Expert Sailing Advice & Information from Wiley Nautical

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Your Sailing Questions

1. How do you make a boat 'foot'?

2. What does it mean when I have to ‘Keep clear’ when racing?

3. What are the advantages and disadvantages of the various types of drives available now?

4. What am I trying to achieve when tuning my dinghy?

5. What’s the easiest way to tell whether I am on a collision course with another vessel?

1. How do you make a boat 'foot'?¹

Jon Emmett replies:

Sometimes it is necessary to really drive the boat to get over to some pressure, a shift, out of the current or over the top of another boat. Here you need to turn distance to windward into speed, sacrifi cing height for speed and sailing so low that you are almost reaching.

The boat trim needs to be back to allow the bow to lift slightly, making it easier to keep the boat born away (bow down). The sails need to be fl at so that gusts will not tend to make you luff, and it may even be worth raking the foils back as well. You may have to allow the boat to come up slightly every so often to lose power. This is better than constantly pulling on the tiller, as it means the rudder is acting as a slight brake (when the rudder is straight it provides the minimum resistance). It may well pay to foot on one tack and pinch on the other (perhaps to get across to one side of the race course, or maybe so as to get a good angle of attack to the waves). If this is the case, you need to be ready to make the changes to your rig promptly.

For more top tips read Be Your Own Sailing Coach: 20 Goals for Racing Success, by Jon Emmett

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¹ Foot i) (Noun) The bottom edge of the sail, ii) (Verb) To foot: Sailing the boat fast and low upwind.

2. What does it mean when I have to ‘Keep clear’ when racing?

Bryan Willis replies

The rulebook says: ‘One boat keeps clear of another if the other can sail her (current straight-line) course with no need to take avoiding action and, when the boats are overlapped on the same tack, if the leeward boat could change course in both directions without immediately making contact with the windward boat.’

In dinghies in a Force 2 on flat water, ‘keeping clear’ can be synonymous with ‘avoiding a collision’ (for example in a port and starboard encounter on a beat in which the port tack boat ducks under the stern of the starboard tack boat), but were they to be large keelboats in a Force 6 and a heavy sea, an obligation on you to keep clear might mean leaving a boat-length or more between you and the right of way boat. Furthermore when you are the give way boat, you must not intimidate the right of way boat such that he thinks there is going to be a collision and is forced to take avoiding action. So even in fairly light conditions it’s as well to look under the boom and give him a friendly smile, so he knows you are paying attention, before diving under his stern and missing him by a millimetre!

Bryan Willis is a member of the International Sailing Federation Racing (ISAF) Rules Committee, on which he has served for over 25 years. He has been chairman of the jury at the Olympic Games and the America’s Cup and was instrumental in the development of umpiring.

Read his Rule in Practice 2005-2008 and look out for his new book on the 2009-2012 rules updates.

3. What are the advantages and disadvantages of the various types of drives available now?

Pat Manley replies

Getting power to the propeller is generally achieved in one of four main ways: shaft drive, stern drive, sail drive and the relatively new Volvo IPS.

	Advantages	Disavantages
Shaft drive	Simple design Relatively cheap to make Easy maintenance Thrust bearings can be used so that no thrust load goes in to the gearbox or through the engine mounts.	Engine and shaft need proper alignment if wear and vibration are to be reduced Thrust line may be angled downwards
Stern drive	Engine weight can be kept far aft giving an advantage in planing boats Installation costs are reduced with no engine alignment costs On aft cockpit boats, engine accessibility is good On aft cockpit boats, engine does not intrude into accommodation Thrust angle can be trimmed fro a basic horizontal thrust line Speed is potentially greater than with a shaft drive	More expensive to build Externally mounted leg and drive units need more frequent and expensive maintenance Electrolytic corrosion of ‘out-drive’ unit in salt water Boat has to be out of the water to service the gearbox/leg unit With a deep V hull configuration and twin engines, the engines have to be mounted so close together that servicing can be almost impossible
Sail drive	Installation costs are minimal No engine alignment required More choice of engine position, so its intrusion on the accommodation can be minimised Often less vibration (no shaft vibration as there would be in a poorly aligned shaft drive)	Large rubber diaphragm sealing hole in hull requires expensive replacement (every seven years fro Volvo Penta, but not for Yanmar which has a double diaphragm and moisture detector) Oil changes require the boat to be out of the water (except for the very latest Volvo and Yanmar models) Possible corrosion of aluminium leg components in salt water Electrolytic corrosion of larger propellers as the leg anode is relatively small and often electrically isolated from the propeller Propeller mounted much further from the rudder, requiring more anticipation in close quarters manoeuvres External water temperature may dictate non-optimal gearbox/leg lubricant External water temperature may require non-standard battery charging until leg oil temperature has risen sufficiently to reduce friction drag Cannot use a thrust bearing, so all thrust is taken by the engine mounts and gearbox
Volvo IPS	Horizontal thrust line for higher speed potential Propeller in front of leg in clear water Exhaust about 80cm below the waterline to give very quiet running Steerable legs, giving good manoeuvrability Cast bronze underwater unit, giving good corrosion resistance Lower installation cost	High unit cost Available only with a limited range of Volvo Penta engines

Pat Manley is a former airline pilot and instructs students in navigation and diesel engines. He has written a number of books including Diesels Afloat, Essential Boat Electrics, Simple Boat Maintenance, the Radar Companion, Electrics Companion and Diesel Companion.

4. What am I trying to achieve when tuning my dinghy?

John Caig and Tim Davison reply

All boats are tuned for the beat. (Having got them right for upwind work, all you have to do offwind is to make the sails fuller, and perhaps rake the mast forward.)

The main objective is to be able to adjust the curve (belly) in the sails for the wind strength. You want maximum fullness (which gives maximum power) in medium winds. As the breeze builds you need gradually to flatten the sails to reduce their power – otherwise you’ll be unable to hold the boat up. Surprisingly you need quite flat sails in light airs too, because the feeble breeze is incapable of bending round highly curved sails.

The mainsail is cut with a curved luff. When this is set on a straight mast, fullness is forced into the sail. To remove the fullness, simply bend the mast: when the curve in the mast matches the curve in the luff, the sail will be almost flat. (Not quite flat because some curve is built into the sail by curving the edges of the panels). The chief aim here is to match the mast bend to the luff curve – if the mast overbends at any point, horrible creases form from that point.

The jib is not set on a mast, but the front edge is controlled in a similar way via rig tension. Sloppy rigging puts curve into the front of the jib, whereas tight rigging pulls the jib luff straight and gets rid of fullness. In general about 160kg (350lbs) tension on the jib luff wire is a good starting point.

One more objective is to balance the helm. With the boat beating in a medium breeze, and upright, there should be a very slight pull on the tiller (this is weather helm). Too much weather helm is bad because the rudder is then going through the water at an angle, which slows the boat down. Lee helm is disastrous because the flow of water over the rudder forces the boat to leeward. Never rig a boat with lee helm.

For more detailed top tips take a look at the Racing: A Beginner’s Guide by John Caig and Tim Davison.

5. What’s the easiest way to tell whether I am on a collision course with another vessel?

Paul Boissier replies:

The No 1 life skill for yachtsmen, and indeed all seafarers is the ability to work out whether a risk of collision exists. This is very simple: risk of collision exists when you are closing another vessel on a steady or near-steady bearing. If you both remain on a steady bearing and the range is decreasing you will, in time, hit eachother. If the bearing is moving, left or right, you will not collide.

So you have to be able to determine whether the bearing of another ship is steady or moving. In a big ship with a stabilised gyro compass, this is a relatively simple matter. In a small yacht, bouncing around in a heavy swell it is something of an artform.

The obvious solution is to use a hand-bearing compass but anyone who has ever tried to use on a motor boat doing 25 knots, or a close-hauled sailboat will know that the result is something of a lottery. It may be possible, and I would recommend taking three or four readings at once and averaging them. Even then you will be lucky to get an accuracy of less than two or three degrees, and this is not enough to tell whether a ship some distance away is moving left or right.

A more sensible solution is to check the ship’s movement against the background. In general you can consider the background, if sufficiently distant, to be on a more or less steady bearing. Watch the other vessel and see if it is moving across the background: it will either be moving left, right or remain steady. This is a pretty good indicator of absolute bearing movement.

As a yachtsman, the thing to remember is that you have a very much more manoeuvrable boat than most other seagoers. You have no deadlines of great importance to keep, and you should be able to keep out of people’s way relatively easily. So why stress yourself?

For more on collision avoidance and the rule of the road, read Paul Boissier’s Understanding the Rule of the Road