I don't see how (two hulls) are decouple not effecting one another as mention. A gyroscope controlling a hydraulic connection point There are two hulls still involved. The decoupling you have mentioned (designing each hull for a specific cause) would cause greater coupling forces between the two hulls. More so than that of a traditional pacific proa design or catamaran with identical hulls in my opinion. The only why I see it so far is to reduce weight and volume of windward hull to reduce coupling forces. Which changes the whole dynamic of the proa as far as through the water sailing balance and forces at play are concerned.
On the hobie rig why not use it just like it would be on a hobie cat turning mast support beam 90 degrees attaching beam to your outrigger structure.
Todd
--- In harryproa@yahoogroups.com.au, Dennis Cox <dec720@...> wrote:
>
> Sorry for the late reply... just getting back from vacation. I needed to get
> FAR further south to get out of the snow and ice up here.
> Â
> tsstproa,
> Â
> I've done my fair share of throwing that term around, so I'll put in my two
> cents worth of how I visualize it. When I started studying boat design
> (amateur) using "Principles of Yacht Design" it struck me how hard it was to
> design a good monohull sailing boat because how coupled everything was. EVERY
> decision impacted every other decision. Every curve of the hull impacted the
> speed, stability, carrying capability, behavior, safety and comfort. AND then
> you had to take into account that at a new healing position or
trim
position,
> you had to start the calculations all over. I still see it as taking an
> insurmountable amount of experience to get a "feel" for how every decision will
> impact every other. The "Design Spiral" is an absolute requirement of the
> process.
>
> I first played with catamaran design. It was a lot EASIER. You can pretty much
> discount hull shape changes as it heals. Rolling stability is a pretty simple
> calculation and is so dominant that the minor affects of a 5 degree heel to the
> hull shape are just noise in the calculations. Now it became just (sarcasm
> included) a matter of designing for trim characteristics. Choices like wave
> piercing versus riding up on the waves with large forward flare. And
> then trying to get all the design coefficients in their correct magnitudes and
> positions for whatever desired goal you have in mind. You get a lot of theories
> about where to put the widest point of the hull and how much volume to carry
> forward or reward of some certain point. Again a massive undertaking balancing
> speed versus safety versus comfort.
>
> Then comes a Proa. Its very decoupled. This is an over simplification, but you
> can see where (compared to catamarans and certainly monohulls) it leads
> you.  Assuming a HarryProa layout... the lee hull can be single minded for
> speed.  You don't have to ride in it. In rough weather you sit comfortably in
> the windward hull. It can bounce around all it wants. Most of the vibration
> will get dampened out across the beams. In good weather and running hard
> (possibly flying the windward)
again, the beams act as a great isolator like car
> springs. Since both hulls are symmetric front to back all the design issues are
> about where to volume dissolve to Cp... putting volume either toward the center
> or toward both ends. From my perspective, 90% of the design details are either
> forced on you or are clearly separated. Some might find that confining, but at
> my level I find it of design ability I find it reassuring.Â
>
>
> For my situation... my needs are very well defined.
> 1) Live 2 for long terms (years)
> 2) Sleep 6-8 for weeks
> 3) Entertain 10-15 at anchor
> 4) Go fast for costal racing
> 5) Go safe for blue water
>
> Looking at production catamarans this requires (in my mind) about 40 footers.Â
> Anything larger gets real expensive fast. Anything smaller is just too
small.Â
> However, on other sites, people seem to think 40 footers are on the small size
> for safe bluewater work. 40 footers also are either considerably slower or have
> significantly lower carrying capability (Extreme 40)
>
> With a Proa, the 40 winward / 60 leeward seems to fit the bill better. A 40/60
> Proa would typically have far higher roll and pitch stability so blue water
> safety is improved. The 60 foot lee hull optimized for speed with a Cp higher
> than 0.8 is going to have far better stability than a 40 foot hull with a Cp
> around 0.65 which seems to be the sweet spot for Cats. I believe that a
> properly design 40/60 Proa could run with and maybe beat a GunBoat 65. This is
> of interest to me! :)
>
> proaconstrictor,
> Â
> Well... I know what I'm going to do.Â
Will it work... yet to be seen. :)
> Â Basically the drawings are still valid in the pictures sections of the forum.Â
> I'm going to make a tube that the Hobie mast will slide down into. I'll build
> up Hobie mast to make round bearings at the top and bottom of the tube. I plan
> on making the tube structure strong enough to handle a free standing mast and
> tipping moment able to fly the windward hull. I'm going to assume the Hobie
> mast can not take that moment above the tube so, it'll have stays going fore/aft
> and to windward to take the bulk of the loading to keep the mast from snapping.Â
> It will have to rely on its own bending strength for the aback case.Â
> Considering that some Proa masts would fall if they went aback... this seems
> like an adequate compromise. I'll make or reinforce a boom
forward/aft of the
> mast to hold the small jib. Hopefully that will do until I build its
> replacement and get rid of all the stays.
>
>
>
>
> ________________________________
> From: proaconstrictor <proaconstrictor@...>
> To: harryproa@yahoogroups.com.au
> Sent: Sat, December 18, 2010 1:31:53 AM
> Subject: [harryproa] Re: Hull slenderness ratios
>
> Â
>
>
> --- In harryproa@yahoogroups.com.au, "tsstproa" <bitme1234@> wrote:
> >
> > I see alot of coupling and decouple thrown around here and there. What exactly
> >do you
mean by this?
>
> I think it is the sidecar concept. The motorcycle and the sidecar are connected,
> but optimized for different uses. So conceptually you could have a racing hull
> and a cruising hull to windward on the same lee hull.
>
> I think some of these comparisons are not helpful returning to the OP for a
> moment. Basically amas function as training wheels with some incidence effect to
> stop capside over buried floats. They also have enormously variable immersion,
> which affects what their operating ratios are at any one time, might even be
> wider than they are long on occasion. Farrier main hulls are some of the fattest
> out there at times, so not always on the median. And I tend to think of Harry
> lee hulls not as being made as long as possible to provide a long waterline, not
> because there is something efficient about incredibly narrow hulls that are way
>
long. It's just good to have a long waterline in certain conditions.
>
> Speaking of MLM, have you figured out how to mount the Hobie rig on it yet?
>