Not convinced Duncan. The spar resists bending and the leverage is enormous
, =0Afrom the centre of lift of the wing 30% span? The load on the root rib
s is shear =0Aand some bending of the pins. Don't forget the lift load is a
spread load =0Awhereas the spar bending of the tangs is a point load appli
ed by the spar pins.=0AYou are right about the stiffening of the fuselage
side. We really should have =0Aflexible sockets at the LE as well as the T
E.=0AI still believe the lift pins (in the root rib) should carry all the l
ift loads =0Aand the spar pins all the bending loads. That's why the tangs
needed to be =0Astrengthened on the glider.=0A=0A=0AGraham=0A=0A=0A=0A=0A__
______________________________=0AFrom: Duncan & Ami <ami-mcfadyean@talktalk
.net>=0ATo: europa-list@matronics.com=0ASent: Monday, 24 January, 2011 21:5
8:21=0ASubject: RE: Europa-List: Re: Main wing bushings=0A=0A =0A<<..would
stiffen the structure in such a way that it could lead to overloading =0Aof
the forward lift pin>>=0A =0AIan,=0AHow does that work, if the lift pins a
re designed to carry the lift loads in the =0Afirst place, there being no g
reater load available?!=0AActually, it was stiffening in bending that might
restrain rotation of the lift =0Apin that was the issue, resulting in an a
dditional bending load (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 =0AH
owever, you are on right path, The earlier discussion in this thread presum
es =0Athat the spar flexes, as it indeed doe. But actually the spar (loaded
in this =0Adirection) is the least flexible part of the whole system. What
about the =0Aforward and aft portions of the root rib? Let=99s say t
hese ribs have equal =0Asection and =98I=99 as the spar, but be
ing laid-up at +/- 45 degrees have x1.41 the =0Aelasticity of the unidirect
ional spar (in the direction of principal stress), =0Aadded to which the le
ngth of these flexing root ribs (between lift pin and spar) =0Ais longer th
an the offset between 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 =0Athe longitudinal offset of lift pin and spar pin centres
is removed, or reversed =0Ato the extent that the spar pins share some lif
t load. =0A=0A =0AAs you say, the flexing of the fus side also contributes,
albeit this had to be =0Astiffened-up to prevent pin disengagement.=0A =0A
Previously I have put a small finger down one of the (1/2=9D) spar pi
n holes with =0Athe wings rigged, while someone else rather violently loade
d the wing, albeit =0Anot even near to 1g. But there was no hint of the
=9Cleverage=9D effect or the spar =0Ahole flexing downwards relati
ve to the pin hole in the seat back.=0A =0ARgds.,=0ADuncan McF.=0A =0A =0A-
----Original Message-----=0AFrom: owner-europa-list-server@matronics.com
=0A[mailto:owner-europa-list-server@matronics.com] On Behalf Of G-IANI=0ASe
nt: 24 January 201112:34=0ATo: europa-list@matronics.com=0ASubject: RE: Eu
ropa-List: Re: Main wing bushings=0A =0AIn support of Bud and Pete=99
s notes I can confirm that flexing of the fuselage is =0Aimportant. The LA
A had considerable concerns that the tail dragger conversion =0Awould stiff
en 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=0AEurop
a Club Mods Specialist=0Ae-mail g-iani@ntlworld.com=0A =0A =0A =0A =0A =0Ah
ttp://www.matronics.com/Navigator?Europa-List=0Ahttp://forums.matronics.com
=== =0A
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