sheeting angle for best drive with roller furling.

Many boats have jib tracks allowing one dimension of adjustment along with the tension in the jib sheet itself gives 2 dimensions where 3 exist.

I am told a roller furling sail can be cut so that you dont need a sail track and a single location can sheet the sail, but it seems this would remove a lot of sail area from the foot of the sail so I am unsure about this.

One dimension controls, the sheeting angle, the other the twist, but there is no way to control camber on most boats I have seen.

So what is the solution?? I have run another sheet further outboard (trimaran has 24ft beam) to pull the sheet out. Similar solution to a whisker pole but the pole cannot easily adjust its length so its mostly only useful in wing and wing. I would like to optimize reaching.

Maybe a fixed wing sail is the future? It solves this and a lot of other problems while creating many more new ones.

 

Add a barberhaul block on the jibsheet as on the older Tornado catamarans.

 

Single point jib control can be arranged regardless of clew height or roller furling. BUT as you alluded to a loss of jib shaping also occurs.

If you have a small jib that doesn't cross the mast, then a jib boom is the most elegant solution for maximum shaping control.

If your jib crosses the mast then an adjustable both for/aft and athourt ships is required to achieve full shaping control. Unfortunately the ideal spot for this fairlead is probably in the middle of your trampoline. There are several options depending on the exact geometry of your vessel. I have found that a barber haul and twang usually provide sufficient control.

 

Draw a line perpendicular to the forestay, through the clew of the sail, to the deck. A jib car in this location should not need adjusting as you furl the sail. However for a given cut of sail this may not give ideal tension on foot and leach.

To add another dimension of control you definitely want a barber-hauler. A solution for boats without tracks is to have two barber-haulers attached to a single low-friction ring allowing 2D control of the clew position, plus sheet tension for the third degree of freedom.

 

Are there any sails that will achieve the correct shape and depth for a fast tri when partly furled?

 

Luff pads and vertical battens help.
BUT all partially furled sails lose performance beyond the reduced area.