Frans, I think he means put the foam PVC weatherstrip about where the gap
between
the forward most part of the retracted flap and the closeout is. So when the
flap is retracted, the "leading edge" of the flap just touches and even
compresses
the foam. This should help keep the higher pressure air under the wing
---From going up top.
So there is no "lip" at the bottom of the slot, the foam strip is attached up
the closeout a bit where the space between the leading edge of the flap and the
closeout is smallest. I have been flying my Mono this way for quite a while
now and have not noticed any negative effects.
So the objective here is to keep the higher pressure air down where it belongs,
not to "smooth out" the gap between the lower wing and flap bottom surface.
I think if you attached a Mylar strip to the bottom of the wing to span the gap
to the flap, it would screw up the air flow thru the "slot" when the flap is
down, making our slotted flaps less effective... I think.
Kevin
On Aug 6, 2012, at 1:58 PM, Frans Veldman <frans@privatepilots.nl> wrote:
>
> On 08/06/2012 04:18 PM, Fred Klein wrote:
>
>>> How much air is going to this gap with the flaps extended? Is it
>>> possible to make the underside of the wing flush with the flaps when the
>>> flaps are retracted?
>>
>> ..."possible"...but not necessarily desireable...this type of gap seal
>> was installed on Cessna 180s with decidedly mixed results...
>
> I know it was an option on Cessna's but I didn't know about the mixed
> results.
>
>>> This would reduce the size of the gap with the flaps extended, does
>>> this have consequences?
>>
>> I would think so, and not necessarily positive. I'd classify the Europa
>> flap as a "slotted flap" which is generally designed to allow
>> substantial airflow thru the slot which I believe is intended to promote
>> the attachment of the boundary layer to the upper surface of the
>> flap...a good thing, no?
>
> Yes. But the current slot is a 90 degree corner, and apperently you can
> also put cell foam in it as a seal. Id doesn't look like it allows lot
> of air through. That's why I wondered whether some "lip" at the bottom
> of this slot would make things different.
>
>> I would think that if the compressible flap gap seal which John Lawton
>> recommends was sliced from a circular rod of closed cell foam (known as
>> "backer rod" and used in the US for sealing the joint between concrete
>> and the sill plate of a wood wall) would have minimal disruption of
>> airflow thru the slot.
>
> Yes, but he mentions in the email that "the XS-wing looks like it has
> been designed with a seal in mind, because it has a flat area at the
> bottom of the slot." But at the bottom of the slot the gap is at its
> widest point, far too wide for a foam seal. So I'm a bit confused here
> as what he means.
>
>> As you can read from my use of terms that I have only a fuzzy awareness
>> of this stuff, so take my comments with a grain of salt.
>
> Same here. I hope to find someone who can shed some more light onto this
> matter.
>
> Frans
>
>
>
>
>
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