Squared trailing edge of control sufraces

[Bruce A. Frank]

A while back I remember seeing an article in one of the aviation
magazines about the affect of squared off trailing edges on control
surfaces of light planes. Anyone know where such an article might exist?
So far I have found several Boeing and NACA publications on wings with
blunt trailing edges, or blunt trailing edges at supersonic speeds. But
little specific to light planes with top speeds of 150 mph and landing
speeds of 40 mph or less.

I seem to remember that the squared off trailing edge of ailerons and
tail surfaces improved control authority, particularly at slow speeds.
Anyone have an idea?

--
Bruce A. Frank

[Andy Asberry]

On Tue, 26 Jul 2005 05:46:12 GMT, "Bruce A. Frank"
> wrote:

>A while back I remember seeing an article in one of the aviation
>magazines about the affect of squared off trailing edges on control
>surfaces of light planes. Anyone know where such an article might exist?
>So far I have found several Boeing and NACA publications on wings with
>blunt trailing edges, or blunt trailing edges at supersonic speeds. But
>little specific to light planes with top speeds of 150 mph and landing
>speeds of 40 mph or less.
>
>I seem to remember that the squared off trailing edge of ailerons and
>tail surfaces improved control authority, particularly at slow speeds.
>Anyone have an idea?

I saw something about this on Space Ship One. I know, not exactly in
your speed range.

[Roger]

On Tue, 26 Jul 2005 05:46:12 GMT, "Bruce A. Frank"
> wrote:

>A while back I remember seeing an article in one of the aviation
>magazines about the affect of squared off trailing edges on control
>surfaces of light planes. Anyone know where such an article might exist?
>So far I have found several Boeing and NACA publications on wings with
>blunt trailing edges, or blunt trailing edges at supersonic speeds. But
>little specific to light planes with top speeds of 150 mph and landing
>speeds of 40 mph or less.
>
>I seem to remember that the squared off trailing edge of ailerons and
>tail surfaces improved control authority, particularly at slow speeds.
>Anyone have an idea?

"As I recall" foggy memory and all, the air tends to attach to one
side or the other with a thin trailing edges. IE, it keeps switching
which can lead to an oscillation, or buffeting of the controls and
increased drag. The squared off trailing edge prevents this.
Although a bit faster, I believe the Cessna Citation has a "T" shaped
piece inserted in the trailing edge of the elevator or rudder (could
be both)

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com

[Don Hammer]

I believe the Cessna Citation has a "T" shaped
>piece inserted in the trailing edge of the elevator or rudder (could
>be both)
>
>Roger Halstead (K8RI & ARRL life member)
>(N833R, S# CD-2 Worlds oldest Debonair)
>www.rogerhalstead.com

It's on the rudder on the smaller Citations. The purpose is so there
is no hard spot when the rudder is centered at high speed. On
aircraft with non-boosted controls, they droop the ailerons for the
same reason

It proved to provide a big drag reduction on the G-550 to square up
the IB flap TE as compaired to the GV. Global Express as well as
Citation X have them squared also.

Do a Google search for Kamm Effect and you'll find things like -

It was once thought that a long tapered end in the shape of a vehicle
would give it the most aerodynamic configuration. W. Kamm discovered
that the length of the end would have to be so long as to make the
vehicle impractical. There would also be an increase in surface area
which would also create its own frictiondrag. He found that if he cut
the theoretically long tail in half he would have both good
aerodynamics and minimal surface drag. This sharply cut off rear end
is named after him.

Seems to me that since drag goes up squared with the speed that it
would work the best at higher speeds.

[Ray Toews]

In the eighties Grumman AA5 aircraft had an aileron flutter problem
and one of the fixes was to chop off the rear of the aileron and make
it square,,,the other was to replace the rubber bushings holding the
tourque tubes to take out the play.

ray


On Wed, 27 Jul 2005 16:16:21 -0500, Don Hammer >
wrote:

> I believe the Cessna Citation has a "T" shaped
>>piece inserted in the trailing edge of the elevator or rudder (could
>>be both)
>>
>>Roger Halstead (K8RI & ARRL life member)
>>(N833R, S# CD-2 Worlds oldest Debonair)
>>www.rogerhalstead.com
>
>It's on the rudder on the smaller Citations. The purpose is so there
>is no hard spot when the rudder is centered at high speed. On
>aircraft with non-boosted controls, they droop the ailerons for the
>same reason
>
>It proved to provide a big drag reduction on the G-550 to square up
>the IB flap TE as compaired to the GV. Global Express as well as
>Citation X have them squared also.
>
>Do a Google search for Kamm Effect and you'll find things like -
>
>It was once thought that a long tapered end in the shape of a vehicle
>would give it the most aerodynamic configuration. W. Kamm discovered
>that the length of the end would have to be so long as to make the
>vehicle impractical. There would also be an increase in surface area
>which would also create its own frictiondrag. He found that if he cut
>the theoretically long tail in half he would have both good
>aerodynamics and minimal surface drag. This sharply cut off rear end
>is named after him.
>
>Seems to me that since drag goes up squared with the speed that it
>would work the best at higher speeds.
>
>
>
>
>

[[email protected]]

The blunt TE also provide a more soft fell around the neutral i.e. kind
of a exponential control. Some aerobatic airplane have TE as thick as
3/8".

[Bruce A. Frank]

Thanks, everyone provided something that was useful.

"Bruce A. Frank" wrote:

> A while back I remember seeing an article in one of the aviation
> magazines about the affect of squared off trailing edges on control
> surfaces of light planes. Anyone know where such an article might exist?
> So far I have found several Boeing and NACA publications on wings with
> blunt trailing edges, or blunt trailing edges at supersonic speeds. But
> little specific to light planes with top speeds of 150 mph and landing
> speeds of 40 mph or less.
>
> I seem to remember that the squared off trailing edge of ailerons and
> tail surfaces improved control authority, particularly at slow speeds.
> Anyone have an idea?
>
> --
> Bruce A. Frank

--
Bruce A. Frank, Editor "Ford 3.8/4.2L Engine and V-6 STOL
Homebuilt Aircraft Newsletter"
| Publishing interesting material|
| on all aspects of alternative |
| engines and homebuilt aircraft.|
*------------------------------**----*
\(-o-)/ AIRCRAFT PROJECTS CO.
\___/ Manufacturing parts & pieces
/ \ for homebuilt aircraft,
0 0 TIG welding

While trying to find the time to finish mine.

[[email protected]]

Bruce A. Frank wrote:
> ...
> So far I have found several Boeing and NACA publications on wings with
> blunt trailing edges, or blunt trailing edges at supersonic speeds. But
> little specific to light planes with top speeds of 150 mph and landing
> speeds of 40 mph or less.
> ...

Have you found anythign on hemicircular trailing edges at any
speeds?

ISTR that struts with a circular cross-section have
more drag than similar sized square tubing. Since some
airfoils have a semicircular seciton on their leading edge,
one might suppose it is the trailing part of the circular
tubing that is responsible.

So maybe whatever benefit is realized from blunt trailing edges
would be enhanced more by semicircular trailing edges.

Then again, maybe not. I always had trouble with vibrations
and waves.

--

FF