On Jan 17, 2009, at 4:07 PM, JR Gowing wrote:
>
> The restraint point in the headrests has been of concern to most of
> us because they is below shoulder height. There have been proposals
> made to raise the headrests and also to hinge additional height from
> behind to lift the direction of the belts. However they all seem to
> impede access some extent.
>
> Why cannot we have a restraint point in the fuselage shell situated
> well behind, and at a little lower level than the fuel filler?
Bob,
I share your concerns and gave the issue a fair amount of thought.
What stopped me from establishing restraint points as you suggest were:
- the limitation of my own knowledge as to how much stress could be
applied to the fuselage top shell, how it could be adequately
distributed, and a concern that if it were ever needed, the result
could break the back of Ms. Europa.
- a concern about dealing w/ potential side loads given the distance
of such a restraint point from the seat back which might allow too
much sideways movement of the shoulder harness,
- and a concern that whatever strap or cable might lead to such a
restraint point could be bothersome when loading/unloading baggage,
possibly requiring disengagement from the harness.
I settled on that little hinged riser (photos previously posted)
because:
- it allowed for standard method of entering and leaving the cabin,
- all stresses could be routed to the CM as designed via the existing
shoulder harness attach point,
- the riser could be bench-tested to ensure that it would not fail (in
compression); I put what would be a tension force of 1500# in the
harness at the appropriate angle and the little hinged riser absorbed
it w/ no sweat; however, the force was applied incrementally rather
than abruptly. I was figuring 100# upper body weight...so,
theoretically, the riser may be good for 15G,
- and, when hinged back, it served to increase the area upon which one
can sit while entering/exiting, and the approximately 4" x 6" area IMO
only marginally reduced access to the baggage bay.
At the time I made mine, I actually bought enough material to produce
a few "kits", but have set that notion aside as I've proceeded with my
build. Incidentally, one aspect of this solution is that it allows the
use of the standard harness and can be added at any time.
Fred
A194
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