On first glance one would see it that way.
The lift pins on the aircraft side (like most gliders) take all the lifting
load so the wing spars don=92t really bend much and the wing spar pins are
in fact set properly to do their one and only job, absorb the bending shea
r load of the two spars. The force of the non bending spars put little for
ce on the cockpit module (in theory). I suppose one could take out the coc
kpit sockets and in a perfect positive load the spar pins would have no eff
ect on the cockpit module. However, as you intuitively figured out, the sp
ars have to be attached to the cockpit/fuselage to keep the wings from shif
ting laterally, as well as aft bending and forward bending and of course ho
w the heck could we rig the wings without the cockpit module pins and socke
ts...
We killed this horse some years ago and somehow all of us engineering types
figured out John Bewley got it right when doing the original structural an
alysis when the prototype was built. His testament is there are no ADs on
his structural work. His rework of the glider wing spar (Mod78) makes that
wing a brute. No need for a spar strap for sure.
Best Regards,
Bud Yerly
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s 10
________________________________
From: owner-europa-list-server@matronics.com <owner-europa-list-server@matr
onics.com> on behalf of Pete <peterz@zutrasoft.com>
Sent: Saturday, August 10, 2019 5:47:37 PM
Subject: Re: Europa-List: Reaming of spar and CM bushes
What i have never understood, is why the cockpit module spar pin bushings a
re not vertical slots, because when the wings are flexing under G, the lift
pins take the fuse lift loads, and the spar flexing (under positive G) ac
tually force the spar pins _downard_ against the cockpit module....obvious
ly totally counter-productive.
Pete
A239
On Aug 10, 2019, at 5:29 PM, Bud Yerly <budyerly@msn.com<mailto:budyerly@ms
n.com>> wrote:
Fred,
Back before my time when mod 52 was done for the GW increase. The classic
had two 3/8 pins originally. Mod 52 uses the =BD inch pins and a spar stra
p .
As the wings pull forward under load, the fuselage would flex so they put i
n the cross bar and the new sockets.
Then the concern was that the starboard wing spar could become dislodged fr
om the socket and interfere with controls. The quick fix was to hold in th
e spar tip with a pip pin. The port wing was figured would stay put, and t
he spar strap would prevent flexing of the spar.
That is all I know. Andy would have the particulars on the detailed histor
y. It sort of all makes sense.
Best Regards,
Bud Yerly
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________________________________
From: owner-europa-list-server@matronics.com<mailto:owner-europa-list-serve
r@matronics.com> <owner-europa-list-server@matronics.com<mailto:owner-europ
a-list-server@matronics.com>> on behalf of Fred Klein <freddythek10@gmail.c
om<mailto:freddythek10@gmail.com>>
Sent: Thursday, August 8, 2019 1:29:43 AM
>>
Subject: Re: Europa-List: Reaming of spar and CM bushes
Bud=85you mention the use of the SouthCo pip pin on the port side and the A
llen bolt pin on starboard.
Do you know the reason for using different types of pins here?
Is there any downside to using SouthCo pip pins both port and starboard?=85
seems I=92ve heard that some builders have done so.
Fred
On Aug 7, 2019, at 8:35 PM, Bud Yerly <budyerly@msn.com<mailto:budyerly@msn
.com>> wrote:
The SouthCo pip pin is nominally .4985 inches.
The Allen bolt pin for the starboard side is .497 to .495.
|