thanks rick. this is the first sane response from the spinnakers-lift-the-bow club i've ever read. it's a hugely important difference, unappreciated by most, that they don't actually lift the bow, rather they just push it down less, for the same forward drive, than the main and jib. this has been my intuition all along and i'm glad you agree!
when overpowered off the wind i have always reefed the main before changing head sails. the main reason being that, on a boat with a stayed mast, you can not fully depower the main in a gust or a wave plough. in the heaviest conditions i completely taken down the main down go under jib alone. nice to hear that there is relative bow lift with this policy as well.
incidentally, the ability to completely feather the main with a harryproa's unstayed mast is the primary reason i find them so appealing. it's a shame wyliecats aren't able to do this (unstayed but not rotating). combined with a fuse in the sheet designed to break at the righting moment, i could probably actually relax when out in open water.
ben
--- In harryproa@yahoogroups.com.au, Rick Willoughby <rickwill@...> wrote:
>
> There is also a brace and a sheet taking some uplift component as
> well as the drive.
>
> The vertical height of the the CoE of the spinnaker will be similar
> to the normal rig however the net force on the spinnaker has an
> upward component that a main and jib will not provide.
>
> The spinnaker may not produce a net bow-up pitching force (it could
> be) but it will be producing a vertical component that is better
> than just a horizontal component with a main and jib.
>
> A spinnaker enables extra drive from forcing the bow deeper by
> providing some lifting component. A main and jib providing the same
> drive would force the bow deeper.
>
> Usually a spinnaker is deployed to go faster downwind. However
> consider the case where you want to maintain the same speed as the
> main and jib provides but reduce the likelihood of pitchpoling.
> Lower the main and jib than set a spinnaker of the same area as the
> main and jib. The bow will now trim higher with the spinnaker than
> with the main and jib for the same speed. Similar drive from the
> spinnaker but some uplift to partially counter the pitching force
> from the drive over the drag.
>
> Rick