In a message dated 11/30/2005 2:58:48 AM Eastern Standard Time,
europa-list-digest@matronics.com writes:
> Can you describe the nature of the gap seals you allude to?
> With regard to flap seals, would they be on the top, underside, or on
> both wing surfaces?
> If on the underside, are you suggesting a closure strip attached to the
> wing and tight to the underside of the flap which would flex and slide
> along the flap surface when the flaps are lowered?
> Would such a strip be taped to the wing, or glued, with the forward
> edge faired into the wing surface to mitigate any bump caused by the
> thickness off the gap seal strip?
> What material would you propose to use for such seals?
Hi Fred,
Positive seals are fairly common in modern sailplanes, especially the racers.
They involve using a strip of lightweight dacron (parachute material) which
is attached to the aileron closeout and the forward edge of the aileron, either
with yellow contact cement (preferably) or double stick tape. This prevents,
or at least reduces, the tendency for pressure equalization between the upper
and lower surfaces of the wing, thus reducing drag and making the aileron more
effective. The same can be done on the rudder.
A thin strip of mylar is often installed over the gap between the aileron and
the rear edge of the wing, top and bottom. This helps the flow to stay
attached and results in better control, less drag, etc. The rudder can also be
mylared, as well as the trim tab top.
The Europa flap closeout must have been designed for a flap gap seal. The
flat portion of the closeout where the flap noses up to when the flaps are up
simply begs for a seal. A simple piece of foam weather-strip here installed so
that the nose of the flap touches it when up is all it would take. Mine is only
about 1/8" thick. Use something UV stable, though. Since the Europa has Fowler
type flaps, I'd avoid using any mylar on them so as to not disrupt the
airflow when the flaps are down. I don't think the weather-strip will interfere
with
the airflow, though. It's likely in a turbulent location when the flaps are
down, so any effects are minimized. I've also installed a thin layer of foam on
the end of the flap so that it seals to the side of the fuselage when the
flaps are up.
There's a good tutorial about positive seals and mylar at
http://www.wingsandwheels.com/page28.htm Tim also sells all the goodies you
need to seal up an
airplane.
Bruce Carmicheal's book about personal aircraft drag reduction has a lot of
very good information on drag reduction, too, although it is a bit heavy on the
math. Certainly not light reading. He says the wing root and cooling flow are
the two biggest places to reduce drag in small airplanes.
BTW, the new prop, hub, spinner, backplate and bolts come in at 10.2 lbs. I'm
going to measure the blade twist today and I'll post it later.
Anyway, hope it helps!
Regards,
John Lawton
Dunlap, TN
A-245 (Left to do: Prop, spinner, cowls, go fly.....)
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