The 'crotch strap' is what used to be known as a 'negative-G'
strap. Usually it works to keep your skull away from
the canopy during the bumpy bits of sky; rarely, it
helps you in a crash by preventing submarining. However,
a single strap is both inconvenient and potentially
painful. A better design is a double strap, like an
inverted V, but it needs two hard points. Another
variation is an upright V, with one hardpoint and some
secure way to fasten the ends of the V to the lapstraps
rather than the buckle.

The conventional 4-point or 5-point harness shows its
ancestry from the lapstrap by having the primary mounting
[the buckle] on the lapstrap. Would a better design
not have the buckle assembly permanently mounted to
the [adjustable] negative-G strap and the two lap and
two shoulder straps plugging in later ?

Ian




At 15:00 06 June 2004, Bill Daniels wrote:

'Robertmudd1u' wrote in message
...
You may be interested in my latest crotch strap experience.

I'm still analyzing my June 2003 accident and the
cause. More later on
this.
The role of the crotch strap is significant and worthy
of mention.

Dr. Byars, thank you for this interesting and important
feedback based on
real
world experience.

The standard line from the German manufactures is
that a crotch strap is
not
needed because the submarining hazard has been taken
care of through use
of the
'H point' when locating the anchoring point of the
lap belts. This system
locates the lap belt a bit further forward than in
older designs with the
aim
being to get the lap belt lower on your hips. This
is supposed to prevent
it
from being pulled out of place when tightening the
shoulder harness. It
does,
but I believe the lap belt has to be tightened to
an un-necessary degree
to get
anywhere near the effect the 'H point' is credited
with bringing about.

My experience is that the 'H point' is not adequate
to keep the lap belt
from
being pulled up when tightening the shoulder straps.
This is especially
true
when flying out west in strong lift at high speed.
A crotch strap helps
keep
you from bouncing around thus providing more comfort
and better control.
The
difference is security in the cockpit is dramatic.
I normally retro fit a
crotch strap to my gliders and feel a lot safer and
more comfortable with
its
use. This holds true even with my Genesis which used
the 'H point' system
to
locate the lap belt anchor points.

Robert Mudd


After reading Ed and Robert's posts, I intend to install
a crotch strap in
my Nimbus. At the very least, it will let me get the
shoulder straps REALLY
tight without pulling the lap belt up too high.

When you are riding 10 - 15 knot mountain thermals
with a stiff carbon wing
you just can't be strapped in too tight.

Bill Daniels