Sail trim / rigging question

[John Radcliff]

Last night the g/f and I went for a late afternoon sail (6ish, back about 7:20) in light winds (my guess was 3 to 5 knots). The high speed we hit was about 3.5 kts SOG while beating upwind.Here is the question - while we were doing this, I was watching the sails more than usual. With the telltails on the luff of jib flying well, the main in tight, the luff of the main would start to luff in the bottom 1/3. It was not major, just a little 'bubble'. Any suggestions? The vang was on tight to reduce twist in the upper 1/3 and the outhaul was not overly tight.

 

[Mike]

Outhaul

Hi John,Ah, sounds like a fine sail out there! In answer to your trimming question- I think a little outhaul (that is, easing the outhaul out slightly) would put a little more draft (slope) in the sail, potentially giving you better airflow in light air like that (3-5 knots). This might take the slight bubble out of the sail. Also if you have a cunningham rigged, you might want to take in on it- so that the luff from masthead to boom is tight/ no bagging. Otherwise sweating the halyard a little more might give you a little more tightness.In strong breezes, I use the opposite: pulling the outhaul tight to depower the sail just slightly, and vang eased of course in really heavy stuff- to spill breeze off the top luff/leach.I hope my theories of sail-airfoil are working as of this posting-- otherwise I've been adjusting those rope thingies and stuff for no reason!Mike

 

[Eric]

mostly right

I mostly agree with Mike, except 3-5 knots of wind speed is light enough that it will be difficult to maintain laminar airflow over a deeper draft. When the wind is that light, you're actually better off tightening your outhaul and decreasing draft.As wind speed increases moderately, you'll want to ease the outhaul to increase draft, as Mike suggests. Then, in heavier winds, you'll once again want to reduce draft to depower.

 

[John Radcliff]

Shrouds?

I will have to try the outhaul both ways (tighter and looser). Could this be caused by my lower shrouds being too tight?

 

[whisper24288]

trim trim trim

I agree, could be also the jenny is pinched in too tight as well, loosen up the rig and work the strings in order, you want the slot to be nice and regular, with no motorboating or flogging. The lighter it gets the looser the rig on all strings, until it is so light the air is not flowing over the sails, then you tighten up a bit. When it blows up you want a lot of tension on all of the strings to make the sails flat and the wing nice and clean.