> Hi all,
>
> I know I should not be in the business of trying to second guess the
> designer but I am really pondering the purpose of the bid strap in the
> middle of the spar. My guess is that under extreme load conditions it may
> be possible for the wing to come off the starboard pin.
> Regards, Paul (363)
As explained by the PFA Chief Engineer to a Club Seminar at the time the XS wing
design was being tested for design approval in the UK, when the last few percent
of load was being applied the wings showed a tendency to distort and fail in a
mode where the exposed spar inner ends twisted and buckled away from each other.
Somewhat like the descriptions one reads of columns failing under compression
due to buckling where the shape and hence strength in the desired direction is
lost.
The strap over the starboard spar seems a simple, light and foolproof way making
sure the spar ends remain vertically aligned under extreme loads.
John Cliff
#0259
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