Subject: Re: [harryproa] Re: Planning Proa squared!!! is it weight to windward!?
From: Rick Willoughby
Date: 6/6/2011, 7:22 PM
To: harryproa@yahoogroups.com.au
Reply-to:
harryproa@yahoogroups.com.au

 

Todd

Were you happy with the way it went?  Speed looked impressive for the scale.

Generally if you scale just on length a full size boat will perform better than the scale boat.  

There is advantage in a slight flare in the sides - say 5 degrees - for improving performance in waves.  Take the flare all the way to the ends so the longitudinal righting moment goes up as the ends bury.  But keep the deck line at the ends low so there is not a large volume to push through waves or a buoyant trailing end to lift that end when running off a wave.  Increasing waterplane area as the bow initially dips will help avoid burying the bow when in waves. You also want a deck shape at the ends to lift easily through green water rather than resisting the lift from the bottom and sides of the hull. 

Rick
On 07/06/2011, at 3:32 AM, tsstproa wrote:

 

Sorry, Rick Let Me add To conduct an experiment for myself to see if narrow planning hulls might be feasible to me ;~)

--- In harryproa@yahoogroups.com.au, "tsstproa" <bitme1234@...> wrote:
>
> The theory, Ho boy bad word ... and the way I worked it out was a spill over of knowledge learned from other models with weight bias. With these seemingly wide flat bottom hulls 1/12 scale 24'' or 2' on model squared 18'' or 1/ 1/2 on leeward hull. moving mast and sail inboard from lw and crew weight and housing etc... from ww . Acouple things happen one the leeward hull now aids in righting moment unloading the leeward hull by moving mast and sail inboard. Un weighting ww hull by moving crew position and its fixtures inboard. With the even distribution of weight amongst the two hulls lowest possible draft with maximum amount of weight not overloadiing one hull or compromising one hull by limiting it to weight.
>
> Some may see it as losing the best possible righting moment. Moving inboard . But how so if your riding on minimum draft possible with the same weight as weight to windward 40 /60 weight bias with a deeper draft. The sail is still to leeward and weight is way from mast a distance not much shorter than the 40/60 weight bias . Sure add heeling and everything changes 40/60bias becomes 50/50 , 50/50weight bias becomes 60/40. Both are designed to sail flat no more heel then 3-8 dgrees. Lowest possible draft is more easily driven Less sail area required to drive same weight that is distributed evenly amongst the two hulls, leeward hull buoyancy is adding to a degree the stiffness of of the boat to overcome heeling forces.
>
> Shown with catproa proacat mast centered vs mast on leeward hull.
>
> Steering boards at each end are 3% of 225 sqft sail area. Boards stay down most of the time to broaden the range in direction efficiency especially at slower speeds and shunting. Both boards down insures no mishaps during shunts. Gaining a sure directional foot hold of hulls on the wtaer keeping the possibility of bows passing through the eye of the wind during shunts and getting back winded. Front board could be lifted on long tacks in the right conditions and sailing course chosen.
>
> Todd
>
>
> --- In harryproa@yahoogroups.com.au, "tsstproa" <bitme1234@> wrote:
> >
> > Thanks for asking.
> >
> > The hulls are sqaure at mid section. Read description below video its not really a question just something to make you think or say HUH ,its mid center balanced. Static model balances at mid beam, weight to leeward matches weight to windward. Catproa Proacat has a weight to windward bias. Echelon my three hull proa has a leeward weight bias. Just acouple more things to consider. The specifics right, do they matter.
> >
> > Todd
> >
> >
> > --- In harryproa@yahoogroups.com.au, Rick Willoughby <rickwill@> wrote:
> > >
> > > Todd
> > > Why is it squared?
> > >
> > > And your question on weight to windward - in regard to what aspect?
> > >
> > > Rick
> > > On 06/06/2011, at 7:11 AM, tsstproa wrote:
> > >
> > > > Rick , Rob and the gang. This may or may not interest you.
> > > >
> > > > http://www.youtube.com/watch?v=ECf5LbG5DM4
> > > >
> > > > Todd
> > > >
> > > >
> > >
> > > Rick Willoughby
> > > rickwill@
> > > 03 9796 2415
> > > 0419 104 821
> > >
> >
>


Rick Willoughby
03 9796 2415
0419 104 821


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