All the lifting loads are taken by the lift pins on the side of the fuse. Th
e pip pins function only to tie the spars together and keep the wings from f
olding up under G.
The geometry is such that when the main spars are flexing under load, the pi
p pin locations on the spars move downward relative to the lift pins at the s
ide of the fuse (as the lift pins are further out along the radius of the fl
exing 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. T
he seat back bushes should be clearance vertically IMHO to avoid this situat
ion.
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 l
oad. 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> w
rote:
> 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 s
eat 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-ser
ver@matronics.com] On Behalf Of GRAHAM SINGLETON
> Sent: Friday, June 07, 2013 04:42
> To: europa-list@matronics.com
> 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 t
wisting away from the
> port spar under high load. The starboard side has no need of retention bec
ause the overlapping
> spar provides that function.
> Strictly speaking the bush in the seat back bulkhead is of no value, in fa
ct 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>
> To: europa-list@matronics.com
> Sent: Friday, 7 June 2013, 9:07
> Subject: Re: Europa-List: You'll Cry Pip Pins
>
>
> On 06/07/2013 09:40 AM, Tony Renshaw wrote:
>
> > Talking about pip pins, does anyone see any merit in using two of the P
ort 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= --> http://
www.matronics.com/Navigator?Europa-List
> _ref="http://forums.matronics.com/"; target="_blank">http://forums.matr
onbsp; Thank you for your generous nbsp; -Matt Dralle, List Admi
n.
>
>
>
>
>
>
>
> http://www.matronics.com/Navigator?Europa-List
> < - MATRONICS WEB FORUMS -
> http://forums.matronics.com
> http://www.matronics.com/contribution
>
>
>
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