Ben
That little boat is intended to have very small weight shift. Intention was to have either 1 or 2 people. With two people it would be level trim in static state. A single person would probably move to the aft seat each shunt.
The idea with this design was essentially to verify that the flat bottom would generate enough lift to overcome any tendency for bow down trim. I have a couple of old hulls I plan to put together later in the year to test the idea. One is flat bottom and the other is longer round bottom.
Once the chine is above surface level at the bow the water is deflected sideways. It does not sheet up the sides. So having rocker combined with dynamic lift will overcome the attached flow up the side of the hull while ever the chine is above the surface. So a hard chine is partially effective in preventing the spray. When the stem is immersed in a wave the water will sheet up the side again. So spray will come and go.
Many power cats are fitted with spray rails to deflect the water sideways to reduce spray. The rail is well above the static water level.
Main point with the lw hull on the proa is why bother about a little spume that costs negligible energy and flys harmlessly to leeward over the bow of the hull. If you are going fast you do not want extra ballast on the lw hull. The ballast should be on the ww hull.
Rick
On 20/09/2011, at 3:30 AM, bjarthur123 wrote:
rick-
how much weight shift (or stern ballast) would be needed to get a degree of bow up trim? depends on the boat of course, but let's consider your snazzy proa with a longer ww hull and single-element wing sail. is there much room in that design for weight shift? if so, how many degrees would it yield?
also, i think gardner was specifically looking for ways to reduce spray, and thinking rocker would help. correct to say you disagree?
ben
--- In harryproa@yahoogroups.com.au, Rick Willoughby <rickwill@...> wrote:
> The lift
> coefficient can never get very high because it takes only 1 degree or
> so of bow up trim before the immersed length is reduced and the lift
> area starts to reduce.
Rick Willoughby
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