Yeah any appendage you add will create drag, Whats your point.
That four instead of two is worse?
Can you prove it?
How much worse if you figure in to make as best as possible for the given compromise?
Can you tell us the performance difference really.
Instead of acieving 18 knots sailing speed in 4foot of water with a 24'' draft you do 15 knots in 2feet of water on a 18'' draft...
I made a foil have to make three more to put on my CatProa PraoCat.
What I did is just half the sq in'' of a single rudder and reshaped it for a shllower draft. Original 7''x1'' shoal draft 3 1/3'' x 2'' at its widest part 25% down from top part of rudder tappering smaller to the bottom. Very similar shape as sail. I have to make 3 more and go test on model draft will be a scaled 18'' with all four rudders down.
In the mean time your not gonna like this idea any better.
The possibilities are endless and so much fun.
http://www.youtube.com/watch?v=--Axuvmclec
enjoy!
Todd
--- In harryproa@yahoogroups.com.au, Arto Hakkarainen <ahakkara@...> wrote:
>
> Every foil, be it rudder, sail, wing, board, keel, whatever that has tip has also tip wortex. It is one of the reasons why multi mast vessel performs worse to windward than single mast (there are other reasons too). If foil generates lift it will also create tip wortex at the tip. Tip wortex adds to resistance. The added resistance which also adds fuel consumption has put airplane industry to work a lot to improve the wingtips in order to minimize the tip vortices. See more here: http://en.wikipedia.org/wiki/Wingtip_vortices
>
> Of course if your design goal is not maximum efficiency you may have better results with bigger number of shorter foils but the tip vortices are one design consideration.
>
> Arto
>
> --- On Tue, 5/24/11, tsstproa <bitme1234@...> wrote:
>
>
> From: tsstproa <bitme1234@...>
> Subject: [harryproa] Re: Design your proa
> To: harryproa@yahoogroups.com.au
> Date: Tuesday, May 24, 2011, 2:00 AM
>
>
>
>
>
>
> How so ?
>
> In what conditions?
>
> and at what cost?
>
> Cost to benefit analysis.
>
> Having four blades interconnected to work as one sure does have some merit in the way of handling ease and shallow draft. If it did work using all four of same size blades on Gardeners design. What would be the draw back. Would it even be noticed if there was a draw back.
>
> Todd
> --- In harryproa@yahoogroups.com.au, Arto Hakkarainen <ahakkara@> wrote:
> >
> > four blades also get four tip vortex.
> >
> > Arto
> >
> > On Mon May 23rd, 2011 9:21 PM EEST tsstproa wrote:
> >
> > >I see, So shallowest possible draft while retaining overall helm balance in most wind cinditions.
> > >
> > >I would say Instead of the long shallow stub keel have you thought about using four steering blades instead of two? Have two leeward with two to windward. Might be able to gain a shallower draft with the four boards.
> > >
> > >Todd
> > >
> > >--- In harryproa@yahoogroups.com.au, Gardner Pomper <gardner@> wrote:
> > >>
> > >> This seems like a thread that might be able to answer a related question
> > >> that has been nagging at me for a while. I am mostly concerned with how
> > >> shallow the water can be for practical sailing (this would be, for example,
> > >> cruising off the south tip of florida, inside the florida keys).
> > >>
> > >
> > >
> >
>