Steve,
I sail a cat rigged Taipan 4.9. I don't claim to be a great sailor but I am able to get upwind as quickly as the local Nacra 5.8's, Nacra F18's and Nacra 16sq. The only local boats that are noticeably quicker than me upwind are the Taipan 5.7's.
I usually have a couple of bits of cassette tape attached to my bridle but I use these as a rough guide only and mainly for going downwind (which by the way I still haven't quite come to grips with).
My sail has three main telltalles on each side. There are an additional couple on each side at the luff to help get the mast rotation right for the wing mast on the Taipan but the three main ones are for sail trim.
The bottom telltale on a sail is used to trim the traveller. When you are going upwind the traveller of course is centred, or just off centre depending on how you like it. You can therefore get a good indication of the direction you need to point the boat by pointing it in such a direction that the lower telltales on both sides of the main are flowing. If the leeward telltale is stalled head up, if the windward telltale is stalled head down. You can get away with the winward telltale stalling occasionally - you should, however, attempt to keep the leeward telltales flowing nicely all the time.
Once you get the boat going in the right direction by using the lower telltales you can then trim the upper telltales so that all the telltales on the sail are flowing nicely. If you have all the telltales flowing nicely and the traveller is centred you will find you are going to weather quite nicely.
You also need to have the sail trimmed to be as powerful as possible. Don't depower the sail (by flattening it with the downhaul) until you are fully trapezed and can't hold the boat down any more. Always sail at maximum power.
Having said the above I tend to sail by feel rather than using the lower telltales as I have described. You should always know when sailing where the true wind is coming from so you should therefore know where approximately fourty five degrees off the wind is. This is the direction I head off on when going to weather. I then trim my sails to a nice shape and adjust my heading so that there is the best balance between pointing high and going fast and keeping the windward hull just out of the water. Because the wind never comes continually from the same direction or at the same strength it is a continual job of trimming the main and changing direction to keep the boat moving along nicely and keeping the hull just skimming the waves.
As you feel the hull start to drop into the water you can head a tad lower to keep the pressure on the sail and to keep the hull out. You may need to ease the mainsheet a little - look at the top telltale.
As you feel the hull start to rise you can head up a little to point higher and ease the pressure on the sail. You may need to trim the main a little tighter - look at the top telltale.
If you find you are having to head up often to keep the hull down and that by heading up the boat is slowing down it's time to start depowering by flattening the sail with the downhaul. The aim is to depower the sail to the point where you are able to be fully out on trapeze and that the changes in direction and sheeting you make to keep that windward hull skimming are at a minimum. Some days are really gusty - especially if the breeze is heated (eg. coming off the land on a hot day) - so you will still have to make some bigish changes in sheeting and heading to keep the boat in the groove.
If the wind is too light to fly a hull the same trimming process applies except that you are trying to point the boat in the direction that gives you the best balance between speed and pointing (best VMG, Velocity Made Good - this is the speed at which you are approaching the point to which you are trying to get). Always keep the telltales flowing. When the wind has laminar flow (below about 5 knots) you will probably find that you have some twist in your main as the higher up the mast you go the higher the wind speed.
When sailing off the wind the process is to point the boat in the direction you want to head then set the traveller using the lower telltales - pull the traveller in until the leeward telltale stalls then ease the traveller until it flows again. You then trim the upper telltales using the mainsheet. Once again keep maximum power all the time - if you flattened the main a little for close hauled you may need to power up again off the wind. You may need to move the traveller as the wind direction changes to keep optimum trim to your sails.
There are several more important points to consider when sailing in very light breezes but this post would end up being much too long. I recommend you read a book called "High Performance Sailing" by Frank Bethwaite. Most sailing shops that carry books will have this book or be able to get it for you.
I hope this is some help.
Rob.
