Duncan=0Amy problem is with the extra load on the lift pins when the spar b
ends, =0Aunnecessary. Maybe the fuse does relax but what's the point of ad
ding a heavy =0Abelt when the braces have enough to do already! =0A=0AGraha
m=0A=0A=0A=0A=0A________________________________=0AFrom: Duncan & Ami <ami-
mcfadyean@talktalk.net>=0ATo: europa-list@matronics.com=0ASent: Tuesday, 25
January, 2011 22:10:16=0ASubject: RE: Europa-List: Re: Main wing bushings
=0A=0A =0AGraham,=0AI agree with all that you say, so unsure why you
=99re not convinced.=0AThe lift load is spread on the wings, but comes to a
point at the lift pins; the =0Astress path being either via the spar and r
oot rib, and/or directly through the =0Awing skin to the root rib (assuming
for the argument no lift contribution from =0Athe spar pins).=0AI recall t
hat when a Europa wing broke in the early tests, it broke across the =0AD-b
ox (LE of wing) adjacent to the rib (and was subsequently reinforced in tha
t =0Aarea).=0AMeaning that this part was overstressed, obviously, but the s
train at failure =0A(being a material constant) was greatest in this part o
f the structure (i.e. up =0Ato the point of failure, the area around the ri
b had flexed more than any other =0Apart of similar =98I).=0A =0A =0A
Duncan.=0A =0A-----Original Message-----=0AFrom: owner-europa-list-server@m
atronics.com =0A[mailto:owner-europa-list-server@matronics.com] On Behalf O
f GRAHAM SINGLETON=0ASent: 24 January 2011 23:20=0ATo: europa-list@matronic
s.com=0ASubject: Re: Europa-List: Re: Main wing bushings=0A =0ANot convince
d Duncan. The spar resists bending and the leverage is enormous, =0Afrom th
e centre of lift of the wing 30% span? The load on the root ribs is shear
=0Aand some bending of the pins. Don't forget the lift load is a spread loa
d =0Awhereas the spar bending of the tangs is a point load applied by the s
par pins.=0AYou are right about the stiffening of the fuselage side. We re
ally should have =0Aflexible sockets at the LE as well as the TE. =0A=0AI
still believe the lift pins (in the root rib) should carry all the lift loa
ds =0Aand the spar pins all the bending loads. That's why the tangs needed
to be =0Astrengthened on the glider.=0A=0AGraham=0A =0A=0A_________________
_______________=0A =0AFrom:Duncan & Ami <ami-mcfadyean@talktalk.net>=0ATo:
europa-list@matronics.com=0ASent: Monday, 24 January, 2011 21:58:21=0ASubje
ct: RE: Europa-List: Re: Main wing bushings=0A<<..would stiffen the structu
re in such a way that it could lead to overloading =0Aof the forward lift p
in>>=0A =0AIan,=0AHow does that work, if the lift pins are designed to carr
y the lift loads in the =0Afirst place, there being no greater load availab
le?!=0AActually, it was stiffening in bending that might restrain rotation
of the lift =0Apin that was the issue, resulting in an additional bending l
oad (not lift load) =0Abeing applied to the forward lift pin. The LAA were
offered a spherical socket =0Athat would articulate and remove the bending
load on the pin, but declined to =0Aaccept that.=0A =0AHowever, you are on
right path, The earlier discussion in this thread presumes =0Athat the spar
flexes, as it indeed doe. But actually the spar (loaded in this =0Adirecti
on) is the least flexible part of the whole system. What about the =0Aforwa
rd and aft portions of the root rib? Let=99s say these ribs have equa
l =0Asection and =98I=99 as the spar, but being laid-up at +/-
45 degrees have x1.41 the =0Aelasticity of the unidirectional spar (in the
direction of principal stress), =0Aadded to which the length of these flexi
ng root ribs (between lift pin and spar) =0Ais longer than the offset betwe
en lift pins and spar pins. So, as the root ribs =0Awill flex more than the
spar and it follows that the =9Cleverage=9D effect between =0A
the longitudinal offset of lift pin and spar pin centres is removed, or rev
ersed =0Ato the extent that the spar pins share some lift load. =0A=0A =0AA
s you say, the flexing of the fus side also contributes, albeit this had to
be =0Astiffened-up to prevent pin disengagement.=0A =0APreviously I have p
ut a small finger down one of the (1/2=9D) spar pin holes with =0Athe
wings rigged, while someone else rather violently loaded the wing, albeit
=0Anot even near to 1g. But there was no hint of the =9Cleverage
=9D effect or the spar =0Ahole flexing downwards relative to the pin hol
e in the seat back.=0A =0ARgds.,=0ADuncan McF.=0A =0A =0A-----Original Mess
age-----=0AFrom: owner-europa-list-server@matronics.com =0A[mailto:owner-eu
ropa-list-server@matronics.com] On Behalf Of G-IANI=0ASent: 24 January 2011
12:34=0ATo: europa-list@matronics.com=0ASubject: RE: Europa-List: Re: Main
wing bushings=0A =0AIn support of Bud and Pete=99s notes I can confi
rm that flexing of the fuselage is =0Aimportant. The LAA had considerable
concerns that the tail dragger conversion =0Awould stiffen the structure in
such a way that it could lead to overloading of =0Athe forward lift pin.
=0A =0A =0AIan Rickard G-IANI XS Trigear, 300hours=0AEuropa Club Mods Speci
alist=0Ae-mail g-iani@ntlworld.com=0A =0A =0A =0A =0A =0Ahttp://www.matroni
cs.com/Navigator?Europa-List=0Ahttp://forums.matronics.com=0Ahttp://www.mat
ronics.com/contribution=0A =0A =0A =0A" target="_blank" href="http://fo
rums.matronics.com">http://forums.matr --> =0A =0Ahttp://www.matronics.co
m/Navigator?Europa-List=0Ahttp://forums.matronics.com=0Ahttp://www.matronic
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