Hi,
I agree what Arto says. I also think it is beneficial the keep the ww-hull and bridgedeck as lightly loaded as possible. The COE of the rig is high above the water. A ketch rig is an answer to this problem and to many other problems. With the effort you build the easy rig you will build two masts and a ketch rig.
Regards,
Arttu
Arto Hakkarainen [ahakkara@yahoo.com] kirjoitti:
> --- On Mon, 3/7/11, Rob Denney <harryproa@gmail.com> wrote:
>
> Rob.
>
> I mostly agree with what you say below. However, I keep coming back intuitively to the fact that the rig is pressing the lee bow hard and even though it has lots of buoyancy it still could be pressed down by rig forces more or less. I know there has been a lot of discussion on the subject and whether the dynamic forces on the hull will counter that force or not.
>
> Things that lead me to this theory were two sources that support each other, namely what Rudolf reported here about the experience on new rudders and Todds model testing. In BD reducing the sail force seemed to help (no luffing without jib wven though that moved the CoE back). Also on many of the videos and tests Todd made with his models they did the same many times: heeling due to too much sail -> bow pressed down -> luffing in more or less uncontrolled way. With all the righting moment of visionarries boat hardly heels but the bow may still go down. Big boats behave differently to models. Both cases support my intuition that the problem is caused by bow pressing down.
>
> The visious circle you described supports different foils for leeway prevention and steering doesn't it? That way the board takes loads and you don't need to have too much angle on rudders. I know it is against your idea of minimising the number of foils...
>
> Still I acknowledge that there are many people here with more experience so please correct me if I'm wrong.
>
> Arto
>
>
> Arto,
>
> Bow down trim does cause weather helm, especially on boats with no
> rocker. However, the bow down in this case is caused by the drag from
> the partially rotated rudders. A vicious circle. On Rare Bird, even
> at 17 knots on a broad reach, the steering remained light and the bow
> was not noticably submerged, although it was difficult to tell because
> of all the spray. I think it would be less on a light boat with the
> same hull, but could be wrong.
>
> rob
>
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