Irons.. WTF is the physics of it?

I had an absolute mare of a race last night, not that windy in fact at what I'd say was an optimum breeze for that EPS, up the first beat and going low into on oncoming tide on the first reach had me overtaking the three sail fast fleet and only the Contender vanishing to the horizon.

Then tactically tacking on a shift the f**king thing went into Irons, well not exactly it just did it's favorite and stalled out of the turn, facing the way it should be going, and at a dead stop. I just don't get why it does it, I get it if I havne't gone far enough through, or the sail didn't transition, it just stops, and no flow gets attached to the new side, either foil then inevitably it drifts back.

Do you dump the kicker? I know about rectifying, push push, but by then you've lost two or three boat lengths down wind, so what is the answer?

Originally posted by Paramedic If it does it all the time it implies that something is wrong with either the set up or design - too much rake or the mast too far back/board too far forward.

I'm not sure you can make generalisations. A boat with the rig well aft behaves quite differently from one with the mast up in the bow.

'Stable stall' comes to mind in describing 'Irons'.....

To get out you have to break the 'stability' - raising centreboard moves the centre of resistance back and the bow can drop down, the boat speeds up and you have rudder control again.  If the centre of effort is a tad close to the centre of resistance anyway this can happen more regularly ... (as in 'too' heavily raked rigs in some classes)

Fully battened mains on singlehanders are also a factor for some classes. .... Why ? because when you dump main trying to get out of irons the full length battens, particularly stiff ones, still effectively hold camber at the front of the sail - the leading edge does not easily 'collapse'.  You cannot let the main out far enough to break the inherent stability in the rig orientation so all you can do is resort to lifting the centreboard.   Many modern rigs have a mix of full length and short battens – not surprising really.

You can usually get away with it in most double hander as the jib can be used to 'pull the bow down' when the main is dumped.

No one factor is totaly responsible but a combination of some features conspires to make some boats prone to it.  The original Blaze sail was a right pain until re-designed many years ago - the 'modern' now standard sail was a revelation... and many other examples can be seen as well.  

The trouble is, it's a fxed up and down dagger, you rake the rig back a bit to depower, but can't rake the plate, inherent design fault with all daggerboarded junk, MPS has the same issue. So rig rake is part of the problem, but it's a lot to think of, rake rig back up, ease kicker, tack, reverse it all again...

But I guess that is the solution, so it means leave the pins on the shrouds at optimum and drop the rig back by some form of controlled measure at the forestay after the tack.

The sail I have is soft, it is nowhere nears as bad as the old full batten rig, but it has a sticky top batten which can be a pain.