Climb wasn't the best word to use. I like "L/D" too. Or just minimum
sink?
Don Dykin's book, "The Design of the Super-efficient Europa Wing," has
graphs of chordwise pressure distributions at varying lift
coefficients. These are probably theoretical (computer-derived) vs.
tested, but they clearly show sharp roll off in pressure differential
at a point forward of the gaps, more so in cruise. However, given the
chordwise size of the flaps, there may some small but measurable
benefit in sealing those things. There is even hint in the text that
the pressure distribution is instrumental in maintaining laminar flow
as far back as possible, but that's putting words in _his_ mouth,
which I don't wish to do!
OTOH, as one looks at the more forward underside gap, and the top side
gap back where it makes no difference, that some leakage is maybe even
proverse. Witness the experiments way back where they used a series
of holes and a pumping system to suck down the boundary layer. But
that's a retired accountant playin' aerodynamicist....
Regards,
Fred F., A063
david joyce wrote:
>
> Fred, Seems to be a bit of a misconception here. Gliders virtually never
> climb in a true sense, only in fact when they are being winch launched or
> when slowing up to enter a thermal. For the remaining 99% of the time they
> are going quietly down hill in their air mass, even though they go out of
> their way to find a rising air mass. Glider design aims for optimum
> lift/drag ratio between their thermalling speed of about 50 knots and the
> between thermal cruise of up to 100 knots.Increasing the L/D ratio is good
> news for Europas too. Regards, David Joyce
> ----- Original Message -----
> > Gap seals are most effective when pressure differential above/below
> > the wing surface is the greatest -- in the climb. Hence they are very
> > popular on gliders.
> >
> > Regards,
> > Fred F., A063
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