The Flying Lentil The log of Festina Lente, Sigma 38

Of late we have left our racing days behind us, having at last the time to do some serious miles offshore. After 20,000 miles two handed, one thing that has constantly surprised me is the relatively small amount of sail we need to carry, for seemingly little or no drop in speed. Once the wind is 20 knots or more, our default rig is two reefs and a number 3, and by 30 knots we are comfortably whizzing along at hull speed under trysail and No 3, with a change down to the storm jib at 35. 

A glance at the maths shows that the force generated by a rig increases by the square, so that a 5 knot increase from 5 to 10 knots of wind speed increases the force 4 fold. The boat is fully powered up upwind at 13 knots, and at 20 there is another threefold  increase in power. 

In the Solent, in flat water, we can get away with the full rig at high wind speeds by a combination of flattened, draft forward, twisted sails, and feathering in the gusts. At sea it is a different matter as you  sometimes need to drive off through a wave , and full hoist mains and big jibs will have you on your ear in no time. Far better to reduce the rig height and foresail size, and weave with impunity through the waves. 

Downwind in a Solent blow, the 9 knots of  boatspeed keeps the apparent wind down , but at sea the waves initiate rolling that only a superhuman crew can control with the kite up , and broaching one way or the other is almost inevitable once the wind reaches 30 knots.  Planing boats go much faster and so can carry sail in higher wind strengths because their very speed keeps the apparent wind low , but in a Sigma a poled out genoa is faster and safer. When it is really rough and rolly,  2 or 3 reefs and a polled out No 3 is a brilliant rig, and the moment we get rid of the main, lash that boom to the deck and speed off under trysail and that nice high clewed No 3 , we breathe a sigh of relief and stop worrying about an involuntary gybe or dipping the pole. 

Remember that downwind in 30 knots, the apparent wind is 22 knots. Turn upwind and it increases to 37 , nearly  doubling the apparent wind and  increasing the force in the rig by a factor of 3.5. In this wind speed, trundling downwind in comfort and safety under small sails will still see you achieving hull speed, and if you have to turn upwind  you are far better prepared to survive the experience.