My apologies for inaccurate statement. On a harryproa drag from ww-hull
is trying to turn the boat windward when it starts to move when sailing.
On an Atlantic proa this effect is opposite, it makes the boat to turn
to lee side, when the rig is pushing the boat forward( and lee). Imagine
your car has bad brakes, the ww side brakes but lw side not , you must
steer to lee side to keep the car on road if you are braking. On
atlantic car the effect is opposite.
It is the dilemma of the CE and the center of drag. The further apart
they get the worse the situation is.
It is not wise to load the ww hull to maximum.
I think on a Harryproa the mast should be canted inwards. Rudders must
be on lw-hull and some mandatory heavy items such as batteries, water,
spare anchor and so on should be kept in the lw hull to minimize WW-hull
drag. Visionarry is wide enough for this . I feel it could even has less
beam. Ours is 8m x 15m so it has a bit less beam than both BD and RB.
The sail area is reasonable I think.
I like the rockered shape of the WW hull. It has such a flat bottom in
the middle and I can see planing quite nicely.
The more we learn to sail the boat, the better it feels.

Regards,

Arttu

> Thank you for the real world experience from a big Proa.
>
> I'm not sure I understand your last statement about Atlantic and
luffing away. 
> I'll keep trying though.  :)
>
> Dennis
>
>
>
>
> ________________________________
> From: "arttuheinonen@heinoset.net" <arttuheinonen@heinoset.net>
> To: harryproa@yahoogroups.com.au
> Sent: Fri, July 30, 2010 11:56:51 AM
> Subject: Re: [harryproa] Leeway Prevention
>
>  
> Hi!
>
> Now I have some experience on Visionarry with daggerboards and rudders.
> WW hull induces drag that is counteracted by negative AOA on the rear
> rudder. So when ww-hull is on the left side must helmsman turn steering
> wheel to the right to compensate the drag. It looks like lowering rear
> daggerboard(asymmetric) reduces the need to compensate this drag with
> rear rudder.
> I can feel the rudder becoming more neutral when rear daggerboard is lowered
> Whether this is caused by increased drag or created lift or both I do
> not know. Yet I do not have found out which gives highest speed.
> When sailing upwind without jib the daggerboards are mandatory. Now that
> the rudders are only 95cm long it is really more difficult to get the
> boat sailing from zero speed and daggerboards do help a lot.
> By the way I could imagine an Atlantic proa is easier to shunt because
> drag does not cause luffing away.
>
> Regards,
>
> Arttu
>
> > OK!  I am about to drill down to China.  (Hope that expression has
the same
> > meaning where you're from... I guess not... if you're in China)  I hope I
> > can explain this without putting you to sleep... and hopefully you can
> slap me
> > out of it.  There are two issues I want you to entertain...
efficiency and
> > strength.  We want to go fast... and we want to stay in one piece. 
I think
> > those are universal.  We are "thinking" about a HarryProa (nothing
> else really
> > matters)...
> >  
> > Efficiency
> > If you raise the front rudder, you have to kick the back rudder till
> the angle
> > of attack (AOA) of the entire hull counters the leeward force of the
> sails.  We
> > all know that low aspect foils are inefficient.  And the leeward hull
> is about
> > as low aspect as you can get.  So even though its big and strong,
> there is a lot
> > of side slip going on.  We are aiming for Europe and we hit Africa. 
> We also
> > have a LOT of induced drag.
> >  
> > Now if we lower the forward rudder, we can get the two rudders (acting
> as highly
> > efficient, high aspect foils) doing all the heavy lifting.  We can now
> set the
> > AOA of the hull to be zero by having positive AOA on the rudders.  In
> this case,
> > the hull is presenting the least drag it can possibly do and the
> rudders are
> > taking all the load.  So we're kicking ass and taking names, until...
> >  
> > Strength
> > ... you start realizing that we need to design for the "lifting
> windward hull"
> > case.  As an approximation... the leeward force is about equal to the
> windward
> > hull's weight.  Split that in two (for the two rudders) and for my
> > case... that's 4000 lbs (17 kN).  (Forgive me Rob... you have the best
> > pictures) http://www.harryproa.com/building_Vis/Vis_img_feb11.htm.  By
> the time
> > you get the moment arms into the issue, the bottom rudder post would
> be taking
> > somewhere around 11,000 lbs (50 kN).  I haven't analyzed these, but
I think
> > these supports would have troubles with that load.  Fortunately, they
> don't have
> > to in Rob's design!  If you'll note the rudder isn't balanced so the
> lateral
> > forces acting on the rudder are resisted... by... you got it... the
> helmsman. 
> > If I were to take a WAG, I'd say Rob has a mechanical advantage
> somewhere around
> > 100:1 on the wheel.  So to hold that, the helmsman would have to
> supply... 100
> > lbs (500 N) On each wheel... not bloodly likely.  So, Rob has used the
> helmsman
> > as a force limiting transducer.  Briliant!
> >  
> > Before I saw Rob's elegant brilliance, I was going to make my rudders
> > (near) balanced.  I wanted some helm feel, but I didn't want a work
> out or blow
> > the autopilot.  Then I realized using delicate members like Rob, I'd
> soon tear
> > them off while sipping my afternoon tea and steering with one finger. 
> >
> >  
> > Can anyone... tell me how I can have my rocket ship and eat it too?
>
>