<<could I please get the layman's definition for what yer'all
are talkin' about please.>>
I shall attempt.
It's not about a problem, but instead, an issue regarding
optimization.
The surface-penetrating foils will suck down air at speed,
eliminating any lift the generate from their shape (in the way a
wing generates lift on its "upper" surface, or a well-tuned sail
generates lift on its leeward surface), and instead turning them
from foils to boards that just catch water (the way a spinnaker
catches air).
When compared to foils that extend from the bottom of a hull, the
surface penetrating foils will require a lot more surface area in
order to achieve effective steerage and leeway prevention. This
will result in extra drag, slowing the boat.
Rob's current two-foil setup is optimized for kickup without
damage, and hopefully, and easy reset to sailing after the kickup.
As a result, it needs larger foils than a boat with foils or foils
and a daggerboard that exit the hull bottom.
Rick's design is optimized for speed. Since the foils are all
under water, and can't suck in in any air at high speeds, or
interfere with various flows of water, they can generate lift as
well as just force water out of the way, and can therefore be
significantly smaller. Adding a knot or two to the top end. In a
three-hour race, that could result in an extra nautical mile (or
several, if you've got good wind and a lot of reaches).
Which is better? That all depends upon your criteria.
Since I don't race, I'll go for the kick-up without a second
thought. Not having to worry about my boat sinking, or becoming
inoperable, due to a sand bar, log, submerged container, or whale,
does a lot for me. We have a lot of shoals and lobster trap warps
in Maine, and there are times it's tough to avoid them, particularly
the trap warps -- boat traffic sometimes determines one's path.
The other benefit of the kick-up design would also like being able
to see the foils, raise them, clear them of seaweed, or work on
them, and so forth. On my current cat, I can easily kick up the
rudders to remove the weed, which slows me down like a drogue, but I
can't quite do the same thing with my daggerboard.
*However*, If I were to race, it would be tough to argue against
smaller, faster, non-ventilating foils. If the goal is shortest
elapsed time, this design wins. It is without a doubt more
optimized.
---
That said, it would definitely be interesting to see how large an
end plate is required to keep Rob's kick-up rudders from
ventilating, and if the resulting design could be competitive with
the underwater foils. My guess is that the plate would definitely
help, but that it also wouldn't quite equal Rick's planned design.
But I don't have the software to prove this hunch.
- Mike
Doug Haines wrote:
could I please
get the layman's definition for what yer'all are
talkin' about please.
It is either onee of the theoretical non issue type
things that gets brought up here by certain
academia, or it is the actual rudder problem that is
happening to a few harry's.
I don't exactly understand what those bigger boats
are having happen, but it does sound like my
troubles on sidecar.
perhaps rudolf would chime in again - just to help
clarify things up for me.
I cleard up every rudder issue i had including
massive "ventilation?" and no bite at all/
unsteerable.
sidecar has had no dilemas whatsoever since i
increased the rudder blade size.
Doug
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