From: Jim Hocut <jhocut@HASimons.com>
Subject: RE: COZY: VNE -Reply
Date: Mon, 19 Jan 1998 04:44:34 -0800


> The wings are known to twist under normal loads and speeds at the
> point
> where they mate against the strakes..the German authorities have
> insisted in an added bolt in this area as a MANDATORY change before
> flight authority is granted.. maybe they know something we don't!
> This bolt serves two purposes. 1) It stops the twist. 2) It holds the
> wing forward against drag forces.
> I'm seriously considering it.
> 
> 
	This issue was raised at Burt's builder support forum at OSH a
couple or three
	years ago in regards to the LE.  Burt insisted that the small
amount of twist
	was not a problem, and in fact the added bolt may cause
problems.

	Jim Hocut
	jhocut@mindspring.com



From: "Fred I. Mahan" <mahan@digital.net>
Subject: COZY: VNE 
Date: Mon, 19 Jan 1998 09:26:23 -0500

Rego burger said:
The wings are known to twist under normal loads and speeds at the point
where they mate against the strakes..the German authorities have
insisted in an added bolt in this area as a MANDATORY change before
flight authority is granted.. maybe they know something we don't!
This bolt serves two purposes. 1) It stops the twist. 2) It holds the
wing forward against drag forces.  I'm seriously considering it.

Jim Hocut replied:
This issue was raised at Burt's builder support forum at OSH a
couple or three years ago in regards to the LE.  Burt insisted that 
the small amount of twist was not a problem, and in fact the added 
bolt may cause problems.

Perhaps the twist allows your airplane to fly faster and keep the benign
low speed characteristics it has.  I've heard some people speculate that as
your speed increases and pressure builds up against the winglets, their
moment (leverage) above the wing takes out some of the washout you've built
into you wing.  If true, this should reduce drag from the washout plus the
overall greater main wing lift would allow you to fly at a slightly lower
angle of attack and make less induced drag.  Did I make it clear as mud?

Fred in Florida
Long-EZ N86LE
Defiant project

From: cdenk@ix.netcom.com
Date: Mon, 19 Jan 1998 08:34:09 -0600 (CST)
Subject: Re: COZY: VNE -Reply

On 01/19/98 09:23:17 you wrote:
>
>High Tom,
>
>Q:
>Have you made any efforts to beef things up?
>Just interested.
>
>In forward flight & calm air I don't think we have anything to worry
>about up to 250 mph indicated..these are thumb suck figures! However in
>a dive with power on one could get to horrific speeds on a clean
>aeroplane. There is a point at which the drag from the winglets and wing
>could start creating pressures that are not so healthy.
>Also steep turns etc. should be limited to the manouvering speed for
>safety.. sadly the only way to find the end of the envelope is to test
>it to destruction which is expensive and dangerous. I take my hat off to
>guys who push these envelopes but I don't have the courage myself....
>:-)
>
>The wings are known to twist under normal loads and speeds at the point
>where they mate against the strakes..the German authorities have
>insisted in an added bolt in this area as a MANDATORY change before
>flight authority is granted.. maybe they know something we don't!
>This bolt serves two purposes. 1) It stops the twist. 2) It holds the
>wing forward against drag forces.
>I'm seriously considering it.
>Ernie Degovia has the Mod. spec.
>Please fly with a chute if you're going to do the testing yourself and
>do them high up. Make sure the canopy can disappear at the wave of a
>hand too. Getting out is not easy as it seems..!
>
>
>
>
>
>
>Rego Burger, web site: http://home.intekom.com/glen/rnb.htm
>(home e-mail) mailto:rnb@intekom.co.za
>
>

Rego Burger writes <Leading Edge Strake/Wing Bolt>
That bolt first appeared on the Cosy Classic Plans. Burt Rutan at OSH forum about 6 years ago said 
not required, may be harmful in response to my question. The issue is that 4 bolts creates what a 
structural engineer calls an indeterminate structure. Consider a 3 leg table, the exact load is 
known on each leg and everywhere in the structure. With 4 legs the load could be on any 3 legs, or 
if the legs were anchored to the floor, the tension in the short leg would have to be reacted by 
additional compression in other legs. This load can be calculated (using mechanics of materials 
principals and calculus) for simple structures, for more complicated structures computer modeling 
is used. In the case of a LongEZ (and COZY) wing, the structure and loading is very difficult to 
model. Load tests in Germany have shown that location to have about 1/8" movement. To make that 
rigid, means that the load necessary to make that movement will be generated by that bolt and 
distributed through the remainder of the structure, sometimes increasing the stress and sometimes 
decreasing the stress. The increase is the concern, not knowing the magnitude, and how much it 
goes into the normal factor of safety.


Date: Mon, 19 Jan 1998 12:42:49 -0800
From: "LCDR James D. Newman" <infaero@flash.net>
Subject: COZY: Re:  Vne

Hi Fred, Rego and All,

	>Rego Burger wrote:
	>In forward flight & calm air I don't think we have anything to worry
about up to 250 mph indicated..these are thumb suck figures! However in
a dive with power on one could get to horrific speeds on a clean
aeroplane.<

	One would be hard pressed to attain 250 knts. IAS with a fixed pitch
prop without over speeding the engine and/or prop.


	>Rego Burger also wrote:
	>There is a point at which the drag from the winglets and wing could
start creating pressures that are not so healthy.  Also steep turns etc.
should be limited to the maneuvering speed for safety.. sadly the only
way to find the end of the envelope is to test it to destruction which
is expensive and dangerous. I take my hat off to guys who push these
envelopes but I don't have the courage myself.... :-)<

	Yes, we talked about this Vne concern ~09/96.  See archives.


	>Rego Burger also wrote:
	>The wings are known to twist under normal loads and speeds at the
point where they mate against the strakes..the German authorities have
insisted in an added bolt in this area as a MANDATORY change before
flight authority is granted.. maybe they know something we don't!  This
bolt serves two purposes. 1) It stops the twist. 2) It holds the wing
forward against drag forces.  I'm seriously considering it.<

	Good idea.


	>Fred Mahan replied:
	>Perhaps the twist allows your airplane to fly faster and keep the
benign low speed characteristics it has.  I've heard some people
speculate that as your speed increases and pressure builds up against
the winglets, their moment (leverage) above the wing takes out some of
the washout you've built into you wing.  If true, this should reduce
drag from the washout plus the overall greater main wing lift would
allow you to fly at a slightly lower angle of attack and make less
induced drag.  Did I make it clear as mud?<

	The wing to strake twist occurs during rolls, rolling maneuvers,
rolling G maneuvers, pulling G's, and turbulence, all usually at higher
speeds.
	If the wing twists enough at higher speeds, one will have a slower roll
rate, or even a roll reversal.  From my 09/96 post:
******************
	Aeroelastic effects refer to the interaction between the aerodynamic
forces and the elasticity of the structure.  One form of this is called
"wing divergence" and causes the wing structure to fail immediately.  If
the aircraft is flown at velocities above the red line speed, a change
in the lift force might produce a positive twisting moment on the wing
because of the high dynamic pressure striking the leading edge.  This
twist of the wing increases the AOA of the wing sections affected; this
produces additional lift force which twists the wing even more.  This
continues until the wing structure fails.
        "Wing flutter" is sometimes experienced at excessive airspeed. 
The natural frequency of the wing, as the result of its elasticity,
occurs at velocities above the designed red line speed.  A fluttering
wing will not fail as quickly as the wing divergence situation, and the
pilot will probably have time to reduce the airspeed and stop the
flutter.  This is one reason why when you test fly your aircraft to
verify the prototype Vg Diagram and/or expand the envelope you have
already established, it is recommended to be done in 5 KNTS IAS
increments.
        There is also a condition called "aileron reversal" that is a
result of an aeroelastic effect.  If the pilot puts in right aileron to
roll the aircraft to the right, the high dynamic pressure striking the
leading edge, coupled with the lift force moving aft on the wing with
the down aileron, causes the wing structure to twist the leading edge
down.  The aircraft rolls to the left instead of the the right.  The
opposite reaction occurs on the right wing.
******************

	No need to get all freaked out about wing twist and Vne.  These planes
are usually very well built.  Just carefully increase your speed
envelope in 5 KNT increments to prove out the POH.  If you want to
expand your envelope beyond the POH, do it in 5 KNT increments.


Infinity's Forever,

	JD


Date: Mon, 19 Jan 1998 20:46:34 -0800 (PST)
From: "Mr. Radon" <grossing@serv.net>
Subject: Re: COZY: VNE -Reply

	I've heard of a few authorities requiring this bolt.  The aircraft
is not designed for the extra bolt and adding it causes an over
constrained condition.  You can not without finite element modeling
determine the load on each bolt.  And the results really vary depending on
how you constrain the model.  In college we faced a simular problem with
another aircraft where the authorities insisted on this extra bolt.  We
were able to prove to them that it was not needed and required a redesign
of the spar to handel the unpredictable load paths. 
	I'm sure Rutan used three bolts since he could resolve the forces,
if you're going to add that fourth bolt, it isn't just adding another hard
point, you'd better do some indepth analysis.  If you don't know how much
the support structure (spar) flexes under loading, don't even try to model
it.  If someone has the data needed to do a good model it would be nice to
know, if not I think the idea should be squashed right now.  (from a pure
safety standpoint, I wouldn't fly in a Cozy with a fourth bolt)

ROY



> High Tom,
> 
> Q:
> Have you made any efforts to beef things up?
> Just interested.
> 
> In forward flight & calm air I don't think we have anything to worry
> about up to 250 mph indicated..these are thumb suck figures! However in
> a dive with power on one could get to horrific speeds on a clean
> aeroplane. There is a point at which the drag from the winglets and wing
> could start creating pressures that are not so healthy.
> Also steep turns etc. should be limited to the manouvering speed for
> safety.. sadly the only way to find the end of the envelope is to test
> it to destruction which is expensive and dangerous. I take my hat off to
> guys who push these envelopes but I don't have the courage myself....
> :-)
> 
> The wings are known to twist under normal loads and speeds at the point
> where they mate against the strakes..the German authorities have
> insisted in an added bolt in this area as a MANDATORY change before
> flight authority is granted.. maybe they know something we don't!
> This bolt serves two purposes. 1) It stops the twist. 2) It holds the
> wing forward against drag forces.
> I'm seriously considering it.
> Ernie Degovia has the Mod. spec.
> Please fly with a chute if you're going to do the testing yourself and
> do them high up. Make sure the canopy can disappear at the wave of a
> hand too. Getting out is not easy as it seems..!
> 
> 
> 
> 
> 
> 
> Rego Burger, web site: http://home.intekom.com/glen/rnb.htm
> (home e-mail) mailto:rnb@intekom.co.za
> 


Date: Mon, 19 Jan 1998 21:21:18 -0800
From: "LCDR James D. Newman" <infaero@flash.net>
Subject: COZY: Re:  Vne

Hi Roy and All,

	>Mr. Radon wrote:
	>snip . . . I'm sure Rutan used three bolts since he could resolve the
forces, if you're going to add that fourth bolt, it isn't just adding
another hard point, you'd better do some in depth analysis.  If you
don't know how much the support structure (spar) flexes under loading,
don't even try to model it.  If someone has the data needed to do a good
model it would be nice to know, if not I think the idea should be
squashed right now.  (from a pure safety standpoint, I wouldn't fly in a
Cozy with a fourth bolt)<

	If memory serves, only two 1/4" bolts are needed to hold each wing on,
but then a confidence thing occurs with the builder / pilot / passenger
- is that really enough?  The 3 bolts are so the wings can be shimmed to
set / change wing incidence and sweep per side.
	There are many canards flying very safely for years in Germany with the
4th bolt.  Since the German FAA certification for their Sport Aircraft
are a little stricter than our FAA (i.e. - I believe German builders
each must load test their canards and wings), and the German FAA
requires the 4th bolt so the leading edge of the wing doesn't twist
where the wing mates to the strake, maybe someone has the data of why
they require it and how to do it, then someone could decide if it is for
them.


Infinity's Forever,

	JD


Date: Tue, 20 Jan 1998 07:58:10 +0200
From: Rego Burger <burgerr@telkom.co.za>
Subject: Re: COZY: VNE

Roy wrote,

Rego Burger, web site: http://home.intekom.com/glen/rnb.htm
(home e-mail) mailto:rnb@intekom.co.za

>>> "Mr. Radon" <grossing@serv.net> 20/January/1998 06:46am >>>
snip..  The aircraft is not designed for the extra bolt and adding it
causes an over
constrained condition.   We were able to prove to them that it was not
needed and required a redesign
of the spar to handel the unpredictable load paths. 
	 (from a pure safety standpoint, I wouldn't fly in a Cozy with a
fourth bolt)

ROY<<<<

It would seem that the spar has a shortcoming?
Would it be better then to add a ply of UNI across the area where the
twist is known to take place, say a 45deg orientation strip about 12"
wide wrapped around the "rib" area.?







From: cdenk@ix.netcom.com
Date: Tue, 20 Jan 1998 15:36:50 -0600 (CST)
Subject: Re: COZY: Re:  Vne

On 01/19/98 21:21:18 you wrote:
>
>Hi Roy and All,
>
>	>Mr. Radon wrote:
>	>snip . . . I'm sure Rutan used three bolts since he could resolve the
>forces, if you're going to add that fourth bolt, it isn't just adding
>another hard point, you'd better do some in depth analysis.  If you
>don't know how much the support structure (spar) flexes under loading,
>don't even try to model it.  If someone has the data needed to do a good
>model it would be nice to know, if not I think the idea should be
>squashed right now.  (from a pure safety standpoint, I wouldn't fly in a
>Cozy with a fourth bolt)<
>
>	If memory serves, only two 1/4" bolts are needed to hold each wing on,
>but then a confidence thing occurs with the builder / pilot / passenger
>- is that really enough?  The 3 bolts are so the wings can be shimmed to
>set / change wing incidence and sweep per side.
>	There are many canards flying very safely for years in Germany with the
>4th bolt.  Since the German FAA certification for their Sport Aircraft
>are a little stricter than our FAA (i.e. - I believe German builders
>each must load test their canards and wings), and the German FAA
>requires the 4th bolt so the leading edge of the wing doesn't twist
>where the wing mates to the strake, maybe someone has the data of why
>they require it and how to do it, then someone could decide if it is for
>them.
>
>
>Infinity's Forever,
>
>	JD
>
>
>

How many is many, how many hours flight time on them?. I got one of few COSY CLASSICS flying, (it 
was the 2nd by a month or 2) in the states and now has 550 hours on it. I don't consider that 
adequate experience time. It DOES NOT have the 4th bolt. As far as I know, it was only the COSY 
CLASSIC that was required to have the 4th bolt in Germany.