BTIZ wrote:

I remember an article somewhere.. can't find it.. the 5 point in a glider
really only keeps you from submarining under the lap belt in case of a
landing accident as you rush forward from a rapid stop..

although there is some credence that the 5th strap will help keep the center
of the seat belt low on your waist/hips.. and hold your hips down, but it's
the shoulder straps that keep your head off the canopy.. your body still
articulates around your waist when you hit that bump that puts your head on
(or into) the canopy

Since the 5th belt holds the buckle in the proper position, you are able
to tighten the shoulder belts much more, and this reduces the severity
of "canopy encounters". Even tight shoulder harnesses won't eliminate
the problem, because they aren't designed to hold you down, but more to
keep you from going forward. If the belts angled down behind you,
instead of going straight back, a crash would likely lead to severe
compression of the spine.

A "work around" I use is to press my body up against the belts. This
tends to reduce the "overshooting" that occurs when you are thrown
against the belts by negative G's, and reduces or eliminates the impact
with the canopy.

--
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Eric Greenwell
Washington State
USA