Tips from the experts: mainsail twist

Olympic sailor Paul Brotherton gives his top tips

Question: I keep reading that twist in the mainsail is optimum when the top batten is parallel with the boom (I take this to mean the last 1/3 or so of the batten). It seems to me that such a situation amounts to zero twist in the sail. If so, what of the twist in the apparent wind with increasing height from the water, and the fact that the mainsail above the hounds in a fractionally rigged boat doesn't suffer the downwash effect of the jib, so requires a different angle of attack? It seems to me that some mainsail twist to account for the combined effect of those two factors is necessary. I'm confused.

Paul answers: You're absolutely right. In any non-planing situation, having the last 10cm of the top batten parallel with the boom is an ideal starting point for trimming the mainsail through the breeze.

This would appear to imply that there is no twist in the mainsail. However, the next time you have your boat rigged in the dinghy park (6-8 knots is ideal) roughly sheet your mainsail so that the top batten is set as above, and stand two to three boat lengths directly behind the centre of the boat. You will notice that even though the boom is on the centre line, the exit angle of the mainsail at the base is considerably above the centre line, and will continue being above the centre line until you get to the top batten, where it is parallel to the centre line.

The difference between the bottom of the sail and the top of the sail is the twist angle. Don't worry about getting confused, so do I and most other people if they're being honest. The bottom line is try it, feel it, test, it , correlate it. There are many things that affect the twist you would require in any given situation, wind shear, sea state, wind strength and tactical situation. The confidence about how to set the mainsail will come with time on the water and knowledge of how different mainsail trim affects performance i.e height and or speed. Practice is key, as well as not trying to win every race you enter, don't be afraid of making mistakes, as long as you make observations and deductions from them.