TOWING UNDER SAIL
Generally towing under sail is much harder than towing under engine, and if it’s a real rescue situation, you will probably choose the most effective and timely way to resolve the situation. For a prolonged tow, however, using your sails may add to your horsepower, which isn’t really suited to heavy towing work, to save fuel, or to avoid rope in the water near the propeller. Of course, you don’t want to exceed a comfortable speed for the vessel being towed, but it can help.
It is worth noting that with the wind aft of the beam, you should be able to sail reasonably well, potentially just under genoa so that you don’t need to round up to hoist or lower the main. Upwind, however, you may well be going slower than normal and you will experience much more leeway. This is exacerbated by having lines attached to your stern, which makes it harder to head up into the wind. With the helm down to leeward, you will only make more leeway until you bear away enough to build sufficient speed to reduce leeway again.
In terms of setting up the tow under sail, very little changes. If anything, it is more important to move the attachment point for your bridle further forward to maintain manoeuvrability and to increase the length of the tow or the weight on the line to make the tow as smooth as possible.
Realistically this is best done on a reach. Upwind the drag will cause so much leeway and it will be impossible to point anywhere near your normal wind angle. Directly downwind with the main up it is difficult to adjust speed which is sometimes necessary to do if the sea conditions are rough.
The extra drag of the tow means you will need power, so hoisting both the main and the jib is usually the best option. If conditions are difficult for hoisting the main then opting for motor sailing with the jib might give more control.