Re: I60 wing
Not sure what you mean here by laminar flow. In general
engineering usage it means that flow in the boundary layer is steady
and increases in a uniform fashion as you move away from the surface.
We don't see this in Bolger boats. Reynold's number is too high and
surfaces are not precisely shaped enough. Laminar flow isn't even seen
on most airplanes, with sailplanes and some very carefully shaped
others that don't have too many squashed bugs on them. Perhaps you
mean unseparated flow?
I think the wings on the cup boats reduce induced drag and of the keel
and spanwise flow when it is acting as a lifting surface. I think
Bolger's endplated rudders act the same way, but in that case drag is
not the primary consideration. To make something like the wings on a
keel or winglets on a plane actually reduce drag, the general
consensus of aero guys is that you have to really mind your p's and
q's.
engineering usage it means that flow in the boundary layer is steady
and increases in a uniform fashion as you move away from the surface.
We don't see this in Bolger boats. Reynold's number is too high and
surfaces are not precisely shaped enough. Laminar flow isn't even seen
on most airplanes, with sailplanes and some very carefully shaped
others that don't have too many squashed bugs on them. Perhaps you
mean unseparated flow?
I think the wings on the cup boats reduce induced drag and of the keel
and spanwise flow when it is acting as a lifting surface. I think
Bolger's endplated rudders act the same way, but in that case drag is
not the primary consideration. To make something like the wings on a
keel or winglets on a plane actually reduce drag, the general
consensus of aero guys is that you have to really mind your p's and
q's.
--- In bolger@y..., "proaconstrictor" <proaconstrictor@y...> wrote:
> To get any hydro effect , you would have to have good laminar flow
> For the lift to be meaningful you need some speed. As David says
the
> reason are probably pragmatic, as with the cup boats, in that case
to
> do with the rule.
>
>
>
>
>
>
> over--- In bolger@y..., David Ryan <david@c...> wrote:
> >
> > >I re-read the MAIB article this afternoon, and it seems that one
> > >reason for the flatter top surface of the wing is to fit snuggly
> > >against the hull in the raised position so that if the boat
settles
> > >
To get any hydro effect , you would have to have good laminar flow
For the lift to be meaningful you need some speed. As David says the
reason are probably pragmatic, as with the cup boats, in that case to
do with the rule.
over--- In bolger@y..., David Ryan <david@c...> wrote:
For the lift to be meaningful you need some speed. As David says the
reason are probably pragmatic, as with the cup boats, in that case to
do with the rule.
over--- In bolger@y..., David Ryan <david@c...> wrote:
>
> >I re-read the MAIB article this afternoon, and it seems that one
> >reason for the flatter top surface of the wing is to fit snuggly
> >against the hull in the raised position so that if the boat settles
> >
>I re-read the MAIB article this afternoon, and it seems that oneThis is my take: The primary consideration of the design is getting
>reason for the flatter top surface of the wing is to fit snuggly
>against the hull in the raised position so that if the boat settles
>onto the bottom against the wing at low tide or on the trailer, the
>stress won't be concentrated.
the most boat in terms of size/performance on a street legal trailer.
The "wing" is primarily a way to get a lot of weight down low while
allowing the boat to be put on a trailer. This dictates the top of
the wing be flat. Once the top is flat, the bottom has to take on a
foil shape. Whatever benefit or harm is done by this shape is trivial
compared to the advantages of a very low C.G. and trailerablity.
YIBB,
David
C.E.P.
415 W.46th Street
New York, New York 10036
http://www.crumblingempire.com
(212) 247-0296
I've been thinking about that I60 wing creating a downward force, and
I realized that while beating, this will increase sail-carrying power
at low angles of heel. The over-simple explanation is that the force
generated is almost in the same direction as the gravity force on the
ballast.
We don't see this effect used in the America's Cup class and other
classes that spend a lot of money on computer modeling and tank
tests, so I guess it doesn't pay all around the course. It would
increase drag while running. The actual direction of the force, and
in fact whether any lift (up or down) is actually generated, depends
on the angle of attack as well as the sectional shape. It would be
interesting to hear what PCB&F have in mind. Will there be an
adjustment anywhere in the system to tweak the angle of attack "just
so?"
I re-read the MAIB article this afternoon, and it seems that one
reason for the flatter top surface of the wing is to fit snuggly
against the hull in the raised position so that if the boat settles
onto the bottom against the wing at low tide or on the trailer, the
stress won't be concentrated.
Peter
I realized that while beating, this will increase sail-carrying power
at low angles of heel. The over-simple explanation is that the force
generated is almost in the same direction as the gravity force on the
ballast.
We don't see this effect used in the America's Cup class and other
classes that spend a lot of money on computer modeling and tank
tests, so I guess it doesn't pay all around the course. It would
increase drag while running. The actual direction of the force, and
in fact whether any lift (up or down) is actually generated, depends
on the angle of attack as well as the sectional shape. It would be
interesting to hear what PCB&F have in mind. Will there be an
adjustment anywhere in the system to tweak the angle of attack "just
so?"
I re-read the MAIB article this afternoon, and it seems that one
reason for the flatter top surface of the wing is to fit snuggly
against the hull in the raised position so that if the boat settles
onto the bottom against the wing at low tide or on the trailer, the
stress won't be concentrated.
Peter