"Twisting" the mainsail?

[epoch]

How is twisting of the mainsail achieved?

[knobblyoldjimbo]

i) release the vang so the boom comes up - leech gets looser and therefore you get twist

ii) pull the traveller in and release the mainsheet - downward force on the leech reduces allowing it to twist

Twisting usually allows airflow at the top of the sail to exhaust although Frank Bethwaite has shown that there is 'twist' in lighter air (not so much in heavier air) so that if your main has twist in it then it could be the appropriate shape from bottom to top.

[epoch]

So when it is recomended to twist the main when using the spinaker is this what you would do? Advice so far has been to have the mainsheet on hard.

[mitchlb44]

epoch - need more info - what sort of boat is it? You may have been told to leave the mainsheet on hard because the mainsheet/mainsail help to hold the mast up under the load of the spin

[knobblyoldjimbo]

Just thinking out loud here but with the chute up on a cat in any wind you're going to be looking for apparent wind, you're going to be hunting up to get it going and then soaking down to use that apparent and get closer to the mark. This will need the main in definitely, not tight though.

If the breeze is lighter (say less than 12knots) then you won't be going flat out with everything pulled in tight so with the traveller central and the mainsheet looser you'll get the main twisting. Use the leech telltales to indicate that wind is flowing over the whole sail.

As the breeze picks up then you'll be keeping a keen eye on mast bend but also on those leech telltales because as you pick up speed you'll need to sheet in both chute and main as the apparent wind goes further forward (and you soak down more to get to the mark quicker). Someone said of Darren Bundock on his A that he never stops moving the rudders downwind - keeping the apparent wind up.