Powerboating - Part Fifteen

If you're a bit of a movie buff and like old films, then you've probably seen scenes in which Errol Flynn, or someone similar, orders the sailing ship to get underway and a football team of willing sailors leap to the capstan, 'Yo-ho-hoing' for all they're worth, faces wreathed in smiles as they bring the anchor aboard.

Possibly that's the way it happened in real life, but I doubt it. I suspect that getting the anchor up was as big a drag then as it is now, and if any words were used while it was windlassed up, I don't think 'yo' or 'ho' would have been among them.

Today, things are a little easier at least: the advent of the small electric windlass has meant that getting the anchor aboard is no longer a demonstration of brute strength and four letter words. Let's look at this marvel in a little more detail.

WINCH MOTORS
The heart of any electric winch is its motor. This is generally either 12 or 24V DC and is almost always a 'Series' type, usually coming in one of three forms. The simplest is the permanent magnet motor, which, as the name suggests, has fields that consist of permanent magnets. The armature operates between the two fixed magnets, and when power is applied, the commutator converts the DC current into an alternating magnetic field that interacts with the fixed magnetic field to produce a rotational force on the armature, causing it to spin.

This alternating magnetic field in the armature also limits the amount of current flowing through the motor and this limitation is called 'Back EMF' (electromotive force). The amount of Back EMF is a function of the speed of the armature. Thus as a load is imposed on the motor, the armature will begin to slow down. This, in turn, reduces the Back EMF, which, as a consequence, allows more current to flow through the motor. The higher level of current produces a higher level of torque, allowing the motor to carry the extra load.

However, the strength of the fixed magnetic field does not alter, since this is provided by the permanent magnets. Because of this, there is a limit to the torque that can be produced. This limitation means this style of motor is usually confined to small anchor winches.

The next type of motor used is the series wound. This means the field coil is connected in such a fashion as to be in series with the armature. Thus all the current flowing through the coil also flows through the armature.

Exactly the same principle of operation applies to the series wound motor as the permanent magnet style, but this method of electrical connection results in a motor that has tremendous torque, because an increase in current produces an increase in the strength of the fixed magnetic field.

The third style of series motor, and by far the most commonly used today, is the split field type. These have two sets of field coils and, by means of a switch, power can be sent through either of these coils.

Because they are wound in opposition, the motor will rotate either clockwise or anti-clockwise. The advantage of having an anchor winch capable of being reversed is that it allows you to lower the anchor without having to go to the foredeck.

CHANGING ROTATION
It can be a nuisance to change the direction of rotation on permanent magnet and single field series motors, so for many years a lot of winch manufacturers simply didn't bother. To change the direction of rotation, the direction of current flow through the field or the armature, but not both, must be reversed.

In a permanent magnet motor, this is just a matter of reversing the polarity (positive and negative) of the supply DC. Since the magnetic field is fixed by the magnets, only the flow through the armature is reversed, and this results in a reversal in rotation.

In all cases, you will need four sets of contacts; two normally closed and two normally open. You could use four separate solenoids (I have on my boat), but the modern way is to use one solenoid to do the job, though it still has four sets of contacts.

To aid understanding, I have drawn the circuits twice in the accompanying diagrams. In the winch-up condition, current flows through the two blue sets of contacts. These are closed when there is no power to the solenoid coil.

In a series wound motor, the circuit is almost the same - note the direction of the current through the field coil. When the reversing switch is placed in the down position, power is applied to the solenoid, opening the blue contacts and closing the green. By tracing the circuit, it can be seen that the flow through the coil is now in the opposite direction, resulting in the winch reversing its rotation.

Although these small motors are very powerful, there are limits to how hard you can work them. Power is the result of multiplying the motor's resistance (to all intents and purposes fixed by the manufacturer) by the current squared. If the current through the motor increases, the power dissipated over the motor increases by the square of that value. Since power is measured in watts, it will rapidly heat up the motor.

LIGHTEN THE LOAD
So, now we come to the point of all this. If you just grind the winch away until the anchor is in its stops, without a thought about the load imposed on it, then the winch will have a short life, regardless of who the manufacturer is.

However, the load on the winch can be reduced by commonsense measures, such as motoring slowly up to the anchor as the winch recovers the chain or rope, or helping the winch break the anchor out of the mud by using the boat's power. Doing this reduces the amount of work the winch has to do, thus heat build-up is decreased and motor life extended enormously.

Even if the winch is under warranty, I think you would have difficulty making a claim if the motor has been reduced to molten destruction through overloading.

ANCHOR LOCKERS
What happens on the foredeck is primarily determined by the boat's design. The best anchoring system will struggle if the anchor locker is poorly designed. Unfortunately, this is often the case.

It's easy to blame the boatbuilder, but the real culprit is the fact that we are getting taller. This means that the forward bunks, which used to be okay at six feet four, now really need to be six feet six or even eight. The temptation to move the forward bulkhead a few inches and steal a little from the anchor locker is always there.

A good anchor locker should have as much depth as possible, as this is the most important dimension from an anchoring point of view. The distance from the centreline of the gypsy to the top of the anchor rode when it is all in the locker is called the 'fall depth'.

Leading Australian anchor winch manufacturer, Muir's of Tasmania, recommends a minimum fall depth of 300mm if the chain is to feed in and out of the locker satisfactorily.

While we are on the subject of anchor lockers, it is a good idea to inspect the drain facilities. When I first bought my current boat, it did not even have a floor in the locker. All the mud, etc, that came in with the chain just gravitated to the bilge, where it would clog and ruin bilge pumps and give the bilge an evil smell.

Even worse was the anchor locker's door, which was above the bunk in the forward cabin. One day after getting the anchor aboard, I went below to find that the door had opened and thirty metres of foul muddy chain was sitting on the end of the bunk. What a mess! It took days to clean up properly.

After that I glassed a proper floor in the locker and made a good drain for it overboard. The door got a burst-proof lock and a complete rubber seal to make it watertight. Since then it hasn't given me a moment's trouble, but if the job had been done correctly in the first place, none of that would have been necessary. Even now, every time after I have raised the anchor, I still approach the forward cabin with trepidation.

HORIZONTAL OR VERTICAL?
Anchor winches come in two styles, vertical and horizontal. As these terms imply, the horizontal winch has its drive shaft aligned to the horizon, the vertical style has the drive shaft at 90° to the horizon. All the terminology used apply to vertical winches as well as horizontal styles.

The horizontal winch is a complete item that simply bolts into position and is connected to the wiring. Its biggest disadvantage is the amount of room it takes up on the foredeck. However, the motor is generally fully enclosed and therefore well protected from the elements.

Another advantage over the vertical style is when using the capstan drum with rope, it is much easier to tail out the rope from a drum in the horizontal position than the vertical.

On the other hand, on a horizontal winch the chain only makes a 90° contact with the gypsy before feeding down the hawsepipe. This can occasionally lead to slippage and jumping, whereas on a vertical winch the chain makes a turn that is nearly 180° around the gypsy, and this makes for much more secure contact.

The vertical design does leave an uncluttered foredeck and, from my observations at marinas, it seems to be the more popular choice. I'm not the biggest fan of this style because the motor takes up room in the chain locker, into which it generally hangs.

Furthermore, the old 'out of sight, out of mind' syndrome really comes into play here. The motors are made from iron because they have to be, and inevitably, as the chain comes onboard, it flicks salt water droplets all over the motor. Twelve months of this, and that shiny, expensive winch still looks good on the top, but underneath the deck it's a ball of rust fit only for the tip.

If your winch motor is mounted in the anchor locker, it's wise to inspect it on a regular basis and to spray it with a good rust inhibitor.

SEA GYPSIES
The winch is able to recover the anchor chain because of the design of the gypsy. This is made in such a fashion that the links of the chain fit into depressions in the casting. This fit is critical, and it's important to make sure when buying a new winch that the supplied gypsy fits the existing chain and vice versa.

Imperfect fit can result in the chain skipping every so often, and if there is a heavy load on the chain at the time, this can be a frightening and dangerous experience. Also, when there is a heavy load on the chain, it can tend to stick in the gypsy. This is why a stripper is incorporated, to force rope or chain from the gypsy.

If a chain/rope combination is used, then the same precautions apply; make sure the gypsy will operate with your equipment. The rope is gripped in the cleft of the gypsy and this provides the friction necessary to recover the rope. The rope-to-chain splice must be as neat as possible, so that the transition occurs smoothly.

When the anchor is in its stops, it's restrained from falling into the water because the gypsy is not free to turn and the chain or rope is firmly engaged into it. The gypsy on both styles is attached to the drive shaft through a cone clutch and releasing it from this allows it to free wheel. This action allows the anchor to fall into the water, taking the rope or chain after it. When it is judged that enough has been released, the clutch is tightened and the gypsy is brought to a halt.

Most anchor winches use worm and pinion gearing in the drive train, and this is self-locking, which means that although the motor can turn the drive shaft, the drive shaft cannot turn the motor. This prevents the anchor load from turning the gypsy and thus pulling more and more chain out of the locker.

However, it's a good idea to take the load off the winch when at anchor, particularly in all-chain systems. Use a bridle or strop made from rope that has a chain claw spliced into one end. As the name suggests, a chain claw fits over a chain link and this enables the rope to be securely attached to a Sampson post or similar. When the boat surges at anchor, the strain is directly transmitted to the post, rather than the shaft bearings of the winch.

In the next article, we'll have a look at how to go about selecting the right winch to suit your boat, plus a few good accessories that can make anchoring even easier, such as anchor wash pumps and chain counters.