Nice to hear you're getting some sailing in. I've had to put up with only surfing and snorkeling.
Any tendency to head up or is it nicely balanced?
--- In
harryproa@yahoogrou ps.com.au, Doug Haines <doha720@... > wrote:
>
> I should report on the first decent sail, since relaunch.
> I had half an hour of nice 12-15 knot winds on about the beam for a sail down to Mandrah.
> The boat did seem a little quicker and smoother. The feeling was different somehow anyway - perhaps it was this new balance that the sail area versus rudder has provided.
> There was probably 12knots at times who knowsthough without a gps. The rudder has not ventilated (air streams offthe blade) at all yet.
> Â
> I am needing to change a few things back up at
Maylands Boat Yard for a few days.
> Am not making statements of possible upcoming voyaages, will wait and see.
> Â
> Also have some more opinions on areas like the new rudders.
> But haven't tested out fully yet.
> Â
> The outboard is great - though my bracket gets the powerhead wet too easily for serious motoring. It has been good help for passing under the bridges and light headwinds. I have never used an outboard on a sailboat much before but luckily this one is going easily.
> Â
> Doug
>
> --- On Tue, 16/2/10, robert <cateran1949@ ...> wrote:
>
>
> From: robert <cateran1949@ ...>
> Subject: [harryproa] Re: Single beam version of sidecar
> To:
harryproa@yahoogrou
ps.com.au> Date: Tuesday, 16 February, 2010, 11:36
>
>
> Â
>
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>
> I gave a lot of thought to the hull ratios and how tris can get away with fatter in the main hull, but when I tried to bring it to bear on a double-ender ww proa hull things didn't work out so well. Weight distribution and need for a fine transom made a mess of the relation. I feel a minimum of 12:1 is needed for the ww hull and preferably higher. The extra wetted area is not as important as the wave making as it is going to very quickly get into being significantly faster than the waterline length speed (about 5 or 6 knots for this length hull). Also I reckon you will need a spray deflector as the fatter ratios are going to produce a fair bit.
>
> --- In harryproa@yahoogrou ps.com.au, "John" <jrwells2007@ ...> wrote:
> >
> > With regard to length/beam ratios for the ww hull, it should
be possible to relate to trimaran design which has had far more work undertaken over many years. After all, a trimaran is similar to an atlantic proa until you tack.
> > A longer finer ww hull will have greater surface area and therefore greater skin resistance at low speeds plus a greater twisting force on the connecting beam(s) to the lw hull.
> > A shorter fatter ww hull will have greater wave-making resistance at higher speeds but does this matter too much as the lw hull is more important as speeds increase? At higher speeds the length of the lw hull inhibits squatting of both the lw and the ww hulls and it is this squatting that is potentially the speed limitation factor. Also at higher speeds the ww hull is being partially unloaded which will reduce its wave making resistance.
> > The wide stern on the main hull of a tri does inhibit squatting but the lw hull of a proa is munch longer than the ama of a tri and should
have a similar effect.
> > Farrier tris are reasonably fast for a cruising boat and they have about a 10 or 12 to 1 fineness of the main hull. However, Ian Farrier is happy that the fatter F31AX is at least as fast as the standard F31. The generalized recommendation for tris is, I believe, to keep the ratio for the main hull above 8 to 1.
> >
> >
> > --- In harryproa@yahoogrou ps.com.au, "robert" <cateran1949@ > wrote:
> > >
> > > My thinking is a little different from Rob's in that I feel there is a minimum length ww hull that is practicable. I feel that making it slightly longer doesn't detract except in adding racking forces. I also feel that a short ww hull either needs to be set up to plane-possible with a single crossbeam and ability to swing the ww hull back a bit, or go on foils, unless you are aiming to fly on the edge. Otherwise I feel the ww hull may drag a little at medium
speeds. Going too light with the ww hull and there is no righting moment (unless you want the top of the sail to be reversed to provide righting moment as in some wings)and power requires righting moment. Going heavy enough for righting moment and it can drag in light winds I am going with a relatively skinny ww hull flared above the waterline to provide lift when going through chop. A bit like having above the waterline looking like two lots of the front half of a hull of a power cat butted
> together with a 165degree dihedral.
> > > >
> > > > 3) I made the ww hull as short as possible, but the waterline beam is still 2', so I only have a 10:1 length/beam ratio. Would I be better off stretching just the hull portion out to 24-26 feet? It would add a bit of weight and windage, but would have a finer profile.
> > > >
> >
>