Well i damned again and you=99re right it=99s not in the
least intuitive. It=99s fascinating!
Did I understand that tie bar between the rear lift pins in the XS is
not present in the classic? If so the these folding forward forces are
merely supported by the fuselage sides.
Thanks
Will
From: owner-europa-list-server@matronics.com
[mailto:owner-europa-list-server@matronics.com] On Behalf Of GRAHAM
SINGLETON
Sent: Friday, June 07, 2013 15:15
Subject: Re: Europa-List: You'll Cry Pip Pins
William
just a bit more ignorant than me! The wing spars stop the wings folding
up, (or down), the rear lift pins take the weight of the fuselage
into the wings and stop them folding forwards at high G loading, (that's
none intuitive isn't it?) the front pins carry the resat of the fuse
weight into the wings.
The spars don't need to be tied the the fuselage.
Graham
_____
From: William Daniell <wdaniell.longport@gmail.com>
Sent: Friday, 7 June 2013, 18:05
Subject: RE: Europa-List: You'll Cry Pip Pins
Well I damned, I=99d never have thought that. Those thick spars
look like they should be supporting the aircraft but the weedy looking
fuze pins are actually do all the (lifting) work. So the spars=99
main job is to prevent the wings folding forward or back?
So the really important thing is to keep the spars together not tie the
spars into the fuze?
I am woefully ignorant.
Will
From: Pete [mailto:peterz@zutrasoft.com]
Sent: Friday, June 07, 2013 10:56
Cc: wdaniell.longport@gmail.com
Subject: Re: Europa-List: You'll Cry Pip Pins
All the lifting loads are taken by the lift pins on the side of the
fuse. The pip pins function only to tie the spars together and keep the
wings from folding up under G.
The geometry is such that when the main spars are flexing under load,
the pip pin locations on the spars move downward relative to the lift
pins at the side of the fuse (as the lift pins are further out along the
radius of the flexing spars), so the net result is that the pip pins
actually push DOWNWARDS on the seat back under high positive
G's.....totally counter productive. The seat back bushes should be
clearance vertically IMHO to avoid this situation.
The seat back bushes may however provide some (weak?) support in keeping
the pip pins from twisting out of the spars under their asymmetrical
twisting load. Many gliders use fork-spar arrangements to avoid this.
Cheers,
Pete
A239
On Jun 7, 2013, at 9:45 AM, "William Daniell"
<wdaniell.longport@gmail.com> wrote:
Graham
I am very interested by this statement .so as I understand it
the spars are the main load bearing structure in the airpcraft
if the seat back bush does not do the this what does? How does the
motorglider work?
Will
From: owner-europa-list-server@matronics.com
[mailto:owner-europa-list-server@matronics.com] On Behalf Of GRAHAM
SINGLETON
Sent: Friday, June 07, 2013 04:42
Subject: Re: Europa-List: You'll Cry Pip Pins
Frans
The pip pin on the port side is there to prevent the starboard spar from
twisting away from the
port spar under high load. The starboard side has no need of retention
because the overlapping
spar provides that function.
Strictly speaking the bush in the seat back bulkhead is of no value, in
fact it increases the load on the spars.
Be better without it as per the motor glider. (but DYOR)
Graham
_____
From: Frans Veldman <frans@privatepilots.nl>
Sent: Friday, 7 June 2013, 9:07
Subject: Re: Europa-List: You'll Cry Pip Pins
<frans@privatepilots.nl>
On 06/07/2013 09:40 AM, Tony Renshaw wrote:
> Talking about pip pins, does anyone see any merit in using two of the
Port pip pins, another for the Std spar too?
If I recall correctly, there was some technical reason why both pip pins
are different. I forgot the details, but this discussion has been held
before and someone with insight argued why using a pip pin on the
starboard side was not such a good idea. It had something to do with the
different arrangement and thus different torsional loads on the
starboard side because the spars overlay "the other way around". The pin
had to be longer there to allow some movement, and because it needs to
have some play a pip pin can not be used (unless you make it longer than
it should be but then you need an additional retaining mechanism which
of course negates the whole idea of using a pip pin in the first place.)
Although I have modified my aircraft quite a lot, this is an area where
I am shy to deviate from the build plan, as it is one of the most
critical structural area's. As all of the other pins are pip pins my bet
is that there must have been a reason why to use a different arrangement
on this specific pin. Surely it can't be because it was cheaper or so,
or the designer was short of one pip pin and decided to wo= -->
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