The O.K. is a very light and sensitive dinghy, and beating to windward in her can be a very satisfying and challenging experience. There are distinctly different techniques for light and strong winds and your ability to cope with all conditions will depend on your weight and fitness, correct choice of rig, and ultimately your skill.
In very gentle winds the O.K. gains greatly from a slight heel to leeward which reduces the wetted surface area and encourages the sail to fall into a smooth curve. Keep your weight well forward in the cockpit (many people even perch on the foredeck) to reduce transom drag, sit very still and steer with a sensitive 'two finger' grip on the tiller extension. The traveller should be about eight or ten inches to leeward of the centreline and the mainsheet tensioned gently. As you increase tension the mast will bend, which flattens the sail entry allowing the boat to point higher into the wind. Resist the temptation to pull on the cunningham to remove the horizontal creases that develop as this will move the fullness of the sail forward again. This increasing tension on the mainsheet is transferred directly to the leech which will eventually become hooked to windward and stall, the tiller then developing a dead and unresponsive feel. Ease the mainsheet just sufficient to cause the boat to come to life and it is at optimum balance.
As the wind increases slightly bring the boat level, and try to keep it absolutely upright through all further increases in strength. The mainsheet will have to be pulled even harder before the point of stall is reached, ease it off slightly and the technique remains the same. The traveller should be let out slightly and some tension applied to the cunningham. You will have to sit further out as the wind increases and strengthen your grip on the tiller extension as waves start to develop.
Eventually, you will be hiking as hard as you can - obviously you can provide no further righting moment and so the search for maximum drive for the rig changes to a controlled easing of power. This point should coincide with your boom 'reaching the deck' and the mainsheet plays no part in coping with further increases in wind- strength. The only remaining controls are the further releasing of your traveller (eventually to the deck edge) and increasing the tension of the cunningham (which 'opens' the leech) and so you are very dependent on your rig 'working' automatically to assist in spilling the wind. If you are still overpowered your only recourse is to feather the boat by allowing it to luff slightly into the wind, thereby easing the wind load. Only in the most extreme conditions will it pay to ease the mainsheet and drive to leeward faster and making less leeway.
The ideal is to be sitting out as hard as you can for as much of the time as possible. To do this through the inevitable fluctuations in wind strength requires co-ordination adjustment of mainsheet, cunningham and traveller.
As the wind eases you will need more power from the rig so you should release the mainsheet slightly (allowing the boom to rise, the mast to straighten and the sail to become fuller), ease the cunningham, and pull the traveller slightly towards the centreline. Obviously you do exactly the opposite to cope with increases in wind strength.
Another very important skill is that of sailing through the waves that will inevitably build up on any open stretch of water. The O.K. stops easily if you catch a wave badly so great care is needed, luffing up the face and then sitting out harder while bearing away to drive the boat down the back of each wave. Look ahead to spot gaps in the oncoming waves that you can work towards and to avoid larger crests. You should try to keep your O.K. absolutely upright and power through the waves. A very firm grip on the tiller extension is essential and you must drive the boat strongly in the intended direction. The braking effect of considerable rudder use is insignificant by comparison with loss of speed suffered from slamming badly into a wave. The most important rig adjustment in waves is the further release of the traveller which increases forward drive at some expense of pointing ability. Since waves generally come from a slightly different direction than the wind, you will usually find that on one tack you are heading more into the waves than on the other, and so must set the traveller further out on one side than on the other.
A large number of people new to the O.K. will never have sailed a centre-mainsheeted boat before. I believe that right from the start they should tack facing forward in the manner described below (or similar). It will almost certainly feel strange, and may even result in the odd swim at first, but will soon become natural and fluent. It can be very hard to school oneself out of poor technique stumbled on initially. The following description was written by Richard creagh-Osborne many years ago, but remains a very accurate commentary of the usual technique.
Imagine you are on the starboard tack hanging right out. You have your right hand on the sheet and your left hand holds the tiller extension. To go about, hold the sheet near the cleat and free it, still keeping the tension on. Push the tiller to leeward and as the boat begins to tack, drive straight into the centre of the cockpit still holding the sheet in exactly the same place and still holding the tiller in your left hand. Your right hand will move down near to the floor block which will automatically ease the sheet enough for you to pass underneath. The next movement is to swivel smartly about (via forwards) without moving your hands off the tiller extension or sheet. You will then find yourself sitting on the new side deck, with tiller behind your back and your right hand across your body still holding the sheet. You can pull in the sheet hand and the sail will be nearly as it was on the other tack. You will find that you can steer with your hand behind your back for as long as you need to get sorted out. Finally, let go of the tiller when you have the boat level (and thus with nearly neutral helm) quickly change hands on the sheet and grab the tiller again.
With practice the whole manoeuvre can be completed in about three seconds and as with all the physical aspects of sailing an O.K., there is no substitute for sailing in company with, and copying, more experienced sailors.
It should also be pointed out that the O.K. (in common with most classes) is most easily controlled whilst level, and therefore in strong winds it is essential to keep your boat absolutely upright whilst bearing away around the windward mark. A confident and deliberate movement, sitting out hard and ignoring the centreboard completely until the manoeuvre is completed, will be certain of success, but if the boat is allowed to heel badly the resultant tendency to round up into the wind will make bearing away difficult and hazardous.
The real joy of sailing this light racing boat comes when you have practiced enough to have got all the basic movements so smooth that you and the boat feel absolutely at one is Creagh-Osborne's summary, and thousands of owners all over the world would undoubtedly agree.
One inch equals 24mm(near enough!).
A very early article, but useful. A much more technical and theoretical article by Trevor Gore will appear later, developing the idea of using the vang to keep the sail flat while allowing the boom further and further away from the gunwhale in heavy weather, up to 600mm, while keeping the luff full and the boat sailing fast.
Richard Creagh-Osborne, mentioned in the article, introduced the OK to Britain in the late 1950's.