Pattern wing design

[John Ferrell]

My personal observations:
You may well be on thin ice if you duplicate the Prophecy wing with built up
balsa. The wing is pretty thin to build that way.

A symmetrical air foil with a 2:1 chord ratio and Leading Edge & Trailing
Edge imitating the Extra 300 that is strong and stiff will do fine.

Build the wing with the top flat on the table and the dihedral will be
close, if not perfect!

The leading edge sweep provides stability in the roll axis, the trailing
edge sweep affects stability in push maneuvers.

The greater wing thickness makes for more drag. It also adds a lot of lift
which leaves the plane twitchy in wind gusts.

The tail feathers play a great role in what we ask to fly our maneuvers. Too
much stab will make snaps next to impossible. So will too much vertical fin.

Too little fin will leave things unstable in the Yaw axis. It will also make
for very poor low speed control.

Sweep back on the leading edges of the tail feather seems to go a long way
toward both yaw and pitch stability.

The shape of the fuselage, its center of lateral area, the relationships of
the thrust line, wing centerline, stab centerline, incidences, thrust
offsets, and the sums of all of the drags are important too.

Where the turbulence has an effect is hard to determine other than flight
testing. It is even harder to fix.

Some designs are yaw stable in more than one angle to the centerline. The
Prophecy is not. It has a fixed angle determined by the amount of right
thrust.

The Hydeout seems to have at least two lockable yaw points. You can usually
set the wind correction at one end of the box and it will track well past
center hands off in a pretty stiff breeze. Some people love it that way and
some of us just cannot get used to it. A fair number just adapt and it does
not matter!

The only way I know to really screw up a KAO's is to build it too heavy.
They always fly well, even the crooked ones. My experience has been that
they fly OK in knife edge but the presentation is poor due to the lack
lateral area. They are mostly hanging on the prop.

These are my observations and subject to change with more experience. I
really can't tell as much about flight characteristics when I am at the
controls as when I am observing other people flying. Sometimes the Masters &
FAI pilots fix the flaws so well they are not observable. The Intermediate &
Advanced pilots struggle with immature designs.

I have been think about another Kaos variation myself.
John Ferrell
6241 Phillippi Rd
Julian NC 27283
Phone: (336)685-9606
johnferrell at earthlink.net
Dixie Competition Products
NSRCA 479 AMA 4190  W8CCW
"My Competition is Not My Enemy"


----- Original Message ----- 
From: <randy10926 at comcast.net>
To: <discussion at nsrca.org>
Sent: Thursday, September 04, 2003 7:40 AM
Subject: Re: Pattern wing design


> Anyone know what wing the KAOS and Prophecy uses.  I recently got a Kaos
kit
> and the plans for a KOAS 90.  Thinking to building a Kaos 90 with Prophecy
> wings.  I would like to use one of the wing programs to generate a balsa
built
> up wing.  For some reason I would like to really build something.

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