How does the slot between jib and main helps by speeding up the air?
This slot working does not help and belongs to the useless theories. The tale of the air speeding up in the slot between main and jib is that the slot becomes smaller, so must be speeding the air to have the same amount of air passing it. Speeding up the air on the leeward side of your main must help to create a lower pressure there. That there is a slot is correct. That the air speeds up is also correct. This results in a lower pressure on the windward side of the jib, and a lower pressure on the leeward side of the main, so cancelling out the supposed advantage. Besides this the pressure needed so speed up the air is more or less blocking the slot, thereby resulting in less air through the slot. The air is forced around the slot, and not through it. This does not mean the main and the jib will influence each other, see the next question.
