REFLECTOR: anyone know the story behind this-musthavemissedit.....

Wed Nov 9 21:11:56 CST 2005

Yes, I am hoping to squeeze out a couple/few knots with that one- might
be one of the significant drag areas on the RG aircraft  I had seen the
winglet article/similar one years back, also have the AR5 drag reduction
video and several other sources- including my switched-to-mechanical in
Junior year aero engineering background,  all claim that the drag at the
intersection of 2 diverging airfoil sections is quite significant. Will
try to post up some pictures  of my fillet mod into the website- can
someone remind me how to do that?  Last I posted was my extended-strake
door lock work-around over a year ago.....

Alex

-----Original Message-----
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Douglas Holub
Sent: Wednesday, November 09, 2005 12:24 AM
To: Velocity Aircraft Owners and Builders list
Subject: Re: REFLECTOR: anyone know the story behind
this-musthavemissedit.....

I noticed a while back that Alex Balic had put a large radius in the
corner 
where the winglet meets the wing.  After reading this article, I think I

will do that, too.

Doug Holub
----- Original Message ----- 
From: "steve korney" <s_korney at hotmail.com>
To: <reflector at tvbf.org>
Sent: Tuesday, November 08, 2005 10:43 PM
Subject: RE: REFLECTOR: anyone know the story behind 
this-musthavemissedit.....

>
> Check out this web-site...Might shed a little more light on the
subject of 
> Winglets..
>
>
> http://www.mh-aerotools.de/airfoils/winglets.htm
>
>
> Best... Steve
>
>
>
> ----Original Message Follows----
> From: "Tom Martino" <tmartino at troubleshooter.com>
> Reply-To: Velocity Aircraft Owners and Builders list
<reflector at tvbf.org>
> To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
> Subject: RE: REFLECTOR: anyone know the story behind 
> this-musthavemissedit.....
> Date: Tue, 8 Nov 2005 21:17:39 -0700
>
> This is the best explanation I have heard for the stability of the
> winglets.  Great job!
>
> -----Original Message-----
> From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org]
On
> Behalf Of Scott Baker
> Sent: Tuesday, November 08, 2005 9:01 PM
> To: Velocity Aircraft Owners and Builders list
> Subject: Re: REFLECTOR: anyone know the story behind
> this-musthavemissedit.....
>
> Picture a sailboat with its bow pointing into the wind and the boom
> trailing straight back (along the centerline of the boat).  This
invites
> a situation whereby the sails luff (i.e. flutter) because they lack
wind
> loading.  Tack the boat at an angle to the wind and the sails fill
true,
> because they are now (my word) "loaded".
> Winglets on the Velocity are toed in.  The shape of the winglet is
> actually a wing with the "top" or cambered side faces inboard; and the
> bottom or flat side faces outboard.  Looking at the outside shape of
the
> winglet and rudder, one will notice a slight cuff (concave shape).
> Builders sometimes mistakenly believe the concave area should be
filled
> in with micro in order to make a straight surface along the winglet
and
> rudder outside line.  Wrong.  The cuff is part of the "wing" shape and
> is designed in this fashion for a purpose - and that is, to allow the
> winglet to create lift in a horizontal direction towards the fuselage.
> The winglet forces mimic that of a person pushing the winglet from the
> outside towards the fuselage.  This "loads" the winglet and adds to
> stability.  It also creates a design that does not support flutter.
It
> is very important that builders who build from the basic kit make
> absolutely sure that the toe-in of the winglets are built according to
> the construction manual.  Straight winglets and the absence of a
slight
> concave line on the outside of the winglet invite flutter.  This is
what
> happened with Brendan and the first "Brazil" set of wings.  The toe-in
> was reduced by a fraction of an inch and the shape of the outside of
the
> winglet did not feature a concave feature.  It was just enough to
begin
> winglet flutter, which once started - could not be stopped once the
> rudder cables broke.
> SB
>
> ----- Original Message -----
> From: Greg Poole <mailto:gpoole at zeta.org.au>
> To: 'Velocity Aircraft Owners and Builders list'
> <mailto:reflector at tvbf.org>
> Sent: Tuesday, November 08, 2005 8:15 PM
> Subject: RE: REFLECTOR: anyone know the story behind this-
> musthavemissedit.....
>
> In a word; Wow!
>
> Knew all about the accident but never got to see the very
> sobering picture of the aircraft afterwards (thanks Alex!) or the
detail
> provided below by Scott (thanks mate!). Would like to know a little
more
> how streamlining invites flutter - or do you mean that the bulk of the
> wings/winglets were reduced to a point that structural rigidity was
> lost?
>
> Yes...now that I have seen it thank God again that Brendan made
> it out OK!
>
> ....You all be careful out there now!
>
> Greg in Sydney.
> Std RG E.
>
> -----Original Message-----
> From: reflector-bounces at tvbf.org
> [mailto:reflector-bounces at tvbf.org] On Behalf Of Scott Baker
> Sent: Wednesday, 9 November 2005 10:20 AM
> To: Velocity Aircraft Owners and Builders list
> Subject: Re: REFLECTOR: anyone know the story behind this- must
> havemissedit.....
>
> Yes, I know all about it.
> The aircraft pictured belonged to Bob Wood.  It is a fixed gear
> Velocity XL and it featured the first "Brazil" wing.  Brendan
O'Riordan
> was the pilot.  The aircraft developed a flutter in the right vertical
> stabilizer immediately after the aircraft was leveled off following
the
> first take off; estimated speed 110 knots.  Brendan attempted to slow
> the aircraft by reducing power - and at the same time deployed both
> rudders.  Deploying the rudder "loads" the winglet to help reduce the
> possibility of flutter.  The flutter action was so violent that it
broke
> the rudder cables and the right rudder was torn from its hinges.  The
> aircraft became almost uncontrollable at that point.  Brendan added
air
> speed by lowering the pitch attitude and headed to a sparsely
populated
> area West of Sebastian Airport.  The aircraft struck the ground at
> approximately 90 knots, hitting Palmetto trees and ultimately flipping
> the aircraft inverted before it came to a stop.  Brendan, thank God,
was
> okay.  He was released from the local hospital emergency room after a
> quick examination - but as you can see in the photo, Bob's aircraft
was
> a total loss.
> The designer of the wings, Dan Maher, and other aeronautical
> engineers were consulted.  The winglet and rudder design were found to
> be too streamline that it invited flutter.  The winglets and rudders
> were redesigned and flight tested on the factory's XL training
aircraft.
> Important: Everyone who has a "Brazil" wing has the new wing design,
> which was thoroughly and professionally flight tested to 210 knots
> without any hint of flutter.
> Velocity built Bob Wood a second aircraft, aka "Bob-II".
> The bottom line is that the first "Brazil" wing had a design
> problem, it resulted in a forced (crash) landing, Brendan escaped
> injury, all of the old winglets and rudders were destroyed, new
winglets
> and rudders were designed and professionally flight tested in excess
of
> normal flight limits, Bob Wood was satisfied with a replacement
aircraft
> , new "Brazil" wings are performing great... and life goes on!
> Reports of this were published on the Reflector years ago when
> the accident occurred.  Many "Reflectorites" were at the Velocity Open
> House when the accident occurred.
> Hope this helps.
> Best regards,
> Scott B.
>
>
>
> ----- Original Message -----
> From: Alex Balic <mailto:alex157 at pwhome.com>
> To: reflector at awpi.com
> Sent: Tuesday, November 08, 2005 5:36 PM
> Subject: REFLECTOR: anyone know the story behind this-
> must have missedit.....
>
> Saw this in the builder site, don't remember about it
> other than the one time that there was a flutter problem with the
> original Brazilian wings- is this the aftermath?
>
http://www.tvbf.org/gallery/?display=.%2Fincidents%2FBrazilian%20wing%2F
> bob_1_1.jpg
>
>
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