On both our First 260 and First 36.7 'blading out' simply makes the entire mainsail luff and shake. It certainly depowers it as flow detaches down the entire length. Reefing of course is an option, but now you have NO way to deal with the lulls.
So traveler up, and adjust the sheet until the boat flattens and stays on its VMG speed and heel. No need to watch the tell tails. Its all about boat speed and heel angle now. And we TORCH anyone around us not doing the same.
With all due respect, thats totally and entirely inane and just simply WRONG.
Controlled blading-out on a mainsail by the
controlled and partial release of AOA either by steering up or by partial traveller release so that ONLY the first few % of air stream 'separates' from the leeside at the luff / and leech. The classic elemental explanation would be a partial/slight 'fishermans reef' caused by traveller easing .... .
In the real world, this is the most common depowering method in one-design and match racing for the control of momentary episodes of being overpowered ... and chiefly to prevent/lessen skids to leeward that affect VMG while
gaining boatspeed which keeps VMG at an optimum, all due to the slightly eased traveller. In high wind venues its also known as 'turbo-sailing' using the boats momentum while bladed (principally by steering up a few degrees) to head-up, followed by partial release of the traveller to come down during the gusts .... a trigonometric advantage.
It is done principally because it is totally controlled and with MOST of the wind still attached to the sails and in ALL panels.
In high wind venues its called 'control dumping/easing the traveller' ... whose affect is to reduce heel but not lose VMG / speed due to the trigonometry affecting the suction peaks in the forward part of the sail acting in a more 'forward' angle (of attack). Such sails used during these overpowering conditions usually are chosen which have a VERY
flat luff entry (on keel boats), and on planing hull forms quite rounded luff entry shapes to accommodate the increase in boatspeed during turbo-sailing.
With an errantly twisted-off sail, the
drag on the sail due to the luffing, especially across the head and the now
over-trimmed foot section momentarily reduces speed and
especially VMG. When top-level racing, twisting off is just mathematically wrong, as turbo sailing and partial traveller dumping is sooooo more efficient to control consistent wind attachment to the sails ....as with 'playing the traveller results in VMG staying high. With a twisted-off sail, and with the traveller on centerline, the foot sections of the mainsail are usually well 'over trimmed' ... there isnt any other possibility.
The first pic is the effect of partial blading with a traveller ... look at the force vectors in the more open AOA (essentially the same force vector advantage between a beating and
approaching, at a theroetical maximum, a beam reach ...
The second pic is a graphical explanation of 'turbo sailing' (while beating) ..... 'UP' in the slows and "DOWN" in the blows ('traveller slightly eased to reduce heel and little loss of boatspeed while pressing
down on the windward side tell tales.)
The following is graphical reference of exactly where the optimized suction peaks occur in a sail, then consider where the suction peaks occur in a twisted off sail occurs ... ie. ONLY in the forward sections of the mid-panels. In such comparisons, clearly the partly bladed out sail and slightly headedup boat will be the better performer in over-powering conditions simply because the bladed out sail reduces HEEL (and skid)
without significant loss of 'drive'.
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