Of course an adjustable traveler is ideal for the sail control and tension with a deck winch, but you should be able to unfurl and furl using control lines. More about sail handling and also more about boating.