My roberts 34 sails
well downwind with a rollerreefing genoa
poled out on a overlong telescopic pole, this flattens it and reduces much of the rolling. In light airs it actually overpowers the main and she has slight leehelm and is very course stable, if she sails by the lee the main blankets the genoa
and she seems to want to come back up, to far towards a reach and the genoa powers up and pushes the head
I also like to have a big light drifter hanked on the removable solent stay and sheeted off the boom to leeward. This helps with any rounding up issue and gives extra speed. If this is set I come up just far enough for it to set nicely, it normaly only takes 10-20 degrees, with the genoa feeding wind
into it, and it in turn powering up the main.
This often requires the windvane control lines to be set slightly to leeward to actually steer the boat onto a reach with the windvane upright. This is important in light air (less than 5-10 knots) as it ensures the boat will not gybe in a lull, instead she steers up as the wind goes light and down in the puffs, as a good helmsman would.
As the wind picks up I roll away some of the genoa to flatten it and angle it forward. both help enormously, but it needs either a long pole, or a small sail to achieve. I then progressively reef the main, drop the drifter and roll away more headsail.
The other half of it is to get the self steering
working properly, going to a tiller rather than a wheel
helps enormously, as does roller blocks and spectra lines and such, but I have found the vane size and balance is critical.
I usually have my very tall light nylon covered wind vane
on the flemming, it has been very carefully balanced to slowly return to vertical. And is made from 6 mm ply with large tapered lightning
holes cut in it. I kept cutting the holes out until it balanced just right, then painted it.. duh and had to cut out some more holes!.
A light nylon sock slips over it, and gets removed if the wind picks up to much (about 25 knots). For regular stronger winds the best vane I have is a tall tapered 6mm ply one, it goes from normal width at the bottom, to about 50mm at the top, and flexs nicely. It is more strongly balanced to return to vertical. On a horizontal axis vane short fat vanes to fit under a mizzen don't work well downwind, height is king.
Adjusting the tiller lines to dial in the right weather/lee helm
is also very important, as is the right position for the lines to make fast on the tiller, to far aft and you get wicked oversteer. To far forward give a nice smooth fast ride but not enough helm
to cope with puffs and waves pushing the boat off course. Once you get this right it shouldn't need changing. It's much harder to get this ratio sorted if it goes to a drum on a wheel
. In this case you might need a reverse tackle to get more movement at the helm, or a normal tackle if it is oversteering.
I added a small delta
shaped wing to the bottom of Snow Petrel's rudder
which helped her steering
in all conditions, and I have seen a few boats improved considerably by lengthening and reshaping the rudder.
Sydney would be a hard place to get one working right, the conditions always seems quite lumpy outside. Also, even on the best set up the wind vane will still often wander more than a good helmsman and it can take time to trust that it won't gybe or broach.
Good luck with it. It's wonderful when it's sorted out.