Trimming Jib Notes from Craig Ferris

If you take this as a diagram of the sails at half way up the rig and it makes more sense.

A= a  slot with jib and main twisted

B= Jib trimmed too hard and main too twisted giving a reduction of airflow by say 60%

C= Jib trimmed hard and now main has less twist. Still 30% less than basic setup.

D= Jib just open enough and the main trimmed harder with leech ribbons flowing 50% of the time then there is  up to 25% increase in airflow through the slot.

This is more important in the lighter air as it has a huge effect on the boat speed.

I just want to reinforce the gains that can be made with steering in the gusts and lulls. When a gust hits the apparent wind goes back and we can steer up a few degrees to gain to windward and when the boat speed comes up due to increase in wind strength the apparent wind goes back to where it was before the gust. This results in big gains to windward.

When we get a lull the the apparent wind goes forward and the jib will luff slightly and it is important to go straight at this point. 

The boat will slow down due to the lower wind strength, and the apparent wind will go back to the original position. So this results in no losses to leeward.

The difficulty is thinking it is a knock vs apparent wind change on the boat.