Depowering sails - when reefed main and smallest jib aren't enough, what next?

[RichH]

Originally Posted by Stearmandriver

Both times, I did notice the very leech of the jib fluttering and curling towards weather. I'm talking just the last inch or 2 of sail - the rest was a nice smooth airfoil.

Is this the "hooking" to weather you mentioned? Am I correct in understanding that to eliminate this, I need more luff tension/and-or forestay tension (achieved with backstay tension)? So I'd trim everything else correctly, then start adding halyard tension and/or backstay tension until this leech hooking was eliminated?

Joe

Probably not the leech 'hooking up to weather' (usually seen as several 'feet length' of sail being deformed' but rather a 'leech tension adjustment cord problem'. With fluttering leech you need to put more tension into the leech adjustment cord. If tensioning the leech cord causes a inch or two of the leech to stand up .... usually means that the leech is permanently overstretched (OR that the UV sun cover was not applied correctly). Suggestion - try using LESS jib sheet winch pressure and see if that doesnt correct the shape AND the 'flutter', also slightly more jib halyard tension (but dont 'jam' the furler with too much luff tension).

BTW - probably THE most important shape function of a sail is that the airflow can leave the 'exit' of the leach with EQUAL flow from both sides of the sail being exactly equal (called the Kutta Condtion) ..... leech tell tales will by flying equal and 'straight back'. If the small 'hook' shape caused by a leech cord problem ... it will cause undue turbulence at the leech and the sail will be more inefficient than if the 'exit' is 'dead-straight'. With a 'hooked up leech' the tell tales at the leech will rarely ever be 'equal' or flying straight back - usually the leeside leech tell tale will be 'twirling' or even 'pointing forward' ... a much worse aerodynamic condition that will radically reduce sail efficiency.
A small anomaly cause by a leech cord will only create a slight decrease in aerodynamic flow, a hooked up leech will radically change the aerodynamic flow & will create more 'weather helm', and artificially deepen the overall draft and 'angle of attack' - SLOW boat with lots of excess heeling.

hope this helps.

[zz4gta]

In addition to Riches suggestion of using slightly less sheet tension, you can also move the jib car back one spot. A car too far forward will also cause the leech to hook.

[Stearmandriver]

Thanks guys. I adjusted sheet tension to minimize the fluttering but couldn't get rid of it altogether. To be honest, I've never even noticed if the jibs HAVE a leech adjustment cord. The main does; I've adjusted that, so I don't know why I didn't think of it on the jibs. I'll check it out.

Joe