REFLECTOR:Lower Winglets- Seaondary function.

Laurence Coen reflector@tvbf.org
Fri, 30 Jan 2004 12:30:21 -0600


Greg,

The thingies on the ends of the main wing were not designed to be winglets
as a primary function. Their primary function is vertical
stabilizer/rudders.  The fact that they are on the ends of the main wing
causes them to act as winglets, albeit poorly designed ones.  If you
remember the Ercoupe, it had twin rudders on the end of it's elevator.  I
can't remember anyone calling them "elevatorets".  The rudders always wind
up on the rear of the aircraft for the same reason the feathers are on the
back end of an arrow.  The Ercoupe had the big wing in front and the little
one in back.  Ours are built the other way around but the vertical
stabilizer/rudder still has to go in the back.  Mounting it on the
centerline isn't practical so they are out on the ends of the big wing which
is where you would mount winglets if you were going to have them.  Their
primary functions are yaw stability, roll stability and yaw control.  The
only one of these that isn't obvious is how they provide roll stability.
Assuming that you understand how dihedral on an aircraft provides roll
stability by tilting the lift vectors in toward the center line of the
aircraft, you should also understand how the "winglets" work.  The winglets
produces lift in the horizontal plane toward the centerline while the main
wing generates lift vertically.  If you sum these two vectors, the result
will be a lift vector tilted toward the centerline of the aircraft, just
like the wings with dihedral.

Are we having fun yet?

Larry Coen
Std. RG-E

----- Original Message ----- 
From: "Greg Poole" <gpoole@zeta.org.au>
To: <reflector@tvbf.org>
Sent: Thursday, January 29, 2004 3:41 PM
Subject: Fw: REFLECTOR:Lower Winglets


> From one of my aircraft designer mates.....
>
>
> Subject: Re: REFLECTOR:Lower Winglets
>
>
> > hi Greg,
> > The lower winglet design on the Velocity is more a wingtip skid than a
> lower
> > Whitcombe winglet. The upper winglet design is more somewhere to put the
> > rudder than a Whitcombe winglet.
> > An efficient design would have a winglet span of only 20% of the main
wing
> > semi-span with the leading edge of the upper winglet starting at the
> thickest
> > point of the main wing profile and ending behind the main wing trailing
> edge.
> > The winglet is more tapered and sweptback than the original wing and the
> > airfoil section changes the camber forward towards the tip( geometric
> > washout).
> > The lower Whitcombe tip should be 5% of the wing semi-span (from
> memory)and
> > start before the leading edge of the wing, ending at the thickest point
of
> > the main wing airfoil section. The upper winglet has the airfoil as a
bent
> up
> > version as the main wing whereas the lower winglet is opposite with the
> main
> > camber facing the fuselage.
> > Modern design also cant the winglet out at 30 degrees to reduce the
> bending
> > moment and pressure area at the winglet root.
> > I hope this gives you a bit of an idea as to winglet designs,
> > Ray
> >
> > On Wed, 28 Jan 2004 17:40:13 +1100, Greg Poole wrote
> > > Al,
> > >
> > > Most of the designs of effective lower winglets as appear on other
> > > aircraft, kick the winglet out at a decent angle (rather than up and
> > > down) and have more of a tapered shape - I would love to know the
> > > reasons why the Velocity is different in this regard...can anybody
> > > shed any light? ....Could be better visual aesthetics I suppose.
> > >
> > > Forever curious!
> > >
> > > Greg in Sydney.
> > >   ----- Original Message ----- 
> > >   From: Al Gietzen
> > >   To: reflector@tvbf.org
> > >   Sent: Wednesday, January 28, 2004 4:59 PM
> > >   Subject: RE: REFLECTOR:Lower Winglets
> > >
> > >   One notable result of not having the lower winglet is increased
> > > speed,
> > >
> > >   which doesn't quite jibe with the above discourse?
> > >
> > >   Scott
> > >
> > >   Oh, I think it could.  Airfoils producing a force cause drag.  The
> > > winglets cause drag, but they produce a force we need for handling
> > > and stability.  I'd expect the Velocity lower winglets to cause drag
> > > at cruise without much in the way of offsetting benefit.  Apparently
> > > there is some handling benefit at lower speeds.
> > >
> > >   Do you have any with/without data about the increased cruise speed?
> > >
> > >   Al
> >
> >
> > --
> > ISPDr Internet WebMail (https://www.ispdr.net.au/mail)
>
> _______________________________________________
> To change your email address, visit
http://www.tvbf.org/mailman/listinfo/reflector
>
> Visit the gallery!  www.tvbf.org/gallery
> user:pw = tvbf:jamaicangoose
> Check new archives: www.tvbf.org/pipermail
> Check old archives: http://www.tvbf.org/archives/velocity/maillist.html
>