Nicely put, though I am not sure if there is speed scrubbed by imbalance, as the rudder simply gives more or less leeway resistance. If there was lee helm, then definitely.
I agree about the shallow sacrificial strake on the bottom providing a bit of leeway prevention for shallow water.
--- In harryproa@yahoogrou
>
>
> If the daggerboard is in the center fore/aft, and you have a single
> mast, the center of leeway resistance could be a meter or two in front
> of the center of effort on the rig, resulting in a weather helm. While
> I personally would rather have a weather helm than a lee helm, something
> that's closer to balanced would be nice. Lighter helm, less speed
> scrubbed by steering against the unbalance.
>
> Due to the long rockerless hull, the weather helm won't be extreme,
> but it will probably be noticeable. Less noticeable with an easyrig
> than with an una rig.
>
> ---
>
> I'm personally not willing to build either a rudder or daggerboard
> into the hull. I know of a local F-31 available for chartering that has
> gone through more daggerboards than I can count. They are designed to
> fail, but the hull/crashbox still get damaged.
>
> Yes, offering a boat like that for charter is questionable in an area
> with so many rocks and shoals. But the risk of grounding is still there
> regardless of who owns the boat. Even if you know what you're doing,
> you can still hit a submerged log, shipping container, whale, or
> unexpected sandbar. Having something that kicks up would be paramount
> for me.
>
> I love the kick-up rudders and centerboard on the Dragonfly trimarans,
> and if I were to get a trimaran, that would be the brand. I can't
> imagine spending $200,000 on a boat that doesn't have such an important
> safety feature.
>
> But I'd rather have a proa than a trimaran, and the Dragonfly design
> of a centerboard in a trunk would only work in one direction.
>
> ---
>
> So, what to do.
>
> For the sake of discussion, I'll make two assumptions based on my
> preferences: a) no requirement for playing with a board on each tack,
> and b) no holes/crashboxes/
>
> That leaves four designs I'd consider;
>
> 1) Two daggerboards that can kick up in both directions, plus two
> rudders for steering. I've not seen one of these yet, but the
> engineering would not be hard.
>
> Pro: lots of leeway resistance, resistance it against fixed
> boards, lighter loads on the rudder.
>
> Con: four foils in the water, plus the rudders will have a tough
> time fighting a long hull without rocker combined with two daggerboards.
>
> 2) One kick-up daggerboard/
> for steering and a big of helm balance.
>
> Pro: leeway resistance on a fixed board, three foils in the water
> instead of four, easier to steer around a centered foil.
>
> Con: three foils instead of two (resistance)
> of two (one more to raise/lower)
>
> 3) Long low-aspect keel in lee hull, two smaller rudders.
>
> Pro: no worries about kicking up, keel could be sacrificial in
> some ways, protecting the hull.
>
> Con: more resistance to steering, requiring larger rudders, less
> leeway resistance when compared to the same wetted surface area in a
> high-aspect foil.
>
> 4) Two larger rudders.
>
> Pro: Minimal number of foils in the water, powerful steering when
> needed (at low speeds) because of two opposing rudders.
>
> Con: Force on the rudders is both leeway and steering.
>
> ---
>
> I'm currently a fan of the two deeper rudders. As long as the loads
> can be handled, why add additional resistance to forward motion or
> resistance to steering?
>
> That said, my buying/building will be influenced by the new rudder
> design being installed on Blind Date. I think it's a great one in
> theory, but it will also be nice to see it in practice.
>
> Actually, I might consider a fifth option. Gardner has me thinking
> about his short keel. Perhaps something just a few cm high could help
> protect the hull in a grounding and/or when drying out on a beach, but
> without adding too much resistance.
>
> - Mike
>
>
>
> Gardner Pomper wrote:
> >
> > Hi,
> >
> > I am afraid that I must expose my ignorance to the list again. I
> > thought that a leeboard/daggerboar
> > provided lift perpendicular to the
> > board. Why can't it be in the middle? What would happen if it was?
> >
> > Thanks
> > - Gardner
> >
>
Change settings via the Web (Yahoo! ID required)
Change settings via email: Switch delivery to Daily Digest | Switch format to Traditional
Visit Your Group | Yahoo! Groups Terms of Use | Unsubscribe