ABOVE: Well trimmed for light wind and flat water with good depth in the headsail

Lets look at how to sail sport boats for optimum performance, beginning with boat preparation.
The hull should be clean and if possible have a fine sanded finish
The keel and rudder trailing edges should be carefully maintained to ensure good water flow off the trailing edges. If the trailing edges are fine, less than 2 mm the edges can have a flat with sharp corners. If larger than 2mm you may experience cavitation and this can be remedied by adjusting the angle of the trailing edge by sanding an angle as shown in the diagram
 
Keel an Rudder trailing edges
Pay particular attention to the bottom of the bulb as this area generally takes a beating and is a very high drag area. Check also that the foils are firmly fixed in their respective cases when down. Not only is it disconcerting to have a keel with a large bulb on the bottom rocking over every wave it can also cause structural damage and slows the boat down. It is important also that the tiller and tiller extension have no slop in them. Check also that the rig is setup for the conditions you are going to race in. As previously mentioned in preceding articles I usually sail with a different rig setting for high and low winds.

A boat log is an important item in a boat of this size for upwind performance. The boatspeed instrument should be calibrated so that there is consistency from one season to the next. The best way to calibrate a speedo on a small boat is to run alongside another larger boat with a calibrated log and check against that and also use a GPS on board.
A compass is a very handy instrument to have on board but this does not need to be calibrated, as it is always relative for the days sailing. A good place to put both of these instruments on a small boat is under the boom on the mast facing aft, this way the whole crew can see what is going on.

The basic rule when sailing upwind is "God is boatspeed". Nothing works in a boat unless you have the optimum boatspeed for the upwind conditions you are sailing in. without boatspeed you cannot get height as there is insufficient water flowing over the foils for them to work efficiently. The boat becomes generally hard to sail and steer. What is the optimum boatspeed to sail?. This of course varies from boat to boat.

When we analyze the polars for the Thompson 7 we find that generally the optimum boatspeed increases up to around 8-10 knots and then remains the same as the wind increases. This is because the boat has reached its hull speed, which on a displacement boat like a sport boat is primarily a function of length. As the wind increases the boatspeed remains the same but the boat tends to sail higher. However over 20 knots of wind there is a trend to have to sail lower again to maintain boatspeed, mainly due to the increase in wave size and increased drag.
It is important to sail the boat at all times to the optimum boatspeed, after tacking keep the sails powered up until the boatspeed is at the target for the conditions then wind the sails on for upwind sailing. You may have to sail up to 10 degrees lower to gain the boatspeed you require but it is worth it. Height comes with speed.


ABOVE: Thompson 7's optimum boat speed increased to around 8-10 knots and then remains the same as the wind increases.
Sail trim on a small boat is very important. In light air the sails should have lots of twist with the traveler above the centerline and the boom somewhere near the center of the boat. The vang should be eased. In flat water the sails can be very flat, as it does not take a lot of power to get the boat through the water. If the seas are choppy a fuller sail is required to provide the grunt needed to get through the waves.
It is a good idea to run a barber hauler on the jib sheeting so that the sail-sheeting angle can be adjusted while sailing. This can be done from on the weather rail with the barber hauler cleating to weather. In the light air it is good to have the forestay slack so that the draft of the jib is pushed further aft to further power up the sail.
As the breeze increases the mainsheet needs to be pulled on hard to help keep the forestay straight and also to allow the mast to work. The rig should be setup so that the tip of the mast bends back and to leeward in the puffs. This allows the mainsail to exhaust the unwanted extra air. The harder the wind blows the more mainsheet is required. It is bad practice to ease the mainsail in the wind puffs as this deepens the sail and further powers up the boat creating a vicious circle for the helmsman to counter. Just simply drop the traveler if the target speed is hard to maintain and remember to ease out the jib barber hauler at the same time so that the slot between the mainsail and the jib is not closed up.

Sport boats in general like to be sailed flat; this is particularly so upwind. You may experience an awkward light feel to the boats helm and it does take some getting used to. But generally it means the boat when sailed to its upwind target and flat is sailing higher than when heeled for the same speed. It is a hard grove to get into but practice and the continual adjustment of sail trim will benefit the overall upwind performance.

Be gentle on the helm. A boat should be setup so that there is not a lot of trimming to be done and the helmsman can do most of the work. In the light it is s good idea to ease the jib in a lift until the woolies are flying and let the helmsman steer the boast up slowly until the boat is again at the right angle to the wind. The jib is pulled on again resulting in less excessive helming and consequently less “applying the breaks”.