Luffing Main

Hi,

sailing solo without a jib, in high winds (gusting 20+ knots), I noticed my main was luffing. I thought that my mainsail was quite flat at this point, with mainsheet & downhaul maxed out, and rotation in its "max" position, and I was on the wire.

I felt a bit hung up / draggy, but wasn't especially off the pace in terms of boat speed.

What should I do in this situation? Options seem to include flatten sail some more (grow some muscles), bear off a bit to fill the luff but risk a capsize, or accept that at high apparent wind speed the sail will "s" a bit.

Maybe try letting the mast rotate to where it wants to? Or, maybe limit it a little from max position. I'm just guessing.

I hear S curves ("curve of death") are VERY bad in monohulls, they backwind you, put you in reverse, and can capsize you. I hear they are not as severe on a cat.

If you can't get them out with sheeting and downhaulin' ... perhaps your main is stretched out and needs replacing?

Just a couple of thoughts. The fully rotated mast will create a lot of drag and is normally used to increase power from the rig. The air trying to get around your mast could be the cause of the sail appearing to luff. Try less than normal rotation in strong winds. You say your sail seemed flat, where? Did it flatten off at the top under downhaul? Did the outhaul flatten the lower section? You can't use other boats as a yardstick of performance in those conditions, maybe they are struggling as much as you.

Try to get the sail to go flat and feather off at the top using the downhaul. If you can't get it to do this try a little more prebend in the rig and maybe try using stiffer upper battens. You still want to get some drive from the rig but it is better if it is lower down with the top section feathering in strong/gusty conditions. If you get this setup right you should absolutely fly on the shadow in those conditions.

Aside from the mast rotation it is possible you might have been luffing the boat!

Cheshirecatman

Once all flattening moves have been exhausted, a little pumping of the main in the upper wind speeds becomes a fact of life. What do you mean by 'max rotation'?

Chris.

If it's a squaretop main and you have maxed downhaul, the top will flap a little bit when you're screaming along...

Thanks - this is a new boat, so I have a lot to learn, and am still finding the magic settings... I should say that by "rotation fully on" I mean fully pulled on, to decrease it, i.e. MINIMUM rotation - sorry!

Cheshirecatman, it's interesting that you mention pre-bend: The sail was flat to my eyes all over, until the luff collapsed. However, I was using less pre-bend than had been recommended. The boat manufacturer had reco'd spreaders forward and max pre-bend as my default setting, which I thought would de-power me too much. Your comment makes me think that with max pre-bend it would be better for these conditions.

I have previously (Spitfire) set the spreaders and pre-bend in the middle and left it alone, and I am trying to find a setting where I can set and forget on this one too. I guess that with this boat a little more tuning is needed to optimise performance. No bad thing, so long as you know to do it!

It is possible I was luffing the boat - it was "quite windy". I thought about bearing off to de-luff it, but it felt overpowered like that (i.e. sideways).

Spreaders forwards and max(although limited) prebend will stiffen the mast allowing you to "power up" for most conditions. Moving the spreaders back will allow you more potential prebend dependent on diamond tension. It also looks like you may have overdone the mast rotation. That could explain why the main would appear to luff. Try not to have the rotation lever pointing further aft than the end of the rear beam.
In strong/gusty conditions DON'T PINCH, unless you have to for survival reasons. When pinching, the boat will stall in the water and you will go sideways. If you sail a few degrees lower with the boat driving through the waves, the ride will be much smoother and considerably faster. Control the gusts on the main but steer straight.

Cheshirecatman

Simon,

If you are thinking about what happeend at Rutland last weekend; I'd not worry too much; it was getting towards the wild side at times (IIRC 24kts on the course) which is a fair amount for the Shadow!

All good fun!