rick,
i think what you're trying to say is that the polar for light winds might be such that the best VMG to weather is made for less than 2.5 kts boat speed, and if you try to go that slow with the rig to lee then you'll go into irons.
it seems to me, however, that if the rudders are ineffective at slow speeds, they will be ineffective no matter which way the wind blows over the boat. if the rig is to lee you'll go into irons; if it's to weather you'll bear away. either way, you won't be able to maintain the best upwind VMG speed or angle. no?
sure, you'll be able to temporarily pinch with the rig to weather. but it's only faster because you reduce the likelihood that minutes will be added to your finish time while idling in irons. not because you're able to sail a better VMG.
ben
--- In harryproa@yahoogroups.com.au, Rick Willoughby <rickwill@...> wrote:
>
> Rob
> The 18m proa moves OK once off the wind. To do a comparison you need
> to sail to windward both ways around. I expect you would find having
> the ww hull on the lee side will give the best pointing ability in
> light air. Need to compare speeds and tacking angle both ways.
>
> There is no problem until you want to pinch up. If you pinch up too
> far there is no way to recover once speed drops below that needed to
> counter the strong weather helm. Only way out of irons is to go in
> opposite direction so angle to wind can be changed. If rig allows
> COE to be shifted forward significantly then that is also an
> alternative means of getting out of it.
>
> The difference to a monohull or cat is that speed can virtually drop
> to zero and you can still turn off the wind. You may get in irons
> trying to complete a tack when speed is near zero but you do not get
> locked up if you pinch up at 2.5kts. On the 18m proa your are going
> to be in irons as soon as the speed drops below 2.5kts.
>
> There is a lot to learn about getting the best from the configuration
> over a range of conditions. If you were racing in flukey conditions
> and other boats were able to sail at same speed but 20 degrees higher
> you would be looking for ways to improve pointing. Easiest way is to
> sail with ww hull on the lee side. You can then pinch up knowing
> that you will be able to bear off no matter how slow you sail.
>
> Rick